ME2304 Engineering Metrology & Measurements Questions Bank 2014

Anna University, Chennai

ME2304 Engineering Metrology & Measurements

PART – B QUESTIONS (16 marks QUESTIONS)

UNIT -1

1.Write down the differences between Precision & Accuracy

2.Differentiate random errors from systematic errors

3.Explain the types of errors with examples

4.Explain the causes of errors with suitable examples

5.Explain the classification of measuring methods

6.Draw the block diagram of generalized measurement system and explain different stageswith examples.

7.Distinguish between Repeatability and reproducibility

8.Distinguish between Systematic and random errors

9.List various types of measuring instruments and explain each one of them

10.List the various measurement methods and explain

11.Briefly discuss on the applications of measuring instruments

12. Briefly discuss on calibration of temperature measuring devices with suitable examples

---

UNIT – 2

1 What is the constructional difference between an autocollimator and an angle dekkor. (16)

2. How the displacements are measurement using laser interferometer. (16)

3. Explain with the help of neat sketches, the principle and construction of an auto-collimator

.(16)

4 Explain the working principle of mechanical comparator with a neat sketch. (16)

5. Explain the working principle of Electrical comparator with a neat sketch (16)

6. Explain the working principle of pneumatic comparator with a neat sketch. (16)

7. Explain with the help of neat sketches, the principle and construction of an

Angle dekkor.

---

UNIT-3

1. Explain the construction and working of floating carriage micrometer (16)

2. How are the major and minor diameters of thread measured. (16)

3. Define various terminologies related with screw thread (16)

4. Define various terminologies related with screw gears (16)

5. Explain any two taper measurements method. (16)

6. Explain the construction and working of Gear tooth vernier (16)

7. Explain a method used in the measurement of surface finish and flatness

---

UNIT-4

1. Explain the interferometric measurement of angle (16)

2. Briefly explain Computer Aided inspection and Digital devices (16)

3. Explain the working of Laser Interferometer (16)

4. Explain Different types of CMM (16)

5. Explain the constructional features and application of CMM. (16)

6. Explain how profiles are checked using laser viewers (16)

7. Explain the laser telemetric system with a suitable diagram (16)

8. Elaborate on the topic of geometrical tolerance

---

UNIT-5

1. Briefly explain various methods of measuring torque (16)

2. Briefly explain various methods of measuring temperature (16)

3. Briefly explain various methods of measuring flow (16)

4. Briefly explain various methods of measuring power (16)

5. Briefly explain various methods of measuring force (16)

6. Explain working of Pressure thermometer and resistance thermometer. (16)

7. Explain the construction and working of Venturimeter and Rotameter (16)

8. Explain the construction and working of Bimetallic strip and Thermocouple

ME1304 – ENGINEERING METROLOGY and MEASUREMENTS Two Marks Questions With Answers 2014

Anna University, Chennai

 

 

DEPARTMENT OF MECHANICAL ENGINEERING FIFTH SEMESTER

ME1304 – ENGINEERING METROLOGY and MEASUREMENTS

TWO MARK QUESTIONS

UNIT I- Concept Of Measurment

1.Differentiate accuracy and Uncertainty with example.

Accuracy - Closeness to the true value.

Example: Measuring accuracy is ± 0.02mm for diameter 25mm. Here the measurement true values lie between 24.98 to25.02 mm

Uncertanity about the true value = ± 0.02mm

2. Differentiate between precision and accuracy.

Accuracy - The maximum amount by which the result differ from true value.

Precision - Degree of repetitiveness. If an instrument is not precise it will give different results for the same dimension for the repeated readings.

3. Differentiate between sensitivity and range with suitable example.

Example: A Instrument have a scale reading of 0.01mm to 100mm.

Here, the sensitivity of the instrument is 0.0lmm i.e. the minimum value in the scale by which the instrument can read. The range is 0.01 to 100mm i.e. the minimum to maximum value by which the instrument can read.

4. Deflne system error and correction.,

Error: The deviation between the results of measured value to the actual value.

Correction: The numerical value which should be added to the measured value to get the correct result.

5. Define: Measurand.

Measurand is the physical quantity or property like length, diameter, and angle to be measured.

6. Define: Deterministic Metrology.

The metrology in which part measurement is replaced by process measurement. The new techniques such as

3D error

compensation by CNC systems are applied.

7.Define over damped and under damped systenL

Over damped - The final indication of measurement ii approached exponentially from one side.

Under damped - The pointer approach the position corresponding to final reading and makes a number of oscillations around it.

8.Give any four methods of measurement

1. Direct method.

2. Indirect method.

3. Comparison method.

4. Coincidence method.

9. Give classification of measuring instruments.

1. Angle measuring Instruments.

2. Length measuring Instruments.

3. Instruments for surface finish.

4. Instruments for deviations.

10 .Define True size:

True size is Theoretical size of a dimension

11. Define Actual size

Actual size = Size obtained through measurement with permissible error.

12. What is Hysteresis

All the energy put into the stressed component when loaded is not recovered upon unloading. So, the output of measurement partially depends on input called hoteresis.

13.What is Range of measurement?:

The physical variables that are measured between two values. One is the higher calibration value H , and the other is Lower value L,

The difference between H, and L, is called range.

14.Define Span:

The algebraic difference between higher calibration values to lower calibration value.

Example: In a measurement of temperature higher value is 200*C and lower value is 1500C means span =

200 - 150 = 50'C

15. What is Resolution:

The minimum value of the input signal is required to cause an appreciable change in the output known as resolution.

16. What is Scale interval:

It is the difference between two successive scale marks in units.

17.What is Response time:

The time at which the instrument begins its response for a change measured quantity.

18. Define Repeatability:

The ability of the measuring instrument to repeat the same results g the act measurements for the same quantity is known as

atability.

19. Explain the term magniftication:

It means the magnitude of output signal of measuring instrument times increases to make it more readable.

20. Classify the Absolute error.

The absolute error is classified into

1. True absolute error

2. Apparent absolute error

21. What is Relative error.

Relative error is defined as the results of the absolute error and the, value of comparison used for calculation of that absolute error. The comparison may be true value or conventional true value or arithmetic rnean for series of measurement.

22. Classify the errors

The errors can be classified into

1. Static errors - Reading errors

- Characteristic errors,

- Environmental errors

2. Loading errors

3. Dynamic error

23. What is LEGAL METROLOGY

Legal metrology is part of Metrology and it is directed by a National Organisation which is called "Notional service of Legal Metrology". The main objective is to, maintain uniformity of measurement in a particular country.

24. What are the applications of Legal metrology ?

1. industrial MeasufWen~

2. Commercial transactions

3. Public health and human safety ensuring.

24. What is the need of inspection

To determine the fitness of new made materials, products or component part and to compare the materials, products to the established standard.

25. What are the important elements of measurments?

The important elements of a measurement is

I . Measurand

2. Reference

3. Comparator

26. What is the basic Principle of measurement:

It is the physical phenomenon utilized in the measurement. If energy kind of quantity measured, there must be a unit to measure it. So this will give the quantity to be measured in number of that unit.

---

UNIT II – Linear and Angular Measurments

27.What are the considerations while manufactureing the slip gauges?

The following additional operations are carried out to obtain the necessary qualities in slip gauges during manufacture.

1. First the approximate size of slip gauges is done by preliminary operations.

2. The blocks are hardened and wear resistant by a special heat treatment process.

3. To stabilize the whole life of blocks, seasoning process is done.

4. The approximate required dimension is done by a final grinding process.

28. How do you calibrate the slip gauges?

Comparators are used to calibrate the slip gauges.

29. List the various linear measurements?

(i) Length (ii) Heights and (iii) Thick fiess

30.What are the various types of linear measuring instruments?

The various devices used for measuring the linear measurements are i.Vernier calipers

ii. Micrometers

iii. Slip gauge or gauge blocks iv. Comparator

31.List out any four angular measuring instrument used in metrology

(i) Angle gauges (ii) Divided scales (iii) Sine bar with slip gauges (iv) Autocollimator (v) Angle dekkor

32.What is comparators?

Comparators are one form of linear measurement device which is quick and more convenient for checking large number of identical dimensions.

33.Classify the comparator according to the principles usedfor obtaining magnification.

The common types are: (i) Mechanical comparators. (ii) Electrical comparators. (iii) Optical comparators. (iv) Pneumatic comparators.

34. How are all mechanical comparator effected?

The method of magnifying small movement of the indicator in all mechanical comparators are effected by means of levers, gear trains or a combination of these elements.

35. State the best example of a mechanical comparator.

A dial indicator or dial gauge is used as a mechanical comparator.

36. Define least count and mention the least count of a mechanical comparator.

Least count. - The least value that can be measured by using any measuring instrument known as least count. Least count of a mechanical comparator is 0.0 1 mm

37. How the mechanical comparator is used? State with any one example.

Let us assume that the required height of the component I s 32.5mm. Initially, this height is built up with slip gauges. The slip gauge blocks are placed under the stem of the dial gauge. The pointer in the dial gauge is adjusted to zero. The slip gauges are removed- Now, the component to be checked is introduced under the stem of the dial gauge. If there is any deviation in the height of the component, it will be indicated by the pointer.

38. State any four advantages of reed type mechanical comparator. (i) It is usually robust, compact and easy to handle.

(ii) There is no external supply such as electricity, airrequired.

(iii) It has very simple mechanism and is cheaper when compared to other types. (iv) It is suitable for ordinary workshop and also easily portable.

39. Mention any two disadvantages of reed type mechanical comparator.

(i) Accuracv of the comparator mainly depends on the accuracy of the rack and pinion arrangement. Any slackness will reduce accuracy.

(ii) It has more moving parts and hence friction is more and accuracy is less.

40. What are the major types of on electrical comparator?

An electrical comparator consists of the following three major parts such as

(i) Transducer

(ii) Display device as meter

(iii) Amplifier

41. On what basis the transducer works?

An iron armature is provided in between two coils held by a leaf spring at one end. The other end is supported against a plunger. The two coils act as two arms of an A.C. wheat stone bridge circuit.

42. How is the accuracy of an electrical comparator checked?

To check the accuracy of a given specimen or work, first a standard specimen is placed under the plunger. After this, the resistance of wheat stone bridge is adjusted that the scale reading shows zero. Then the specimen is removed. Now, the work is introduced under the plunger.

