Me Interview Ques Libre

8/10/2019 Me Interview Ques Libre

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MECHANICAL ENGINEERING I NTERVIEW QUESTIONS

1. Why Entropy decreases with increase in temperature?

Ans. ds=dQ/T Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases.

2. Why different types of sound are produced in different bikes, though they run on SI Engines?

Ans. Engine specifications are different in different manufactures like as Bore Diameter (CC), Ignition timing. Also the exhaustpassage takes more responsible for sound.

3. How much Watt means 1Hp?

Ans. 746.2 Watt

4. Explain Bicycle Rear Wheel Sprocket working?

Ans. Rear wheel sprocket works under the principle of ratchet and pawl.

5. Definition of Octane Number and Cetane Number?

Ans. Octane No.- Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine.

Cetane No.- Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methylnaphthalene. It is the measure of rating of CI engine.

6. Which Mechanism is used in Automobile gearing System?

Ans. Differential mechanism

7. When Crude Oil is Heated, Which Hydro Carbon comes first?

Ans. Natural gas (Gasoline) at 20 Celsius

8. How to calculate Bearing number ti Diameter of the inner and outer?

Ans. Divide the shaft diameter size by 5, it will give last two digit of the bearing no. and according to type of load we have tochoose the type of bearing and that will give prior number of the bearing.

9. The Fatigue life of a part can be improved by?

Ans. Improving the surface finish by Polishing & providing residual stress by Shot peening.

10. What happens if gasoline is used in a Diesel Engine, Siesel Engine will work?

Ans. No, It will not work, as the Compression ratio of Petrol engine is 6 to 10& that of Diesel engine is 15 to 22. Thus on suchhigh compression, gasoline gets highly compressed & it may blast.

11. Poissons Ratio is Higher in, Rubber/Steel/Wood?

Ans. When a material is compressed in one direction, it usuallytends to expand in the other two directions perpendicular tothedirection of compression. This phenomenon is called thePoisson effect. Poissons ratio is a measure of the Poisson effect.

For rubber = 0.5

For steel = 0.288

For wood < 0.2

Thus Poissons ratio is higher in RUBBER.

12. Why the Centrifugal Pump is called High Discharge pump?

Ans. Centrifugal pump is a kinetic device. The centrifugal pump uses the centrifugal force to push out the fluid. So the liquidentering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to ahigh velocity, transferring mechanical (rotational) energy to the liquid. So it discharges the liquid in high rate. It is g iven in thefollowing formulae:

Centrifugal force F= (M *V2)/R.

Where,

M-Mass

V-Velocity R-Radius


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13. How Cavitation can be eliminated by Pump?

Ans. Cavitation means bubbles are forming in the liquid.

To avoid Cavitation, we have to increase the Pump size to One or Two Inch;

To increase the pressure of the Suction Head, or

Decrease the Pump Speed.

14. Why Cavitation will occur in Centrifugal Pump and not in Displacement Pump?

Ans. The formation of cavities (or bubbles) is induced by f low separation, or non-uniform flow velocities, inside a pump casing. Incentrifugal pumps the eye of the pump impeller is smaller than the flow area of pipe. This decrease in flow area of pump results inincrease in flow rate. So pressure drop happened between pump suction and the vanes of the impeller. Here air bubbles or cavitiesare formed because of liquid vapour due to increase in temperature in impeller. This air bubbles are transmitted to pump whichforms cavitation.

15. Which Pump is more Efficient Centrifugal Pump or Reciprocating Pump?

Ans. Centrifugal pump. Because flow rate is higher compared to reciprocating pump. Flow is smooth and it requires less space toinstall. Lower initial cost and lower maintenance cost.

16. Why Centrifugal Pump is not called as a Positive Displacement Type of Pump?

Ans. The centrifugal has varying flow depending on pressure or head, whereas the Positive Displacement pump has more or lessconstant flow regardless of pressure.

Likewise viscosity is constant for positive displacement pump where centrifugal pump have up and down value because the higherviscosity liquids fill the clearances of the pump causing a higher volumetric efficiency. When there is a viscosity change in supplythere is also greater loss in the system. This means change in pump flow affected by the pressure change.

One more example is, positive displacement pump has more or less constant efficiency, where centrifugal pump has varyingefficiency rate.

17. What is the difference between Critical Speed and Whirling Speed?

Ans. In Solid mechanics, in the field of rotor dynamics, the critical speed is the theoretical angular velocity which excites thenatural frequency of a rotating object, such as a shaft, propeller or gear. As the speed of rotation approaches the objects naturalfrequency, the object begins to resonate which dramatically increases system vibration. The resulting resonance occurs regardlessof orientation.Whirling Speed is due to the unbalanced forces acting on a rotating shaft.

18. How a Diesel Engine Works as Generator?

Ans. Diesel engine is a prime mover, for a generator, pump,and for vehicles etc. generator is connected to engine by shaft.mostly in thermal power plat ,there is an engine is used to drive generator to generate power.

19. Explain Second Law of Thermodynamics?

Ans. The entropy of the universe increases over time and moves towards a maximum value.

20. Compare Brayton Cycle and Otto Cycle?

Ans. The heat addition and rejection processes in Otto cycle are of constant volume, whereas in Brayton cycle, they are ofconstant pressure.

-Otto cycle is the ideal cycle for spark ignition engines.-Brayton cycle is the ideal cycle for gas power turbines.

21. What is the purpose of Scrapper Ring?

Ans. scrap the excess lube oil from the cylinder walls. there by preventing oil from entering combustion zone.

22. What is DTSI Technology?

Ans. DTSI stands for Digital Twin Spark Plug Ignition. The vehicles with DTSI Technology use 2 spark plugs which are controlledby digital circuit. It results in efficient combustion of air fuel mixture.

Digital - Since the spark generation will be initiated by a microchip.

Twin -Since two spark plugs will be used.

Spark ignition - Since the ignition will be done via a spark.


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23. How to Find, Ductile-Brittle Transition Temperature in Metals?

Ans. The point at which the fracture energy passes below a pre-determined point for a standard Impact tests. DBTT is importantsince, once a material is cooled below the DBTT, it has a much greater tendency to shatter on impact instead of bending ordeforming.

24. What is the importance of Thermodynamics?

Ans. All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the

mechanical engineers.

25. What is the difference between P11 and P12 Pipes?

Ans. P11 the chromium molybdenum composition that is 1% ofchromium and 1/4% of molybdenum

P12 the chromium molybdenum composition that is 1% ofchromium and 2% of molybdenum

26. State difference between AnitiFriction Bearing and Journal Bearing?

Ans. Generally, journal bearings have higher friction force, consume higher energy and release more heat, but they have largercontact surface, so normally used in low speed high load applications. In anti friction bearings friction is less. One object just rollsover each other.

27. What is the difference between Fan and Blower?

Ans. Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotatedby a motor separately.

When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.

28. What is Heat Rate of Power Plant?

Ans. Heat rate is a measure of the turbine efficiency. It is determined from the total energy input supplied to the Turbine dividedby the electrical energy output

29. What is Hydrodynamic Cavitation?

Ans. Hydrodynamic cavitation describes the process of vaporization in a constrained channel at a specific velocity.

Bubble generation and Bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase inpressure.

30. What is Difference between Hardness and Toughness?

Ans. Toughness is the ability of a material to absorb energy.

Hardness is the ability of a material to withstand wear.

31. What is the hottest part of Refrigerant in Refrigeration?

Ans. Compressor

32. What does F.O.F Stand for Piping Design?

Ans. Face of Flange, The F.O.F (Raised face and Flat face) is used to know the accurate dimension of the flange in order toavoid the minute errors in measurement in case of vertical or horizontal pipe lines.

33. Where Multi stage Pump is Used?

Ans. Pressure washing of Aircraft, Trains, Boats and Road vehicles as well as Spray washing of industrial parts and Electroniccomponents.

34. What does pump develop:- (a) Flow (b) Pressure

Ans. A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.

35. How to measure temperature of Bearing?

Ans. Normally the temperature range from 80 degree to 110 degree Celsius. So the following temperature measurement devicesare used.

Dial Type Bearing Temperature Detector

Stator Winding Temperature Detector

Resistance Bearing Temperature Detector (Bearing RTD)


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Specialized in Pin type RTD

35. Difference between Performance and Efficiency?

Ans. The accomplishment of a given task measured against preset known standards of accuracy, completeness, cost, and speedis called as Performance.

Efficiency is defined as the input given and the work obtained from that input like money, time, labour etc. Its the main factor ofproductivity.

36. What is Sentinel Relief Valve?

Ans. Its a special type valve system. The valve will open when exhaust casing pressure is excessive (high). The valve warns theoperator only; it is not intended to relieve the casing pressure.

37. What is the difference between Specification,Codes, Standards?

Ans. Specification is describing properties of any type of materials.

Code is procedure of acceptance and rejection criteria.

Standard is accepted values and compare other with it.

38. Which is heavier 1kg Cotton or 1kg Iron?

Ans. Both of them have same weight.

39. What is Auto Dosing?

Ans. Auto dosing is an automated system of feeding the equipment with liquid products. It is the ideal way to ensure the correctcalibrated dose at the right time every time in auto.

