Most Important basic concept of mechanical engg

8/13/2019 Most Important basic concept of mechanical engg.

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49. The maximum size of fillet weld that can be made in single pass in 6 mm50. A rolled steel flat designated as 50 ISF 8 means the flat is 50 mm wide and 8 mm thick.51. The column splice is used for increasing length of column52. The minimum thickness steel member exposed to weather and accessible for painting is 10 mm53. For determination of allowable stress in axial compression, IS: 800-1962 has adopted secant formula54. For accurately, cut gears operating at velocities upto 20 m/sec, the velocity factor v, is given by 6/6+v55. Zero axial thrust is experienced in herinnghbone gears56. In order to realize the advantage of fluid friction, it is essential to have parallel oil film in bearing57. A Shaft rotating in anti-clockwise direction at slow speed inside a bearing will be towards left side of bearing and

making metal to metal contact

58. Bearing characteristics number relating Z-absolute viscosity of lubricant, N-speed of journal and p-bearing pressure onprojected bearing area is ZN/p

Basic concepts for theory of machine/Dynamics of Machine

1. A kinematics chain needs a minimum of 4 link and 4 turning pairs.2. If the frequency of oscillation on earth is n then the frequency of oscillation on the moon will be n/6. 3. The biflar suspension method is used to find out moment of inertia.4. The total number of instantaneous centers for a mechanism of n link is equal to n(n-1)/2.5. In case of an elliptical trammel two pairs turn and two pairs slide.6. A shaft revolving in a bearing forms a lower pair.

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For kinematic chains formed by lower pair the relation between the number of link L and the number of joint J is givenby L = 2/3 (J+2).8. The mechanism used to enlarge or reduce moments for reproducing drawings to different scales is called pantograph.9. The number of links in a pantograph is to 4.10. If a practical of a link has a velocity that changes both in magnitude and direction at any instant, then it must have two

components of acceleration e.g., centripetal. And tangential.11. The Kleins method of construction for reciprocating engine mechanism utilities a quadrilateral similar to the diagram of

mechanism for reciprocating engine.12. In elliptical trammels have two pairs turning and two pairs sliding.13. When a ship travel in a sea, the effect of the pitching is more dangerous.14. If is angle of friction, the limiting value of tan will be . 15. Multiple collars are provided on a flat collar pivot bearing to distribute the axial load due to limiting bearing pressure on

a collar.16. Slip in belt drive is different between the linear speed of the rim of pulley and the belt on it.17. In case of flat belt drive the length of belt in case of gross belts depends on the sum of the diameters of pulleys.18. A pantograph is a mechanism having lower pairs.19. Kinematic pairs are those pairs that have two elements that allow relative motion.20. A cam with a roller follower would constitute higher pair.21. Peaucellier mechanism has eight links.22. Hart mechanism has six links.23. For a kinematic chain to be considered as mechanism one link should be fixed.24. The cam angle is the angle of rotation of the cam for a definite displacement of the follower.25. Kleins construction is us ed to find out acceleration of various parts.

26. For a stable governor there is one radius of the governor weight for each equilibrium speed.27. In case of a governor isochronous is only one equilibrium which is constant for all radii of rotation of the bells within theworking range.

28. Module can be expressed in mm.29. The bipolar suspension method I used to find out moment of inertia.30. Instantaneous centre of rotation of a link in a four bar mechanism lies on a point obtained by intersection of extending

adjoining links.31. A reverted gear train is one in which the first and last gear are on the same shaft.32. In case of spur gears the flank of the tooth is the part of the tooth surface lying below the pitch surface.33. In case of cross helical worm the axes of two shafts are non parallel-non-interesting.34. In case of gears the addendum is given by one module.35. Gears for watches are generally manufactured by stamping.36. A cam where in the follower reciprocates or oscillates in plane parallel to the axis of the cam is called cylindrical cam.