43. State the working principle of an electronic comparator.

In electronic comparator, transducer induction or the principle of application of frequency modulation or radio oscillation is followed.

44. Mention the importantparts of an electronic comparator.

(i) Transducer (ii) Oscillator (iii) Amplifier(iv) Demodulator (v) Meter

45. Classify pneumatic comparators.

(i) Flow or Velocity type. (ii) Back pressure type

46. What are the advantages of electrical and electronic comparator? (i) It has less number of moving parts.

(ii) Magnification obtained is very high.

(iii) Two or more magnifications are provided in the same instrument to use various ranges. (iv) The pointer is made very light so that it 'IS more sensitive to vibration.

47. What are the disadvantages of electrical and electronic comparator? (i) External agency is required to metre for actuation.

(ii) Variation of voltage or frequency may affect the accuracy of output. (iii) Due to heating coils, the accuracy decreases.

(iv) It is more expensive than mechanical comparator.

48. List the various parts of an optical comparator

The optical comparator consists of the following parts such as

(i) Pivoted lever. (ii) Objective lens (iii) Scale

(iv) Plunger (v) Table and (vi) Base.

48. What are the advantages ofpneumatic comparator?

(i) The wear of measuring heads is avoided due to absence of direct contact. (ii) Friction is less due to less number of moving parts.

(iii)Work piece is cleaned by supplying of all during the measurement. (iv)High magnification is possible.

(v) There is no interference of measuring head and indicating device because the measuring head is kept away from the indicating device.

(vi)lt is a suitable method to check ovalty and taperness of circular bore.

Unit 3 Form Measurement

49. Name the various types of pitch errors found in screw? (i) Progressive error (ii) Drunken error

(iii) Periodic error (iv) Irregular errors.

50. Name the various methods of measuring the minor diameter of the thread. (i) Using taper parallels. (ii) Using rollers and slip gauges.

51.Name the various methods used for measuring the major diameter

(i) Ordinary micrometer (ii) Bench micro meter

52. Name the various methods for measuring effective diameter. (i) One wire method (ii) Two wire method

(iii) Three wire method. I

53. Name the various methods for measuring pitch diameter.

(i) Pitch measuring machine (ii) Tool maker ic (iii) Screw pitch gauge.

54. Name the two corrections are to be applied in the measurement of effective diameter. (i)rake corrections (ii) Compression correction,

55. What is best size of wire?

Best size of wire is a wire of such diameter that it makes contact with the flanks of the thread on the pitch line.

56. Define. Drunken thread

This is one, having erratic pitch, in which the advance Of the helix is irregular in one complete revolution of thread.

57. What is the effect of flank angle error?

Errors in the flank cause a virtual increase in the effective diameter of a bolt and decrease in that, of nut.

58. What are the applications of toolmaker's microscope?

(i) Linear measurement (ii) Measurement of pitch of the screw (iii) Measurement'of thread angle.

59. Define: Periodic error.

The periodic error repeats itself at equal intervals along the thread.

60. What are the commonly usedforms of gear teeth? (1) Involute (ii) Cycloidal

61. what are the types of gears?

(i) Spur (ii) Helical (iii) Bevel (iv) Worth and Worm wheel (v) Rack and pinion.

62. Define: Module

Module= pitch circle diameter/ number of teeth

63. Define: Lead angle

It is the angle between the tangent to the helix and plane perpendicular to the axis of cylinder.

64. What are the various methods used for measuring the gear tooth thickness?

(i) Gear tooth vernier (ii) Constant chord method (iii) Base tangent method (iv) Measurement over pins.

65. Name four gear errors.

(i) Pitch error (iii) Alignment error (ii) Composite error (iv) Thickness error

66. Name the method used for checking the pitch of the gear. (i) Step by step method. (ii) Direct angular measurement.

67. What are the direct angular measurements methods?

1. Profile checking: a) Optical projection method b) Involute measuring method.

2. Thickness measurement: a) Chordarl thickness method b) Constance chord method.

68. Define : constant chord

Constant chord is the chord joining those points, or opposite Aaces of the tooth.

69. Give the formula for measuring radius of circle.

R = (I - d)2

8d

Where, R=Radius of the job

1 = Distance between the balls d = Diameter of pins.

70. What are the two methods used in measuring radius of concave surface. a) Edges are well defined. b) Edges are rounded up.

71. What are the factors affecting surface roughness?

a) Vibrations b) Material of the work piece c) Tool d) Machining type

72. What are the methods used for evaluating the surface finish?

a) Peak to valley height method.

b) The average roughness method. c) Form factor method.

73. Define fullness and emptiness in form factor.

Degree of fullness (K)= area of metal /Area of enveloping rectangle

Degree of emptiness = 1 - K

74 What are the methods used for measuring surface roughness?

a) Inspection by comparison b) Direct instrument measurements.

75. What are the stylus probe instruments?

a) Profilo meter b) Taylor Hobson Talysurf c) Tomlinson surface meter

76. Define: Straightness of a line in two planes.

A line is said to be straight over a given length, of the variation of the distance of its points from two planes perpendicular to each other and parallel to the direction of a line remaining within the specified tolerance limits.

77. Define: Roundness. Name the four measurement of roundness.

It is a surface of revolution where all the surfaces intersected 'by any plane perpendicular to a common axis in case of ,cylinder and cone. a. Heart square circle. b. Minimum radial separation circle. c. Maximum inscribed circle. d. Minimum circumscribed circle.

78. Name the devices used for measurement of roundness.

1. Diametral

2. Circumferential confining gauge.

3. Rotating on center.

4. V-Block

5. Three point probe

6. Accurate spindle.

79. Define : lay

Lay: -Direction of the 'predominate surface pattern'

80. What is runout?

Run out. -Total range of reading of a fixed indicate Or with the contact points applied to a Surface rotated, without axial movement, about 3 fixed axis.

UNIT 4- Laser and advances in Metrology

81 What is interferometer?

Interferometer is optical instruments used for measuring flatness and determining the lengths of slip gauges by direct reference to the wavelength of light.

82 Name the different types of interferometer?

1) NPL flatness interferometer

2) Michelson interferometer

3) Laser interferometer

4) Zesis gauge block interferometer.

83 Name the common source of light used for interferometer

5) Mercury 198

6) Cad minus

7) Krypton 86

8) Helium

9) Hydrogen

84 What is crest and trough?

The light is a form of energy being propagated by electromagnetic waves, which is a sine curve. The high point of the wave is called crust and the low Point is called is trough.

85. What is wavelength?

The distance between two crust or two rough is called the wavelength

86.What is meant by alignment test on machine tools?

The alignment test is carried out to check the grade of manufacturing accuracy of the machine tool.

87.List the various geometrical checks made on machine tools.

a. Straightness of guide ways and slide ways of machine tool. b. Flatness of machine tables and slide ways.

c. Parallelism, equidistance and alignment of the slide ways. d. True running and alignment of shaft and spindle.

e. The pitch error or lead of lead screw. f. Pitch errors of gears.

88. Distinguish between geometrical test and practical test on a machine tool

The alignment test is carried out to check the grade of manufacturing accuracy of the machine tool. Performance test consist of checking the accuracy of the finished component. Alignment test consist of checking the relationship between various machine elements when the machine tool is idle. Performance test consists of preparing the actual test jobs on the machine and checking the accuracy of the jobs produced.

89. What are the main spindle errors?

a) Out of round. b) Eccentricity

c) Radial throw of an axis. d) Run out

e) Periodical axial slip f) Camming

90. Write the various tests conducted on any machine tools

1.Test for level of installation of machine tool in horizontal and vertical planes.

2.Test for flatness of machine bed and for straightness and parallelism of bed ways on bearing surface.

3.Test for perpendicularity of guide ways to other guide ways.

4.Test for true running of the main spindle and its axial movements.

91. Why the laser is used in alignment testing?

The alignment tests can be carried out over greater distances and to a greater degree of accuracy using laser equipment. Laser equipment produces real straight line, whereas an alignment telescope provides a, imaginary line that cannot be seen in space.

92. Classify the machine tool test.

It can be classified into

L Static tests

2. Dynamic tests.

93. What are the different types of geometrical tests conducted on machine tools?

1. Straightness. , 2. Flatness. ,3. Parallelism, equi-distance and coincidence.

94. What is the principle of laser.

The photon emitted during stimulated emission has the same energy, phase and frequency as the incident photon.

This principle states that the photon comes in contact with another atom or molecule in the higher energy level E2 then it will cause the atom to return to ground state energy level E, by releasing another photon.

The sequence of triggered identical photon from stimulated at In is known as stimulated emission. This multiplication of photon through stimulated emission' leads to coherent, powerful, monochromatic, collimated beam of light emission. This light emission is called laser.

95.What is CMM?

It is a three dimensional measurements for various components. These machines have precise movement is x,y,z coordinates which can be easily controlled and measured. Each slide in three directions is equipped with a precision linear measurment transducer which gives digital display and senses positive and negative direction.

96. Define axial length measuring accuracy

it is defined as difference between the reference length of gauges aligned with a machine axis and the corresponding measurement results from the machine.

97. Write the types of coordinate measuring machines

1. Bridge type

2. Horizontal bore mill

3. Vertical bore mill

4. Spherical coordinate measuring machine

98. Explain CNC, CMM briefly.

A computer numerical control system can be used with CN4M to do calculations while measuring complex parts. Error can be stored in memory while doing calculations. For automatic calibration of probe, determination of co-ordinate system, calculation, evaluation and recording etc., special software's are incorporated.

99.Write some features of CMM software.

Measurement of diameter, center distance can be measured as follows:

1. Measurement of plane and spatial curves

2. Minimise CNC programme.]

3. Data communications.

4. Digital input and output command

5. Interface to CAD software

100. Define machine vision.

Machine vision can be defined as a means of simulating the image recognition and analysis capabilities of the human system with electronic and electromechanical techniques.

101. What are thefour basic types of machine, vision system? (i) Image formation.

(ii) Processing of image. ( iii) Analyzing the image (iv) Interpretation of image.

102. Write the advantages of machine vision system. (i) Reduction of tooling and fixture cash.

(ii) Elimination of need for precise part location.

(iii) Integrated automation of dimensional verification

(iv) Defect detection.

