164
1 INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous) Dundigal, Hyderabad - 500 043 DEPARTMENT OF CIVIL ENGINEERING Course: Elements Of Mechanical Engineering Course Code: AME551 B.Tech VI Sem IARE- R16 Prepared by : Mr. P.SADANANDAM Assistant Professor Mr. A Anudeep Kumar Assistant Professor

Course: Elements Of Mechanical Engineering · • ∆U < 0, internal energy of system decreases. 15 Non-flow Processes • Constant Volume Process • Constant Pressure Process •

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1

INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous)

Dundigal Hyderabad - 500 043

DEPARTMENT OF CIVIL ENGINEERING

Course Elements Of Mechanical Engineering

Course Code AME551 BTech VI Sem

IARE- R16

Prepared by Mr PSADANANDAM

Assistant Professor

Mr A Anudeep Kumar Assistant Professor

2

UNIT 1 INTRODUCTION TO ENERGY SYSTEMS

3

Introduction

Thermodynamics is a branch of science and engineering that deals with interaction of energy mainly in the forms of heat and work

There are different forms of energy

bull all the energy cannot be used as a work

bull the convertibility of energy into work depends on its availability

Thermodynamics is studied in two forms

bull Classical

bull Statistical

4

bull Classical thermodynamics is concerned with the macrostructure

of matter and addresses the major characteristics of large

aggregations of molecules and not the behavior of individual

molecules

bull Statistical thermodynamics is concerned with the microstructure

of the matter and addresses behavior of individual molecules of

the matter

5

Important Terminologies

Thermodynamics It is the field of thermal engineering that studies the properties of systems that have a temperature and involve the laws that

bull govern the conversion of energy from one form to another

bull the direction in which heat will flow

bull the availability of energy to do work

System System is the fixed quantity of matter andor the region that can be separated from everything else by a well-defined boundarysurface

6

State At any instant of time the condition of a system is called state

The state at a given instant of time is defined by the properties of

the system such as pressure volume temperature etc

Property It is any quantity whose numerical value depends on the state but not on the history of the system There are two types of properties extensive and intensive

bull Extensive properties depend on the size or extent of the system Volume mass energy and entropy are the examples of extensive properties

bull Intensive properties are independent of the size or extent of the system Pressure and temperature are the examples of intensive properties

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

2

UNIT 1 INTRODUCTION TO ENERGY SYSTEMS

3

Introduction

Thermodynamics is a branch of science and engineering that deals with interaction of energy mainly in the forms of heat and work

There are different forms of energy

bull all the energy cannot be used as a work

bull the convertibility of energy into work depends on its availability

Thermodynamics is studied in two forms

bull Classical

bull Statistical

4

bull Classical thermodynamics is concerned with the macrostructure

of matter and addresses the major characteristics of large

aggregations of molecules and not the behavior of individual

molecules

bull Statistical thermodynamics is concerned with the microstructure

of the matter and addresses behavior of individual molecules of

the matter

5

Important Terminologies

Thermodynamics It is the field of thermal engineering that studies the properties of systems that have a temperature and involve the laws that

bull govern the conversion of energy from one form to another

bull the direction in which heat will flow

bull the availability of energy to do work

System System is the fixed quantity of matter andor the region that can be separated from everything else by a well-defined boundarysurface

6

State At any instant of time the condition of a system is called state

The state at a given instant of time is defined by the properties of

the system such as pressure volume temperature etc

Property It is any quantity whose numerical value depends on the state but not on the history of the system There are two types of properties extensive and intensive

bull Extensive properties depend on the size or extent of the system Volume mass energy and entropy are the examples of extensive properties

bull Intensive properties are independent of the size or extent of the system Pressure and temperature are the examples of intensive properties

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

3

Introduction

Thermodynamics is a branch of science and engineering that deals with interaction of energy mainly in the forms of heat and work

There are different forms of energy

bull all the energy cannot be used as a work

bull the convertibility of energy into work depends on its availability

Thermodynamics is studied in two forms

bull Classical

bull Statistical

4

bull Classical thermodynamics is concerned with the macrostructure

of matter and addresses the major characteristics of large

aggregations of molecules and not the behavior of individual

molecules

bull Statistical thermodynamics is concerned with the microstructure

of the matter and addresses behavior of individual molecules of

the matter

5

Important Terminologies

Thermodynamics It is the field of thermal engineering that studies the properties of systems that have a temperature and involve the laws that

bull govern the conversion of energy from one form to another

bull the direction in which heat will flow

bull the availability of energy to do work

System System is the fixed quantity of matter andor the region that can be separated from everything else by a well-defined boundarysurface

6

State At any instant of time the condition of a system is called state

The state at a given instant of time is defined by the properties of

the system such as pressure volume temperature etc

Property It is any quantity whose numerical value depends on the state but not on the history of the system There are two types of properties extensive and intensive

bull Extensive properties depend on the size or extent of the system Volume mass energy and entropy are the examples of extensive properties

bull Intensive properties are independent of the size or extent of the system Pressure and temperature are the examples of intensive properties

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

4

bull Classical thermodynamics is concerned with the macrostructure

of matter and addresses the major characteristics of large

aggregations of molecules and not the behavior of individual

molecules

bull Statistical thermodynamics is concerned with the microstructure

of the matter and addresses behavior of individual molecules of

the matter

5

Important Terminologies

Thermodynamics It is the field of thermal engineering that studies the properties of systems that have a temperature and involve the laws that

bull govern the conversion of energy from one form to another

bull the direction in which heat will flow

bull the availability of energy to do work

System System is the fixed quantity of matter andor the region that can be separated from everything else by a well-defined boundarysurface

6

State At any instant of time the condition of a system is called state

The state at a given instant of time is defined by the properties of

the system such as pressure volume temperature etc

Property It is any quantity whose numerical value depends on the state but not on the history of the system There are two types of properties extensive and intensive

bull Extensive properties depend on the size or extent of the system Volume mass energy and entropy are the examples of extensive properties

bull Intensive properties are independent of the size or extent of the system Pressure and temperature are the examples of intensive properties