40. What is the difference between Sudden Force and Impact Force?

Ans. An impact is a high force or shock applied over a short time period when two or more bodies collide.

A force which applies on the body (material) suddenly is known as sudden force.

41. What is Geyser Pressure Valve?

Ans. To release the pressure created inside due to evaporation of water.

42. What is difference between Corrective actions and Preventive actions?

Ans. Corrective actions are taken on discrepancies noticed during inspection of products/documents/process whereas preventive

actions are taken to eliminate the possibility ofdiscrepancy in future.

43. How do you know air is fully saturated?

Ans. In its Dew point. (100% relative humidity condition)

44. What is the function of scoop in BFP (Boiler Feed water pump) in Thermal Power Station?

Ans. The Function of Scoop tube is regulating the varying amount of oil level in the coupling during operation of infinite variablespeed.

45. What is Operating Pressure?

Ans. The amount of pressure nearest the point of performing work at the output end of a pneumatic system. The systemoperating pressure is used to specify the capability of valves and actuators.

46. What is the difference between Technology and Engineering?

Ans. Engineering is application of science. Technology shows various methods of Engineering. A bridge can be made by usingbeams to bear the load,by an arc or by hanging in a cable; all shows different technology but comes under civil engineering andscience applied is laws of force/load distribution.

47. How to Measure Temperature in Wet Bulb Thermometer?

Ans. Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. Itcorresponds to the dew point temperature and relative humidity.


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48. What are the Advantages and Disadvantages of using LPG in Car?

Ans. Advantages

1. Complete combustion

2. Fuel saving

3. Homogenous combustion

Disadvantages

1. As complete combustion is occurring ,more heat liberated,not advised for long journey, engine will be over heated

2. Installation is difficult

3. Reduce engine life efficiency

49. What is the difference between Speed and Economic Speed?

Ans. The rated speed tells us about the maximum speed which can be achieved by a vehicle or some other machine but theeconomical speed means the speed limit at which the machine works efficiently with least consumption of fuel.eg-in normalbikes(not racing),the max.speed limit shown on speedometer is upto 120 kmph but companies always advice their customers todrive such bikes at around 60 kmph to have maximum mileage.

50. What is Powder Technology?

Ans. Powder technology is one of the ways of making bearing material. In this method metals like bronze, Al, Fe are mixed andcompressed to make an alloy.

51. State all the laws of Thermodynamics?

Ans. There are three laws of the thermodynamics.

First Law:Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the totalenergy remains the same.

Second Law:When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, butnot in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems,and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of theinitial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a newthermodynamic equilibrium, entropy has increased, or at least has not decreased.

Third Law:As temperature approaches absolute zero, the entropy of a system approaches a minimum.

52. State the difference between Unilateral and Bilateral Tolerance?

Ans. A unilateral tolerance is tolerance in which variation is permitted only in one direction from the specified direction.e.g. 1800+0.000/-0.060

Bilateral tolerance is tolerance in which variation is permitted in both direction from the specified direction.e.g. 1800 +0.060/-0.060

53. What is the abbreviation of welding rod 7018?

Ans. 7018 =

70=tensile strength 70000psi

1= welding position

8=current flux

54. What is difference between Welding and Brazing?

Ans. In Welding concentrated heat (high temperature) is applied at the joint of metal and fuse together.

In Brazinginvolves significantly lower temperatures and does not entail the melting of base metals. Instead, a filler metal is meltedand forced to flow into the joint through capillary action.

55. Which has more Efficiency Diesel Engine or Petrol Engine?

Ans. Diesel engine has the better efficiency out of two.

1. What is the difference between isotropic and anisotropic materials ?


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Ans: If a material exhibits same mechanical properties regardless of loading direction, it isisotropic, e.g., homogeneous cast materials. Materials lacking this property are anisotropic.2. What are orthotropic materials ?Ans: It is a special class of anisotropic materials which can be described by giving theirproperties in three perpendicular directions e.g. wood; composites.3. What is view factor ?Ans: View factor is dependent upon geometry of the two surfaces exchanging radiation.4. What properties need to be considered for applications calling for following requirements :

(i) rigidity(ii) strength for no plastic deformation under static load(iii) strength to withstand overload without fracture.(iv) wear resistance(v) reliability and safety.Ans: (i) RigidityElastic modulus and yield strength(ii) Strength (for no plastic deformation under static loading)yield point(iii) Strength (overload)Toughness and impact resistance(iv) Wear resistanceHardness(v) Reliability and safetyEndurance limit and yield point.5. Explain the effects of alloying chromium and nickel in stainless steel.Ans: Addition of nickel and chromium increases the tensile strength and increase inresistance to corrosion takes place.6. Mention two types of dislocations.Ans: Dislocation refers to a break in the continuity of the lattice. In edge dislocation, oneplane of atoms gets squeezed out. In screw dislocation the lattice atoms move fom theirregular ideal positions.

7. What are the principal constituents of brass?Ans: Principal constituents of brass are copper and zinc.8. What is Curie point ?Ans: Curie point is the temperature at which ferromagnetic materials can no longer bemagnetised by outside forces.9. Specific strength of materials is very high when they are in fibre size but lower when theyare in bar form Why ?Ans: Crystal structure has ordered, repeating arrangement of atoms. Fibres are liable tomaintain this and thus have high specific strength. As size increases, the condition of orderedand repeating arrangements can't be guaranteed because of several types of defects anddislocations and thus the specific strength gets lower.10. What is the percentage of carbon in cast iron ?Ans: 2.5%.11. Which element is added in steel to increase resistance to corrosion ?Ans: Chromium.12. Whether individual components in composite materials retain their characteristics or not?

Ans: yes.13. An elastomer is a polymer when its percentage elongation rate is ?Ans: Greater than 100%.14. If percentage elongation of a material is more than 200%, it is classed as ?Ans: Rubber.15. Why is it that the maximum value which the residual stress can reach is the elastic limit ofthe material ?Ans: A stress in excess of elastic limit, with no external force to oppose it, will relieve itself byplastic deformation until it reaches the value of the yield stress.16. Why fatigue strength decreases as size of a part increases beyond around 10 mm?Ans: Perfection of material conditions is possible at lower sizes and as size increases, it is notpossible to attain uniform structure of the material.17. Distinguish between creep and fatigue.Ans: Creep is low and progressive deformation of a material with time under a constant stressat high temperature applications. Fatigue is the reduced tendency of material to offerresistance to applied stress under repeated or fluctuating loading condition.18. While normal carburising and nitriding surface treatments increase fatigue strength,

excessive treatment may decrease the fatigue strength. Why ?.Ans: Normal carburising/nitriding treatments increase volume due to phase transformation atSurface and introduce residual compressive surface stress and thus increase the fatiguestrength. By excessive treatment the high compressive stresses are introduced but these arebalanced by high internal tensile stresses of equal value and the subsurface fatigue cracksmay develop in the regions of high tensile stress and lead to early fatigue failure.19. List at least two factors that promote transition from ductile to brittle fracture.Ans: Manner of loading, and the rate of loading promote transition from ductile to britt lefracture. A machine member may have ductile failure under static loading but may fail inbrittle fashion when the load is f luctuating. Similarly a material may evidence ductile failureunder tensile loading at ordinary testing speed but if load is applied at a high velocity thenfailure may be brittle.


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20. Which theories of failure are used for (a) ductile materials, and (b) brittle materials ?Ans: For ductile materials, theories of failure used are maximum shear stress theory, andmaximum energy of distortion theory; while for brittle materials, theory of maximum principalstress, and maximum strain are used.21. What does thermal diffusivity of metals signify.Ans: Thermal diffusivity is associated with the speed of propagation of heat into solids duringchanges in temperature with time.22. For conduction of heat, the instantaneous rate of heat flow is product of three factors.

What are these ?Ans: (i) Area of the section of the heat flow path, perpendicular to the direction of heat flow.(ii) temperature gradient, i.e. change of temperature w.r.t. length of path.(ii) Thermal conductivity of material.23. How convective heat transfer is effected and on what factors it depends ?Ans: Convective heat transfer is effected between a solid and fluid by a combination ofmolecular conduction within the fluid in combination with energy transport resulting from themotion of fluid particles. It depends on boundary layer configuration, fluid properties andtemperature difference.24. Which is the common element between brass and bronze ?Ans: Copper.25. What does following alloy designation indicate FG 250 ?Ans: Grey cast iron with tensile strength of 250 MPa.26. How is ceramic defined ?Ans: It is a solid formed by combination of metallic and non-metallic elements.27. Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.Ans: BCC (body centred cubic) structureMolybdenum