103. Define grayscale analysis.

In these techniques, discrete areas or windows are formed around only the portions of the image to be inspected. For determining if brackets are present, high intensity lighting is positioned so that a bracket, when the bracket is missing no shadow will be cash. When the bracket is present, a large number of darker pixels can be observed in the window due to the cast shadow then when a bracket is missing. A contrast threshold between the dark and light pixel value area can be set. This type of discrete area analysis is a powerful too] can be used for inspection of absence, correct part assembly, orientation, part, integrity, etc.

104 Mention the advantages of CMM.

(i) The inspection rate is increased. (ii) Accuracy is reduced.

(iii) Operator's error can be minimized. Skill of the operator is reduced. (iv) Reduction in calculating, recording and set up time.

(iv) No need of GO/NOGO gauges.

(vi) Reduction of scrap and good part rejection.

105. Mention the disadvantages of CMM.

(i) The table and probe may not be in perfect alignment. (ii) The stylus may have run out.

(iii)The stylus moving in z-axis may have some perpendicularity errors. (iv)Styius while moving in x and y direction may not be square to each other. (v) There may be errors in digital system.

106. Mention the application of CMM.

(i)CMM's to find application in automobile., machine to,,electronics, space and many other large companies. (ii) These are best suited for the test and inspection Of test equipment, gauges and tools.

(iii)For aircraft and space vehicles of hundred Percent inspections is carried out by using CMM. (iv)CMM can be used for determining dimensional accuracy of the component.

(v) CMM can also be used for sorting tasks to achieve optimum pacing of components within tolerance limits.

107. Describe the features of a flexible inspection system.

(i) A powerful computer serves as a real tirne processor to handle part dimensional data and as a multi

'programming system to perform such tasks as manufacturing p I rocess control.

(ii) The terminal provides interactive communication with personnel Computer where the programmes are stored.

(iii) Input devices microprocessor based gauges and other inspection devices are used in CMM.

108. Write brief note about (i) Co-ordinate measuring machine equipped with a laser probe (ii) Virtual measuring system

(i) A CMM equipped with a laser probe can convert a part of physical model into a digitize file.

Such a file can be compared with other file and can be manipulated by designers to improve quality. Manufactures can verify that each finished part measures exactly as designed.

(ii) Virtual measuring System uses a rnicroscope system to' examine an electronic replica of the Surface texture of part. Such a system is non-contact 3-1) Surface measurement system and provide image of the surface. The images are processed on a PC using vertical scanning interferornetry and vision analysis software to produce 2D-profile, 3-D plots and counter plots.

It generates statistics for average roughness, average profile height, reduced peak height, cares roughness depth, reduced valley depth and a number of other parameters. It also determines the depth, spacing and angle of groove in a hared surface optical probe of a cylinder bore can be rotated 360 degrees and moved vertically along the cylinder wall.

109. Explain briefly the three important fields of machine vision system

Inspection: ]t is the ability of an automated vision system to recognize well-defined pattern and if these pattern match these stored in the system makes machine vision ideal for inspection of raw materials, parts, assemblies etc.

Part identification: It is the ability of part recognition provides positive identifications of an object for decision-making purposes.

Guidance and Control. Machine vision systems are used to provide sensor feedback for real time guidance.

---

UNIT 5 – Measurement of Power, Flow and Temperature related properties

110.What are load cells?

Are devices for the measurement of force through indirect methods.

111. Give the principle of hot wire anemometer

When a fluid flows over a heated surface heat is transferred from the surface and so the temperature reduces.The rate of reduction of temperature is related to flow rate.

112. State any four inferential type of flowmeters

Venturi meter, orificemeter, rotameter, pitot tube.

113. What is thermopile?

When thermocouples are connected in series it is called thermopile.

114. Mention the principle involved in bimetallic strip. Is based on change in dimension

115 What is thermocouple?

When two metals are joined together it will create an emf and it is primarily a function of the junction temperature.

116 What is a Kentometer?

It is a device for measurement of absolute pressure.

117 What is the principle involved in fluid expansion thermometer?

Change in pressure in the bulb is taken as an indication of the temperature.

DESIGN OF MACHINE ELEMENTS Questions Bank 2014

Anna University, Chennai

 16 MARKS

DESIGN OF MACHINE ELEMENTS

UNIT- I (STEADY STRESSES AND VARIABLE STRESSES IN MACHINE MEMBERS)

1. (a) A piston of a reciprocating compressor has a diameter of 60mm. The

maximum pressure on the piston fall is 1.25MN/m2.Assuming the gudgeon

pin passing through the small end of the connecting rod can be safely loaded

in shear up to 10MN/m2, Calculate the minimum diameter of the gudgeon

pin. (8)

(b) Explain with mathematical expressions. Maximum principal stress theory

and Von-Mises-Henky theory (8)

2. (a) Determine the diameter of the steel bar, which is a ductile in a nature

subjected to an axial load of 60KN and torsional moment of 1600N-m.Use

the factor of safety 2.5.E=200GPa. (8)

(b) Explain with mathematical expressions. Maximum shear theory and

Venant's theory (8)

ME2303– DESIGN OF MACHINE ELEMENTS

3. A steel member is subjected to a 3-D stress system and resulting principal

stress are 120N/mm2 tension, 80N/mm2and 40N/mm2 compression. If the

proportional limit of the material in simple tension is 280N/mm2 and its

poison's ratio is O.3.Determine the factor of safety according to (a)

Maximum principal stress theory (b) Maximum principal strain theory (c)

Maximum shear stress theory. (16)

4. A bolt is subjected to a tensile load of 25KN and a shear load of 10KN.

Determine the diameter of the bolt according to (a) Maximum principal

stress theory (b) Maximum principal strain theory (c) Maximum shear stress

theory. Assume factor of safety 2.5, Yield point stress in simple tension

300N/mm2, Poisson's ratio is 0.25. (16)

5. Taking stress concentration in to account find the maximum stress

induced when a tensile load of 20KN is applied to (i) A rectangular plate

80mm wide and 12mm thick with a transverse hole of 16mm diameter.(ii)A

stepped shaft of diameters 60mm and 30mm width a fillet radius of

6mm.(16)

6. A circular bar is simply supported with a span of 0.5mand is subjected to

a concentrated cyclic load at its midspan. The load varies from a minimum

value of20KN to maximum value of 45 KN. The load 3 direction is transverse

to the shaft axis. Decide upon the diameter of the bar taking a factor of

safety of 1.5 and factor of 0.85 and 0.89 respectively for size effect and

surface finish. Take often following values for material properties. Ultimate

strength = 650N/mm2, Yield strength = 450N/mm2

Endurance strength =350N/mm2 (16)

7. The bending stress in a machine part fluctuates between a tensile stress

of 280N/mm2 and a compressive stress of 140N/mm2. What should be the

minimum ultimate tensile strength of this part to carry this fluctuation

indefinitely according to (i) Goodman's formula (ii) Soderberg formula Factor

of safety is 1. 75. Assume that the yield point is never likely to be less than

55% of the Ultimate tensile strength or greater than 93 % of it. (16)

8. Determine the thickness of a 120mm wide uniform plate for safe

continuous operation if the plate is to be subjected to a tensile load that has

a maximum value of 1000N.The properties of the plate materials are as

follows. Endurance limit stress is 225MPa and yield point stress is

300MPa.The factor of safety based on yield point may be taken as 1.5. (16)

9. A hot rolled bar of steel is subjected to a torsional load varying from-

150N-m to 450N-m. Determine the required diameter of the bar using a

factor of safety of 1.7. Properties of the material may be assumed as follow.

Ultimate tensile stress = 450MPa Yield stress = 300MPa (16)

10.A transmission of shaft made C45 steel subjected to a fluctuating torque

varying from -100N-m to +500N-m.Also a fluctuating bending moment acts

on the shaft which varies from +500N-m to -500Nm. Let the stress

concentration factor be 2. The shaft is machined for a factor of safety

1.5.Determine the required diameter of the shaft. (16)

---

UNIT -II (DESIGN OF SHAFTS, KEYS AND COUPLINGS)

1. A line shaft rotating at 200rpm is to transmit 20KW power. the allowable

shear stress for the shaft material is 42N/mm2.If the shaft carries a central

load of 900N and is simply supported between bearing 3meters apart

determine the diameter of the shaft. The maximum tensile or compressive

stress is not to exceed 56N/mm2 (16)

2. An electric generator rotates at 200rpm and receives 300KW from the

driving engine. The armature of the generator is 60cm long and located

between bearing 120cm center to center. Owing to the combined weight of

armature and magnetic pull, the shaft is subjected to 9000kg acting at right

angles to the shaft. The ultimate stress for the shaft is 4480kg/cm2 and

shear stress is 3920kg/cm2.Find the diameter of the shaft for a factor of

safety of 6. (16)

3. A mild steel shaft transmit 23KW to 200rpm.It carries a central load of

900N and is simply supported between the bearing 2.5meters apart.

Determine the size of the shaft, if the allowable shear stress is 42MPa and

the maximum tensile or compressive stress is not exceed 56MPa. What size

of the shaft will be required, if it is subjected to gradually applied load? (16)

4. A shaft to transmit 50KW at 1200rpm.It is also subjected to a bending

moment of 275NNm.Allowable shear stress is 60N/mm2.The shaft is not to

twist more than 20 in a length of 2m.G=80XI03N/mm2.Design a shaft. (16)

. A factory line shaft is 4.5m long and is to transmit 75KW at

200rpm.The allowable stress in shear is 45MPa and maximum

allowable twist is 10 in a length of 20mm diameter. Determine the

required shaft diameter. (16)

8. Design and draw a cast iron flange coupling for a mild steel shaft

transmitting 90KW at 250rpm. The allowable shear stress in the shaft

is 40MPa and the angle of twist is not to exceed 10mm in a length of

20mm diameters. The allowable shear stress in the coupling bolt is

30MPa. (16)

9. Design a cast iron protective type flange coupling to transmit 15KW at

900rpm from an electric motor to a compressor. The service factor may

be assumed as 1.35. The following permissible stress may be used: Shear

stress for the shaft, bolt and key material=40MPa Crushing stress for bolt

and key=80Mpa Shear stress for cast iron=8Mpa (16)

10. A rigid type coupling is used to connect two shaft transmit 15KW at

200rpm.The shaft, key and bolts are made ofC45 steel and the coupling is

of C.I. Design the coupling. (16)

11. Design and sketch protective type C.I flange coupling to transmit

10KW at 250rpm. The permissible shear stress for key, shaft, and bolt as

50N/mm2.Take crushing stress of key as 90N/mm2 and shear stress for

C.I as 14N/mm2.Assume maximum torque is 30% higher than mean

torque.