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37. Rope break Dynamometers uses no lubricant.38. Tesla fluid friction dynameters used for power measurement when the speed is high and the viscous force is small.39. Hydraulic Dynamometers is widely used for absorption of wide range power at wide range of speed.40. The secondary disturbing force because of inertia of reciprocating mass is given by W/g 2 r/n cos . 41. In a balancing machine the units for unbalance measurements are gm-cm.42. In a hartnell governor if the stiffness of spring is increased the governor will become less sensitive.43. The supply of working fluid to the engine to suit the load conditions can be controlled by governor.44. The governor used in gramophone is of pickening type.45. A porter governor could be classified as dead weight type governor.46. The function of a governor is to adjust variation of speed by varying the input to the engine.

47. If D and T be the pitch circle diameter and no. of teeth of a gear, then its circular pitch p = D/T. 48. If D1 and T1 be the diameter and no. of teeth of gear 1 and D2 and T2 the corresponding value of other gear in mesh,

then ratio N1/N2, will be equal to D2/D1.49. A scott-russel mechanism is made up of sliding and turning pairs.50. Ackerman steering gear is made up of turning pairs.51. A sliding crank chain is made up of three turning and one sliding pairs.52. A motor car takes a bend of certain radius in right hand direction when moving at some speed. If engine rotates in a

clockwise direct when viewed from front, then because of centrifugal force reaction on outside wheel is increased andon inside wheels decreased.

53. If be the static deflection of shaft under the gravity load, then natural frequency of the system in case of thelongitudinal and transverse vibration is equal to 1/2 g/.

54. Cold working increased the fatigue strength.55. Coaxing is the procedure of increasing fatigue limit by overstressing the metal by successively increasing loadings.56. The notch angle of the Izod impact test specimen is 450.57. In vickers hardness testing, the pyramid indentor apex is 400.

Basic Concepts in Thermodynamics

1. In the polytropic process we have pvn = constant, if the value of n is infinitely large, the process is called constantvolume process.

2. The molecular volume of any perfect gas at 600 +103 N/m2 and 270c will be 4.17 m3/kg mol.3. The thermodynamic cycle used in a thermal power plant is Rankine.4. For the same heat input and same compression ratio efficiency depend mainly on working substance.5. The change in enthalpy for small temperature change T for an ideal gas is given by the relation H = Cp T. 6. Entropy, for reversible flow, is given by the relation dS = dqh/T.7. The S.I. unit of pressure is Pascal.8. Superheated vapour behaves approximately as a gas.9. A sterling cycle has two isothermal and two constant volume processes.10. Brayton cycle has two isentropic and two constant pressure processes.11. Otto cycle consists of two isentropic and two constant volume processes.12. Diesel cycle consists of two isotropic, one constant volume one constant pressure processes.13. Ericsson cycle has two isothermals and two constants pressure processes.14. Brayton cycle cannot be used in reciprocating engines even for same adiabatic compression ratio and work output

because large volume of low pressure air cannot be efficiently handled in rotation engines.

15. Brayton cycle is generally used for gas turbine.16. Antifreeze chemicals are those that lower down the freezing points of liquids.17. Clog point of an oil refer to the temperature at which paraffin and waxes in oil start precipitating.18. If value of n is defiantly large in a polytropic pVn = C. Then the process is called constant volume process.19. A heat exchange process where the product of pressure and volume remains constant is called hyperbolic process.20. Zeroth law of thermodynamics provides the basis for measuring thermodynamic property of temperature.21. 1 watt = 1 Nm/s.22. For a six compression of air set, with the minimum work condition the temperature rise in the cylinders will be the

same.23. In case of steam engine the cut off ratio is the ratio of piston stroke which the piston has travelled when cut off occurs.24. The reason for insulating the pipe is to minimize the heat loss from the surface.25. Under ideal conditions isothermal, isobaric, isochoric and adiabatic processes are quasi-static processes.26. Isentropic flow is reversible adiabatic flow.