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

5

Important Terminologies

Thermodynamics It is the field of thermal engineering that studies the properties of systems that have a temperature and involve the laws that

bull govern the conversion of energy from one form to another

bull the direction in which heat will flow

bull the availability of energy to do work

System System is the fixed quantity of matter andor the region that can be separated from everything else by a well-defined boundarysurface

6

State At any instant of time the condition of a system is called state

The state at a given instant of time is defined by the properties of

the system such as pressure volume temperature etc

Property It is any quantity whose numerical value depends on the state but not on the history of the system There are two types of properties extensive and intensive

bull Extensive properties depend on the size or extent of the system Volume mass energy and entropy are the examples of extensive properties

bull Intensive properties are independent of the size or extent of the system Pressure and temperature are the examples of intensive properties

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

6

State At any instant of time the condition of a system is called state

The state at a given instant of time is defined by the properties of

the system such as pressure volume temperature etc

Property It is any quantity whose numerical value depends on the state but not on the history of the system There are two types of properties extensive and intensive

bull Extensive properties depend on the size or extent of the system Volume mass energy and entropy are the examples of extensive properties

bull Intensive properties are independent of the size or extent of the system Pressure and temperature are the examples of intensive properties

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

7

bull Change in State

Thermodynamic system undergoes

changes due to flow of mass and

energy The mode in which the changes

in the state of a system takes place is

known as process such as isobaric

(constant pressure) process isochoric

(constant volume) process isothermal

(constant temperature) process

adiabatic (constant entropy) process

etc

bull The path is loci of series of state changes from initial state to final state

during a process

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

8

Process Two states are identical if and only if the properties of the two states are same When any property of a system changes in value there is a change in state and the system is said to undergo a process

Cycle When a system from a given initial state goes into a sequence of processes and finally returns to its initial state it is said to have undergone a cycle

Phase Phase refers to a quantity of matter that is homogeneous throughout in its chemical composition and physical structure

bull A system can contain one or more phases

bull A pure substance is one that is uniform and invariable in chemical composition

bull A pure substance can exist in more than one phase but its chemical composition must be the same in each phase

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

9

Equilibrium In thermodynamics the concept of equilibrium includes not only a balance of forces but also a balance of other influencing factors such as thermal equilibrium pressure equilibrium phase equilibrium etc Zeroth law of thermodynamics is law of thermal equilibrium which states that if a system A is in thermal equilibrium with systems B and C then systems B and C will be in thermal equilibrium as well

Quasi-static Process When a process proceeds in such a way that the system remains infinitesimally close to an equilibrium state at all times it is called a quasi-static process

bull A quasi-static process can be understood as sufficiently slow process that allows the system to adjust internally so that properties in one part of the system do not change faster than those at other parts

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

10

Temperature Temperature is a property of a substance by which it can be differentiated from other substance in terms of degree of hot or cold

degC = degK minus 27315 degR = 18degK

degF = degR minus 45967

degF = 18degC + 32

Internal Energy The Internal Energy (U) of a system is the total energy

content of the system

bull It is the sum of the kinetic potential chemical electrical and all

other forms of energy possessed by the atoms and molecules of the

system

bull The Internal Energy (U) is path independent and depends only on

temperature for an ideal gas

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

11

Work Work in thermodynamics may be defined as any quantity of energy that flows across the boundary between the system and surroundings which can be used to change the height of a mass in the surroundings

Heat Heat is defined as the quantity of energy that flows across the boundary between the system and surroundings because of a temperature difference between system and surroundings The characteristics of heat are as follows

bull Heat is transitory and appears during a change in state of the system and surroundings It is not a point function

bull The net effect of heat is to change the internal energy of the system and surroundings in accordance to first law

bull If heat is transferred to the system it is positive and if it is transferred from the system it is negative

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

12

Enthalpy Enthalpy h of a substance is defined as h = u + PV It is

intensive properties of a substance and measured in terms of kJkg

Specific Heat at Constant Volume (Cv) The rate of change of internal

energy with respect to absolute temperature at constant volume is known as specific heat at constant volume (Cv)

Specific Heat at Constant Pressure (CP) The rate of change of enthalpy

with respect to absolute temperature when pressure is constant is known as specific heat at constant pressure (Cp)

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

13

First Law of Thermodynamics

First Law of Thermodynamics The first law of thermodynamics is equivalent to law of conservation of energy It deals with the transformation of heat energy into work and vice versa

bull When a small amount of work (dw) is supplied to a closed system undergoing a cycle the work supplied will be equal to the heat transfer or heat produced (dQ) in the system

bull If Q amount of heat is given to a system undergoing a change of state and

W is work done by the system and transferred during the process the net

energy (Q ndash W) will be stored in the system named as internal energy or

simply energy of the system (∆U)

Q ndash W = ∆U

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

14

Sign Convention The convention is adopted that Q indicates the heat added to the system and W the work done by it Thus

bull dQ gt 0 heat added to system or system absorbs heat

bull dQ lt 0 heat removed from system or system rejects heat

bull dW gt 0 work is done by system

bull dW lt 0 work is done on the system

bull ∆U gt 0 internal energy of system increases

bull ∆U lt 0 internal energy of system decreases

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

15

Non-flow Processes

bull Constant Volume Process

bull Constant Pressure Process

bull Constant Temperature Process

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

16

bull Adiabatic Process

bull Polytropic Process

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

17

Application of First Law of Thermodynamics in Steady Flow Process and Variable Flow Process

Steady Flow Process In a steady flow process thermodynamic properties at any section remain constant with respect to time it can vary only with respect to space

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

18

Variable Flow Process In some flow process mass flow rate is not steady but varies with respect to time In such a case the difference in energy flow is stored in system as ∆Ev

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

19

The Second Law of Thermodynamics

KelvinndashPlanck Statement It is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single thermal reservoir