FCC (face centred cubic) structureAluminiumHCP (hexagonal closed packed) structureZincCCP (cubic dosed packed) structure-Copper.28. What is the name of solid solution of carbon in alpha iron and delta iron ?Ans: Ferrite and austenite respectively.29. Explain the difference between pearlite and cementile ?Ans: Pearlite is eutectoid mixture of ferrite and cementile. Cementite is chemical compound ofiron and carbon.30. Give one example each of the following proportion of materials dimensional, physical,technological and mechanical.Ans: Roughness, enthalpy, toughness, and hardness respectively.31. For which parts the Wahl factor and Lewis form factor used ?Ans: For springs and gears respectively.32. How oxygen can be removed from steel during melting? What are fully killed steels ?Ans: Oxygen can be removed by adding elements such as manganese, silicon or aluminiumwhich, because of their high affinity for oxygen, react with it to form non-metallic oxides which

rise into the slag. Steels which have had most of their dissolved oxygen removed are called"fully killed steels".33. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has onproperty of steel ?Ans: Execessive hydrogen results in the formation of small fissures often described as hairlinecracks or flakes in the steel. Large forgings in alloy steel are particularly sensitive to thisphenomenon.34. What is allotrope ? In what forms of cubic pattern, iron exists ?Ans: Some elements exist in more than one crystalline form. Each form is known as"allotrope". Iron exists in two forms of cubic pattern, namely body centered cubic (bcc) andface-centered cubic (fee).35. What is the difference between alpha iron, delta iron and gamma iron ?Ans: The bcc form of iron exists between room temperature and 910C, and between 1400Cand the melting point at 1539C. The lower temperature form is known as " alpha"-iron and thehigher temperature form as "delta"-iron. The face-centered cubic form existing between910C and 1400C is referred to as "gamma -iron".36. Metals, in general are of low strength and do not possess required physio-chemical and

technological properties for a definite purpose. Alloys are therefore more than metals alone.Discuss the arrangement of atoms and structures of alloys.Ans: Alloys are produced by melting or sintering two ore more metals, or metals and a nonmetal,together. Alloys possess typical properties inherent in the metallic state. The chemicalelements that make up an alloy are called its components. An alloy can consist of two or morecomponents. The phase and structures of alloys describe the constitution, transformationsand properties of metals and alloys. A combination of phases in a state of equilibrium is calleda system. A phase is a homogeneous portion of a system having the same composition andthe same state of aggregation throughout its volume, and separated from the other portionsof the system by interfaces. For instance, a homogeneous pure metal or alloy is a singlephasesystem. A state in which a liquid alloy (or metal) coexists with its crystals is a two-phasesystem. Structure refers to the shape, size or the mutual arrangement of the corresponding


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phases in metals or alloys. The structural components of an alloy are its individual portions,each having a single structure with its characteristic features.37. What is the difference between isotropic material and homogeneous material ?Ans: In homogeneous material the composition is same throughout and in isotropic materialthe elastic constants are same in all directions.38. Explain the difference between the points of inflexion and contraflexure.Ans: At points of inflexion in a loaded beam the bending moment is zero and at points ofcontraflexure in loaded beam the bending moment changes sign from increasing to

decreasing.39. What is the difference between proof resilience and modulus of resilience ?Ans: Proof resilience is the maximum strain energy that can be stored in a material withoutpermanent deformation. Modulus of resilience is the maximum strain energy stored in amaterial per unit volume.40. What is the difference between column and strut ?Ans: Both column and strut carry compressive load. Column is always vertical but strut asmember of structure could carry axial compressive load in any direction.41. Explain the difference between ferrite, austenite and graphite ?Ans: Ferrite is the solid solution of carbon and other constituents in alpha-iron. It is soft,ductile and relatively weak.Austenite is the solid solution of carbon and other constituents in gamma-iron. It exists inordinary steels at elevated temperatures, but it is also found at ordinary temperatures insome stainless steels.Graphite has a hexagonal layer lattice. '42. Explain the terms solid solution, eutectic, eutectoid and peritectic.Ans: Solid Solution. When a homogeneous mixture of two (or more) atomic forms exists in

solid state, it is known as solid solution.Eutectic. A mixture of two (or more) phases which solidify simultaneously from the liquid alloyis called an eutectic. Alloys in which the components solidify simultaneously at a constanttemperature the lowest for the given system, are called eutectic alloys.Eutectoid. Eutectoid alloys are the alloys for which two solid phases which are completelysoluble become completely insoluble on cooling before a certain temperature called eutectoidtemperature.Peritectic. A peritectic transformation involves a reaction between a solid and liquid that forma different and new solid phase. This three phase transformation occurs at a point calledperitectic point.43. What do you understand by critical points in iron, iron-carbide diagram ?Ans: The temperatures at which the phase changes occur are called critical points (ortemperatures).45. Why PERT is preferred over CPM for evaluation of project ?Ans: PERT is based on the approach of multiple time estimates for each activity.46. What is the percentage of chromium in 18 : 4 : 1 IISS ?

Ans: 4%.47. What is stellite ?Ans: It is a non-ferrous cast alloy containing cobalt, chromium and tungsten.48. Which rays are produced by cobalt-60 in industrial radiography ?Ans: Gamma rays.49. What are killed steels and what for these are used ?Ans: Killed steels are deoxidised in the ladle with silicon and aluminium. On solidification nogas evolution occurs in these steels because they are free from oxygen.50. What is critical temperature in metals ?Ans: It is the temperature at which the phase change occurs in metals.51. Car tyres are usually made of ?Ans: Styrene-butadine rubber.52. What is the structure of pure iron and whether it is soft or hard ?Ans: Ferrite and it is soft.53. Which elements increase the corrosion resistance of steel ?Ans: Chromium and nickel.54. What causes hardness in steel ? How heat treatment alters properties of steel ?

Ans: The shape and distribution of the carbides in the iron determines the hardness of thesteel. Carbides can be dissolved in austenite is the basis of the heat treatment of steel. Ifsteel is heated above the A critical temperature to dissolve all the carbides, and then cooled,suitable cooling through the cooling range will produce the desired size and distribution ofcarbides in the ferrite, imparting different properties.55. Explain the formation of microstructures of pearlite, bainite and martensite in steel.Ans: If austenite containing about 0.80 percent carbon is slowly cooled through the criticaltemperature, ferrite and cementite are rejected simultaneously, forming alternate plates orlamellae. This microstructure is called pearlite. At temperatures just belot the A1, thetransformation from austenite.to pearlite may take an appreciable time to initiate andcomplete, but the product will be lameller pearlite. As the transformation temperature islowered, the time to initiate transformation shortens but the product is pearlite of increasing


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fineness, and at temperatures approaching 550C it cannot be resolved into i ts lamellarconstituents. Further deerease in transformation temperature causes a lengthening of thencubation period and a change in structure of the product to a form known as "bainite".If the temperature is lowered suff iciently, the diffusion controlled nucleation and growth modesof transformation are suppressed completely and the austenite transforms by a diffusionlessprocess in which the crystal lattice effectively shears to a new crystallographic configurationknown as "martensite". This phase has a tetragonal crystal structure and contains carbon insupersaturated solid solution.

56. How with alloying of steel it is possible to a achieve properties which can not be achievedwith heat treatment ?Ans: A prerequisite to the hardening of steels is that martensite should be formed on cooling,but this can only be achieved if the rate of cooling is great enough to suppress the formationof pearlite or bainite and in plain carbon steels this can be achieved by quenching relativelysmall specimens57. What are the major effects of alloying elements?Ans: (1) To alter the transformation temperatures and times(2) To modify the room temperature and elevated temperature strengths of given structuresby (a) stiffening the crystals and (b) introducing complex precipitates which tend to harden thesteel.(3) To modify the type of oxide film formed on the surface of the steel and thereby affect itscorrosion resistance.58. What is the difference between austenite stabilisers and ferrite stabilisers ?Ans: Austenite stabilisers have the effect of extending the temperature range overwhichaustenite is formed. Such elements are carbon, manganese, nickel, copper and cobalt.Ferrite stabilisers have the effect of extending the temperature range over which alpha and

delta ferrite are formed, which consequently reduces temperature range over which austeniteis formed. Such elements are silicon, chromium, molybdenum, tungsten, titanium and niobium.59. What are the effects of carbon on the properties of steel.Ans: In general, an increase in carbon content produces higher ultimate strength andhardness but lowers ductility and toughness of steel alloys. Carbon also increases airhardeningtendencies and weld hardness, especially in the presence of chromium. In low-alloysteel for high-temperature applications, the carbon content is usually restricted to a maximumof about 0.15% in order to assure optimum ductility for welding, expanding, and bendingoperations. To minimize intergranular corrosion caused by carbide precipitation, the carboncontent of austenitic (18-8 type) alloys is limited in commercial specifications to a maximum of0.08%, or even less, i.e. 0.03% in the extremely low-carbon grades used in certain corrosionresistantapplications.In plain carbon steels in the normalised condition, the resistance to creep at temperaturesbelow 440C appears to increase with carbon content up to 0.4% carbon, at highertemperatures there isbut little variation of creep properties with carbon content.