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27. Exhaust gases from a engine possess kinetic energy28. The extension and compression of a helical spring is an example of reversible process.29. At critical point the latent enthalpy of vaporization is zero.30. Change in temperature = zero relation is not applicable in a free expansion process.31. An ideal engine absorbs heat at a temperature of 1270c and exhausts heat at a temperature of 770c.Its efficiency will

be 13%.32. The triple point of a substance is the temperature and pressure at which the solid does not melt, the liquid does not

boil and the gas does not condense.

Basic concepts of Thermal Engg

1. The pressure of the gas in terms of its mean kinetic energy per unit volume E is equal to 2E/3 and Kinetic Energy isalways proportional to temperature.

2. The super heated vapor acts as perfect gas and obeys all gas laws3. Absolute zero pressure will occur when there is no molecular momentum4. No liquid can exists at absolute zero pressure and absolute pressure can be attained at 0 Kelvin5. Behavior of gas can be fully determined by four gas laws6. For air ratio of specific heats is 1.47. Mono-atomic gas has highest ratio of specific heat = 1.668. As per Joules law internal energy is function of temperature. 9. The same volume of all gases would represents their molecular weights

10. Gases have two value of specific heat. One is at constant pressure and one is at constant volume11. The molecular weights of all the perfect gases occupy the same volume under same conditions of pressure andtemperature.

12. Work done in free expansion process is always zero13. Work done for rigid container having gas, is zero14. Heat and work are not properties of system15. Absolute value of internal energy cannot be found but only change in internal energy can be found16. On weight basis air contains 23 parts of oxygen17. Heat and work are path functions18. N.T.P means Normal Temperature Pressure19. Change in the enthalpy is the heat supplied during constant pressure20. Change in the internal energy is the heat supplied during constant volume21. For isothermal process, process index is unity22. The basis for measuring thermodynamic property of temperature is given by zeroth law of thermodynamics23. First law of thermodynamic gives concepts of internal energy24. Second law of thermodynamic gives concepts of entropy25. Third law of thermodynamic deals with concept of zero entropy at absolute zero temperature of 0 Kelvin.26. Throttling is the process during which cooling is produced27. 1 calorie = 4.186 Joule28. Integration of pdv is non flow work29. On volume basis air contains 21 parts of oxygen30. Molecular weight of gas x characteristics gas constant = value of universal gas constant31. For a perfect gas, internal energy and enthalpy are functions of temperature only.

Basic concepts of Fluid Mechanics

1. The velocity of fluid particle is Maximum at the center of the pipe section.2. Density is defined in terms of viscosity as dynamic viscosity/kinematic viscosity.3. The Reynolds number for pipe flow is given VD/. 4. SI unit of viscosity is 10 times poise.5. Kinetic viscosity is not a dimensionless parameter.6. The upper critical importance Reynoldss number for pipe flow is of no practical importance to designers. 7. A liquid compressed in a cylinder has a volume of 1 liter at 1 MN/m2 and a volume of 995 cu cm at MN/m2. The bulk

modulus of elasticity is 200 MPa.8. The length of mercury column at a place at an altitude will change with respect to that at ground first slowly and then

steeply.


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9. Gear tooth vernier is used for measuring gear tooth profile.10. Undercutting is cutting from the base of a work-piece.11. Laser welding is widely used in electronic industry.12. Un- like materials or materials of different thickness can be butt welded by control of pressure and current.13. In are welding operations the current value is decided by the size of the electrode.14. The phenomenon of weld decay takes place in stainless steel.15. Arc below takes place in welding stainless steel.16. Swab is used in foundry for repairing the mould.17. Gagger is used in foundry for cleaning of castings.18. Bellows are used in foundry for smoothening and cleaning out depression in the mould.

19. Permeability of a foundry sand is capacity to hold moisture.20. What for are metal pattern used in large scale production of castings.21. An important factor to be considered while designing a core print is moulding sand characteristics.