(16)

12. A knuckle joint is to transmit a force of 140KN.Allowable stresses in

tension, shear and compression are 75N/mm2, 65N/mm2 and 140N/mm2

repectively.Design the joint. (16)

---

UNIT-III (DESIGN OF FASTNERS AND WELDED JOINTS)

I. The cylinder head of a steam engine with 250mm bore is fastened by

eight stud bolts made of 30C8 steel. Maximum pressure inside the cylinder is

1MPa.Determine the bolt size and approximate tightening torque. Take 20%

over load. Assume _y=300MPa. (16)

2. A steam of effective diameter 300mm is subjected to a steam pressure of

1.5N/mm2.The cylinder head is connected by 8 bolts having yield point

330MPa and endurance limit at 240MPa.The bolts are tightened with an

initial per load 1.5 times the steam load. A soft copper gasket is used to

make the joint leak proof. Assuming a factor of safety 2, find engine size of

bolt required. The stiffness factor for copper gasket may be taken as 0.5.

(16)

3. A steam engine cylinder has an effective diameter of350mm and the

maximum steam pressure acting on the cylinder cover is 5N/mm2.calculate

the number and the size of studs are required to fix the cylinder cover.

Assume the permissible stress in the stud 70N/mm2 (16)

4. A plate 100m wide and 12.5mm thick is to be welded to another plate by

means of two parallel fillet welds. The plates are subjected to a load of

50KN.Find the length of the weld so that the maximum stress does not

exceed 56N/mm2. (Do the calculations under static loading). (16)

5. A plate 75mm wide and 10mm thick is jointed with another plate by a

single transverse weld and double parallel fillet as shown in fig. The joint is

subjected to a maximum tensile force of 55KN. The permissible tensile and

shear stress are 70MPa and 50MPa respectively. Find the length of each

parallel fillet weld. (16)

6. Determine the length of the weld run for a plate of size 120mm wide and

15mm thick to be welded to another plate by means of (1) A single

transverse weld (2) Double parallel fillet welds when the joint is subjected to

variable loads. Assume (Tensile stress =70MPa, shear stress =56MPa.) (16)

---

UNIT -IV (DESIGN OF SPRINGS AND LEVERS)

1. A helical valve spring is to be designed for an operating load range of 90N

to 135N.The deflection of the spring for this load range is 7.5mm.Assuming

a spring index of 10, a permissible shear stress of 480N/mm2 and a

modulus of rigidity of 0.8Xl 05 N/mm2for the material, determine the

dimensions of the spring. (16)

2. A gas engine valve spring is to have a mean diameter 37.5mm.The

maximum load will have to sustain is 450N with a corresponding deflection

of 12.5mm.The spring is to be subjected to repeated loading and fatigue

must be considered a low working stress of 300N/mm2 will be used. Find the

sizefor the wire and number of coil used. Take rigidity of modulus as 0.8XI05

N/mm2 (16)

3. A compressive helical spring is required to exert a minimum force 250N

and maximum force of 600N and the deflection for this change in load to be

15mm. The spring must fit in a hole of 30mm diameter. The load is static.

Ultimate tensile stress is 1393N/mm2 and shear stress is 606Mpa. (16)

4. A closely coil helical spring is made of 10mm diameter steel wire, the coil

consisting of 10 complete turns with a mean diameter of 120mm.The springs

carries an axial pull of 200N.Determine also deflection in the spring, its

stiffness and strain energy stored by it if the modulus of rigidity of the

material is 80KN/mm2 (16)

5. A helical compression of spring made of oil tempered carbon steel is

subjected to a load which varies from 400N to 1000N. The spring index is 6

and the design factor of safety is 1.25.If the yield stress in shear is 770Mpa

,and endurance stress in shear is 350Mpa,find,(1) Size of the spring wire (2)

Diameter of the spring wire (3) Number of turns of the spring (4) Free

length of the spring. The compression of the spring at the maximum load is

30mm.The modulus of rigidity for the spring material may be taken as

80KN/mm2. (16)

6. A semi-elliptical leaf spring of 1m long and is required to resist a load of

50KN.The spring has 15 leaves of which three are full length leaves. The

width of central band is 100mm. All the leaves are to be stressed to

420MPa.The ratio of total depth to width is 3.Take, =2.1Xl05MPa.Determine,

(i) The thickness and width of the leaves. (ii)The initial gap that should be

provided between the full lengths and graduated leaves before assembly.

(iii)The load exerted on the band for the assembly. (16)

7. A leaf spring for a small trailer is to support a load of 8KN. The spring has

8 graduated leaves and 2 free full length leaves of spring steel of safe stress

380MPa.The over all length 1m and the central band is 80mm wide. Taking

ratio of total depth of leaves as 3.Design the spring and also determine the

deflection of the spring. Take, E=2.1XI05MPa. (16)

8. Design of leaf spring for a truck to the following specifications:

Maximum load on the spring = 140KN No of spring = 4 Material for spring

chromium vanadium steel Permissible tensile stress = 600N/mm2 Maximum

number of leaves =10 Span of spring = 1000mm Permissible deflection =

80mm Young's modulus of the spring = 200N/mm2 (16)

9. Design a cantilever leaf spring to absorb 600N-m energy without

exceeding a deflection of 150mm and a stress of 800N/mm2• The length of

the spring is 600mm. The material of the spring is

steel.Take,E=200KN/mm2 (16)

---

UNIT-V (DESIGN OF BEARING AND FLYWHEELS)

1. Design a journal bearing for a centrifugal pump with the following data:

Diameter of the journal = 150mm Load on bearing = 40KN Speed of journal

= 900rpm (16)

2. Design a journal bearing for a centrifugal pump from the following data:

Load on the journal=20000N, Speed of the journal=900rpm, Type of oil is

SAElO, for which the absolute viscosity at 55°C=0.017kg/m-s, Ambient

temperature of oil = 15.50C, Maximum bearing pressure for the

pump=1.5N/mm2.Calculate also mass of the lubricating oil required for

artificial cooling, If the rise of temperature, if the rise of temperature of oil

be limited to lOoC heat dissipation coefficient=1232W/m2/oC (16)

3. A full journal bearing of 50mm diameter and 100mm long has a bearing

pressure of l.4N/mm2• The speed of the journal is 900rpm and the ratio of

journal diameter to the diametric clearance is 1000. The bearing is

lubricated with oil, whose absolute viscosity at the operating temperature of

75°C may be taken as 0.011 kg/m-s. The room temperature is 350C.Find,

(1) The amount of artificial cooling required. (2)The mass of lubricating oil

required, if the difference between the outlet and inlet temperature of the oil

is 10°C. Take specific heat of oil as 1850J/Kg/0C. (16)

4. A 150mm diameter shaft supporting a load of 10KN has a speed of

1500rpm.The shaft run in whose bearing length is 1.5 times the shaft

diameter. If the diametric clearance of bearing is 0.15mm and the absolute

viscosity of the oil at the operating temperature is 0.011 Kg/m-s. Find the

power wasted in friction. (16)

5. The turning moment diagram of a multi-cylinder engine is drawn with a

scale of (1 mm = 1°) on the abscissa and (1 mm = 250 Nm)on the ordinate.

The intercepted between the torque developed by the engine and the mean

resisting torque of the machine, taken in order from one are -350,+800,-

600,+900, 11-550,+450,-650 mm2.The engine is running at a mean speed

fluctuations is limited to 0.02.A rimmed flywheel made of grey cast iron FG

200 (Density=7100Kg/m3) is provided. The spokes, shaft and hub are

assumed to contribute 10% of the required moment of inertia. The rim has

rectangular cross section and the ratio of width to thickness is 1.5.Determine

the dimensions of the rim. (16)

Design of Machine Elements Two Marks Questions With Answers 2014

Anna University, Chennai

SRINIVASAN ENGINEERING COLLEGE,

PERAMBALUR-621212

DEPARTMENT OF MECHANICAL ENGINEERING

Design of Machine Elements

UNIT I

1.Define: Factor of safety

The ratio between maximum stresses to working stress is known as factor of safety.

Factor of safety = Maximum stress / Working stress

2. Define endurance limit.

Endurance limit is the maximum value of completely reversed stress that the standard specimen can sustain an infinite number (106) of cycles without failure.

3. What is impact load?

If the time of load application is less than one third of the lowest natural period of vibration of the part, it is called an impact load.

4. What are the various phases of design process?

i.Recognition of need. ii.Definition of problem iii.Synthesis iv.Analysis and optimization v.Evaluation vi.Presentation

5. What are the different types of loads that can act on machine components?

a.Steady load. b.Variable load. c.Shock load d.Impact load.

6. What are the factors affecting endurance strength.

Factors affecting endurance strength are i. Load ii. Surface finish iii. Size iv. Temperature v. Impact vi. Reliability

7. What are the types of variable stresses?

a.Completely reversed or cyclic stresses b.Fluctuating stresses c.Repeated stresses

8. Differentiate between repeated stress and reversed stress.

Repeated stress refers to a stress varying from zero to a maximum value of same nature. Reversed stress of cyclic stress varies from one value of tension to the same value of compression.

9. What are the types of fracture?

a.Ductile fracture b.Brittle fracture

10. Distinguish between brittle fracture and ductile fracture.

In brittle fracture, crack growth is up to a small depth of the material. In ductile fracture large amount of plastic deformation is present to a higher depth.

11. Define stress concentration and stress concentration factor.

Stress concentration is the increase in local stresses at points of rapid change in cross section or discontinuities. Stress concentration factor is the ratio of maximum stress at critical section to the nominal stress

12. Explain size factor in endurance strength. Size factor is used to consider the effect of the size on endurance strength. A large size object will have more defects compared to a small one. So, endurance strength is reduced.

If K is the size factor,

Actual endurance strength = Theoretical endurance limit x K

13. Explain Griffith theory. (Or) State the condition for crack growth.

A crack can propagate if the energy release rate of crack is greater than crack resistance.

14. What are the modes of fracture?

a.Mode I (Opening mode) – Displacement is normal to crack surface.

b.Mode II (Sliding mode) – Displacement is in the plane of the plate.

c.Mode III (Tearing mode) – Out of plane shear.