An increase in carbon content lessens the thermal and electrical conductivities of steel andincreases its hardness on quenching.60. What is the role of s ilicon as alloying element in steels ?Ans: Silicon contributes greatly to the production of sound steel because of i ts deoxidizingand degasifying properties. When added in amounts up to 2.5%, the ultimate strength of thesteel is increased without loss in ductility. Silicon in excess of 2.5% causes brittleness, andamounts higher than 5% make the steel non-malleable.Resistance to oxidation and surface stability of steel are increased by the addition of silicon.These desirable effects partially compensate for the tendency of silicon to lower the creepproperties of steel. Silicon increases the electrical resistivity of steel and decreases hysteresislosses.61. Discuss the role of manganese in alloying steels.Ans: Manganese is an excellent deoxidizer and sulfur neutralizer, and improves themechanical properties of steel, notably the ratio of yield strength to tensile strength at normaltemperatures. As an alloying element, manganese serves as an inexpensive means ofpreventing "hot shortness". It improves rolling properties, hardenability, and resistance towear. However manganese increases the crack sensitivity of weldments, particularly with

steels of higher carbon content.62. Define buckling factor.Ans: It is the ratio of the equivalent length of column to the minimum radius of gyration.63. What do you understand by catenary cable ?Ans: A cable attached to the supports and carrying its own weight.64. What is coaxing ?Ans: It is the process of improving fatigue properties by first under-stressing and thenincreasing the stress in small increments.65. What is difference between conjugate beam and continuous beam ?Ans: A conjugate beam is an imaginary beam of same size as original beam and carrying adistributed load in accordance with the bending moment diagram.A continuous beam is one which is resting on more than two supports.


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66. What is isotropic material ?Ans: It is a material having same elastic constants in all directions.67. Explain difference between modulus of resilience and modulus of rigidity ?Ans: Modulus of resilience is the maximum strain energy stored in a material per unit volumeand modulus of rigidity is the ratio of shearing stress to the shearing strain within the elasticlimit.68. What is the difference between basic hole and basic shaft ?Ans: A basic hole is one whose lower deviation is zero and in case of basic shaft the upper

deviation is zero.69. What for pyranometer is used ?Ans: It is used to measure the total hemispherical solar radiation.70. Describe transfer machines in brief.Ans: It is an automatic machine in which workpiece alongwith fixture is transferred from onestation to other automatically and several operation on workpiece are performed at eachstation.71. What is burnt-out point ?Ans: It corresponds to maximum heat flux at which transition occurs from nucleate boiling tofilm boiling.72. What do you understand by eutectic ?Ans: It is mechanical mixture of two or more phases which solidify simultaneously from theliquid alloy.72. Explain the difference between grey iron and white iron. What is mottled iron ?Ans: The carbon in cast iron could exist at room temperature as either iron carbide, or asgraphite which is the more stable form. Irons containing carbon as graphite are soft, easilymachinable and are called "grey irons". Irons with carbon present as iron carbide are

extremely hard, difficult to machine and are called "white" irons. Irons with fairly equalproportions of graphite and iron carbide have intermediate hardness and are called "mottled"irons.73. The graphite in grey irons exists in the form of flakes which act as stress-raisers undertensile loading and consequently grey irons have relatively low tensile strength and ductility.Still grey iron is extensively used in engineering. Why ?Ans: Grey iron is extensively used in engineering because of following characteristics.(a) Cheapness.(b) Low melting point and high fluidity making it suitable for castings of intricate shape.(c) Relatively good erosion and corrosion resistance.(d) High damping capacity, with respect to vibration.(e) Relatively good mechanical properties under compressive loading.74. Under what condition a convergent divergent nozzle required ?Ans: When pressure ratio is greater than critical pressure ratio.75. What is endurance limit and what is i ts value for steel ?Ans: Endurance limit is the maximum level of fluctuating stress which can be tolerated

indefinitely. In most steels this stress is approximately 50% of the ultimate tensile strength andit is defined as the stress which can be endured for ten million reversals of stress.76. How the net work to drive a compressor and its volumetric efficiency behave with increasein clearance volume ?Ans: Work remains unaltered and volumetric efficiency decreases.77. What do you understand by sulphur print ?Ans: Sulphides, when attached with dilute acid, evolve hydrogen sulphide gas which stainsbromide paper and therefore can be readily detected in ordinary steels and cast irons. Whilesulphur is not always as harmful as is sometimes supposed, a sulphur print is a ready guideto the distribution of segregated impurities in general.78. What is the different between brass and bronze ?Ans: Brass is an alloy of copper with zinc; and bronze is alloy of copper with tin.79. What is the effect of addition of zinc in copper? What is the use of 70/30 brass ?Ans: By addition of zinc in copper, both tensile strength and elongation increases. The 70/30brass has excellent deep drawing property and is used for making radiator fins.80, What for admirality brass used ?Ans: Admirality brass with 29% zinc and 1% tin has good corrosion resistance and is used for

condenser and feed heater tubes. Aluminium is also added to brass to improve corrosionresistance.81. What is the maximum use of magnesium ?Ans: Magnesium is used to alloy with aluminium and as an additive for making SG (SpheroidalGraphite) iron.82. What for zinc finds applications ?Ans: Galvanizing consumes the largest proportion of zinc. Zinc is resistant to corrosion but isattacked by acids and alkalies. Zinc alloy.s are suited for making die casting since the meltingpoint is reasonably low.83. Which factors influence the type of fracture in failure of a material ?Ans: Seven factors influencing type of failure are :(i) Type of material (inherent structure properties),


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(ii) Manner of loading (Static versus dynamic),(iii) Range of imposed stress,(iv) Strain rate (static, dynamic, impact),(v) Stress distribution (discontinuity in material/shape),(vi) temperature, and(vii) surface treatment.84. What is the name given to ratio of actual cycle efficiency and ideal cycle efficiency.Ans: Efficiency ratio.

85. List two effects of manganese in plain carbon steels. ,Ans: Manganese increases tensile strength and hardness. It decreases weldability.86. Name the strongest and weakest type of atomic bonds.Ans: Metallic bond is strongest and molecular bond also known as Vander Waals bond isweakest.87. In which process internal energy remains constant ?Ans: Isothermal process.88. What is temper embrittlement in alloy steels and what are its effects ?Ans: Embrittlement attack is usually intergranular in metals, i.e. cracks progress between thegrains of the polycrystalline material. It imparts a tendency to fail under a static load after agiven period of time in those alloy steels which are susceptible to embrittlement.89. What are whiskers ?Ans: Whiskers are very small crystals which are virtually free from imperfections anddislocations.90. What is Bauschinger effect ?Ans: According to Bauschinger, the limit of proportionality of material does not remainconstant but varies according to the direction of stress under cyclic stresses.

91. What is the difference between heat capacity and specific heat of a material ?Ans: The heat capacity of a material is the amount of heat transformed to raise unit mass of amaterial 1 degree in temperature.The specific heat of a material is the ratio of the amount of heat transferred to raise unit massof a material 1 degree in temperature to that required to raise unit mass of water 1 degree oftemperature at some specified temperature.For most engineering purposes, heat capacities may be assumed numerically equalto;specific heats.92. Explain the rule to find specific heat of aqueous solutions.Ans: For aqueous solutions of salts, the specific heat can be estimated by assuming thespecific heat of the solution equal to that of the water alone. Thus, for a 15% by weightsolution of sodium chloride in water, the specific heat would be approximately 0.85.93. What do you understand by latent heat ? Give four examples of latent heats.Ans: For pure substances, the heat effects accompanying changes in state at constantpressure (no temperature change being evident) are known as latent heats. Examples oflatent heats are : heat of fusion, vaporisation, sublimation, and change in crystal form.

94. Define the terms free energy and free enthalpy. What is their significance and importance?Ans: Free energy (or Helmholtz function) is defined as/= u -Ts.It is equal to the work during a constant-volume isothermal reversible nonflow process.Free enthalpy (or Gibbs function) is defined as g = h - Ts(where u = internal energy, h = enthalpy, T = temperature, s = entropy)Gibbs function is of particular importance in processes where chemical changes occur. Forreversible isothermal steady-flow processes or for reversible constant-pressure isothermalnonflow processes, change in free energy is equal to net work.95.Which parameter remains constant in isochoric process ?Ans: Volume.96. What is polytropic process ? Under what conditions it approaches isobaric, isothermal,and isometric process ? In which reversible process no work is done ?Ans: A polytropic process is one that follows the equation pun = constant (index n may havevalues from - oc to + oo. This process approaches isobaric when n = 0, isothermal when n =1, and isometric when n = . No work is done in isometric process.97. Whether superheated steam can be treated like ideal gas ?

Ans: Yes.98. Out of constant pressure and constant volume lines on TS diagram which line has higherslope ? And whether slope is constant or variable ?Ans: Constant volume line. Slope is variable.99. Whether entropy is intensive property or extensive property ?Ans: Entropy is extensive property.100. In which process fluid expands but does no work ?Ans: Throttling process.

1. How shear forces are incurred in fluid flow ?Ans: Shear forces between fluid particles and boundary walls and between the fluid particlesthemselves, result from the viscosity of the real fluid.


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2. In laminar flow, how discharge is related to viscosity ?Ans: Discharge varies inversely as viscosity.3. What is best hydraulic section ?Ans: Best hydraulic section is one in which for a given cross-section area, the channelsection has least wetted perimeter.4. What is best hydraulic trapezoidal section ?Ans: It is a half-hexagon in shape.5. What is specific energy in a channel section ?

