Friday 25 July 2014

Design Of Machine Elements (ME30602) - Class test Question Bank with answers

INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
End/Mid Semester Examination
DESIGN OF MACHINE ELEMENTS
ME30602

Class Test
1. Answer all questions. All questions carry equal marks
2. Make suitable assumptions wherever necessary
3. Put √ on your chosen answer.
4. Any data, if not furnished, may be assumed.




1.     A new model of a car is a typical example of
a)     Adaptive design
b)    Developmental design
c) New design
2.     Adaptive design is based on
a)     Existing design adapted for new application
b)    New inventions for new application
c)     Conceptual design for new application
d)    New Technology for new application

3.     Which of the following design is based on based on experience and experiments?
a)     Rational design
b)    Empirical design
c)     Industrial design


4.     Use of factor of safety in designing the elements is to
a)     optimize the design to avoid over-design for reliability
b)    prevent loss of material and premature failure
c)     have good aesthetics of the designed product
d)    increase efficiency of the element

5.     A stainless steel is described as 18/8 steel. This indicates that it contains:
a)     8% Nickel and 18% Chromium
b)    18% Nickel and 8% Chromium
c)     18% Chromium and 8% Silicon
d)    8% Chromium and 18% Silicon

6.     Resilience is
a)     the property of the material that enables it to resist shock and impact by storing energy
b)    the property of the material that enables it to be twisted, bent or stretched under impact load or high stress before rupture
c)     the property of the material that enables it to be drawn out or elongated to an appreciable extent before rupture
d)    the property of the material that enables it to resist permanent deformation, penetration, indentation

7.     Resilience is the property of a material:
a)     that enables it to resist indentation
b)    that enables it to resist wear
c)     that enables it to resist shock and impact
d)    that enables it to resist scratching

8.     A standard alloy steel used for making engineering components is 20Cr18Ni2. The composition of this steel is:
a)     20% carbon, 18% chromium and 2% nickel
b)    0.2% chromium, 18% nickel and 2% carbon
c)     0.2% carbon, 18% chromium and 2% nickel
d)    20% chromium, 18% nickel and 2% carbon

9.     The composition of 20Cr18Ni2 is:
a)     20% Cr, 18%Ni, 2%Carbon
b)    0.2% carbon, 18% chromium and 2% nickel
c)     2% Cr, 0.18%Ni, 0.2%Carbon
d)    2% carbon, 0.18% chromium and 0.2% nickel

10.                        Allowance of a shaft-hole system is the difference between
a)     maximum dimension of shaft and minimum dimension of hole
b)    maximum dimension of shaft and maximum dimension of hole
c)     minimum dimension of shaft and minimum dimension of hole
d)    minimum dimension of shaft and maximum dimension of hole

11.                         Tolerance is the difference between:
a)     Maximum and minimum dimensions of a component
b)    Maximum dimension of the shaft and maximum dimensions of the hole
c)     Minimum and minimum dimensions of a component
d)    Minimum dimension of the shaft and the maximum dimension of the hole

12.                        In a unilateral system of tolerance, the tolerance is allowed on
a)     one side of the actual size
b)    one side of the nominal size
c)     both sides of the actual size
d)    both sides of the nominal size

13.                        Nominal size of a hole and shaft is 40 mm, the tolerance grade for making the hole is IT6 and for shaft is IT5. The fundamental deviation of shaft basis is positive and for hole is zero. Which of the following designation suits the above hole-shaft system?
a)     40M6/h5
b)    40M5/h6
c)     40H5/m6
d)    40H6/m5

14.                        Which of the following standard series is used for Capacities of hydraulic cylinder?
a)     R5
b)    R10
c)     R20
d)    R40

15.                         What is the bearing stress developed at the faces of a rectangular key fixing a gear hub on a shaft acted upon by a torque T as shown in figure?
                                                                                                       



16.                         Let the cross-sectional area of the plate, the larger hole H1 and the smaller holes H2 be A, a1, a2 respectively. If 2a2 > a1 , the critical section in the loaded plate is:

a)     A-A
b)    B-B
c)     C-C
d)    D-D




17.                         A 3m long cantilever beam of solid rectangular cross-section of 100mm width and 150mm depth is subjected to an end loading P as shown in the figure. If the allowable shear stress in the beam is 150 MPa, the safe value of P based on shear alone is

a)     1 MN
b)    1.5 MN
c)     2.3 MN
d)    3.5 MN


18.                         A vertical load Py = 20 kN is applied at the free end of a cylindrical bar of radius 50 mm as shown in figure. The principal stress at the point A is


a)     56MPa, 7.4MPa
b)    84MPa, −8.9MPa
c)     105MPa, 9.3MPa
d)    112.5MPa, −14.72MPa