15. What are the factors to be considered in the selection of materials for a machine element?

i.Required material properties ii.Manufacturing ease iii.Material availability iv.Cost

16. What are various theories of failure?

i.Maximum principal stress theory. ii.Maximum shear stress theory. iii.Maximum principal strain theory.

17.List out the factors involved in arriving at factor of safety

i.material properties ii.nature of loads iii.presence of localized stresses

iv.mode of failures

18. Give some methods of reducing stress concentration.

i.Avoiding sharp corners. ii.Providing fillets. iii.Use of multiple holes instead of single hole iv.Undercutting the shoulder parts.

19. Explain notch sensitivity.

State the relation between stress concentration factor, fatigue stress concentration factor and notch sensitivity.

Notch sensitivity (q) is the degree to which the theoretical effect of stress concentration is actually reached.

The relation is, Kf = 1 + q (Kt-1)

20. What are the factors that effect notch sensitivity?

i.Material ii.Notch radius iii.Size of component iv.Type of loading v.Grain Structure 21. What is the use of Goodman & Soderberg diagrams?

They are used to solve the problems of variable stresses.

22 Define machinability

It is the property of the material, which refers to a relative case with which a material can be cut. It is measured in a number of ways such as comparing the tool life for cutting different material

23. What is an S-N Curve?

An S- N curve has fatigue stress on Y axis and number of loading cycles in

X axis. It is used to find the fatigue stress value corresponding to a given number of cycles.

24. Define Ductility

It is the property of the material enabling it to be drawn into wire, with the application of tensile force. It must be both strong and plastic. It is usually measured in terms of percentage elongation and reduction in area. (eg) Ni, Al, Cu

25.Define fatigue

When a material is subjected to repeated stress, it fails at stresses below the yield point stress; such type of failure of the material is called fatigue.

26. What is curved beam?

In curved beam the neutral axis does not coincide with the centroidal axis.

27. Give some example for curved beam.

C frame, crane hook

28. What is principle stress and principle plane?

A plane which has no shear stress is called principle plane the corresponding stress is called principle stress.

29. Write the bending equation.

M/I = E/R = Fs/Y.

M – Bending moment

I - Moment of intertia

E - Youngs modulus

R - Radius of the shaft

Fs – Shear stress

Y - Distance from neutral axis

30. Write the torsion equation.

T/J = CØ/L = Fs/R

T – Torque J - Polar moment of intertia C- Rigidity modulus Ø – Angle of twist L – Length of the shaft Fs – Shear stress R - Radius of the shaft

---

UNIT II

1.Define the term critical speed.

The speed, at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite, is known as critical or whirling speed.

2. Factor is considered to design a shaft?

i.strength ii.stiffness

3.What is a shaft?

A shaft is a rotating machine element,which transmits power from one point to another point.

4.What are the types of shafts?

i.Line shaft ii.Spindle iii. Stub shaft iv. Counter shaft

5.What is key?

A key is device, which is used for connecting two machine parts for preventing relative motion of rotation with respect to each other.

6.What is key?

Key is a device which is used for connecting tow machine parts for preventing relative motion of rotation with respect to each other.

7. What are the types of keys?

i. Saddle key ii.Tangent key iii.Sunk key iv.Round key and taper pins.

8. How are sunk key designed?

Sunk keys are designed to fit in a sunk key way. Whose bed is parallel to the axis of the shaft.

9. What is the main use of woodruff keys?

A woodruff key is used to transmit small value of torque in automotive and machine tool industries. The keyway in the shaft is milled in a curved shape whereas the key way in the hub is usually straight.

10. List the various failures occurred in sunk keys.

1.Shear failure 2.Crushing failure

11. What is simple torsion?

When a shaft is subjected to pure torsional moment M, the shaft diameter can be found from torsional shear strength equation.

Shear strength = 16M/3.14d³

12.What is simple bending moment?

When a shaft is subject to a pure bending load,the principal stress induced in the shaft are tension and compression.The maximum stress induced in the shaft can be determined by the theory of simple bending moment relation .

13.What are the types of rigidity?

i.Torsional rigidity ii. Lateral rigidity.

14.What are the different measures followed to control the lateral deflection?

i. Reducing the span length ii. Increasing the number of supports iii. Selecting the cross-section in which the area moment of inertia as in case of hollow shaft.

15.Define the term critical speed?

The speed at which the shaft runs so that the additional deflection of the shaft from the axis of rotation becomes infinite, is known as critical speed.

16. What is the function of a coupling between two shafts?

Couplings are used to connect sections of long transmission shafts and to connect the shaft of a driving machine to the shaft of a driven machine.

17. Under what circumstances flexible couplings are used?

They are used to join the abutting ends of shafts when they are not in exact alignment. They are used to permit an axial misalignment of the shafts without under absorption of the power, which the shafts are transmitting.

18. What are the purposes in machinery for which couplings are used?

1.To provide the connection of shafts of units those are manufactured separately such as motor and generator and to provide for disconnection for repairs or alterations.

2.To provide misalignment of the shafts or to introduce mechanical flexibility.

3.To reduce the transmission of shock from one shaft to another.

4.To introduce protection against over load.

19.What are the types of Rigid coupling?

i.Sleeve, ii.Flange, iii.Clamp coupling.

20. What are the types of Flexible coupling?

i.Universal, ii.Oldham’s,iii.Pushed pin type coupling.

21.What are the main functions of the knuckle joints?

It is used to transmit axial load from one machine element to other.

22.What material used for flange coupling?

Cast iron

23. Define helical springs.

The helical springs are made up of a wire coiled in the form of a helix and is primarily intended for compressive or tensile load.

24. What are the different types of helical springs?

The different types of helical springs are

a.Open coil helical spring b Closed coil helical spring

25. What are the differences between helical torsion spring and tension helical springs?

Helical torsion springs are wound similar to that of tension springs but the ends are shaped to transmit torque. The primary stress in helical torsion spring is bending stress whereas in tension springs the stresses are torsional shear stresses.

---

UNIT III

1 How is a bolt designated?

A bolt is designated by a letter M followed by nominal diameter and pitch in mm.

2. What factors influence the amount of initial tension?

I.External load ii.Material used iii.Bolt diameter

3. What is bolt of uniform strength?

A bolt of uniform strength has equal strength at the thread and shank portion.

4. What are the ways to produce bolts of uniform strength?

i.Reducing shank diameter equal to root diameter. ii. Drilling axial hole

5. What stresses act on screw fastenings?

I.Initial stresses due to screwing up ii.Stresses due to external forces iii.Combined stresses.

6. What are the different applications of screwed fasteners?

The different applications of screwed fasteners are

a. For readily connecting & disconnecting machine parts with out damage

b. The parts can be rigidly connected

C.Used for transmitting power

7. What are the advantages of screwed fasteners?

The advantages of screwed fasteners are

a.They are highly reliable in operation

b.They are convenient to assemble & disassemble

c.A wide range of screws can be used for various operating conditions

d.They are relatively cheap to produce.

8.Define pitch.

Pitch is defined as the distance from appoint on one thread to the corresponding on the adjacent thread in the same axis plane.

9. Define lead.

Lead is defined as the distance, which a screw thread advances axially in one rotation of the nut.

10. What are the different types of metric thread?

1. BSW (British standard Whit worth) 2. BSE (British standard End

11. Define welding.

Welding can be defined as a process of joining two similar or dissimilar metals with or without application of pressure along with or without addition of filler material.

12. What are the types of welded joints?

i.Butt joint ii.Lap joint iii.T – joint iv.Corner joint v.Edge joint.

13. What are the two types of stresses are induced in eccentric loading of loaded joint? 1.Direct shear stress. 2.Bending or torsional shear stress.

14 Define butt and lap joint

Butt joint:

The joint is made by welding the ends or edges of two plates.

Lap joint:

The two plates are overlapping each other for a certain distance. Then welded. Such welding is called fillet weld.

15.When will the edge preparation need?

If the two plates to be welded have more than 6mm thickness, the edge preparation should be carried out.

16 What are the two types of fillet weld?

i.Longitudinal or parallel fillet weld ii.Transverse fillet weld

17 State the two types of eccentric welded connections.

i.Welded connections subjected to moment in a plane of the weld.

ii.Welded connections subjected to moment in a plane normal to the plane of the weld.

18 What are the practical applications of welded joints?

It has employed in manufacturing of machine frames, automobile bodies, aircraft, and structural works.

19.What is Tee-joint?

The two plates are arranged in T shape which means the plates are located at right angles to each other.

20.What is corner joint?

Two plates are arranged at right angles such that it forms an angle.

21.What are types of fillet weid?

i. Longitudinal or parallel fillet weld. Ii.Transverse fillet weld.

22.When will the weld deposit be weaker?

When the components are made of high carbon steel or alloy steel, the weld becomes weaker.

23.Define eccentrically loaded welded joints?

The external loaded where applied may not pass through the geometric centre in structural joints are called as eccentrically loaded joints.

24.What are the two types of stress are induced in eccentric loading of loaded joint?

i.Direct shear stress ii.Bending shear stress.

25.State the two types of eccentric welded connections.

i. Welded connections subjected to moment in a plane of the weld.

ii. Welded connections subjected to moment in a plane normal to the plane of the weld.

---

UNIT IV

1. What is a spring?

A spring is an elastic member, which deflects, or distorts under the action of load and regains its original shape after the load is removed.

2. State any two functions of springs.

i.To measure forces in spring balance, meters and engine indicators. ii.To store energy.

3. What are the various types of springs?

i.Helical springs ii.Spiral springs iii.Leaf springs iv.Disc spring or Belleville springs

4. Classify the helical springs.

a.Close – coiled or tension helical spring. b.Open –coiled or compression helical spring.

5. Define : Leaf springs

A leaf spring consists of flat bars of varying lengths clamped together and supported at both ends, thus acting as a simply supported beam.

6. Define : Belleville Springs

They are made in the form of a cone disc to carry a high compressive force. In order to improve their load carrying capacity, they may be stacked up together. The major stresses are tensile and compressive.

7. What is spring index (C)?

The ratio of mean or pitch diameter to the diameter of wire for the spring is called the spring index.

8. What is pitch?

The axial distance between adjacent coils in uncompressed state.

9. What is solid length?

The length of a spring under the maximum compression is called its solid length. It is the product of total number of coils and the diameter of wire.

Ls = nt x d Where, nt = total number of coils.