Ans: It is defined as the energy head measured with respect to the channel bottom at thesection. At any section, it is equal to sum of the velocity head and the water depth at thesection.6. What is critical depth and critical flow ?Ans: Critical depth is the depth, at which the discharge may be delivered through the sectionat minimum energy.Critical flow is the flow in open channel corresponding to critical depth.7. What causes boundary layer separation ?Ans: An adverse pressure gradient.8. What is the improtance of Nose radius ?Ans: Nose radius is favourable to long tool life and good surface finish. A sharp point on theend of a tool is highly stressed, short lived and leaves a groove in the path of cut.9. At what point below free surface in a uniform laminar flow in a channel the pointvelocity is equal to mean velocity of flow ?Ans: At 0.577 depth of channel.10. What is the value of friction factor for smooth pile when Reynolds number isapproximately = 10G ?

Ans: 0.01.11. How hydraulic grade line and free surface of open channel flow related ?Ans: They coincide.12.What are the first and last elements of tool signatures ?Ans: Back rake angle and nose radius.14. What is open channel flow ? Explain 4 types of open channel flows.Ans: Open channel flow has a free water surface which is normally subject to the atmosphericpressure.Steady open channel flow : In this case the discharge and water depth at any section in thereach do not change with time during the period of interest.Unsteady open channel flow : In this case the discharge and the water depth at any section inthe reach change with time.Uniform open channel flow : In this case the discharge and the water depth remain the samein energy section in the channel reach. It is mostly steady.Varied open channel {low : In this case the water depth and/or the discharge change alongthe length of the channel. It may be steady (such as flow over a spillway crest) or unstgeady

(as in the case of flood waves or tidal surge).15. When does wake occur ?Ans: It occurs after a separation point.16. In straight polarity, to which terminal the electrode is connected ?Ans: Negative.17. What is hydraulic radius ?Ans: It is the ratio of fluid flow area/shear perimeter.18. Define flow work.Ans: Flow work is the amount of mechanical energy required to push or force a flowing fluidacross a section boundary.19. What do you understand by dimensional analysis ?Ans: Dimensional analysis is the mathematics of dimensions and quantities and providesprocedural techniques whereby the variables that are assumed to be significant in a problemcan be formed into dimensionless parameters, the number of parameters being less than thenumber of variables.20. What is hydraulic depth for open channel flow ?Ans: It is the ratio of area and the top width of the channel section.

21. Which welding set will you select for welding both f errous and non ferrousmaterials.Ans: D.C. generator set.22. Which welding process is a combination of arc welding and gas weldingprocesses?Ans: Atomic hydrogen welding.23. What is hydraulic jump ?Ans: It is a natural phenomenon in open channel. It is an abrupt reduction in flow velocity bymeans of a sudden increase of water depth in the down stream direction. Through a hydraulicjump, and high-velocity supercritical flow is changed to a low-velocity subcritical flow.24. What is gradually varied flow ?Ans: The changes in water depth in the open channel take place very gradually with


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distance. Depending on the channel slope, the surface conditions, the sectional geometry,and the discharge, these may be classified into five categories : steep channel, criticalchannel, mild channel, horizontal channel, and adverse channel.25. Explain 5 types of channels.Ans: Steep channel : In this case normal depth < cri tical depth.Critical channel : In this case normal depth = crit ical depth.Mild channel : In this case, normal depth > critical depth.Adverse channel : In this case, the slope of channel bed < 0

Horizontal channel : In this case, the slope of channel bed = 0.26. Mention two major differences between shaper and planer ?Ans: Shaper Planer(a) The cutting tool reciprocates (a) Work reciprocates(b) The work is stationary (b) Tool is stationary(c) Meant for small work pieces (c) Meant for large work pieces(d) Only lighter cut can be taken (d) Heavy cuts can be taken(e) Tools are smaller in size (e) Tools are bigger in size27. Differentiate between drilling and reaming ?Ans: Drilling Reaming(a) It is the operation of initiating hole (a) Reaming is the operation of finishingandsizing a drilled/bored hole(b) It can be done at relatively high speeds (b) It should be done only at slow speeds(c) Larger chips are produced (c) Less chips are produced(d) Drill has only two flutes (d) Reamer has more than 4 flutes(e) Drill has chisel edge (e) Reamer has a bevel edge

28. What is similarity between normal shock wave and hydraulic jump ?Ans: Both are analogous and irreversible.29. For what purpose chills are used in moulds ?Ans: Chills are used to achieve directional solidification.30. What is tumbler gear mechanism ?Ans: Tumbler gear mechanism is a mechanism consisting of number of different sized gearskeyed to the driving shaft in the form of cone and is used to give the desired direction ofmotion of the lathe spindle.31. What is relative roughness of pipe ?Ans: It is the ratio of the size of the surface imperfections to the inside diameter of the pipe.32. What is conicity ?Ans: The ratio of the difference in diameter of the taper to its length is termed conicity.33. Under what condition the effect of compressibility of fluid can be neglected ?Ans: When Mach number is less than 0.4.34. For which type of flow the velocity distribution in a pipe is parabolic.Ans: For uniform laminar flow.

35. What is the relationship between center line velocity and average velocity for alaminar flow in a pipe ?Ans: Average velocity = 1/2 centre line velocity.36. On which factor the friction factor for a smooth pipe in turbulent f low depends ?Ans: Reynolds number.37. What do you understand by pipe branchings ?Ans: When water is brought by pipes to a junction where more than two pipes meet, them thetotal amount of water brought by pipes to a junction must always be equal to that carried awayfrom the junction by other pipes, and all pipes that meet at the junction must share the samepressure at the junction.38. What is pipe networks and what are the condition for network ?Ans: Pipe network comprises a number of pipes connected together to form loops andbranches. For a network,(i) at any junction, Y.Q = 0 and(ii) between any two junctions the total head loss is independent of the path taken.39. What is Hardy-Cross Method ?Ans: It is a commonly used computer program for a pipe network.

40. Explain water hammer.Ans: The force resulting from changing the speed of the water mass (say in a pipe due tosudden change of flow rate) may cause a pressure rise in the pipe with a magnitude severaltimes greaterthan the normal static pressure in the pipe. Pressure head caused by water hammer = C (V -velocity in pipe, C = celerity).41. What happens to impurities in centrifugal casting ?Ans: They get collected at the center of the casting.42. Define the terms hydraulic similitude and dimensional analysis.Ans: Hydraulic similitude is the principle on which the model studies are based.Dimensional analysis is the analysis of the basic relationship of the various physical quantitiesinvolved in the static and dynamic behaviors of water flow in a hydraulic structure.


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43. Explain the difference between geometric similarity, kinematic similarity anddynamic similarity.Ans: Geometric similarity : It implies similarity of form. The model is a geometric reductionof the prototype and is accomplished by maintaining a fixed ratio for all homologous lengthsbetween the model and the prototype.Kinematic similarity : It implies similarity in motion. Kinematic similarity between a model andthe prototype is attained if the homologous moving particles have the same velocity ratioalong geometrically similar paths. It involves the scale of time as well as length.

Dynamic similarity : It implies similarity in forces involved in motion.44. Define Reynolds law ?Ans: When the inertial force and the viscous force are considered to be the only forcesgoverning the motion of the water, the Reynolds number of the model and the prototype mustbe kept at the same value.45. When a built up edge is formed while machining ?Ans: While machining ductile materials at high speed.46. On what factor the friction factor for a rough pipe in turbulent flow depends ?Ans: Relative roughness.47. What is unit power of a turbine ?Ans: PHP12.48. How cavitation causes damage ?Ans: In a a closed system (pipelines, or pumps), water vaporises rapidly in regions where thepressure drops below the vapour pressure. This phenomenon is called cavitation. The vapourbubbles formed in cavitation usually collapse in a violent manner, which may causeconsiderable damage to the system.49. In milling process, how the arbor torque can be smoothend ?

Ans: Arbor torque can be smoothened by increasing number of teeth, using higher spiralangle of teeth, using higher cutting depth.49. What are webs in a twist drill ?Ans: Webs are the metal column in the drill which separates the flutes.50. What is bluff body ?Ans: It is a body with such shape that the flow is separated much ahead of its rear endresulting in a large wake, the pressure drag being much greater than the friction drag.51. What is bulk modulus ?Ans: It is the ratio of hydrostatic stress to volumetric strain within the elastic limits.52. Define boundary layer.Ans: It is the fluid layer in the neighborhood of a solid boundary where the effects of fluidfriction are predominant.53. What is creep flow ?Ans: It is flow at very low Reynolds number where viscous forces are larger than the inertiaforces.54. What is Torricellis theorem ?

Ans: According to it velocity of jet flowing out of a small opening is proportional to the squareroot of head of liquid above it.55. How does cavitation manifest itself in a centrifugal pump ?Ans: Usual symptoms of cavitation of pump are noise, vibration, a drop in head and capacitywith a decrease in efficiency, accompanied by pitting and corrosion of the impeller vanes.56. What happens if centrifugal pump is operated at excessive speeds ?Ans: When a pump is operated at excessive speeds, the differential pressure developedincreases and causes a powerful pulsating vacuum on the underside of the blade tips andeach particle of water is pulled away from the blade, taking away with it a small particle ofmetal, producing pitting/grooved effect. Repeated erosive action results in complete honeycombing and total destruction of blade, with resultant loss in pump performance.57. On what parameters the head developed by a centrifugal pump depends ?Ans: It depends upon the impeller diameter and its rotative speed.58. Which factors determine the selection of electrolyte for electrochemicalmachining process ?Ans: Electrolyte should be chemically stable and have high electrical conductivity.59. What is the disadvantages of centrifugal pump having very low specific speed ?