19.                         An axially loaded brass (Ebrass = 90GPa) strut hinged at both ends is 1m long and is of a square cross-section of sides 20mm. The dimension of steel (Esteel = 200 GPa) strut of the same length and subjected to the same axial loads is:
a)     24.40 mm
b)    13.42 mm
c)     16.38 mm
d)    32.62 mm


20.                         The theoretical stress concentration factor at hole in a plate with transverse elliptical hole and subjected to a tensile load as shown in figure is:

                                                                                                             




21.                         Notch sensitivity factor, q is
                                                                                                     




22.                         The endurance or fatigue limit is defined as the maximum value of the stress which a polished standard specimen can withstand without failure, for infinite number of cycles, when subjected to
a)     static load
b)    dynamic load
c)     static as well as dynamic load
d)    completely reversed load


23.                         In the plate shown below it is required that the stress concentration at hole does not exceed that at the fillet. The hole diameter is

a)     21.5 mm
b)    35 mm
c)     41.9 mm
d)    53 mm
Data Provided:

24.                         Dowel pins are used for
a)     proper alignment
b)    loosening
c)     both for proper alignment and loosening


25.                         Dowel Pins are used
a)     To get a better grip
b)    To transmit torque smoothly
c)     For proper alignment


26.                         Studs are
a)     single headed fasteners
b)    double headed fasteners
c)     headless fasteners
d)    twin headed fasteners


27.                         A heat treated steel shaft of tensile yield strength of 350 MPa has a diameter of 50mm. The shaft rotates at 1000 rpm and transmits 100 kW through a gear. An appropriate key set of dimensions is:
a)     Width = 16 mm, Length = 45 mm, Depth = 10 mm
b)    Width = 10 mm, Length = 35 mm, Depth = 8 mm
c)     Width = 18 mm, Length = 55 mm, thickness = 11 mm
d)    Width = 20 mm, Length = 65 mm, thickness = 12 mm
Data Provided:
Shaft Diameter
(mm)
30-38
38-44
44-50
50-58
58-65
65-75
75-85
Key width, w
(mm)
10
12
14
16
18
20
22
Key depth, t
(mm)
8
9
9
10
11
12
14
Key length, L
(mm)
22-110
28-140
36-160
45-180
50-200
56-220
63-250




28.                         In a steam engine the steam pressure is 2 MPa and the cylinder diameter is 250 mm. The contact surfaces of the head and cylinder are ground and no packing is required. Assuming that the number of bolts to be used is 12, a suitable bolt for the joint to be leak proof would be:
a)     M20 x 1.5
b)    M16 x 1.5
c)     M5 x 0.8
d)    M10 x 1.25
Data provided:
Designation
Pitch
(mm)
Minor Diameter
Stress area
(mm2)
Bolt (mm)
Nut (mm)
M2
0.40
1.509
1.567
207
M5
0.8
4.019
4.134
14.2
M10
1.25
8.466
8.647
61.6
M16
1.5
14.160
14.376
167
M20
1.5
18.160
18.376
272
M24
2
21.546
21.835
384




29.                         Shear stress developed in the weld in the figure shown below is

a)     16.7 MPa
b)    21.9 MPa
c)     26.2 MPa


30.                         Considering unit weld width the polar moment of inertia of the weld group in above question is
a)     0.00365 m3
b)    0.000198 m3
c)     0.0000325 m3


31.                         If the yield strength of the weld material is 150MPa, the safe value of F is

a)     108 kN
b)    213 kN
c)     269 kN
d)    313 kN


32.                         In a triple riveted butt joint with two unequal straps 30 mm diameter rivets and 10mm plates (both main and straps) are used. The pitch at the outer row is 250mm. Considering that the joint fails only due to shearing of all the rivets and taking the working stresses to be σt = 75MPa, Ï„y = 60MPa and σc = 130MPa, the joint efficiency is
a)     76.3%
b)    81.3%
c)     98.3%


33.                         Two plates of 7 mm thickness are connected by a double riveted lap joint of zigzag pattern. If the rivet diameter is 19mm and σt = 90MPa, σc = 120MPa, Ï„ = 60 MPa, the rivet pitch is
a)     19 mm
b)    54 mm
c)     73 mm
d)    102 mm


34.                         According to Unwin's formula, the diameter of the rivet hole (in mm) can be obtained by:                   (t = thickness of the plate in mm)

                                                                                                         



35.                         Wahl correction factor takes care of:
a)     curvature effect
b)    shear stress correction
c)     both curvature effect and shear stress correction


36.                         In spring design, Wahl correction factor
a)     takes care of the direct shear stress in springs
b)    takes care of the curvature effect in springs
c)     takes care of the direct stress together with the curvature effect in springs