Clausius Statement It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower temperature body to higher temperature body

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

20

The Carnot Cycle

1ndash2 Reversible Isothermal Expansion

2ndash3 Reversible Adiabatic Expansion

3ndash4 Reversible Isothermal Compression

4ndash1 Reversible Adiabatic Compression

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

21

The Clausius Inequality

or

Entropy Defining entropy in an exact word or line is impossible It can

be viewed as a measure of molecular disorder or molecular randomness

As a system becomes more disordered the positions of the molecules

become less predictable and the entropy increases Thus the entropy of a

substance is lowest in the solid phase and highest in the gas phase

bull SGEN gt 0 for an irreversible (real) process

bull SGEN = 0 for a reversible (ideal) process

bull SGEN lt 0 for an impossible process

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

22

Third Law of Thermodynamics

Third law of thermodynamics is law of entropy It is a statement about the ability to create an absolute temperature scale for which absolute zero is the point at which the internal energy of a solid is zero Third law of thermodynamics states that it is impossible to reduce any system to absolute zero in a finite series of operations

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

23

Gas Laws

Boyle‟s law is stated as bdquovolume and pressure of a sample of gas are inversely proportional to each other at constant temperature‟

bull Charle‟s law can be stated as bdquovolume of a sample of gas is directly

proportional to the absolute temperature when pressure remains constant‟

bull GayndashLussac‟s law states that the pressure of a sample of gas is directly

proportional to the absolute temperature when volume remains constant‟

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

24

bullCombined Gas Law

bullGas Constant

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

25

UNIT-II STEAM TURBINES HYDRAULIC

MACHINES

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

26

The Theory of Producing Steam

bull Water boils and evaporates at 100degC under atmospheric pressure

bull By higher pressure water evaporates at higher temperature - eg a pressure of 10 bar equals an evaporation temperature of 184degC

bull During the evaporation process pressure and temperature are constant and a substantial amount of thermal energy is used for bringing the water from liquid to vapour phase

bull When all the water is evaporated the steam is called dry saturated

bull In this condition the steam contains a large amount of latent heat

bull Further heating of dry saturated steam will lead to increase in temperature of the steam

bull Superheated steam

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

27

Steam generator versus steam boiler

bull Opposite the principle of the steam boilers the water in the steam generators evaporates inside the tube winded up into serial connected tube coils

bull The feed water is heated up to the evaporation temperature and then evaporated

bull The intensity of the heat the feed water flow and the sizelength of the tube are

adapted so that the water is exactly fully evaporated at the exit of the tube

bull This ensures a very small water and steam volume (content of the pressure

vessel)

bull Thus there are no buffer in a steam generator and is it temporary overloaded

bull The advantages using a steam generator compare to conventional steam boilers

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

28

bull Easy to operate - normally no requirement for boiler authorization

bull Rapid start-up and establishing full steam pressure Compact and

easy to adapt in the existing machinery arrangement

bull Price attractive - especially at low steam rates

bull The advantages using a steam generator compare to conventional

steam boilers

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Steam Generation Theory

bull Within the boiler fuel and air are force

into the furnace by the burner

bull There it burns to produce heat

bull From there the heat (flue gases) travel throughout the boiler

bull The water absorbs the heat and eventually absorb enough to change into a gaseous state - steam

bull To the left is the basic theoretical design of a modern boiler

bull Boiler makers have developed various designs to squeeze the most energy out of fuel and to maximized its transfer to the water

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

30

bull Water enters the boiler preheated at the top The hot water naturally circulates through the tubes down to the lower area where it is hot The water heats up and flows back to the steam drum where the steam collects Not all the water gets turn to steam so the process starts again

bull Water keeps on circulating until it becomes steam Meanwhile the control

system is taking the temperature of the steam drum along with numerous other readings to determine if it should keep the burner burning or shut it down

bull As well sensors control the amount of water entering the boiler this water

is know as feedwater Feedwater is not your regular drinking water

bull It is treated with chemicals to neutralize various minerals in the water

which untreated would cling to the tubes clogging or worst rusting them

bull This would make the boiler expensive to operate because it would not be

very efficient

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

31

bull On the fire side of the boiler carbon deposit resulting from improper combustion or impurities in the fuel can accumulate on the outer surface of the water tube

bull This creates an insulation which quickly decrease the energy transfer from the heat to the water

bull To remedy this problem the engineer will carry out soot blowing At a specified time the engineer uses a long tool and insert it into the fire side of the boiler

bull This device which looks like a lance has a tip at the end which blows steam

bull This blowing action of the steam scrubs the outside of the water tubes cleaning the carbon build up

bull Water tube boilers can have pressures from 7 bar to as high as 250 bar

bull The steam temperatures can vary between saturated steam 100 degrees Celsius steam with particle of water or be as high as 600 - 650 degrees Celsius know as superheated steam or dry steam

bull The performance of boiler is generally referred to as tons of steam produced in one hour

bull In water tube boilers that could be as low as 15 thr to as high as 2500 thr

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

32

Heat Engine

bull A heat engine is a device that absorbs heat (Q) and uses it to do useful

work (W) on the surroundings when operating in a cycle

bull Sources of heat include the combustion of coal petroleum or

carbohydrates and nuclear reactions

bull Working substance the matter inside the heat engine that undergoes

addition or rejection of heat and that does work on the surroundings

Examples include air and water vapour (steam)

bull In a cycle the working substance is in the same thermodynamic state at

the end as at the start

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

33

Hot Body (source of heat)

Cold Body (absorbs heat)