22. Weld spatter refers to welding defect.23. If t is the thickness of sheet to be spot welded, then electrode tip diameter is equal to t. 24. A sprue is a tool used in mould repairing.25. Gate is a vent hole to allow for the hot gases to escape.26. Core prints provided to from seat to support and hold the core.27. The equipment that is used in pit for supply of air is known as centrifugal blower.28. Draft allowance on castings is generally 1-2 mm/M.29. Tumbling is done so as to clean the surface of small parts.30. The purpose of inoculation is to modify the structure and properties of a cast metal.31. The draft allowance on metallic pattern as compared to wooden ones is less.32. Angle iron is not a angle measuring device.33. The mould for casting ferrous materials in continuous casting process is made of copper.34. If V is the volume of metal in a casting and A its surface areas, then time of solidification will be proportional to V 2

1/A 2. The purpose of riser is to help feed the casting until all solidification takes place.35. A silver refers to the temperature of equilibrium between solid silver and liquid silver at normal atmospheric pressure.36. The gold point refers to 1063 0C.37. The silver point refers to 960.50 0C.38. Rotameter is used for flow of liquids and gases.39. The impedance of piezo-electric crystal is high.

40. Hot wire anemometers are generally used for measuring velocity of air steam.41. Scale sensitivity is defined as ratio of a change in scale reading to the corresponding change in pointer deflection.42. In carthias process cavity is filled with a pre-calculated quantity of metal and a core or plunger is inserted to force the

metal in to cavity.43. In slush casting process metal is poured in to die cavity, and after a predetermined time the mould is inverted to permit

a part of metal still in molten to flow out of cavity.44. Ornaments are cast by gravity casting.45. During MIG welding the metal is transferred in the from of fine spray of metal.46. A collimated light beam is used for producing heat in laser welding.47. Wipping is the process of connecting loss pipes by soldering alloy.48. In water jet machining process hydraulic fluid acts as transfer media.

49. The power consumption in ultrasonic machining in kW/cm

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/min is of the order of 10 kW/m3

/min.50. Sweep pattern is used for moulding parts having uniform symmetrical shape.51. The helix angle on a HSS (High Speed Steel) twist drill for drilling cast iron is of the order of 24-32 0.52. The usual value of helix angle of a drill is 30 0.53. A twist drill is specified by shank, material and diameter.54. Broaching operation is generally used in automobile industry as semi-skilled operators can be employed.55. For proper broaching operation at least three number of teeth should be in the work at a time.


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Basic concepts in Engineering metallurgy

1. Delta iron occurs at temperature between 1400 oC and 1539 oC .2. Gamma iron exists at temperature between 910 oC and 1400 C .3. Ferromagnetic alpha iron exists in temperature range below 723 C .4. Para-magnetic alpha iron changes to gamma iron at 910 C.5. Fatigue failure : Fatigue failure occurs when a part is subjected to compressive stress.6. Homogeneous : A body having identical properties all over7. Elastic behavior : If a material recovers its original dimensions, when load is removed.8. A ductile fracture is characterized by appreciable plastic deformation prior to propagation of crack.

9. Resilience: The ability of a material to absorb energy when deformed elastically10. Machining properties of steel can be improved by adding sulphur, lead, phosphorus.11. Eutectoid steel the percentage of carbon is 0.8%.12. A cold chisel is made of high carbon steel.13. An engineers hammer is made of forged steel.14. Cyaniding: The process of adding carbon and nitrogen by heat treatment of steel to increase its surface hardness.15. Tensile strength of common varieties of cast iron is in the range 840-500 Mpa.16. In carbon steel casting the percentage of carbon is less than 1.7%.17. Aluminium alloys for pressure die casting must posses considerable fluidity.18. Electro forming is Specially valuable for thin walled parts requiring a high order of accuracy and internal surface finish.19. In power metallurgy the process of heating the cold pressed metal power is called sintering.

20. The hardness of steel increases if it contains martensite .21. The presence of sulphur in pig iron makes the casting unsound.