37.                         In a close coiled helical spring, the spring index (C) is given by D/d where D and d are the mean coil diameter and wire diameter respectively. For considering the effect of curvature, the Wahl’s stress factor K is given by
                                                                                       



38.                         Which of the following threads is used for transmission of power only in one direction?
a)     Acme thread
b)    Knuckle thread
c)     Buttress thread
d)    Square thread


39.                         V-threads are normally used for
a)     power transmission
b)    for securing two components
c)     not normally used


40.                         A bolt of M 24 × 2 means that
a)     the pitch of the thread is 24 mm and depth is 2 mm
b)    the cross-sectional area of the threads is 24 mm2 and number of starts is 2
c)     the nominal diameter of bolt is 24 mm and the pitch is 2 mm
d)    the effective diameter of the bolt is 24 mm and there are two threads per cm


41.                         The shear stress developed in the centre bolt (no-2) is

a)     35.3 MPa
b)    43.6 MPa
c)     6.4 MPa


42.                         For zero collar friction, the efficiency of a square-thread screw is:
(λ is lead angle and f is coefficient of friction of the screw)
                                                                                     



43.                         A single square thread power screw is to raise a load of 50 kN. A screw thread of major diameter of 34 mm and a pitch of 6 mm is used. The coefficient of friction at the thread and collar are 0.15 and 0.1 respectively. If the collar frictional diameter is 100 mm and the screw turns at a speed of 1 rev per second. The power input to the screw is
a)     1549 watts
b)    2300 watts
c)     2614 watts
d)    3167 watts


44.                         In the above question, the combined efficiency of the screw and collar is
a)     11.5%
b)    22.3%
c)     33.5%
d)    44.3%


45.                         The machine shown in the figure can be used for a tension test but not for a compression test. Should both screws have the same hand?

a)     Yes
b)    No, screws should always have different hands
c)     No, screws can have either same or different hands


46.                         In the machine shown below, both the screws have the same hand

a)     the machine can be used for a compression test only
b)    the machine can be used for a tension test only
c)     the machine can be used for both tension and compression tests


47.                         The purpose of Rebound clips in Laminated semi-elliptic spring is:
a)     to share the load from the master leaf to the graduated leaf
b)    to hold the leaves of the spring
c)     to prevent the deflected spring from touching the attached machine member
d)    to attach the spring with another machine member



48.                         The purpose of central clamp in Laminated semi-elliptic spring is:
a)     to share the load from the master leaf to the graduated leaf
b)    to hold the leaves of the spring
c)     to prevent the deflected spring from touching the attached machine member
d)    to attach the spring with another machine member


49.                         The purpose of camber in Laminated semi-elliptic spring is:
a)     to share the load from the master leaf to the graduated leaf
b)    to hold the leaves of the spring
c)     to prevent the deflected spring from touching the attached machine member
d)    to attach the spring with another machine member


50.                         Which of the following methods reduces additional stresses in laminated spring hinged at supports?
a)     Master leaf is made of stronger material than the other leaves
b)    Master leaf is made thinner than the other leaves
c)     Increase the radius of curvature of the master leaf than the next leaf
d)    All the above


51.                         Nipping of leaf spring
a)     Increases the stress in master leaf
b)    Decreases the stress in master leaf
c)     Doesn’t affect the stress in master leaf


52.                         A helical spring of wire diameter 6mm and spring index 6 is acted by an initial load of 800N. After compressing it further by 10mm the stress in the wire is 500MPa. Taking G = 84000MPa the number of active coils is
a)     13 turns
b)    21 turns
c)     27 turns
d)    32 turns


53.                         For a simple cantilever type leaf spring with uniform strength the leaf thickness can be given by
a)     σmax L3/2/(E δmax1/2)
b)    σmax L3/(E δmax2)
c)     σmax L2/(E δmax)
d)    σmax L4/(E δmax3)
Where δmax is the spring deflection, L is the characteristic length, σmax is the design stress or maximum stress and E is the Modulus of elasticity



54.                         Thermoplastic materials are those materials which
a)     are formed into shape under heat and pressure and results in a permanently hard product
b)    do not become hard with the application of heat and pressure and no chemical change occurs
c)     are flexible and can withstand considerable wear under suitable conditions
d)    are used as a friction lining for clutches and brakes


55.                         A cotter joint is used to transmit
a)     axial tensile load only
b)    axial compressive load only
c)     combined axial and twisting loads
d)    axial tensile or compressive loads


56.                         To ensure self-locking in a screw jack, it is essential that the helix angle is
a)     larger than friction angle
b)    smaller than friction angle
c)     equal to friction angle
d)    such as to give maximum efficiency in lifting