Ans: For a.centrifugal pump having very low specific speed, the impeller diameter is largeand narrow having excessively high disc friction and excessive hydraulic losses.60. On what factors the eff iciency of pump depends ?Ans: Efficiency of a pump (centrifugal) depends on the size, speed, and proportions of theimpeller and casing.61. On what factors the cavitation in centrifugal pumps is dependent ?Ans: Cavitation in centrifugal pumps depends on the velocity of water entering tne impellerand on the relatiave velocity of the impeller blades where the water is picked up.62. What are the losses in a centrifugal pump ?Ans: The losses in a centrifugal pump are : Fr iction losses due to eddies in flow, leakage,friction loss due to rotation of impeller in chamber of water, gland and bearing power losses.63. What should be done to avoid cavitation in pumps ?


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Ans: In order to avoid cavitation, the suction lif t and the operating speed must be carefullychosen.64. What will happen if speed of reciprocating pump is increased ?Ans: If speed of a reciprocating pump is increased beyond a limit, then atmospheric pressurewould be insufficient to force water into the pump at the same speed as the piston. This woulda break in the continuity of the water in suction pipe (cavitation) and give rise to vibration,noise, and chemical attack by any dissolved gases which may be released from the waterowing to the high vacuum and the breaking of the water column.

65. What is the order of efficiency of cenetrifugal and reciprocating pumps ?Ans: The efficiency of centrifugal pump is of the order of 45% whereas that of reciproctingpump is around %.66. What are the basic operations performed in a slotter ?Ans: The different operations done in slotter are :1. Machining grooves2. Machining cylindrical surface3. Machining irregular profiles.67. How the positive displacement is obtained in rotary pumps ?Ans: Positive displacement in rotary pumps is achieved in two ways :(i) A rotor carries radially adjustable vanes, the outer tips of which are constrained by acircular casing, whose centre is remote from that of the rotor.(ii) Various combinations of gears, lobes, helices, etc. within a casing arranged so that thelobes or teeth attached to each rotor pass in sequence through the same pumping space.68. How a slotter differs from shaper ?Ans: Slotter Shaper(a) Ram reciprocates vertically (a) Ram reciprocates horizontally

(b) It has a circular table (b) It has a rectangular table(c) Suited for machining internal surfaces (c) Suited for machining external surfaces(d) Table can take less load (d) Table can take much load69. Under what condition the flow and power of pump vary as square of the size ?Ans: The flow and power vary as size2 when the geometric size changes as inverse ofchange of speed.70. How the incidence of cavitation detected ?Ans: The incidence of cavitation is detected by the following in order of appearance.(i) stroboscopic observation of bubble appearance and size(ii) sensitive acoustic tests of cavitation noise(iii) reduction of efficiency and/or head of 3%.71. How cavitation erosion is assessed ?Ans: Cavitation erosion is assessed by depth of attack or weight of metal removed.72. At which temperature the cavitation erosion is negligible and why ?Ans: Cavitation erosion is negligible at above 300C because the water and steam ha vesame densities at critical temperature of 374C and thus there is no volume chang e or bubble

collapse in the vicinity of this range.73. What is an arbor ?Ans: An arbor is an accurately machined shaft for holding and driving the arbor type cutter. Itis tapered at one end to fit the spindle nose and has two slots to fit the nose keys for locatingand driving it.74. For a body to float in stable equilibrium where the e.g. should be located w.r.t. metacentre?Ans: e.g. should be below metacentre.75. What is the condition for a flow to be fully developed through a pipe ?Ans: Ratio of maximum velocity to average velocity should be 2.76. When a fluid is moving with uniform velocity, whether the pressure of fluid will depend onits depth and orientation ?Ans: No.77. How much is the vertical component of force on a curved surface submerged in a staticliquid ?Ans: It is equal to weight of the liquid above the curved surface.78. On which factors depends the friction factor in a rough turbulent flow in a pipe?

Ans: It depends on pipe diameter and the condition of the pipe.79. What does the realisation of velocity potential in fluid flow indicate ?Ans: It indicates that flow is irrotational.80. What is the difference between potential flow and creep flow ?Ans: Potential flow assumes viscous forces to be zero but same is considered larger thaninertia forces in creep flow.81. For which application Mach number and Froude numbers are significant ?Ans: Mach no. is significant in the study of projectiles and jet propulsion. Froude number issignificant in the study of ship hulls.82. What is the difference between geometric, kinematic, and dynamic similarities betweenmodel and prototype ?Ans: Geometric similarity is mainly for same shape for model and prototype, kinematic


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similarity is concerned with stream line pattern, whereas dynamic similarity concerns the ratioof forces.83. A body is floating in water. If it is displaced slightly then about which point it will oscillate.Ans: It will oscillate about centre of buoyancy.84. Why uniform ramming is considered desirable in green sand moulding process ?Ans: Uniform ramming results in greater dimensional stability of a casting.85. On what account the friction drag is experienced ?Ans: Friction drag is experienced on separation of boundary layer.

86. What is the characteristic of centrifugally cast components ?Ans: These have fine grain structure with high density.87, Under what condition the separation of flow occurs ?Ans: When pressure gradient changes abruptly.88. What is the criterion for shaping of streamlined body ?Ans: It is shaped to suppress the flow separation about the body and to shift the boundarylayer separation to near most part of body to reduce the wake size.89. What do you understand by entrance length and what is its value for turbulent flow insmooth pipe ?Ans: Entrance length of flow is the initial length in which the flow develops fully such that thevelocity profile remains unchanged downstream. For turbulent flow in smooth pipe, entrancelength is taken as 50 x diameter of pipe.90. Explain the difference between friction drag and pressure drag.Ans: Friction drag is the drag force exerted by a fluid on the surface due to friction actionwhenthe flow occurs past a flat surface at zero incidence. Pressure drag is the additional dragforce on

account of the differences of pressure over the body surface when flow occurs past a surfacewhich isnot everywhere parallel to the fluid stream. Pressure drag depends upon separation ofbondary layerand the size of wake. Friction drag is due to shear stresses generated due to viscous action.91. What do you understand by choking in pipe line ?Ans: When specified mass flow is not able to take place in a pipe line.92. What is the difference between streamline body and bluff body ?Ans: In streamline body the shape is such that separation in flow occurs past the nearmostpart of the body so that wake formed is small and thus friction drag is much greater thanpressure drag. In bluff body the flow gets separated much ahead of its rear resulting in largewake and thus pressure drag is much greater than the friction drag.93. What is the difference between dressing and trueing of a grinding wheel ?Ans: Dressing is the process used to clear the cutting surface of the grinding wheel of anydull grits and embedded swarf in order to improve the cutting action. Trueing is the processemployed to bring the wheel to the required geometric shop and also to restore the cutting

action of a worn wheel.94. Whether hard grade or softer grade is required for internal grinding than externalgrinding?Ans: Softer graders of wheel are required for internal grinding than for external grinding.95. How is the velocity profile and stress distribution due to laminar flow of an incompressibleflow under steady conditions in a circular pipe.Ans: Velocity profile is parabolic with zero velocity at boundary and maximum at the centre.Shear stress distribution is linear, being maximum at boundary and zero at centre.96. Where the maximum velocity occurs in open channels ?Ans: Near the channel bottom.97. Define hydraulically efficient channel cross section.Ans: The shape of such section is that which produces minimum wetted perimeter for a givenarea of flow and carries maximum flow.9. What is follower rest ?Ans .For slender work a travelling or follower rest is used. This f its on the lathe - saddle andtravels to and fro with it. By this means support is constantly provided at the position of cut.Thus the work piece being turn is rigidly held against the tool.

99. What is the meaning of the term sensitive drill press ?Ans: A sensitive drilling press is a light, simple, bench type machine for light duty working withinfinite speed ratio.100. Why carburised machine components have high endurance limit ?Ans: In carburised machine components, the process of carburisation introduces acompressive layer on the surface and thus endurance limit is increased.

1. What is anisotropy ?Ans: The phenomenon of different properties in different directions is called anisotropy.2. What is vapour pressure and when it becomes important ?