22. Compressive strength of grey cast iron in tones per square cm is of the order of 5-7.23. The machinability of steel can be increased by phosphorous, lead and sulphur.24. Steel with 0.8% carbon and 100% pearlite is known as eutectoid steel 25. The maximum hardenability of any steel depends on the carbon content.26. In 18-4-1 high speed steel the maximum percentage is of iron.27. In compression, a prism of brittle material will break by shearing along oblique plan.28. Cast-alloy contains nickel and molybdenum.29. Trimming is a process associated with forging.30. Addition of lead and bishmuth to aluminium results in improving machinability 31. Foundry crucible is made of graphite.32. Age-hardening is related with duralumin .33. For heavy loads in aircraft bearings the malarial used with lead to reduce the risk of seizure, is silver.34. As compared to steel the tensile strength of wood is generally 1/5.35. Compressive strength of wood is generally more along the grains.36. Superconducting property exist at temperatures below 10 K.37. Weld Decay: The phenomenon of weld decay is associated with stainless steels.38. Bloom: Bloom are obtained by passing hot ingots through the rolling mills and are of size 150 mm x 150mm to 350mm x

350mm.39. A knoop indenter is a diamond group to a pyramdidal from.40. A unit cell that contains nine atoms is known as body centered cubic space lattice.41. The process commonly used for thermo-plastic material is injection moulding.

42. The most important element that controls the physical properties of steel is carbon.43. In process annealing process, the hypoeutectoid steel is heated below A 1 line with a view to make steel ductile for coldworking.

44. The imperfection in the crystal structure of metal is known as dislocation. 45. Polyesters belong to the group of thermosetting plastics .46. The effect of alloying zinc to copper is to increase strength and ductility (if added up to 10-30 %.)


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The following topics are important from the exam point of view

1. Carburization (Metallurgy)2. Shear force in riveted joint (Machine Design)3. Current requirement in spot welding (Joining method)4. Sheet metal working (Joining method)5. Low carbon steel (Metallurgy)6. Rake angles effect (Theory of metal cutting) 7. Mean friction angle (Theory of metal cutting)8. Tool geometry, Tool signature (Theory of metal cutting)9. Single cutting point tool (Theory of metal cutting)10. ECM electrodes (Modern machining methods)11. Point to point cutting NC system (CAD/CAM)12. Boiler rating (Power plant application)13. Steam and vapor cycle, Rankine cycle (Power plant application)14. Brake thermal efficiency (Thermodynamics)15. Diffuser, super and subsonic diffuser geometry (Turbo machinery)16. Specific speeds of pumps and turbines (Fluid machines)17. Unit speeds of pumps and turbines (Fluid machines)18. Thermal efficiency (Thermodynamics, Power plant)19. Heat transfer from fin, insulated tips (Heat transfer)

20. COP of refrigeration and heat pump (Refrigeration)21. Deformation (Strength of Materials)22. Instantaneous centre (Theory of machines)23. Spherical roller bearing ( Machine Design)24. Fatigue strength ( Machine Design)25. Iron carbon diagram (Metallurgy)26. Casting types and design of castings (Manufacturing)27. Type of non-conventional processes (Manufacturing)28. Pitot tubes, Mcloyed gauge, planimeter, LVDT (Measurement systems)29. Unit speed of turbines(Fluid machines)30. Bernoulli's equation (Fluid mechanics)31. DC/AC welding, straight and reverse polarity (Welding Technology - manufacturing)32. Shaft and hole, tolerance and interference (Machine Design)33. Milling table speed, turning and drilling speed, feed rate ( manufacturing)34. Centrifugal casting ( manufacturing)35. NC machines ( manufacturing)36. Gas turbine cycles, reheating processes (Power plant engineering)37. Regeneration and co-generation (Power plant engineering)38. Properties of Refrigerant (Refrigeration)39. Radiative heat transfer, Stefan Boltzmann constant. (Heat and mass transfer)40. Equivalent evaporation of boiler and enthalpy of evaporation (Power plant engineering)41. Cavitation and vapor pressure (Thermodynamics-Fluid mechanics)42. Mohrs circle radius (Strength of Materials)

43. Strain energy due to bending (Strength of Materials)44. No of degree of freedom (Theory of Machines)45. Soderberg equation (Machine Design)

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Most Important basic concept of mechanical engg