10. What are the requirements of spring while designing?

a.Spring must carry the service load without the stress exceeding the safe value.

b.The spring rate must be satisfactory for the given application.

11 What are the end conditions of spring?

a.Plain end. b.Plain and ground end c.Squared end d.Squared and ground end.

12. What is buckling of springs?

The helical compression spring behaves like a column and buckles at a comparative small load when the length of the spring is more than 4 times the mean coil diameter.

13. What is surge in springs?

The material is subjected to higher stresses, which may cause early fatigue failure. This effect is called as spring surge.

14. What is a laminated leaf spring?

In order to increase, the load carrying capacity, number of flat plates are placed and below the other.

15. What semi – elliptical leaf springs?

The spring consists of number of leaves, which are held together by U- clips. The long leaf fastened to the supported is called master leaf. Remaining leaves are called as graduated leaves.

16. What is nipping of laminated leaf spring?

Prestressing of leaf springs is obtained by a difference of radii of curvature known as nipping.

17. What are the various application of springs?

The springs are used in various applications, they are

a.Used to absorb energy or shocks (e.g. shock absorbers, buffers, e.t.c.)

b.To apply forces as in brakes clutches, spring-loaded valves, e.t.c.

c.To measure forces as in spring balances and engine indicators

d.To store energy as in watches

18. Define free length.

Free length of the spring is the length of the spring when it is free or unloaded condition. It is equal to the solid length plus the maximum deflection or compression plus clash allowance.

Lf = solid length + Ymax + 0.15 YMax

19. Define spring index.

Spring index (C) is defined as the ratio of the mean diameter of the coil to the diameter of the wire.

C =D/d

20. Define spring rate (stiffness).

The spring stiffness or spring constant is defined as the load required per unit deflection of the spring.

K= W/y Where W-load y-deflection

21. Define pitch.

Pitch of the spring is defined as the axial distance between the adjacent coils in uncompressed state.

Mathematically Pitch = free length/ n-1

22. What are the points to be taken into consideration while selecting the pitch of the spring?

The points taken into consideration of selecting the pitch of the springs are

a.The pitch of the coil should be such that if the spring is accidentally compressed the stress does not increase the yield point stress in torsion.

b.The spring should not be close up before the maximum service load is reached.

23. Define active turns.

Active turns of the spring are defined as the number of turns, which impart spring action while loaded. As load increases the no of active coils decreases.

24. Define inactive turns.

Inactive turns of the spring is defined as the number of turns which does not contribute to the spring action while loaded. As load increases number of inactive coils increases from 0.5 to 1 turn.

25. What are the different kinds of end connections for compression helical springs?

The different kinds of end connection for compression helical springs are

a.Plain ends b.Ground ends c.Squared ends d.Ground & square ends

26. Write about the eccentric loading of springs?

If the load acting on the spring does not coincide with the axis of the spring, then spring is said to be have eccentric load. In eccentric loading the safe load of the spring decreases and the stiffness of the spring is also affected.

27. Explain about surge in springs?

When one end of the spring is resting on a rigid support and the other end is loaded suddenly, all the coils of spring does not deflect equally, because some time is required for the propagation of stress along the wire. Thus a wave of compression propagates to the fixed end from where it is reflected back to the deflected end this wave passes through the spring indefinitely. If the time interval between the load application and that of the wave to propagate are equal, then resonance will occur. This will result in very high stresses and cause failure. This phenomenon is called surge.

28.What are the methods used for eliminating surge in springs?

The methods used for eliminating surge are

a.By using dampers on the center coil so that the wave propagation dies out

b.By using springs having high natural frequency.

29. What are the disadvantages of using helical spring of non-circular wires?

a.The quality of the spring is not good

b.The shape of the wire does not remain constant while forming the helix. It reduces the energy absorbing capacity of the spring.

c.The stress distribution is not favorable as in circular wires. But this effect is negligible where loading is of static nature.

30 Why concentric springs are used?

a.To get greater spring force with in a given space

b.To insure the operation of a mechanism in the event of failure of one of the spring

31.What is the advantage of leaf spring over helical spring?

The advantage of leaf spring over helical spring is that the end of the spring may be guided along a definite path as it deflects to act a structural member in addition to energy absorbing device.

32. Write notes on the master leaf & graduated leaf?

The longest leaf of the spring is known as main leaf or master leaf has its ends in the form of an eye through which bolts are passed to secure the spring. The leaf of the spring other than master leaf is called the graduated leaves.

33. What is meant by nip in leaf springs?

By giving greater radius of curvature to the full length leaves than the graduated leaves, before the leaves are assembled to form a spring thus a gap or clearance will be left between the leaves. This initial gap is called nip.

34. What is the application of leaf spring?

The leaf springs are used in automobiles as shock absorbers for giving suspension to the automobile and it gives support to the structure.

35. Define flat spiral spring.

A flat spiral spring is a long thin strip of elastic material wound like a spiral. These springs are frequently used in watch springs, gramophones, e.t.c

---

UNIT - V

1.What is bearing?

Bearing is a stationery machine element which supports a rotating shafts or axles and confines its motion.

2. Classify the types of bearings.

i. Depending upon the type of load coming upon the shaft:

a.Radial bearing b.Thrust bearings.

ii. Depending upon the nature of contact:

a.Sliding contact b.Rolling contact bearings or Antifriction bearings.

3. What are the required properties of bearing materials?

Bearing material should have the following properties.

i.High compressive strength ii.Low coefficient of friction iii.High thermal conductivity iv.High resistance to corrosion v.Sufficient fatigue strength vi.It should be soft with a low modulus of elasticity vii.Bearing materials should not get weld easily to the journal material.

4. What is a journal bearing?

A journal bearing is a sliding contact bearing which gives lateral support to the rotating shaft.

5. What are the types of journal bearings depending upon the nature of contact?

1.Full journal bearing 2.Partial bearing 3.Fitted bearing.

6. What are the types of journal bearing depending upon the nature of lubrication?

1.Thick film type 2.Thin film type 3.Hydrostatic bearings 4.Hydrodynamic bearing.

7. What is known as self – acting bearing?

The pressure is created within the system due to rotation of the shaft, this type of bearing is known as self – acting bearing.

8. What is flywheel?

Flywheel is a machine elements used to minimize the fluctuation of speed in a engine.

9. What is the function of flywheel?

A flywheel used in machine serves as a reservoir which stores energy during the period when the supply of energy is more than the requirement and releases it dulling the period when the requirement of energy is more than the supply.

10. Define the term ‘fluctuation of speed’ and ‘fluctuation of energy’.

The ratio of maximum fluctuation of speed to the mean speed is called co efficient of fluctuation of speed. The ratio of fluctuation of energy to the mean energy is called coefficient of fluctuation of energy.

11. State the type of stresses induced in a rim flywheel?

1.Tensile stress due to centrifugal force 2.Tensile bending stress caused by the restraint of the arms and 3.The shrinkage stresses due to unequal rate of cooling of casting.

12. What are the stresses induced in flywheel arms?

1.Tensile stress due to centrifugal force. 2.Bending stress due to torque. 3.Stress due to belt tension.

13. How does the function of flywheel differ from that of governor?

A governor regulates the mean speed of an engine when there are variations in the mean loads. It automatically controls the supply of working fluid to engine with the varying load condition & keeps the mean speed with contain limits. It does not control the speed variation caused by the varying load. A flywheel does not maintain const speed.

14. What is the nature of contact involved in a ball bearing element?

Instead of sliding, the contact between the bearing elements is rolling.

15. Define antifriction bearing?

The contact between the bearing elements is rolling, this type has very small friction.

16. What are the types of rolling contact bearing?

Depending upon the type of rolling element,

i. Ball bearing

ii. Roller bearing

Depending upon the load to be carried,

i. Radial

ii. Angular contact

iii. Trust bearing

17. State the components of rolling contact bearings?

i. Outer race ii. Inner race iii. Rolling element iv. Seperator.

18. What are the several types of radial ball bearing?

i. Deep groove ball bearing ii. Self aligning ball bearing iii. Angular contact ball bearing iv. Filling notch bearing v. Double row bearing.

19. What are the types of trust ball bearings?

i.One directional flat race ii. One directional Grooved race iii. Two directional Grooved race.

20. What is load rating?

The load carrying capacity of a rolling element bearing is called load rating.

21. What is basic static load rating?

It is defined as load acting on a non rotating bearing under which permanent deformation is 0.0001 times the ball of roller diameter.

22. Explain the term dynamic load carrying capacities of rolling contact bearing?

Dynamic load rating is defined as the radial load in radial bearing that can be carried for a minimum life of one million revolution.

23. List the types of bearing materials?

i. Lead base babbit ii. Tin base babbit iii. Leaded bronze iv. Copper laed alloy v. Gun metal vi. Phosphor bronze.

24. State the theory of lubrication?

i. Hydrostatic theory of lubrication.

ii. Hydrodynamic theory of lubrication.

25. Define Kinematic viscosity?

The kinematic viscosity is defined as the ratio of absolute viscosity to the density of oil.

ME2302-DYNAMICS OF MACHINERY Questions Bank 2014

Anna University, Chennai

 

SRINIVASAN ENGINEERING COLLEGE, PERAMBALUR DEPARTMENT OF MECHANICAL ENGINEERING ME2302-DYNAMICS OF MACHINERY

16 MARKS

UNIT-I FORCE ANALYSIS AND FLYWHEELS

1.The length and connecting rod of a horizontal reciprocating engine are 200mm and

1meter respectively. The crank is rotating at 400rpm.When the crank has turned 30° from

the inner dead center, the difference of pressure between cover end and piston rod is 0.4 N/mm2. If the mass of the reciprocating parts is 100Kg and a cylinder bore is 0.4meters.Calculate (i)Inertia force (ii) Force on piston (iii) Piston effort (iv) Thrust on the side of the cylinder walls (v) Thrust in the connecting rod (vi)Crank effort. (16)

2. A horizontal gas engine running at 210rpm has a bore of 220mm and a stroke of 440mm.The connecting rod is 924mm long the reciprocating parts weight 20kg.When the crank has turned through an angle of 30° from IDC, the gas pressure on the cover and the crank sides are 500KN/m2 and 60KN/m2 respectively. Diameter of the piston rod is 40mm.Determine,1. Turning moment on the crank shaft 2.Thrust on bearing 3. Acceleration of the flywheel which has a mass of 8kg and radius of gyration of 600mm while the power of the engine is 22KW. (16) [MU, April 2000]

3. A single cylinder vertical engine has a bore of 300mm and a stroke of 400mm.The connecting

rod is 1000mm long. The mass of the reciprocating parts is 140kg.On the expansion stroke with the crank at 30°from the top dead center, the gas pressure is 0.7MPa.If it runs at 250rpm, determine;

1. Net force acting on the piston 2.resultant load on the gudgeon pin 3. Thrust on cylinder walls 4.

The speed above which other things remaining same, gudgeon pin loads would be reversed in direction. (16)

4. A vertical double acting steam engine has a cylinder 300mm diameter and 450mm stroke and runs at 200rpm.The reciprocating parts has a mass of 225kg and the piston rod is 50mm diameter. The connecting rod is 1.2m long. When the crank has turned 125° from IDC the steam pressure above the piston is 30KN/m2.calculate,

(i)Crank-pin effort[MS U. Nov’97]

(ii)The effective turning moment on the crank shaft. (16) [MS U. Nov’97]

5. The turning moment diagram for a petrol engine is drawn to a scale of 1mm to 6N-9-9m and the horizontal scale of 1mm to 1°.The turning moment repeat itself after every half revolution of the engine. The area above and below the mean torque line are 305, 710, 50,350,980and 275mm2.

