Machine Design - Machine Design
Exam Duration: 45 Mins Total Questions : 30
The stress which vary from a minimum value to a maximum value of the same nature (i.e., tensile or compressive) is called
- (a)
repeated stress
- (b)
yield stress
- (c)
alternating stress
- (d)
fluctuating stress
In static loading, stress concentration is more serious in
- (a)
brittle materials
- (b)
ductile materials
- (c)
Both (a) and (b)
- (d)
None of these
In cyclic loading, stress concentration is more serious in
- (a)
brittle materials
- (b)
ductile materials
- (c)
Both (a) and (b)
- (d)
None of these
Failure of a material is called fatigue when it fails
- (a)
at the elastic limit
- (b)
below the elastic limit
- (c)
above the yield point
- (d)
below the yield point
In below figure a bi-axial stress acting on the block. The maximum yield stress of the material is 40 N/m2. The value of factor of safety is (according to maximum distortion energy theorem)
- (a)
1.88
- (b)
1.72
- (c)
1.80
- (d)
1.81
What is the value of hoop stress in cylinder at point A, if thickness of cylinder is 20 cm?
- (a)
2 MPa
- (b)
3.15 MPa
- (c)
4 MPa
- (d)
2.5 MPa
Stress concentration is 2.5 and notch sensitivity is 2 then, the value of fatigue stress concentration is
- (a)
62.5 MPa
- (b)
60 MPa
- (c)
50 MPa
- (d)
25 MPa
In above question value of factor of safety according to Goodman theory is
- (a)
8.69
- (b)
7.14
- (c)
6.59
- (d)
7.35
A cylindrical shaft is subjected to an alternating stress of 150 MPa. Fatigue strength to sustain 1000 cycle is 600 MPa. If corrected endurance limit is 100 MPa, what is the life of shaft?
- (a)
213796 cycle
- (b)
198576 cycle
- (c)
200000 cycle
- (d)
210813 cycle
The contact surfaces in a cone clutch have an effective diameter of 100 mm. The angle of cone is 30°. If an axial force of 200 N is applied then, torque required to produce slipping of clutch is (μ=0.3)
- (a)
11.60 N-m
- (b)
8.93 N-m
- (c)
12.70 N-m
- (d)
4.27 N-m
A single block brake has a drum brake diameter of 1 m and angle of contact is 30°. It takes 200 N-m torque at 100 rpm (μ = 0.35).
This arrangement is shown in figure. Calculate the required force P to be applied when rotation of drum is clockwise.
- (a)
240 N
- (b)
210 N
- (c)
287.02 N
- (d)
236.5 N
A band brake acts on 2/3 rd circumference of drum of 100 mm diameter. The band brake provides a braking torque of 100 N-m. One end of band is attached to a fulcrum pin of the lever and other end to a pin, 100 mm from the fulcrum. (μ = 0.25)
(I) Angle of lap is
- (a)
4.18 rad
- (b)
2.72 rad
- (c)
3.27 rad
- (d)
None of these
A band brake acts on 2/3 rd circumference of drum of 100 mm diameter. The band brake provides a braking torque of 100 N-m. One end of band is attached to a fulcrum pin of the lever and other end to a pin, 100 mm from the fulcrum. (μ = 0.25)
If operating force is applied at 1000 mm from the fulcrum which rotates drum clockwise then, value of operating force is
- (a)
308.6 N
- (b)
501.2 N
- (c)
491.3 N
- (d)
621.01 N
Consider a hand operated brake (differential band brake) as shown in figure. If radius of gyration of wheel is 45 cm then, evaluate the value of braking torque. Given, a = 5 cm, b = 10 cm, 1= 25 cm, and P = 100 N, μ = 0.20.
- (a)
99.72 N-m
- (b)
100.01 N-m
- (c)
89.13 N-m
- (d)
92.3 N-m
In a band brake system, braking torque is 103.26 N-m. Mass of drum is 250 kg and radius of gyration is 350 mm. If drum rotates with 300 rpm then, the number of revolutions of drum before it comes to
- (a)
26.09
- (b)
25.71
- (c)
23.29
- (d)
28.72
In a band brake system, braking torque is 103.26 N-m. Mass of drum is 250 kg and radius of gyration is 350 mm. If drum rotates with 300 rpm then, time taken by flywheel to come to rest is
- (a)
7.2 s
- (b)
8.19 s
- (c)
4.65 s
- (d)
3.27 s
A bolt of M 24 x 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
- (c)
the nominal diameter of bolt is 24 mm and the pitch is 2 mm
- (d)
None of the above
When a nut is tightened by placing a washer below it, the bolt will be subjected to
- (a)
tensile stress
- (b)
compressive stress
- (c)
shear stress
- (d)
All of these
The longitudinal joint in boilers is used to get the required
- (a)
length and diameter of boiler
- (b)
efficiency of boiler
- (c)
diameter of boiler
- (d)
length of boiler
The strength of the unriveted or solid plate per pitch length is equal to
- (a)
p x d x σt
- (b)
p x t x σt
- (c)
(p-d) x t x σt
- (d)
(p-t) x d x σt
The parallel fillet welded joint is designed for
- (a)
bending strength
- (b)
shear strength
- (c)
tensile strength
- (d)
compressive strength
For a parallel load on a fillet weld of equal legs, the plane of maximum shear occurs at
- (a)
45°
- (b)
22.5°
- (c)
30°
- (d)
60°
A double fillet welded joint with parallel fillet weld of length L and leg s is subjected to a tensile force P. Assuming uniform stress distribution, the shear stress in the weld is given by
- (a)
\(\frac { \sqrt { 2 } P }{ s.L } \)
- (b)
\(\frac { P }{ \sqrt { 2 } sL } \)
- (c)
zero
- (d)
\(\frac { 2P }{ sL } \)
Primary shear stress on each bolt is
- (a)
88.46 MPa
- (b)
90 MPa
- (c)
10 MPa
- (d)
14 MPa
A bolt assembly is tightened by means of spanner a preload 2.5 kN in bolt. The external load acting on the bolt assembly is 5 kN. The effective stiffness of parts held together by bolt is 2.5 times of the bolt stiffness. The maximum load on the bolt will be
- (a)
3928.57 N
- (b)
7.5 kN
- (c)
4.5 kN
- (d)
6 kN
If thickness of the plate is t then, tearing strength of the plate is given by
- (a)
(P-d) σt.t
- (b)
(P-d/2) t σt
- (c)
Pσtt
- (d)
dt σt
Diameter of the rivet will be
- (a)
12 mm
- (b)
20.78 mm
- (c)
15.78 mm
- (d)
19.78 mm
If the diameter of rivet is 10 mm then, margin in joint to prevent tearing should be
- (a)
15 mm
- (b)
25 mm
- (c)
10 mm
- (d)
18 mm
What is throat length in this fillet weld joint?
- (a)
10 mm
- (b)
20 mm
- (c)
9.6 mm
- (d)
12 mm
If fillet leg is 3 mm and shear stress of weld material is 60 MPa
The strength of weld material is
- (a)
7144.64 N
- (b)
8144.64 N
- (c)
7544.64 N
- (d)
6844.64 N