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Ans: Vapour pressure is the partial pressure created by the vapour molecules whenevaporation takes place within an enclosed space. It becomes important when negativepressures are involved.3. Explain absolute viscosity ?Ans: It is the ratio of shear stress and the gradient of velocity with distance between a fixedplate and moving plate (Its unit is Pa . s).4. Define surface tension ?Ans: Surface tension of a liquid is the work that must be done to bring enough molecules

from inside the liquid to the surface to form one new unit area of that surface. (Its unit isNm/m2 or N/m).5. What is capillarity and when liquid rises or falls ?Ans: Capillarity : The rise or fall of a liquid in a capillary tube caused by surface tension.The magnitude of rise or fall depends on the relative magnitudes of the cohesion of the liquidand adhesion of the liquid to the walls of the containing vessels. Capillarity is of importance intubes smallerthan 10 mm diameter.Rise of liquid : Liquids rise (in capillary tube) when they wet and adhesion of the liquid to thewalls is greater than the cohesion of the liquid.Fall of liquid : Liquids fall (in capillary tube) when they do not wet and the cohesion of theliquid is greater than the adhesion of the liquid to the walls.6. What is the difference between perfect and real fluids ?Ans: Perfect fluids are treated as if all tangential forces created by friction can be ignored.Real fluids refer to the cases in which friction must properly be taken into account.7. Which factors affect tool size ?Ans: Following factors influence tool size :

1. Process variable (speed, feed and depth of cut)2. Tool material3. Tool geometry4. Work piece material, its hardness, microstructure and surface condition5. Cutting conditions.8. When the motion of fluid is fully known ?Ans: The motion of a f luid is fully known when the velocity of each of its particles can bespecified.9. Define fluid.Ans: A fluid is a substance that can't remain at rest under the action of any shear force.10. How is the size of a vertical boring machine designated ?Ans: The specifications of vertical boring machine are :(i) Column height(ii) Table size(iii) Floor area(iv) Weight of the job

(v) Spindle of the motor.11. What do you mean by drill sleeve and a drill socket ?Ans: The drill sleeve is suitable for holding only one size of shank. If the taper shank of thetool is smaller than the taper in the spindle hole, a taper sleeve is used.When the tapered tool shank is larger than the spindle taper, drill sockets are used to holdthe tools. Drill sockets are much longer in size than the drill sleeves.12. What is nonbarotropic fluid ?Ans: Fluid such as air for which the density is not a single-valued function of the pressure(aerostatics).13. On account of which property, the falling drops of rain acquire superical shape.Ans: Surface tension.14. How you can definte standard atmospheric pressure ?Ans: By international agreement, the standard atmospheric pressure is defined as 101.325kN/m2.15. What do you understand by acoustic velocity ?Ans: Accoustic velocity is the speed of a small pressure (sound) wave in a f luid.16. Explain the difference between centipoise and centistoke ?

Ans: Centipoise is the unit of dynamic viscosity. It is equal to 1/100 of poise, and poise = 0.1Pa . s. Value of dynamic viscosity of water at 20C is approximately equal to 1 Centipoise.Centistoke is the unit of kinematic viscosity and is equal to 1/100 x stoke. Stoke is defined as1 square centimeter per second.17. What is saybolt seconds universal ?Ans: Saybolt Seconds Universal (SSU) is the unit of viscosity and is equal to the timerequired for a gravity flow of 60 cc through saybolt universal viscometer.18. Explain difference between cohesion, adhesion and capillarity ?Ans: Cohesion is the attraction of like molecules.Adhesion is the attraction of unlike molecules for each other.Capillarity is the elevation or depression of a liquid surface in contact with a solid.19. Differentiate between gear hobbing and gear shaping with reference to various relative


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motions and applications.Ans: Gear hobbing is a continuous indexing process in which both cutting tool (a hob) andwork piece rotate in a constant relationship while the hob is being fed into work. Hob is alsoimparted a radial feed.Gear shaping uses a pinion type of cutter which is reciprocated with required cutting speedalong the face of workpiece and is gradually fed radially to plunge. Continuous generationmotion is obtained by feeding cutter to full depth and rotating the cutter and workpiece slowly.20. What is bulk modulus of elasticity ?

Ans: It represents the compressibility of a fluid. It is the ratio of the change in unit pressure tothe corresponding volume change per unit of volume.21. What is is entropic exponent ?Ans: It is the ratio of the specific heat of a gas at constant pressure to the specific heat atconstant volume.22. The best shape of a runner in sand casting is an inverted frustum of a cone why ?Ans: Tapered shape with bigger diameter at top and smaller at bottom ensures avoidance ofentrainment or absorption of air/gases into the metal while passing through the runner.23. Explain difference between ideal fluid and non-newtonian fluid.Ans: Ideal fluid is one for which resistance to shearing deformation is zero.Non-netwtonian fluids deform in such a way that shear stress is not proportional to the rate ofshearing deformation.24. Explain the difference between poise and stoke.Ans: Poise is the unit of viscosity in CGS unit and is measured in dyne sec/cm2.1 poise =10_1 Pa s.Stoke is the unit of kinematic viscosity in CGS units and is measured in cm2/s.25. How does the pressure in an isothermal atmosphere behave ?

Ans: It increases exponentially with elevation.26. The centre of pressure for a plane surface immersed vertically in a static liquid comparedto centroid of area is always ... ?Ans: Below.27. What is buoyant force equal to ? Define centroid of the area.Ans: Volume of liquid displaced.Centroid of the area : The point at which the area might be concentrated and still leaveunchanged the first moment of the area around any axis. It is also the centre of gravity.28. Define vapour pressure and on what parameters it depends ?Ans: The pressure exerted when a solid or liquid is in equilibrium with its own vapour is calledvapour pressure. It is a function of the substance and its temperature.29. Explain the difference between steady flow, one dimensional flow, two dimensional flowand three dimensional flow ?Ans: If at every point in the continuum, the local velocity and other fluid property, remainsunchanged with time, it is referred to as steady flow.One dimensional flow is one in which a line is necessary to describe the velocity profile.

Two dimensional flow is one in which an area is necessary to describe the velocity profile.Three dimensional flow is one in which a volume is necessary to describe the velocity profile.30. What is aquifer and explain difference between confined and unconfined aquifers.Ans: Groundwater occurs in permeable, water-bearing geologic formations known asaquifers.Confined aquifer : It is a relatively high-permeable, water-bearing formation.Unconfined aquifer : It is a water-bearing formation with a free water table, below which thesoil is saturated.31. What do you understand by flurial hydraulics ?Ans: The channels may be classified as rigid boundary or mobile boundary channels. Mobileboundary channels include rivers and unlined alluvial canals, the boundaries of which aremade of loose soil which can be easily eroded and transported by flowing water. The study offlow of water in mobile boundary channels is dealt in flurial hydraulics.32. By which instruments the shear stress in fluids can be measured directly ?Ans: By Stanton tube or Preston tube.33. On what factors does the pressure at a point as a static mass of liquid depends upon?Ans: Specific weight of liquid and the depth below the free liquid surface.

34. What is the difference between hoop or longitudinal tension and circum-ferencial tension?I Ans: Hoop tension is created in the walls of a cylinder subjected to internal pressure. Forthin walled cylinder (t < 0.1 d), hoop stress = pressure x radius/thickness.Longitudinal tension in thin-walled cylinders closed at the ends is equal to half the hooptension.35. How much force is exterted by liquid ?Ans: Force exerted by a liquid on a plane area A is equal to the product of the unit weight pgof the liquid, the depth hcg of the centre of gravity of the area, and the area.36. State standard point angle and helix angle of a twist drill.Ans: Standard point angle of twist drill is 118and helix angle varies from 16to 30depending as diameter of hole.


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37. Explain the difference between horizontal and vertical components of hydrostatic force ?Ans: The horizontal component of the hydrostatic force on any surface is equal to the normalforce on the vertical projection of the surface and acts through the center of pressure for thevertical projection.Vertical component of the hydrostatic force on any surface is equal to the weight of thevolume of liquid abaove the area and passes through the e.g. of the volume.38. What should be diameter of capillary tube to avoid correction for effect of capillarity inmanometer ?

Ans: Greater than 6 mm.39. How much hydrostatic pressure acts on a curved surface ?Ans: The horizontal component of the total hydrostatic pressure force on any surface isalways equal to the total pressure on the vertical projection of the surface, and can belocated through the center of pressure of this projection.The vertical components of the total hydrostatic pressure force on any surface is alwaysequal to the weight of the entire water column above the surface extending vertically to thefree surface, and cvan be located through the cemntroid of this column.40. How much is the horizontal component of force on a curved surface ?Ans: Force on a vertical projection of the curved surface.41. State Archimedes principle.Ans: Any weight, floating or immersed in a liquid, is acted upon by a buoyant force equal tothe weight of the liquid displaced. This force acts through the center of buoyancy, i.e. the e.g.of the displaced liquid.42. What do you understand by center of buoyancy ?Ans: Center of buoyancy is the center of gravity of the displaced liquid and buoyant forceacts through it.