Heat Engine

Q1

W

Q2

E

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

34

Example of a Heat Engine

Open system

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

35

Internal Combustion Engine

d

a

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

36

Comparison of Otto and Diesel Cycles

combustion

Work per cycle

= Area inside

Q=0

Q=0

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

37

Nuclear Power Plant A Very Large Heat Engine

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

38

Efficiency of a Heat Engine

Efficiency h = Work outHeat in W

Q 1

Apply First Law to the working substance

DU = Q1 ndash Q2 ndash W

But in a cycle DU = 0

Thus W = Q1 ndash Q2

Substituting W

Q 1

Q

1 Q

2

Q 1

Q 1

2

Q 1

h is maximum when Q2 is minimum

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

39

The Stirling Engine

bull Closed system

bull Operates between two bodies with (small) different temperatures

bull Can use ldquostrayrdquo heat

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

The Stirling Cycle TH gtTC

Heat in

isothermal (TH - TC ) is proportional to

the amount of work that is done in a cycle

= air temp

=hot water

2

isothermal Heat out

40

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

41

Q1

C

Q2

Cold Reservoir

T2

Hot Reservoir

T1

Carnot Cycle

W

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Volume 42

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Volume 43

Carnot Cycle

Pressure

a

bull Q1

nRT 1

P = V

bullb

nRT 2

P = V

Q=0W

bull d

Q2

Q=0

T1

P =

cbull T2

const

V

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

44

V

Carnot Cycle

From a to b isothermal so that DU = 0 and Q = - W

Thus Q1 = +nRT1ln(VbVa) (+ve quantity)

From b to c adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

1 b 2 c T V

1

1

c

T 2 b

Similarly from c to d isothermal so that DU = 0 and Q = - W

Thus Q2 = +nRT2ln(VdVc) = -nRT2ln(VcVd) (-ve)

Similarly d to a adiabatic Q = 0 so that TVg-1 is constant Thus T V g-1 = T V g-1 or

2 d 1 a

T V 1

1

d

T 2 V

a

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

V V

Carnot Cycle

T V 1 V

1

We see that 1

c d

T

2 b a

Which means that V

c

V d

V b

V a

Now also Q 1

nRT 1 ln( V

b V

a )

T1 ln( V

b V

a )

But as the volume

ratios are equal

Q 2

nRT 2

Q 1

Q 2

ln( V c

T1

T 2

V d ) T

2 ln( V

c V

d )

This is an important result Temperature can be defined (on the absolute

(Kelvin) scale) in terms of the heat flows in a Carnot Cycle

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

46

Carnot Cycle

bull Heat is transferred tofrom only two reservoirs at fixed temperatures T1 and

T2 - not at a variety of temperatures

bull Heat transfer is the most efficient possible because the temperature of the

working substance equals the temperature of the reservoirs No heat is

wasted in flowing from hot to cold

bull The cycle uses an adiabatic process to raise and lower the temperature of

the working substance No heat is wasted in heating up the working

substance

bull Carnot cycles are reversible Not all cycles are

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

47

Carnot Cycle

The Carnot theorem states that the Carnot cycle (or any reversible cycle) is

the most efficient cycle possible The Carnot cycle defines an upper limit to

the efficiency of a cycle

bull Recall that for any cycle the efficiency of a heat engine is given as

W Q 2

E = = 1 Q 1 Q 1

bull For an engine using a Carnot cycle the efficiency is also equal to

T 2

C = 1 T

1

bull Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively in degrees Kelvin

As T2 gt 0 hc is always lt1

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

48

Efficiency of a Stirling Engine

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and boiling water (100 degC)

Maximum efficiency would be achieved by a Carnot cycle operating between

reservoirs at T1 = 373 K and T2 = 298 K

c = 1 298

373

W = 0 20 =

Q 1

Question What is the maximum possible efficiency of a Stirling engine

operating between room temperature (25 degC) and ice (0 degC)

c = 1 273

298

W = 0 08 =

Q 1

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

49

E

Refrigerator A heat engine operating in reverse

Q1

Refrigerator Efficiency

h eat

out

R

Q 2 W

work in

W

Q2

Hot Body

Cold Body

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

1

c

1

Refrigerator Efficiency

heat

R

work

out

in

Q

2

W

First Law tells us that Q2 + W -Q1 = 0

Thus W = Q1 ndash Q2

Q 2

R

Q Q

For a Carnot refrigerator the efficiency is

1 Q Q Q T T T

1 2

R Q

2

1 1

Q 2

1 1

T 2

1 2

T 2

c

T

2

Efficiency is usually gt1

R

T T The smaller the T difference the more efficient is the

refrigerator

2

2

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

51

UNIT-III INTERNAL COMBSUTION ENGINES REFRIGERATION AND

AIR-CONDITIONING

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

52

bull In an Internal combustion engine combustion takes place within working fluid

of the engine thus fluid gets contaminated with combustion products

bull Petrol engine is an example of internal combustion engine where the working

fluid is a mixture of air and fuel

bull In an External combustion engine working fluid gets energy using boilers by burning fossil fuels or any other fuel thus the working fluid does not come in contact with combustion products

bull Steam engine is an example of external combustion engine where the working

fluid is steam

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

53

bull Internal combustion engines may be classified as

bull Spark Ignition engines

bull Compression Ignition engines

bull Spark ignition engine (SI engine) An engine in which the combustion process in each cycle is started by use of an external spark

bull Compression ignition engine (CI engine) An engine in which the combustion process starts when the air-fuel mixture self ignites due to high temperature in the combustion chamber caused by high compression

bull Spark ignition and Compression Ignition engine operate on either a four stroke cycle or a two stroke cycle

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

54

bull Four stroke cycle It has four piston strokes over two revolutions for each cycle

bull Two stroke cycle It has two piston strokes over one revolution for each cycle

bull We will be dealing with Spark Ignition engine and Compression Ignition engine operating on a four stroke cycle

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

55

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

56

Figure Engine components

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

57

Internal combustion Engine Components

IC Engine components shown in figure1 and figure2 are defined as follows

bull Block Body of the engine containing cylinders made of cast iron or aluminium

bull Cylinder The circular cylinders in the engine block in which the pistons reciprocate back and forth

bull Head The piece which closes the end of the cylinders usually containing part of the clearance volume of the combustion chamber

bull Combustion chamber The end of the cylinder between the head and the piston face where combustion occurs

bull The size of combustion chamber continuously changes from minimum volume when the piston is at TDC to a maximum volume when the piston at BDC

