## Aptitude Series

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## [MCQ] Design of mechanical systems

**1) Which of the following ergonomic factors are encountered in engineering applications?**

a. Thermal radiations

b. Lubrication failure

c. Fatigue

d. Corrosion

ANSWER: Fatigue

**2) Which of the following statements is/are true about safety/risk?**

a. Risk is potential for damage

b. Hazard is likely hood of damage

c. Danger is combination of risk and hazard

d. All of the above

ANSWER: Danger is combination of risk and hazard

**3) Which of the following processes is used for surface finishing?**

a. Shaping

b. Broaching

c. Lapping

d. All of the above

ANSWER: Lapping

**4) In forging process, forging plane is the plane __________**

a. parallel to die motion

b. perpendicular to die motion

c. where two die halves meet

d. none of the above

ANSWER: perpendicular to die motion

**5) What are the factors affecting selection of casting process?**

a. Tolerances

b. Surface finish

c. Both a. and b.

d. None of the above

ANSWER: Both a. and b.

**6) Which of the following is a property of bulk load?**

a. Hardness

b. Cake forming tendency

c. Suspension part

d. Weight

ANSWER: Cake forming tendency

**7) Which of the following is not a hoisting equipment with lifting gear?**

a. Cage elevators

b. Jib cranes

c. Pulleys

d. Troughed belts

ANSWER: Troughed belts

**8) What are bulk loads?**

a. Lump of material

b. Single rigid mass

c. Homogeneous particles

d. Heterogeneous particles

ANSWER: Single rigid mass

**9) Which belt conveyor prevents sliding down of material at an inclination of 55o with horizontal?**

a. Flat belt conveyor

b. Troughed belt conveyor

c. Blanket belt conveyor

d. Woven wire belt conveyors

ANSWER: Blanket belt conveyor

**10) Which of the following statements is false for troughed belt conveyors?**

1. Troughed belt conveyors use flexible belts

2. They contain five idlers

3. Depth of trough decreases with increasing number of idlers

4. Flexibility of belt increases as depth of trough decreases

a. 1 and 2

b. 2 and 3

c. 3 and 4

d. None of the above

ANSWER: 3 and 4

**11) Diameter range is high in geometric progression due to _________ spindle speed.**

a. low

b. high

c. constant

d. none of the above

ANSWER: low

**12) What is harmonic progression?**

a. Difference between reciprocal of two successive spindle speeds is constant

b. Difference between two successive spindle speeds is constant

c. Ratio of two successive spindle speeds is constant.

d. Ratio of two successive spindle speeds is variable.

ANSWER: Difference between reciprocal of two successive spindle speeds is constant

**13) Ratio of two spindle speeds is constant in _________ progression.**

a. Arithmetic

b. Geometric

c. Harmonic

d. None of the above

ANSWER: Geometric

**14) What is the purpose of using a gear box?**

a. To increase torque

b. To increase speed

c. Converts single input speed into multiple output speeds

d. All of the above

ANSWER: All of the above

**15) Which of the following statements is true for structure/speed diagrams?**

a. Structure diagrams gives range ratio of spindle speeds

b. Speed diagrams do not give range ratio of spindle speeds

c. Speed diagrams consider motor speed

d. All of the above

ANSWER: Speed diagrams consider motor speed

**16) What causes infant mortality in mechanical equipments?**

a. Design errors

b. Manufacturing defects

c. Installation defects

d. All of the above

ANSWER: All of the above

**17) A plain carbon steel has mean yield strength of 300 N/mm2 and standard deviation of 50 N/mm2. What is the mean and standard deviation of margin of safety, if mean tensile stress of 250 N/mm2 and standard deviation of 65 N/mm2 acts on it?**

a. 23.45 N/mm2, 50 N/mm2

b. 50 N/mm2, 82 N/mm2

c. 82 N/mm2, 7.07 N/mm2

d. 7.07 N/mm2, 50 N/mm2

ANSWER: 50 N/mm2, 82 N/mm2

**18) What is meant by mean time to failure (MTTF)?**

a. Mean time between two successive failure components

b. Maximum time between two successive failure components

c. Sum of survival time for number of components divided by number of failures

d. Sum of number of failures divided by survival time for number of components

ANSWER: Sum of survival time for number of components divided by number of failures