The mass of rotating parts is 40kg at a radius of gyration of 140mm.Calculate the coefficient of

fluctuation of speed if the mean speed is 1500rpm.(16)

6. The torque delivered by a two stroke engine is represented by T= (1000+300sin2_-500cos2_) N- m where _ is the angle turned by the crank from the IDC. The engine speed is 250rpm.The mass of

the flywheel is 400kg and radius of gyration 400mm.Determine, (i)the power developed (ii)the total percentage fluctuation of speed (iii)the angular acceleration of flywheel when the crank has rotated through an angle of 60° from the IDC. (iv) the maximum angular acceleration and retardation of the flywheel. (16)[Au May-11]

7. A single cylinder horizontal steam engine has a stroke of 0.7 m and a connecting rod 1.8m long. The mass of reciprocating parts is 520kg and that of the connecting rod is 230kg. Centre of gravity of the connecting rod is 0.8m from crank pin and the moment of inertia about an axis through the centre of gravity perpendicular to the plane of motion is 100kg-m2. For an engine speed of 90rpm and a crank position of 45° from the IDC, determine the torque on the crankshaft due to the

inertia of these parts.[Au Dec-11]

---

UNIT-II BALANCING

8. A shaft is rotating at a uniform angular speed. Four masses M1, M2, and M3and M4 of magnitudes 300kg, 450kg, 360kg, 390kg respectively are attached rigidly to the shaft. The masses are rotating in the same plane. The corresponding radii of rotation are 200mm, 150mm, 250mm and 300mm respectively. The angle made by these masses with horizontal are 0°, 45°, 120°and

255°respectively. Find (i) the magnitude of balancing mass(ii) the position of balancing mass if its radius of rotation is 200mm. (16)

9. Four masses M1, M2, M3, and M4 are 200kg, 300kg, 240kg and 260kg respectively. The corresponding radii of rotation are 0.2m, 0.15m, 0.25m and 0.3m respectively and the angle between successive masses45°, 75°, and135°.Find the position and magnitude of balance mass required if its radius of rotation is 0.25m. (16) [MS U. Nov’97]

10. The data for three rotating masses are given below:- M1=4kg r1=75mm θ1=45

M2=3kg r2=85mm θ2=135

M3=2.5kg r3=50mm θ3=240

Determine the amount of counter mass at a radial distance of 65mm required for their static balance (16) [MKU, Oct’97, Au Dec-11]

11. Four masses A, B, C, and D are completely balanced masses C and D makes angles of 90° and

195°respectively with B in the same sense. The rotating masses have the following properties:

mA=25kg rA=150mm mB=40kg rB=200mm mC=35kg rC=100mm rD=180mm Planes B and C are

250mm apart. Determine (i) the mass A and its angular position (ii) the position of planes A and D. (16)

12. A, B, C and D are four masses carried by a rotating shaft at radii 100mm,125mm,200mm and

150mm respectively. The planes in which the masses revolve are spaced 600mm apart and the

masses of B,C and D are 10kg,5kg and 4kgrespectively.Find the required mass A and relative angular setting of the four masses so that the shaft be in complete balance. (16)[ AU, DEC-12]

13. Four masses A, B, C and D revolves at equal radii and equally spaced along a shaft. The mass B is 7kg and the radii of C and D make angle s of 90° and 240 °respectively with the radius of B. Find the magnitude of masses A,C and D and angular position of A . So that the system may be completely balanced. (16) [MU, April 2000]

14. A shaft caries four rotating masses A, B, C and D which are completely balanced. The masses B, C and Dare 50kg, 80kg and 70kg respectively. The masses C and D make angles of 90° and 195° respectively with mass B in the same sense. The masses A,B,C and D are concentrated at radius

75mm,100mm,50mm and 90mmrespectively.The plane of rotation of masses B and C are 250mm apart. Determine (i) the magnitude of mass A and its angular position(ii) the position of planes A and D. (16)

15. A four cylinder vertical engine has cranks 150mm long. The plane of rotation of the first,

second and fourth cranks are 400mm,200mm and 200mm respectively from that of the third crank and their reciprocating masses are 50kg,60kg and 50kg respectively. Find the mass of the reciprocating parts for the third cylinder and relative angular position of the cranks in order that the engine may be in complete balance. (16) [MS U. Nov’97]

16. A four cylinder vertical engine has cranks 300mm long. The plane of rotation of the first, third and fourth cranks are 750mm,1050mm and 1650mm respectively from that of the second crank and their reciprocating masses are 10kg,400kg and 250kg respectively. Find the mass of the reciprocating parts for the second cylinder and relative angular position of the cranks in order that the engine may be in complete balance. (16)

17. Derive the following expression of effects of partial balancing in two cylinder locomotive engine (i) Variation of tractive force (ii) Swaying couple (iii) Hammer blow (16) [MU, April 2000]

---

UNIT-III FREE VIBRATION

18. Derive an expression for the natural frequency of the free longitudinal vibration by

(i)Equilibrium method (ii) Energy method (iii)Rayleigh’s method (16)

19. In a single degree of damped vibration system a suspended mass of 8kg makes 30 oscillations in 18 seconds. The amplitude decreases in 18 seconds. The amplitude decreases to 0.25 of the initial value after 5 oscillations. Determine (i) the spring stiffness (ii) logarithmic decrement (iii) damping factor (iv) Damping coefficient. (16)[Au Dec-11],[ AU, DEC-12].

20. Determine equation of motion when a liquid column vibrating in a ‘U’tube by

(i) Newton’s method (ii) Energy method and hence find its natural frequency. (16)

21. (i)Deduce the expression for the free longitudinal vibration in terms of spring stiffness, its inertia effect and suspended mass. (8) [MU, April 2000]

(ii)A spring mass system has spring stiffness ‘s’N/m and has a mass of ‘m’kg.It has the natural frequency of vibration as 12Hz.An extra 2kg mass is coupled to ‘m’ and natural frequency reduces by 2Hz.Find the value of ‘s’ and ‘m’. (8)

22.Avibrating system consists of a mass of 8kg,spring of stiffness 5.6N/m and dashpot of damping coefficient of 40N/m/s.Find,(i)Critical damping coefficient (ii) the damping factor (iii)the natural frequency of damped vibration (iv)the logarithmic decrement(v)the ratio of two consecutive amplitude (vi)the number of cycle after which the original amplitude is reduced to 20 percent. [MU, April 2000]

23. An instrument vibrates with a frequency of 1Hz when there is no damping. When the damping is provided, the frequency of damped vibration was observed to be 0.9Hz.

Find, (i) damping factor (ii) logarithmic decrement. (16)

24. Find the equation of notion for the spring mass-dashpot system for the cases when

(i) ζ= 2 (ii) ζ= 1 and (iii) ζ= 0.3. The mass ‘m’is displaced by a distance of 30mm and released[MS U. Nov’97]

25. Between a solid mass of 0kg and the floor are kept two slabs of isolates, natural rubber and felt, in series. The natural rubber slab has a stiffness of 3000N/m and equivalent viscous damping coefficient of 100 N-sec/m.The felt has a stiffness of 12000N/m and equivalent viscous damping coefficient of 330Nsec/m.Determine undamped and the damped natural frequencies of the system in vertical direction. (16) [Bharathiyar Univ. Nov’97]

26. (i) A cantilever shaft 50mm diameter and 300mm long has a disc of mass 100kg at its free end. The young’s modulus for the shaft material is 200GN/m2.SDetermine the frequency of longitudinal and transverse vibration of the shaft. (10)

(ii)Explain the sketches different cases of damped vibrations. (6)

27. The barrel of a large gun recoils against a spring on firing. At the end of the firing, a dashpot is engaged that allows the barrel to return to its original position in minimum time without oscillation. Gun barrel mass is 400kg and initial velocity of recoils 1m.Determine spring stuffiness and critical damping coefficient of dashpot. (16)

28. A steel shaft 100mm in diameter is loaded and support in shaft bearing 0.4m apart. The shaft carries three loads: first mass 12kg at the centre, second mass 10kg at a distance 0.12m from the left bearing and third mass of 7kg at a distance 0.09m from the right bearing. Find the value of the critical speed by using Dunker ley’s method. E=2X1011N/m2 (16)

29. write short notes on a. vibration isolation and transmissibility b. Whirling of rotating shafts.[Au

May-11]

UNIT-IVFORCED VIBRATION

30.A mass of 50kg is supported by an elastic structure of total stiffness 20KN/m.The damping ratio of the system is 0.2.A simple harmonic disturbing force acts on the mass and at any time ‘t seconds, the force is 60sin10t newtons. Find amplitude of the vibration and phase angle caused by the damping. (16) [MS U. Nov’97]

31. A mass of 50kg is supported by an elastic structure of total stiffness 20KN/m.The damping ratio ofthe system is 0.25.A simple harmonic disturbing force acts on the mass and at any time ‘t seconds, the force is 75cos12t newtons. Find amplitude of the vibration and phase angle caused

by the damping. (16) [Bharathiyar Univ. Nov’97]