43. How one can establish stability of submerged body and floating body ?Ans: A submerged body floats in stable equilibrium when the center of gravity of the body liesdirectly below the center of buoyancy.44. What is neutral equilibrium ?Ans: A submerged body is in neutral equilibrium for all positions when the center of gravity ofbody coincides with the center of buoyancy.45. On what factors the stability of f loating objects depends ?Ans: Stability of floating objects depends upon whether righting or overturning moment isdeveloped when the center of gravity and center of buoyancy move out of vertical alignmentdue to the shifting of position of center of buoyancy.46. State two products each produced by forward extrusion and reverse impact extrusion.Ans: Two examples of products made by direct extrusion are : gear profile, solder wire.Two examples of reverse impact extrusion are : Short tubes of soft alloys, tooth pastecontainers.47. What are the best geometrical shapes suggested for sheet metal drawing and spinning?Ans: Cup shape is best suited by drawing operation. Conical shape is easiest to produce by

spinning operation.48. What are the conditions for stability of buoyant bodies ?Ans: A floating body is stable if the center of gravity is below the metacentre.A submerged body is stable if the center of gravity is below the center of buoyancy.49. Define pipe flow ?Ans: It refers to full water flow in closed conduits of circular cross section under a certainpressure gradient.50. How much is vertical component of pressure force on a submerged curved surface ?Ans: The weight of liquid vertically above the curved surface.51. Multiple coated, disposable carbide tips have more-or-less replaced brazed carbidetipped tools in CNC applications. Why ?Ans: Disposable tips are usually indexable type and have a number of cutting edges. Veryconvenient gripping devices for holding such inserts on tool holders are available. A widevariety of ready made inserts are available which require no grinding or adjustment.52. State, sequentially elements of a canned CNC drilling cycle.Ans: Canned cycles are fixed cycles for general sequences of operations. For drillingoperation, sequence of operations will be movement of drill or workpiece to position of actual

drilling, movement of drill downwards till it is in the proximity of workpiece, then movement ofdrill at desired feed rate to sufficient depth of hole, retracting the drill above the workpiece.54. Explain the difference between one and two dimensional f low ?Ans: True one-dimensional flow occurs when the direction and magnitude of the velocity at allpoints are identical. Velocities and accelerations normal to the streamline are negligible. Twodimensional flow occurs when the fluid particles, move in planes or parallel planes and thestream-line patterns are identical in each plane.55. What is the difference between irrotational and rotational flow ?Ans: Irrotational flow : An ideal fluid f low in which no shear stresses occur and hence notorques exist. Rotational motion of fluid particles about their own mass centers can not exist. Itcan be represented by a flow net.Rotational flow occurs when the velocity of each particle varies directly as the distance from


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the center of rotation.56. Explain the difference between steady and unsteady flows.Ans: In steady flow, at any point, the velocity of successive fluid particles is the same atsuccessive periods of time.Flow is unsteady when conditions at any point in a fluid change with time,57. What is the difference between uniform and non-uniform flows ?Ans: Uniform flow occurs when the magnitude and direction of the velocity do not changefrom point to point in the fluid.

Non uniform flow occurs when velocity, depth, pressure, etc. change from point to point in thefluid flow.58. Explain the difference between stream lines and stream tube.Ans: Stream lines are imaginary curves drawn through a fluid to indicate the direction ofmotion in various sections of the flow of the fluid system. There can be no f low across astreamline at any point.Stream tube represents elementary portions of a flowing fluid bounded by a group ofstreamlines which confine the flow.59. What is the advantage of independent jaw chuck ?Ans: Irregular job can be fixed.60. Define vorticity ?Ans: It equals twice the angular velocity.61. What is irrational How ?Ans: If a flow is uniform in one region (without rotation), this property is conserved as the fluidmoves into a region of space where the motion is not uniform, and the flow is termedirrotational flow.62. What is one-seventh power law ?

Ans: According to one-seventh power law of turbulent, velocity variation corresponds to amuch favoured velocity profile and the mean velocity increases as the one-seventh power ofthe distance from the boundary wall.63. Mention the major difference between drilling and boring ?Ans: Drilling Boring(a) It is the operation of initiating a hole Boring is the operation of enlarging a drilledhole(b) It can produce only standard holes We can produce non-standard hole(c) Drill is a multi point tool A single point tool is used64. What is the magnitude of buoyant force and where does the line of action of buoyantforce act ?Ans: It is equal to the volume of the liquid displaced. The line of action of buoyant force actsthrough the centroid of the displaced volume of the fluid.65. What is metacentre ?Ans: Metacentre is the point at the intersection of the buoyancy with the vertical axis of thebody.

66. Define Prandtl's pitot-static tube.Ans: It is a combination of pressure probe and pitot tube. It is widely used for pressuremeasurements in wind-tunnel installations.67. Define the term fluid friction.Ans: The deformation of real fluids is resisted by forces caused by internal friction orviscosity. Viscosity is that property of a real fluid which creates shear forces (fluid friction)between two fluid selements.68. Why are hydrodynamic bearings used for grinding machines in preference to ball or rollerbearings ?Ans: Hydrodynamic bearings are more suitable at high speed, better tolerances, quietoperation, higher capacity to withstand shock, lesser space requirement, better life underfatigue conditions etc.69. Distinguish between a jig and fixture.Ans: Jig clamps and locates parts in positive manner and guides cutting tools (drills, reamers,taps etc). Fixture is bolted or fixed securely to the machine table so that work is in correctlocation ship to the cutter. Fixtures are used for mass milling, turning and grinding, etc.70. State the similarities and differences between a fixture and a jig.

Ans: Both jig and fixture positively locate, hold and clamp the workpiece. Jigs guide the toolfor drilling etc but fixture has no facility to guide the cutting tools. Jigs are used for drilling etcand fixture for mass milling, turning, grinding, etc.71.Explain the difference between relative density, viscosity and kinematic viscosity ?Ans: Relative density is that pure number which denotes the ratio of the mass of a body tothe mass of an equal volume of a substance taken as a standard. This standard is usuallywater (at 4C) for solids and liquids, and air free or C02 or hydrogen (at 0C and 1atmosphere = 1.013 x 105 Pa pressure) for gases.Viscosity of a fluid is that property which determines the amount of its resistance to a shearingforce. It is due primarily to interaction between fluid molecules.Kinematic viscosity is the ratio of absolute viscosity and mass density. (Its unit is m2/s).72. A right hand helical gear is being cut on a milling machine. What changes in machine


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settings have to be made to cut a left hand helical gear of same pitch and number of teeth ?Ans: For cutting right hand helical gear right side of milling table is tilted up from normalposition by the helix angle. For cutting left hand helical gear, right side of table needs to betilted down at helix angle, all other settings remaining unchanged.73. Explain what you understand by the term hydrostatic paradox ?Ans: Hydrostatic paradox is the phenomenon that the floor load of water in vessels ofdifferent shapes carrying water at same level depends only on the area of the bottom surfaceand not on the shape of the vessel.

74. Define buoyancy in brief.Ans: Buoyancy is the vertical force exerted on the body by the f luid at rest. The buoyancy ofa submerged body in a fluid at rest is equal to the weight of the fluid displaced by the bodyand it acts upward through the center of gravity of the displaced volume (the center ofbuoyancy).75. What is the necessary condition for a body to f loat in stable equilibrium ?Ans: Meta center should be above the center of gravity.76. If liquid rotates at constant angular velocity about a vertical axis as a rigid body, then howits pressure varies at various radial distances ?Ans: As square of the radial distance.77. How does the velocity vary along radius in a few vortex ? .Ans: It decreases with radius.78. What type of flow will occur when liquid discharges at constant rate through a long,straight tapering pipe ?Ans: Steady non-uniform flow.79. What does continuity equation represent ?Ans: It relates mass rate of f low along a stream tube.

80. Under what condition steady flow occurs ?Ans: When conditions do not change with time at any point.81. Why a drill can not drill deeper than its flute length ?Ans: If flute submerges in a drilled hole, the chips disposal passage is blocked and the drillwill get jammed in the hole.82. When do you recommend the use of straight f luted drill ?Ans: Drills used for brass and other soft materials and thin sheets need not be provided withany helix angle, to prevent the lips digging into the workpiece.83. Explain velocity distribution for laminar and turbulent flows.Ans: In case of laminar flow, the velocity distribution follows a parabolic law of variation. Themaximum velocity at center of pipe is twice the average velocity. For turbulent flow, moreuniform velocity distribution results.84. In which type of flow the stream lines, streak lines and path lines are identical ?Ans: In steady flow.85. Under what condition a drill may not cut ?Ans: When the cutting lips are not provided with clearance angles. It will cut if 12clearance

angle is ground.86. Some drills have straight shanks and some have tapered shank. Why ?Ans: Small drills (less than 12 mm diameter) are provided with straight shanks which can beheld in Dniren chucks. Bigger drills have tapered shank using self holding Morse tapers whichprevent gravitational fall of drill.87. What are the main factors that are responsible for the formation of built up edge ?Ans: The main factors that are responsible for the formation of built up edge are :1. Extreme pressure in the cutting zone2. High friction in the tool chip interface3. High local temperature.88. In which type of flow the Navier-strokes equation is useful ?Ans: Viscous flow.89. Explain the difference between energy line and hydraulic grade line ?Ans: The energy line is a graphical representation of the energy at each section.Hydraulic grade line lies below the energy line by an amount equal to the velocity head at thesection.90. What is the characteristic of equipotential line ?

Ans: It has no velocity component tangent to it.91. How specific cutting pressure behaves with feed rate and what conclusion can be drawnfrom this ?Ans: As feed rate increases, the specific cutting pressure decreases. It leads to concludethat feed rates be maximised in metal cutting process.92. What is hydraulically rough pipe ?Ans: When Reynolds number is very small, friction factor f becomes independent of theReynolds number and depends only on the relative roughness height. Such a pipe behavesas hydraulically rough pipe.93. What are the qualities of ideal tool material ?Ans: It should be hard to resist flank wear and deformation, have high toughness to resistfracture, be chemically inert to the workpiece, be chemically stable to resist oxidation and


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dissolution, and have good resistance to thermal shocks.94. What are the factors to be considered while evaluating the machinability ?Ans: 1. Tool life2. Rate of metal removal3. Power required4. Surfac

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