**19) If a relief valve has reliability of 0.989, how many failures are expected in testing 1000 such relief valves?**

a. 111

b. 100

c. 10

d. 11

ANSWER: 11

**20) Failure rate for safety valve working for 400 hours is 3 x 10–6 failures/hour. What is the reliability of safety valve?**

a. 0.998

b. 0.989

c. 0.888

d. 0.899

ANSWER: 0.998

**21) A piston made of gray cast iron has piston head thickness of 20 mm. What will be thickness of piston barrel under piston rings if it has allowable tensile stress of 30 N/mm2? ( Bore diameter = 50 mm & Pmax =15 N/mm2)**

a. 10 mm

b. 20 mm

c. 30 mm

d. Insufficient data

ANSWER: 20 mm

**22) A piston has allowable tensile stress of 50 N/mm2 and has bore diameter 150 mm. Considering strength of piston, what will be the thickness of piston head if maximum pressure of 10 N/mm2 acts on it?**

a. 29 mm

b. 35 mm

c. 53 mm

d. Insufficient data

ANSWER: 29 mm

**23) What is the function of gudgeon pin?**

a. Acts as stiffeners

b. Supports piston head

c. Connects piston to connecting rod

d. All of the above

ANSWER: Connects piston to connecting rod

**24) Which of the following parts of piston act as bearing for connecting rod side thrust? **

a. Reinforcing ribs

b. Piston barrel

c. Piston gudgeon

d. Piston skirt

ANSWER: Piston skirt

**25) Single cylinder four stroke engine has brake power of 8 kW and brake mean effective pressure of 0.55 Mpa. What is the length of cylinder which is 1.2 times of bore diameter? (n = 3000 rpm)**

a. 110 mm

b. 103 mm

c. 70 mm

d. 65 mm

ANSWER: 103 mm

**26) Which type of formed threads are used for vertical pressure vessels in the pressure range of 0.1 N/mm2 to 1.5 N/mm2?**

a. Plain formed head

b. Torispherical dished head

c. Semi-elliptical dished head

d. All of the above

ANSWER: Torispherical dished head

**27) Internal pressure of 2.5 Mpa acts on a pressure vessel of thickness 15 mm and internal diameter of 1500 mm. What is the stress induced in longitudinal direction?**

a. 36.63 N/mm2

b. 59.13 N/mm2

c. 65.62 N/mm2

d. 131.25 N/mm2

ANSWER: 65.62 N/mm2

**28) Design pressure for unfired pressure vessels is 1.05 times of _______**

a. minimum working pressure

b. maximum working pressure

c. hydrostatic test pressure

d. none of the above

ANSWER: maximum working pressure

**29) Class 3 pressure vessels having welded joints are __________**

a. fully radio-graphed

b. partially radio-graphed

c. spot radio-graphed

d. not radio-graphed

ANSWER: not radio-graphed

**30) Which type of welded joints are not included in class 3 pressure vessels?**

a. Double welded butt joint with full penetration

b. Single welded but joint with back strip

c. Single full fillet lap joints

d. None of the above

ANSWER: Single full fillet lap joints

**31) Which of the following principle recognizes human capabilities and limitations using design effective handling equipment?**

a. Safety principle

b. Obsolescence principle

c. Ecology principle

d. Ergonomic principle

ANSWER: Ergonomic principle

**32) What does DFMA stand for?**

a. Design for Manual Assembly

b. Design for Manufacture and Assembly

c. Both a. and b.

d. None of the above

ANSWER: Both a. and b.

**33) A cylinder made of plain carbon steel has inner diameter 100 mm. What is the thickness of cylinder if maximum internal pressure of 20 Mpa acts on it? ( σall = 100 N/mm2 & poisson’s ratio = 0.3)**

a. 11 mm

b. 15.36 mm

c. 22.32 mm

d. 80 mm

ANSWER: 11 mm

**34) The ratio of di / t for thick cylinder is __________**

(where di = inner diameter, t = wall thickness)

a. greater than 20

b. less than 20

c. equal to 20

d. none of the above

ANSWER: less than 20

**35) Which criteria of failure is used to indicate St Venent’s theory?**

a. Maximum principle stress theory

b. Maximum principle strain theory

c. Shear stress theory

d. None of the above

ANSWER: Maximum principle strain theory

**36) Which of the following parameters are to be considered for parts with non rotational symmetry in machining process?**

a. Avoid long parts

b. Avoid tin parts

c. Machined surfaces should be parallel to each other and with the base

d. All of the above

ANSWER: All of the above

**37) Selection of welding process does not depend on ___________**

a. thickness of material

b. availability of equipments

c. economics of the process

d. none of the above

ANSWER: none of the above

**38) In which of the following designs, system provides its minimum critical function even after failure of the component?**