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

58

bull Crankshaft Rotating shaft through which engine work output is supplied to external systems

bull The crankshaft is connected to the engine block with the main bearings

bull It is rotated by the reciprocating pistons through the connecting rods connected to the crankshaft offset from the axis of rotation This offset is sometimes called crank throw or crank radius

bull Connecting rod Rod connecting the piston with the rotating crankshaft usually made of steel or alloy forging in most engines but may be aluminum in some small engines

bull Piston rings Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

59

bull Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle either directly or through mechanical or hydraulic linkage (push rods rocker arms tappets)

bull Push rods The mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase

bull Crankcase Part of the engine block surrounding the crankshaft

bull In many engines the oil pan makes up part of the crankcase housing

bull Exhaust manifold Piping system which carries exhaust gases away from the engine cylinders usually made of cast iron

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

60

bull Intake manifold Piping system which delivers incoming air to the cylinders usually made of cast metal plastic or composite material

bull In most SI engines fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor

bull The individual pipe to a single cylinder is called runner

bull Carburetor A device which meters the proper amount of fuel into the air flow by means of pressure differential

bull For many decades it was the basic fuel metering system on all automobile (and other) engines

bull Spark plug Electrical device used to initiate combustion in an SI engine by creating high voltage discharge across an electrode gap

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

61

bull Exhaust System Flow system for removing exhaust gases from the

cylinders treating them and exhausting them to the surroundings

bull It consists of an exhaust manifold which carries the exhaust gases away

from the engine a thermal or catalytic converter to reduce emissions a

muffler to reduce engine noise and a tailpipe to carry the exhaust gases

away from the passenger compartment

bull Flywheel Rotating mass with a large moment of inertia connected to the

crank shaft of the engine

bull The purpose of the flywheel is to store energy and furnish large angular

momentum that keeps the engine rotating between power strokes and

smooths out engine operation

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

62

bull Fuel injector A pressurized nozzle that sprays fuel into the incoming air (SI engines )or into the cylinder (CI engines)

bull Fuel pump Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine

bull Glow plug Small electrical resistance heater mounted inside the combustion chamber of many CI engines used to preheat the chamber enough so that combustion will occur when first starting a cold engine

bull The glow plug is turn off after the engine is started

bull Starter Several methods are used to start IC engines Most are started by use of an electric motor (starter) geared to the engine flywheel Energy is supplied from an electric battery

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

63

Figure Engine Terminology

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

64

Engine Terminology

bull Top Dead Center (TDC) Position of the piston when it stops at the furthest

point away from the crankshaft

bull Top because this position is at the top of the engines (not always) and dead because the piston stops as this point Because in some engines TDC is not at the top of the

bull engines(eg horizontally opposed engines radial engines etc) Some sources call this position Head End Dead Center (HEDC)

bull Some source call this point TOP Center (TC)

bull When the piston is at TDC the volume in the cylinder is a minimum called the clearance volume

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

65

bull Bottom Dead Center (BDC) Position of the piston when it stops at the point closest to the crankshaft

bull Some sources call this Crank End Dead Center (CEDC) because it is not always at the bottom of the engine Some source call this point Bottom Center (BC)

bull Stroke Distance traveled by the piston from one extreme position to the other TDC to BDC or BDC to TDC

bull Bore It is defined as cylinder diameter or piston face diameter piston face diameter is same as cylinder diameter( minus small clearance)

bull Swept volumeDisplacement volume Volume displaced by the piston as it travels through one stroke

bull Swept volume is defined as stroke times bore

bull Displacement can be given for one cylinder or entire engine (one cylinder times number of cylinders)

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

66

bull Clearance volume It is the minimum volume of the cylinder available for the charge (air or air fuel mixture) when the piston reaches at its outermost point (top dead center or outer dead center) during compression stroke of the cycle

bull Minimum volume of combustion chamber with piston at TDC

bull Compression ratio The ratio of total volume to clearance volume of the cylinder is the compression ratio of the engine

bull Typically compression ratio for SI engines varies form 8 to 12 and for CI engines it varies from 12 to 24

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

67

SI Engine Ideal Otto Cycle

bull We will be dealing with four stroke SI engine the following

figure shows the PV diagram of Ideal Otto cycle

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

68

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

69

Four strokes of SI Engine Cycle

SuctionIntake stroke Intake of air fuel mixture in cylinder through intake

manifold

The piston travel from TDC to BDC with the intake valve open and exhaust

valve closed

This creates an increasing volume in the combustion chamber which in turns creates a vacuum

The resulting pressure differential through the intake system from atmospheric pressure on the outside to the vacuum on the inside causes air to be pushed into the cylinder

As the air passes through the intake system fuel is added to it in the desired

amount by means of fuel injectors or a carburettor

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Figure5 Compression Stroke

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

71

bull Compression stroke When the piston reaches BDC the intake valve closes and the piston travels back to TDC with all valves closed

bull This compresses air fuel mixture raising both the pressure and temperature in the cylinder

bull Near the end of the compression stroke the spark plug is fired and the combustion is initiated

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

72

bull Combustion of the air-fuel mixture occurs in a very short but finite length of time with the piston near TDC (ie nearly constant volume combustion)

bull It starts near the end of the compression stroke slightly before TDC and lasts into the power stroke slightly after TDC

bull Combustion changes the composition of the gas mixture to that of exhaust products and increases the temperature in the cylinder to a high value

bull This in turn increases the pressure in the cylinder to a high value

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Figure6 Combustion followed by Expansion stroke

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

74

bull Expansion strokePower stroke With all valves closed the high pressure created by the combustion process pushes the piston away from the TDC

bull This is the stroke which produces work output of the engine cycle

bull As the piston travels from TDC to BDC cylinder volume is increased causing pressure and temperature to drop