57.                         The figure shows a clamp coupling. If the effective number of bolts in each shaft is n/2, the allowable tensile stress for the bolt material is σt and the root diameter of the bolt is dc, then the clamping pressure between the shaft and the sleeve is

a)     nÏ€dc2σt/(dL)
b)    nÏ€dc2σt/(4dL)
c)     3nÏ€dc2σt/(4dL)



58.                         In a typical clamp coupling the clamping pressure between the shaft and the sleeve is given by
a)     nÏ€dc2σt/(dL)
b)    0.5nÏ€dc3/2σt/(dL1/2)
c)     0.75nÏ€dc4σt/(dL)2
d)    0.25nÏ€dc2σt/(dL)
Where dc is the core diameter of the bolts, d is the clamp diameter, L the clamp length and σt is the tensile yield stress.




59.                         In a disc clutch, maximum pressure occurs
a)     at the inner radius
b)    at the centre
c)     at the outer radius


60.                         In which of the following, uniform pressure theory is more approximate?
a)     a new clutch
b)    an old clutch
c)     friction clutch


61.                         For a self-locking brake
a)     A large actuating force is needed
b)    A small actuating force is needed
c)     No actuating force is needed



62.                         If in the band brake shown below, drum diameter = 400mm, lining width = 75mm, rotational speed is 200 rpm, a = 250mm, m = 75mm, α = 2700, μ = 0.2 and the maximum lining pressure is 0.5 MPa, the torque is

a)     632 Nm
b)    915 Nm
c)     1150 Nm
d)    3160 Nm


63.                         Hydrodynamic Lubrication occurs at:
a)     Very low Sommerfeld Number
b)    Low Sommerfeld Number
c)     Medium Sommerfeld Number
d)    High Sommerfeld Number


64.                         Hydrodynamic Lubrication occurs at:
a)     At zero Sommerfeld number
b)    At relatively low Sommerfeld number
c)     At relatively high Sommerfeld number


65.                         Hydrodynamic lubricated bearings are
a)     Thick film bearings
b)    Thin film bearings
c)     Zero film bearings


66.                         When a shaft rotates in anticlockwise direction at slow speed in a bearing, then it will
a)     have contact at the lowest point of bearing
b)    move towards right of the bearing making metal to metal contact
c)     move towards left of the bearing making metal to metal contact
d)    move towards right of the bearing making no metal to metal contact



67.                         If Z = Absolute viscosity of the lubricant in kg/m-s, N = Speed of the journal in rpm, and p = Bearing pressure in N/mm2, then the bearing characteristic number is
a)     ZN/p
b)    Zp/N
c)     Z/Pn
d)    pN/Z



68.                         A ball bearing subjected to a radial load of 5 kN is expected to have a life of 8000 hours at 1450 rpm with a reliability of 99%. The dynamic load capacity of the bearing so that it can be selected from the manufacturer's catalogue based on a reliability of 90% is
a)     86.5 kN
b)    68.5 kN
c)     58.6 kN
d)    1 kN



69.                         The ball bearings are usually made from
a)     low carbon steel
b)    medium carbon steel
c)     high speed steel
d)    chrome nickel steel



70.                         The tapered roller bearings can take
a)     radial load only
b)    axial load only
c)     both radial and axial loads



71.                         The listed life of a rolling bearing, in a catalogue, is the
a)     minimum expected life
b)    maximum expected life
c)     average life



72.                         Which of the following are called as Anti-friction bearings?
a)     Fluid Film bearings
b)    Rolling contact bearings
c)     Sliding contact bearings
d)    Journal bearings



73.                         The load rating of a bearing is given for
a)     Axial loads only
b)    Radial loads only
c)     Both axial and radial loads



74.                         If two groups of identical ball bearings are tested under loads P1 and P2 for respective lives of L1 and L2 , then L1/L2 is
a)     (P1/P2)1/3
b)    (P2/P1)1/3
c)     (P1/P2)3
d)    (P2/P1)3


75.                         Which of the following is best suitable for high speeds of shaft and high loads?
a)     Journal bearing
b)    Ball bearing
c)     Roller bearing



76.                         Can a block moving over a constant height fluid film carry load?
a)     Yes
b)    No
c)     Depends upon viscosity of the fluid


77.                         If Sommerfeld number increases, then the Eccentricity ratio
a)     Increases
b)    Decreases
c)     Remains same



78.                         If Sommerfeld number increases, then the minimum film thickness
a)     Increases
b)    Decreases
c)     Remains same



79.                         If Sommerfeld number increases, then the ratio of side flow to total flow
a)     Decreases
b)    Increases
c)     Remains same



80.                         If Sommerfeld number increases, then the coefficient of friction
a)     Decreases
b)    Increases

c)     Remains same


************* THE END *************

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