a. Fail passive design

b. Fail active design

c. Fail operational design

d. None of the above

ANSWER: Fail operational design

**39) What will be the number of tests required in an experiment to obtain maximum information based on factorial design if, number of levels and number of factors are 2 and 5 respectively?**

a. 32

b. 25

c. 10

d. None of the above

ANSWER: 32

**40) Which of the following methods is most efficient method of design of experiments (DOE)?**

a. Factorial design

b. Fractional factorial design

c. Taguchi method

d. All of the above

ANSWER: Taguchi method

**41) Which of the following belt conveyors have low volume carrying capacity?**

a. Flat belts

b. Troughed belts

c. Both a. and b.

d. None of the above

ANSWER: Flat belts

**42) Which discharge method provides only intermediate discharge for low speed flat belt conveyor?**

a. Plow discharge

b. Tripper discharge

c. Both a. and b.

d. None of the above

ANSWER: Plow discharge

**43) Mass capacity of a conveyor is 200 ton/hr, if speed of the belt is 4 m/s then what is the width of horizontal flat belt conveyor carrying the load? (Surcharge factor = 0.075 & ρ = 1000 kg/m3)**

a. 499.23 mm

b. 500.0 mm

c. 533.7 mm

d. Insufficient data

ANSWER: 533.7 mm

**44) What is the mass capacity of flat belt conveyor if volumetric capacity 0.55 m3/hr? (ρ = 1500 kg/m3)**

a. 825 tons/hr

b. 825 kg/hr

c. 2.727 tons/hr

d. 2722 kg/hr

ANSWER: 825 kg/hr

**45) An inclined belt conveyor is used for loading goods. If speed of the belt having 1500 mm width is 3 m/s then what is the volumetric capacity of the conveyor?**

(For 21o, k= 2.35 x 10–4)

a. 1.19 x 10-3 m3/s

b. 1.75 x 10-3 m3/s

c. 1.5 x 10-3 m3/s

d. 2.5 x 10-3 m3/s

ANSWER: 1.19 x 10-3 m3/s

**46) A machine tool has minimum speed of 100 r.p.m. How many speed steps are required by it to achieve speed of 200 rpm? (Geometric progression ratio = 1.06)**

a. 11

b. 12

c. 13

d. 14

ANSWER: 12

**47) Maximum and minimum diameter of a shaft to be machined is 100 mm and 80 mm respectively. What is the maximum spindle speed if cutting velocity is 40 m/min?**

a. 120 r.p.m

b. 127 r.p.m

c. 160 r.p.m.

d. 636 r.p.m.

ANSWER: 160 r.p.m.

**48) Economic cutting speed is minimum if geometric ratio is _________**

a. minimum

b. maximum

c. equal to economic cutting speed

d. none of the above

ANSWER: minimum

**49) What is the geometric progression ratio if maximum and minimum spindle speeds are 500 r.p.m and 300 r.p.m respectively? (Number of speed steps = 7)**

a. 0.91

b. 1.5

c. 1.08

d. 2.0

ANSWER: 1.08

**50) What is the maximum percentage loss of economic cutting speed if geometric progression ratio = 1.06 ?**

a. 17.0 %

b. 11.5 %

c. 5.7 %

d. 2.9 %

ANSWER: 2.9 %

**51) What is meant by hazard rate?**

a. Number of failures per unit time per number of items when exposed for same time

b. Probability of test specimen fails between time t1 and t1 dt1 which survives for time t1

c. Both a. and b.

d. None of the above

ANSWER: Both a. and b.

**52) What is the standard deviation of clearance population for the diameter of shaft and hole assembly specified below?**

Shaft diameter = 30 ± 0.15

Hole diameter = 30.5 ± 0.25

a. 0.097 mm

b. 0.059 mm

c. 0.036 mm

d. 0.390 mm

ANSWER: 0.097 mm

**53) Which of the following curves have the mean value equal to zero in the graph of frequency vs random variable?**

a. Normal distribution curve

b. Standard normal distribution curve

c. Both a. and b.