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

75

bull Exhaust Blowdown Late in the power stroke the exhaust valve is opened and exhaust blowdown occurs

bull Pressure and temperature in the cylinder are still high relative to the surroundings at this point and a pressure differential is created through the exhaust system which is open to atmospheric pressure

bull This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the exhaust system when the piston is near BDC

bull This exhaust gas carries away a high amount of enthalpy which lowers the cycle thermal efficiency

bull Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time needed for exhaust blowdown

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

76

Figure Exhaust blowdown followed by Exhaust stroke

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

77

bull Exhaust stroke By the time piston reaches BDC exhaust blowdown is complete but the cylinder is still full of exhaust gases at approximately atmospheric pressure

bull With the exhaust valve remaining open the piston travels from BDC to TDC in the exhaust stroke

bull This pushes most of the remaining exhaust gases out of the cylinder into the exhaust system at about atmospheric pressure leaving only that trapped in the clearance volume when the piston reaches TDC

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

78

bull Near the end of the exhaust stroke before TDC the intake valve starts to open so that it is fully open by TDC when the new intake stroke starts the next cycle

bull Near TDC the exhaust valve starts to close and finally is fully closed sometime after TDC

bull This period when both the intake valve and exhaust valve are open is called valve overlap it can be clearly seen in valve timing chart given below

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Figure Ideal diesel cycle P-V Diagram

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Figure Four strokes of ideal Diesel cycle 80

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

81

FigureFuel injection and combustion followed by Expansion stroke

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

82

AIR COMPRESSOR

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

83

IDEAL COMPRESSION CYCLE

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

84

MODELS OF COMPRESSION

ISOTHERMAL This model assumes that the compressed gas remains at a constant temperature hroughout the compression or expansion process

ADIABATIC This model assumes that no energy (heat) is transferred to or from the gas during the compression and all supplied work is added to the internal energy of the gas resulting in increases of temperature and pressure

POLYTROPIC This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressors components Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs actual (polytrophic)

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

85

TYPES OF COMPRESSOR

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

86

ROTARY SCREW TYPE

Capacity control for these compressors is accomplished by variable speed and variable compressor displacement

For the latter control technique a slide valve is positioned in the casing As the compressor capacity is reduced the slide valve opens bypassing a portion of the compressed air back to the suction

RECIPROCATING TYPE

Capacity control for these compressors is accomplished by unloading individual cylinders Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

87

Refrigeration amp Air Conditioning

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

88

1 Room air conditioners

2 Central air conditioning systems

3Heat pumps

4 Evaporative coolers

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

89

Room air conditioners cool rooms rather than the entire home Less expensive to operate than central units Their efficiency is generally lower than that of central air conditioners Can be plugged into any 15- or 20-amp 115-volt household circuit that is not shared with any other major appliances

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

90

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

91

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

92

Circulate cool air through a system of supply and return ducts Supply ducts and registers (ie openings in the walls floors or ceilings covered by grills) carry cooled air from the air conditioner to the home

bull

bull This cooled air becomes warmer as it circulates through the home then it flows back to the central air conditioner through return ducts and registers

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

93

bull Air conditioners are rated by the number of British Thermal Units

(Btu) of heat they can remove per hour Another common rating term

for air conditioning size is the ton which is 12000 Btu per hour

Room air conditioners range from 5500 Btu per hour to 14000 Btu per

hour

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

94

Energy Saving Methods

Locate the air conditioner in a window or wall area near the center of

the room and on the shadiest side of the house

Minimize air leakage by fitting the room air conditioner snugly into its

opening and sealing gaps with a foam weather stripping material

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

95

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

96

bull The mechanism used for lowering or producing low temp in a body or a space whose temp is already below the temp of its surrounding is called the refrigeration system

bull Here the heat is being generally pumped from low level to the higher one amp is rejected at high temp

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

97

bull A refrigerator is a reversed heat engine or a heat pump which takes out heat

from a cold body amp delivers it to a hot body

The refrigerant is a heat carrying medium which during their cycle in a

refrigeration system absorbs heat from a low temp system amp delivers it to a

higher temp system

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

98

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

99

bull This is the most important system from the point of commercial amp domestic

utility amp most practical form of refrigeration

bull The working fluid refrigerant used in this refrigeration system readily

evaporates amp condenses or changes alternatively between the vapour amp liquid

phases without leaving the refrigerating plant

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

100

bull During evaporation it absorbs heat from the cold body or in condensing or

cooling it rejects heat to the external hot body

bull The heat absorbed from cold body during evaporation is used as its latent heat

for converting it from liquid to vapour

bull Thus a cooling effect is created in working fluid

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

101

This system of refrigeration thus act as latent heat pump since its pump its latent heat from the cold body or brine amp rejects it or deliver it to the external hot body or the cooling medium

According to the law of thermodynamics this can be done only on the expenditure of energy which is supplied to the system in the form of electrical energy driving the compressor

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

102

bull Smaller size for a given refrigerating capacity

bull Higher coeff of performance

bull Lower power requirements for a given capacity

bull Less complexity in both design amp operation

bull It can be used over large of temp

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

103

bull Refrigerator is provided with a door push switch which closes on opening of refrigerator and puts the lamp on

bull Capacitor start single phase induction motor is used in open type refrigerators and split phase induction motor is used in sealed unit refrigerators