32. A mass of 10kg is suspended from one end of a helical spring, the other end being fixed. The stiffness of the spring is10N/mm.The viscous damping causes the amplitude to decreases to one- tenth of the initial value in four complete oscillations. If a periodic force of 150cos50t N is applied at the mass in the vertical direction .Find the amplitude of the forced vibrations? What is its value of resonance? (16)

33. A harmonic exiting force of 25N is acting on a machine part which is having a mass of 2Kg and vibrating in viscous medium. The exciting force causes resonant amplitude of 12.5mm with a period of 0.2sec. (16) [MS U. Nov’97]

34. A body having a mass of 15kg is suspended from a spring which deflects 12mm under the weight of the mass. Determine the frequency of the free vibrations. What is the viscous damping force needed to make the motion a periodic at a speed of 1mm/s?If, when damped to this extend a disturbing force having a maximum value of 100N and vibrating at 6Hz is made to act on the body, determine the amplitude of the ultimate motion. (16) [MU, April 2000]

35. A single cylinder vertical petrol engine of total mass of 200kg is mounted upon a steel chassis frame. The vertical static deflection of the frame is 2.4mm due to the weight of the engine .The mass of the reciprocating parts is 18kg and stroke of piston 160mm with S.H.M. If dashpot of damping coefficient of 1N/mm/s used to damped the vibrations, calculate al steady state (i)Amplitude of vibrations at 500rpm engine speed.(ii)The speed of the driving shaft at which resonance will occurs. (16) [MKU, Oct’97]

36. A vertical single stage air compressor having a mass of 500kg is mounted on spring having stiffness of 1.96X105N/m and dashpot with damping factor of 0.2m.The rotating parts are completely balanced and the equivalent reciprocating parts weight 20kg.The stroke is

0.2m.Determine the dynamic amplitude of vertical motion of the excitation force if the compressor is operate at 200rpm. (16)

37. A machine 100kg has a 20kg rotor with 0.5mm eccentricity. The mounting spring have s=85x103. The operating speed is 600rpm and the unit is constrained to move vertically. Find (i) Dynamic amplitude of machine (ii) the force transmitted to the support. (16)

38.A single cylinder engine has an out of balance force of 500N at an engine speed of 30rpm.The total mass of engine is 150kg and its carried on a set of total stiffness 300N/cm. (i) Find the amplitude of steady motion of the mass and maximum oscillating force transmitted to the foundation. [MKU, Oct’97]

(ii)If a viscous damping is interposed between the mass and the foundation the damping force

1000N at 1m/s of velocity, find the amplitude of force damped oscillation of the mass and its angle of lag with disturbing force. ` (16)

39. An industrial machine weighting 445kg is supported on a spring with a statical deflection of

0.5cm.If the machine has rotating imbalance of 25kg-cm.Determine the force transmitted at

1200rpm and the dynamic amplitude at the speed. (16)

40. The mass of an electric motor is 120kg and it runs at 1500rpm.The armature mass is 35kg and its centre gravity lies 0.5mm from axis of rotation. The motor is mounted on five springs of negligible damping. So that the force transmitted is one-eleventh of the impressed force. Assume that the mass of the motor is equally distributed among the five springs. Determine (i) the stiffness of the spring (ii) the dynamic force transmitted to the base at the operating speed. (iii) Natural frequency of system. (16) [MU, April 2000]

41. Find the stiffness of each spring when a refrigerator unit having a mass of 30kg is to be support by three springs. The force transmitted to the supporting structure is only 10% of the impressed force. The refrigerator unit operates at 420rpm. (16) [MS U. Nov’97]

42. A 100kg machine is mounted on a spring stiffness 1× 106N/m and damping factor 0.3. A 3kg piston within the machine has a reciprocating motion with a stroke of 100 mm and a speed of

1500 rpm, thus producing a harmonic force. Determine the amplitude of vibration of the machine and the force transmitted to the foundation.[Au dec-11]

43. Describe the principle of undamped dynamic vibration absorber with suitable illustrations.[Au

May-11]

---

UNIT-V MECHANISMS FOR CONTROL

44. A porter governor has equal arms each 250mm long and pivoted on the axis of rotation. Each ball has a mass of 5kg and mass of the central load on the sleeve is 25kg.The radius of rotation of the ball is 150mm when governor is at maximum speed. Find the maximum and minimum speed and range of speed of the governor. (16)

45. The length of the upper and lower arms of a porter governor are 200mm and 250mm respectively. Both the arms are pivoted on the axis of rotation. The central load is 150N, the weight of the each ball is 20N and the friction of the sleeve together with the resistance of the operating gear is equivalent to a force of 30N at the sleeve. If the limiting inclinations of the upper arms to the vertical are 30° and 40° taking friction in to account. Find the range of speed of the governor. (16) [MKU, Oct’97]

46. Calculate the rage of speed of a porter governor which has equal arms of each 200mm long and pivoted on the axis of rotation .The mass of each ball is 4kg and the central load of the sleeve is 20kg.The radius of rotation of the ball is 100mm when the governor being to lift and 130mm when the governor is at maximum speed. (16) [MU, April 2000]

47. A hartnell governor having a central sleeve spring and two right angled bell crank lever operates between 290rpm and 310rpm for a sleeve lift of 15mm.The sleeve and ball arms are

80mm and 120mm respectively. The levers are pivoted at 120mm from the governor axis and mass

of the ball is 2.5kg.The ball arms are parallel at lowest equilibrium speed. Determine (i) load on the spring at maximum and minimum speeds and (ii) Stiffness of the spring. 16) [MS U. Nov’97]

48. A governor of hartnell type has equal balls of mass 3kg, set initially at a radius of 200mm.The arms of the bell-crank lever are 110mm vertically and 150mm horizontally. Find (i) the initial compressive force on the spring at a radius of 200mm at240rpm and (ii) the stiffness of the spring required to permit a sleeve movement of 4mm on a fluctuation of 7.5 % in the engine speed. (16) [AU. May 2004, Au May-11]

49. The controlling force in a spring controlled governor is 1500N when radius of rotation is

200mm and 887.5N when radius of rotation is 130mm.The mass of each ball is 8kg.If the controlling force curve is a straight line, then find (i) Controlling force at 150mm radius of rotation (ii) Speed of the governor at 150mm radius.(iii)Increase in initial tension so that governor is isochronous.(iv) Isochronous speed. (16)

50. In a spring controlled governor, the controlling force curve is a straight line. When the balls are

400mm apart, the controlling force is 1200N and when 200mm apart, the controlling force is

450N.Determine the speed at which the governor runs when the balls are 250mm apart. When initial tension on the spring would be required for isochronisms and what would be the speed. Take mass of each ball to be 10kg. (16)

51. Calculate the minimum speed of a proell governor, which has equal arms each of 200mm and are provided on the axis of rotation. The mass of each ball is 4kg and the central mass on the sleeve is 20kg.The extension arms of the lower links are each 60mm long and parallel to the axis when the minimum radius of the ball is 100mm.of load. (16)

52. (i) Explain the effect of Gyroscopic couple on a Naval ship during pitching.(8) (ii) Explain the effect of Gyroscopic couple on a aero plane. (8) [MKU, Oct’97]

53.Each paddle wheel of a steamer have a mass of 1600kg and a radius of gyration of

1.2meters.The steamer turns to port in a circle of 160meters radius at 24Km/hr.The speed of the paddle is 90rpm.Find the magnitude and effect of the gyroscopic couple acting on the steamer. (16) [MU, April 2000]

54. The rotor of a turbine yatch rotates at 1200rpm clockwise when viewed from stern. The rotor has a mass of 750 kg and radius of gyration of 250mm.Find the maximum gyroscopic couple transmitted to the hull when yacht pitches with a maximum angular velocity of 1 rad/s. What is the effect of this couple? (16)

55. The turbine rotor of a ship has a mass of 20 tonnes and a radius of gyration 0.75.Its speed is

2000rpm.The ship pitches 6° above and below the horizontal position .One complete oscillation takes 18 seconds and the motion is simple harmonic. Determine (i) the maximum couple tending to shear the holding down bolt of the turbine (ii)The maximum angular acceleration of the ship during pitching

(iii) The direction in which the bow will tend to turn while, if the rotation of the rotor is clockwise when locking from rear. (16) [Anna Univ. May 2004]

56. The controlling force Fc and radius of a spring controlled governor is given by the expression

Fc=2000r-76. The mass of the ball is 5kg and extreme radii of rotation, of the ball are 0.1m and

0.175m respectively for maximum and minimum speeds. If the friction on the governor is 5N at each ball. Find the coefficient of insensitiveness of the governor at extreme radii. [Au May-11]

57. The hartnell governor having ball mass 1.5kg each has ball arms 55mm long and sleeve arms

45mm long. The total movement of sleeve is 24mm. In mid position of sleeve, sleeve arms are horizontal and perpendicular to the governor axis and ball rotates at 80mm radius. Equilibrium speed at the top stop of the sleeve is 425rpm and the bottom stop is 440rpm. Find (a) Stiffness of spring and spring compressive force at the bottom stop (b) If top stop equilibrium speed is required to be 12rpm greater than the bottom stop speed, what will be spring force at bottom stop and (c) What bottom stop spring force will make the governor isochronous? [Au Dec-11]

58. A ship is propelled by a turbine rotor having a mass of 6 tonnes and speed of 2400 rpm. The direction of rotation of the rotor is clockwise when viewed from the stern. The radius of gyration of the rotor is 450 mm. Determine the gyroscopic effect when (a) The ship steers to the right in a curve of 60 m radius at a speed of 18 knots(1 knot=1860 m/hr) (b) The ship pitches 7.5 degrees below the normal position and the bow is descending with its maximum velocity. The pitching motion is SHM with a periodic time of 18 seconds. (c) The ship rolls and at the instant its angular velocity is 0.035 rad/s counter clockwise when viewed from the stern. Also find the maximum angular acceleration during pitching. Explain how the direction of motion due to gyroscopic effect is determined in each case.[Au Dec-11, AU DEC-12]

59. The radius of rotation of the balls of a Hartnell governor is 80 mm at the minimum speed of

300 rpm. Neglecting gravity effect, determine the speed after the sleeve has lifted by 60 mm. Also determine the initial compression of the spring, the governor effort and the power. The particulars of the governor are given below: Length of the ball arm=150 mm, length of sleeve arm=100 mm, mass of each ball=4kg, and stiffness of the spring=25 N/mm.