d. None of the above

ANSWER: Standard normal distribution curve

**54) What is the relation between standard deviation(σ) and arithmetic mean (μ) to determine coefficient of variation (C)?**

a. C = σ μ

b. C = σ – μ

c. C = σ / μ

d. C = σ x μ

ANSWER: C = σ / μ

**55) Assignable causes are caused due to changes in _________**

a. manufacturing process

b. material

c. inspection process

d. all of the above

ANSWER: all of the above

**56) Which stress is induced in cylinder wall due to side thrust of the piston?**

a. Axial stress

b. Circumferential stress

c. Longitudinal stress

d. Bending stress

ANSWER: Bending stress

**57) Thermal stress in cylinder liners can be reduced by _______**

a. increasing the wall thickness of cylinder liner

b. increasing velocity of flowing water through jacket

c. both a. and b.

d. none of the above

ANSWER: increasing velocity of flowing water through jacket

**58) Which of the following materials are used for cylinder liners?**

a. Alloy cast iron

b. Grey cast iron

c. Both a. and b.

d. None of the above

ANSWER: Both a. and b.

**59) Which type of cylinder liners are used in engines having bore diameter more than 125 mm?**

a. Dry liners

b. Wet liners

c. Both a. and b.

d. None of the above

ANSWER: Wet liners

**60) Which of the following statements is/are false if separate cylinder liner is pressed inside the cylinder of large engines?**

a. Easy replacement of liner in case of wear and tear

b. Cheap grade material cannot be used for jacket

c. Liner is to be made of heat resistant cast iron

d. None of the above

ANSWER: Cheap grade material cannot be used for jacket

**61) What does Ψ mean in Lagrange’s equation (LE = U ** λΨ)?

a. Lagrange’s multipliers

b. Functional constraints

c. Multiple variable objective

d. None of the above

ANSWER: Functional constraints

**62) The limit equation st = Sut / Nf is expressed as _________**

a. loose limit equation

b. rigid limit equation

c. rigid on one side and loose on other side

d. none of the above

ANSWER: rigid limit equation

**63) Which of the following is not expressed by primary design equation?**

a. Functional parameters

b. Material parameters

c. Geometrical parameters

d. None of the above

ANSWER: None of the above

**64) In unfired pressure vessels, category A consists of _________**

a. joints connecting flanges and flat heads

b. welded joints connecting nozzles with main shell

c. circumferential welded joints joints

d. longitudinal welded joints

ANSWER: longitudinal welded joints

**65) Which of the following is not an unfired pressure vessel?**

a. Heat exchanger

b. Storage vessels

c. Steam boilers

d. None of the above

ANSWER: Steam boilers

**66) What is the weld joint efficiency if pressure vessel is fabricated with single full fillet lap joint?**

a. 1.0

b. 0.55

c. 0.65

d. 0.85

ANSWER: 0.55

**67) A cylindrical pressure vessel is subjected to an internal pressure of 3 Mpa on internal diameter of 1000 mm. The vessel is fabricated with single weld butt joint with back strip and is not radio-graphed. What is the thickness of flat head, if head made of alloy steel has an ultimate tensile strength of 400 N/mm2 ? (corrosion allowance = 2)**

a. 110 mm

b. 120 mm

c. 150.23 mm

d. 152.13 mm

ANSWER: 110 mm

**68) A cylindrical pressure vessel is subjected to operating pressure of 0.55 Mpa and corrosion allowance of 2. What is the thickness of pressure vessel shell if its internal diameter is 2000 mm? (σall = 120 N/mm2 & ηl = 0.75)**

a. 6.5 mm

b. 7 mm

c. 9 mm

d. 9.5 mm

ANSWER: 9 mm

**69) Which equation is used to determine wall thickness for brittle materials?**

a. Brinie’s equation

b. Claviro’s equation

c. Lame’s equation

d. All of the above

ANSWER: Lame’s equation

**70) Claviro’s equation is applicable to cylinders with _______**

a. close ends

b. open ends

c. both a. and b.

d. none of the above

ANSWER: close ends

**71) Due to which effect, compressive residual stress of strain-hardening model is smaller than elastic-perfectly plastic model?**

a. Seeback effect

b. Peltier effect

c. Bauschinger effect

d. None of the above

ANSWER: Bauschinger effect

**72) Why is autofrettage process used in pressure vessels?**

a. Increase fatigue lifetime

b. To enhance carrying capacity

c. To introduce compressive residual stress in them

d. All of the above

ANSWER: All of the above

**73) Which equation is used to calculate thickness of an alloy steel cylinder with open ends?**

a. Clavarino’s equation

b. Birnie’s equation

c. Lame’s equation

d. None of the above

ANSWER: Birnie’s equation

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