bull Electromagnetic relay is provided to connect auxiliary winding

on the start amp disconnect it when the motor picks up the speed

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

104

Thermal overload release is provided to protect the motor from damage against

flow of over current

Thermostat switch is provided to control the temp inside the refrigerator

Temp inside the refrigerator can be adjusted by means of temp control screw

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

105

UNIT-IV

MACHINE TOOLS AND AUTOMATION

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

106

Basic Operations Performed on a Lathe Machine

1 Turning ndashPlain turning Step turning

2 Facing

3 Taper Turning

4 Drilling 5 Boring 6 Reaming 7 Knurling 8 Forming 9 Chamfering 10 Parting Off 11 Threading or thread cutting

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

107

Turning

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

108

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

109

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

110

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

FIG- DRILLING AND BORING

111

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

Drilling on lathe machine

112

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

113

Boring on lathe machine

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

114

Reaming on lathe machine

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

115

AUTOMATION AND ROBOTICS

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

116

AUTOMATION

Automation can be explained as a process to create control and monitor

the applications of technology Automation is the process of handling the

operation of equipment such as processors machinery stabilization of

ships aircraft boilers and many applications with minimum human

efforts

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

117

FIXED AUTOMATION

bull Is a machine refer to totally hardware that can operate automatically

without human interference

bull Examples ndash door with spring load ndash watch gravity machine water-

wheel animalwind ndash wheel

bull Used in low and medium production manufacturing

bull Special machine for production process efficiency at higher

numberrate of product

bull An Automatic machine and numerical control machine is an example of

fixed automation because the inner construction and function can‟t be

change

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

118

PROGRAMMABLE AUTOMATION

Example ndash Production line assemble Air condition screen saver

traffic light radiator

Used when rate of production are small and there is a variation at

the product

An equipments can be easily change their setup according to the

product configuration needs after the first production is finish

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

119

FLEXIBLE AUTOMATION

Combination of hardware and software ( same as programmable) but can easily changed during the operation without waiting the whole operation completed But usually configuration product are limited compare to the programming automation

Allows combination of certain system

In flexible automation different product can be made in the same time at the same manufacture system Flexible Automation System mostly consist of series of workstation that is connected to the material operation and storage system assembly line and control of operation of work by using a program for a different work station

Example ndash Automobile assemble line

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

120

ROBOTICS

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

121

ROBOTICS TIMELINE

bull 1922 Czech author Karel Capek wrote a story called Rossum‟s

Universal Robots and introduced the word

bull ldquoRabotardquo(meaning worker) 1954 George Devol developed the first

programmable

bull 1962 Unimation was formed first industrial Robots

bull appeared

bull 1973 Cincinnati Milacron introduced the T3 model

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

122

CLASSIFICATION OF ROBOT

Possible classification schemes are 1Anatomy (Body) 2 Control of movement

base on

3 Kinematics geometry 4Energy source 5Authority body 6Industrynon industry 7Technology level 8Based on design 9Applicationjob 10By number of degree

structure

of freedom (gripper configuration)

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

123

BASED ON ANATOMY

1 Arm

2 Two arm

3 Arm and leg

4 Arm leg

5 Finger

and face

bull 2 fingers

bull 3 fingers

bull 5 fingers

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

124

BASED ON CONTROL OF MOVEMENT

a) Limited sequence Robot

b) From point to point Robot

c) Continues Robot

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

125

POINT TO POINT ROBOT

bull The movement of robot is in linear direction

bull At the end of the tool will be programmed at sequence discrete points

in the work space

bull No control for movement speed Move at different speed and distance

bull Axes can reach the destination and stop before another axes

bull Usually used in industry environment where amount of

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

126

BASED ON KINEMATICS COORDINATE

(MOVEMENT)

a) Cartesian Coordinate Movement

b) Cylindrical Movement(Oslash r z)

c)Spherical Movement(Oslash R Oslash)

d)SCARA Movement(Oslash Oslash Z)

e) Revolute Movement(Oslash Oslash Oslash)

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

127

INDUSTRIAL ROBOTS

bull Industrial robots is more complex

bull Consist of some subsystem that operate together to perform function

that have been determined

bull Main importancy in the subsystem for the robot is kinematic control

system and driver

bull Robots are used in a wide range of industrial

bull The earliest applications were in materials handling spot welding

and spray painting

bull Robots were initially applied to jobs that were hot heavy and

hazardous such as die casting forging and spot welding

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

128

bull Manual manipulator A manipulator worked by a human operator

bull Fixed-sequence robot A manipulator that performs successive steps of a

given operation its instructions cannot be easily changed

bull Variable-sequence robot A manipulator similar to the fixed-sequence

robot but its instructions can be changed easily

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

129

bull Playback robot A manipulator that can reproduce operations

originally executed under human control

bull Numerically controlled (NC) robot A manipulator that can perform a

sequence of movements which is communicated by means of

numerical data

bull Intelligent robot A robot that can itself detect changes in the work

environment by means of sensory perception and adjust its

movements accordingly

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

130

ROBOT COMPONENTS

1 Manipulator or Rover Main body of robot (Links Joints other

structural element of the robot)

2 End Effecter The part that is connected to the last joint hand) of a

manipulator

3 Actuators Muscles of the manipulators (servomotor stepper motor

pneumatic and hydraulic cylinder)

4 Sensors To collect information about the internal state of the robot or To

communicate with the outside environment

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

131

5 Controller Similar to cerebellum It controls and coordinates the motion of

the actuators

6 Processor The brain of the robot It calculates the motions and the velocity

of the robot‟s joints etc

7 Software Operating system robotic software and the collection of routines

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

132

UNIT-V ENGINEERING MATERIALS JOINING

PROCESS

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

133

Engineering Materials

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

134

The Three Basics

Metals

Polymers bull Composites

Ceramics

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

135

Metal

Cast Iron

Steel bull Mild steel medium carbon steel high carbon steel

Specialty steel

bull Stainless (tin plated or galvanized)

Alloys (two or more pure metals) bull Steel= iron amp carbon

bull Brass= copper amp zinc

bull Bronze= copper amp tin

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

136

Polymers

Natural

bull Animal cellulose

Synthetic-

bull Thermoplastics

bull Thermosets

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

137

Natural Composites

Hardwood

bull Deciduous Trees

Softwood

bull Coniferous

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

138

Ceramics

Clay based

bull Structural clay-tile brick

bull Porcelain

Refractories

bull Heat resistant (fire bricks)

