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(Established under
section 3 of UGC Act,1956)
Course & Branch :B.E - M&P/MECH
Title of the Paper :Design of Machine Elements Max. Marks:80
Sub. Code :6C0078/SMEX1014(2009/2010/2011)Time : 3
Hours
Date :02/05/2014 Session
:AN
___________________________________________________________________________________________________________________________
(Use of
approved data book is permitted during the examination)
PART – A
(10 x 2 =
20)
Answer All the Questions
1. What do you mean by optimum design?
2. Define stress concentration and stress
concentration factor.
3. A
line shaft at 200 rpm is to transmit 20 kW, it may be assumed to be made of
mild steel with an allowable stress of 42 MPa. Determine the diameter of the
shaft, neglecting the bending moment on the shaft.
4. Under what circumstances woodruff keys are
used.
5. Name the stresses acts on screw fastenings.
6. Sketch
any two types of welded joints.
7. When
two concentric springs of stiffness 100N/mm and 50N/mm respectively are
subjected to an axial load of 750 kN, what will be the deflection of each
spring?
8. Write briefly about Belleville Springs.
9. What
is known as self-actuating bearing?
10. State
the type of stresses induced in a rim flywheel.
PART – B (5
x 12 = 60)
Answer All the Questions
11. A
simply supported bam has a concentrated load at the center which fluctuates
from a value of P to 4P. The span of the beam 500 mm and its cross section is
circular with a diameter of 60mm. Taking for the beam material an ultimate
stress of 700 MPa, a yield stress of 500 MPa, endurance limit of 330 MPa for
reversed bending and factor of safety of 1.3, calculate the maximum value of P.
Take a size factor of 0.8 and a surface finish factor of 0.9.
(or)
12. A
mild steel bracket as shown in figure – 1 is subjected to a pull of 5 kN acting
at 45° to its horizontal a xis. The bracket has a rectangular
section whose depth is twice the thickness. Find the cross sectional dimensions
of the bracket. If the permissible stress in the material of the bracket is
limited to 50 MPa.
13. A
mild steel shaft transmits 23 kW at 200 rpm. It varies a central load of 900 N
and is simply supported between the bearings 2.5 meters apart. Determine the
size of the shaft, if the allowable stress is 42 MPa and maximum tensile or
compressive stress is not to exceed 56 MPa. What size of the shaft will be
required, if it is subjected to gradually applied loads?
(or)
14. Design
a cast iron flange coupling for a mild steel shaft transmitting 90 kW at 250
rpm. The allowable shear stress in the shaft 40 MPa and the angle of twist is
not to exceed 1° in a length of 20 diameters. The allowable shear stress in the
coupling bolts is 30 MPs.
15. A
bracket is welded to a column as shown in figure – 2. Determine the size of the
weld if permissible shear stress in the weld is 80 N/mm2.
(or)
16. A
bracket, subjected to a force of 5 kN, inclined at an angle of
60° with vertical, is shown in Figure – 1. The bracket is fastened by
means of four identical bolts to the structure. The bolts are mode of plain
carbon steel 30CS (sYt = 400
N/mm2) and the factor of safety is 5 based on maximum shear stress.
Assume maximum shear stress theory and determine the size of the bolts.
17. Design
a close-coiled helical compression spring for a service load ranging from 2250
N to 2750 N. The axial deflection of the spring for the load range is 6mm.
Assume a spring index of 5. The permissible shear stress intensity is 420 MPa
and modulus of rigidity 84 KN/mm2. Neglect the effect of stress
concentration.
(or)
18. A
truck spring has 12 numbers of leaves, tow of which are full length leaves. The
spring supports are 1.05 m apart and the central band is 85 mm wide. The
central load is to be 5.4 kN with a permissible stress of 280 MPa. Determine
the thickness and width of the steel spring leaves. The ratio of the total
depth of the width of the spring is 3. Also determine the deflection of the
spring.
19. The
operating conditions of a journal for a centrifugal pump are as follows:
Load
on journal = 11.5 kN
Speed
of journal = 1440 rpm
Diameter
of journal = 75mm
Operating
temperature = 70°
Ambient
temperature = 40°
Design
the bearing.
(or)
20. A
single cylinder double acting engine delivers 185 kW at 100 rpm. The maximum
fluctuation of energy per revolution is 15 percent of the energy developed per
revolution. The speed variation is limited to 1 percent either way from the
mean. The mean diameter of the rim is 2.4m. Design the suitable fly wheel.
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