Glasses

Inorganic cements

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

139

WELDING PROCESSES

1 Arc Welding

2 Resistance Welding

3 Oxyfuel Gas Welding

4 Other Fusion Welding

5 Solid State Welding

6 Weld Quality

7 Weldability

Processes

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

140

Two Categories of Welding Processes

Fusion welding - coalescence is accomplished by melting the

two parts to be joined in some cases adding filler metal to the

joint

Examples arc welding resistance welding oxyfuel gas

welding

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

141

Arc Welding (AW)

bull A fusion welding process in which coalescence of the

metals is achieved by the heat from an electric arc between

an electrode and the work

bull Electric energy from the arc produces temperatures 10000

F (5500 C) hot enough to melt any metal

bull Most AW processes add filler metal to increase volume and

strength of weld joint

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

142

Electric Arc

An electric arc is a discharge of electric current across a gap in

a circuit

bull It is sustained by an ionized column of gas (plasma)

through which the current flows

bull To initiate the arc in AW electrode is brought into

contact with work and then quickly separated from it by

a short distance

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

143

Arc Welding

Figure Basic configuration of an arc welding process

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

144

Plasma Arc Welding

Figure Plasma arc welding (PAW)

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

145

Advantages Disadvantages of PAW

Advantages

bull Good arc stability

bull Better penetration control than other AW

bull High travel speeds

bull Excellent weld quality

Disadvantages

bull High equipment cost

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

146

Resistance Welding (RW)

bull group of fusion welding processes that use

combination of heat and pressure to accomplish

coalescence

bull Heat generated by electrical resistance to current flow

at junction to be welded

bull Principal RW process is resistance spot welding

(RSW)

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

147

Resistance Welding

Fig Resistance

welding showing the components in spot

welding the main process in the RW group

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

148

Advantages Drawbacks of RW

Advantages

bull No filler metal required

bull High production rates possible

bull Lends itself to mechanization and automation

bull Lower operator skill level than for arc welding

bull Good repeatability and reliability

Disadvantages

bull High initial equipment cost

bull Limited to lap joints for most RW processes

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

149

Oxyacetylene Welding

Figure A typical oxyacetylene welding operation

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

150

Other Fusion Welding Processes

FW processes that cannot be classified as arc resistance or

oxyfuel welding

Use unique technologies to develop heat for melting

Applications are pically unique

Processes include

bull Electron beam welding

bull Laser beam welding

bull Electroslag welding

bull Thermit welding

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

151

Electron Beam Welding (EBW)

Fusion welding process in which heat for welding is provided by

a highly-focused high-intensity stream of electrons striking work

surface

Electron beam gun operates at

High voltage (eg 10 to 150 kV typical) to

accelerate electrons beam currents are low

(measured in milliamps)

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

152

EBW Advantages Disadvantages

Advantages

bull Limited heat affected zone low thermal distortion

bull High welding speeds

bull No flux or shielding gases needed

Disadvantages

bull High equipment cost

bull Precise joint preparation amp alignment required

bull Vacuum chamber required

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

153

Laser Beam Welding (LBW)

Fusion welding process in which coalescence is achieved by

energy of a highly concentrated coherent light beam focused

on joint

bull Laser = light amplification by stimulated emission of

radiation

bull LBW normally performed with shielding gases to prevent

oxidation

bull Filler metal not usually added

bull High power density in small area so LBW often used for

small parts

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

154

Ultrasonic Welding

Figure Ultrasonic welding (USW) (a) general

a lap joint and (b) close-up of weld area

setup for

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

155

USW Applications

Wire terminations and splicing in electrical and electronics

industry

Eliminates need for soldering

bull Assembly of aluminum sheet metal panels

bull Welding of tubes to sheets in solar panels

bull Assembly of small parts in automotive industry

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

156

Composite Materials

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

157

Introduction

A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other The history of composite materials dates back to early 20th century In 1940 fiber glass was first used to reinforce epoxy

Applications

bull Aerospace industry

bull Sporting Goods Industry

bull Automotive Industry

bull Home Appliance Industry

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

158

Composite Structural Organization the design variations

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

159

Composite Manufacturing Processes

bull Particulate Methods Sintering

bull Fiber reinforced Several

bull Structural Usually Hand lay-up and atmospheric curing or vacuum curing

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

160

Open Mold Processes

Only one mold (male or female) is needed and may be made of any material such

as wood reinforced plastic or for longer runs sheet metal or electroformed

nickel The final part is usually very smooth

Shaping Steps that may be taken for high quality

1 Mold release agent (silicone polyvinyl alcohol fluorocarbon or sometimes

plastic film) is first applied

2 Unreinforced surface layer (gel coat) may be deposited for best surface quality

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

161

Hand Lay-Up The resin and fiber (or pieces cut from prepreg) are placed

manually air is expelled with squeegees and if necessary multiple layers are built

up

Hardening is at room temperature but may be improved by heating

Void volume is typically 1

Foam cores may be incorporated (and left in the part) for greater shape

complexity Thus essentially all shapes can be produced

Process is slow (deposition rate around 1 kgh) and labor-intensive

Quality is highly dependent on operator skill

Extensively used for products such as airframe components boats truck bodies

tanks swimming pools and ducts

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

162

SPRAY-UP MOLDING

A spray gun supplying resin in two converging streams into which roving is

chopped

Automation with robots results in highly reproducible production

Labor costs are lower

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

163

Filament Winding

bull Ex pressure tanks

bull Continuous filaments wound onto mandrel

Adapted from Fig 1615 Callister 7e [Fig

1615 is from N L Hancox (Editor) Fibre

Composite Hybrid Materials The Macmillan

Company New York 1981]

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way

164

Filament Winding Characteristics

bull Because of the tension reentrant shapes cannot be produced

bull CNC winding machines with several degrees of freedom (sometimes 7) are

frequently employed

bull The filament (or tape tow or band) is either precoated with the polymer or is

drawn through a polymer bath so that it picks up polymer on its way to

the winder

bull Void volume can be higher (3)

bull The cost is about half that of tape laying

bull Productivity is high (50 kgh)

bull Applications include fabrication of composite pipes tanks and pressure

vessels Carbon fiber reinforced rocket motor cases used for Space

Shuttle and other rockets are made this way