This post covers the unit wise important questions
asked by the Anna University, Chennai for the subject ME6503 Design of Machine
Elements.
Unit
1 Steady Stresses and Variable Stresses in Machine Members
Syllabus:
Introduction
to the design process- Factors influencing machine design, selection of
materials based on mechanical
properties-preferred numbers, fits and tolerances-Direct, bending and torsion
stress equations-Impact and shock loading-Calculation of principle stresses for
various load combinations, eccentric loading-curved beams-crane hook and C
frames-factor of safety-theories of
failure-design based strength and stiffness-stress concentration-design for
variable loading.
Unit
1 Steady Stresses and Variable Stresses in Machine Members
Part-A
(2 Marks)
1. What are the factors to be considered
while design process?
2. What are the factors influencing machine
design?
3. What are the mechanical properties were
used while selecting the materials?
4. What are preferred numbers?
5. Define fits and tolerance with its types.
6. Write the bending and torsion equations.
7. Differentiate impact and shock loading.
8. What do you meant by factor of safety?
9. Define stress concentration factor.
10. What are the theories of failure used in
design process?
11. Define stress concentration.
12. What is meant by curved beams? Give its
types.
13. List the various steps involved in the
design of a machine element?
14. State difference between straight beams and curved beams?
Part-B
(16 Marks)
1.
A hot rolled steel shaft is subjected to a torsion moment that varies from
330Nm clockwise to 110Nmcounter clockwise and an applied bending moment at a
vertical section and no keyway is present at the critical section. Determine
the required shaft diameter .the material has an ultimate strength of 550Mpa
and yield strength of 410Mpa.take the endurance limit as half the ultimate
strength, factor of safety of 2, size factor of 0.85 and a surface finish
factor of 0.62
2.
A bar of circular cross-section is subjected to alternating tensile forces
varying from a drawn diameter of the bar
using safety factors of 3.5 related to ultimate tensile strength and 4 related
to an durance limit and a stress concentration factor of 1.65 for fatigue load.
Use Goodman straight line as basis for
design.
3.
A hollow shaft of 40mm outer diameter and 25mm inner diameter is subjected to a
twisting moment of 120 N-m, simultaneously; it is subjected to an axial thrust
of 10Kn and a bending moment of 80N-m.calculate the maximum compressive and
shear stresses.
4.
A pulley is keyed to a shaft midway between two bearings. The shaft is made of
cold drawn steel for which the ultimate strength is 550MPa and the yield
strength is 400Mpa. The bending moment at the pulley varies from -150N-m to
+400Mpa.as the torque on the shaft varies from -50Nm to +150Nm. obtain the
diameter of the shaft for an indefinite life. The stress concentration factors
for the keyway at the pulley in bending and in torsion are 1.6 and 1.3 respectively.
Take the following values: factor of safety =1.5; load correction factors=1.0
in bending, and 0.6 in torsion; size effect factor=0.85; surface effect
factor=0.88.
5.
A hollow shaft is required to transmit 600kW at 110 r.p.m., the maximum torque
being 20% greater than the mean. The
shear stress is not to exceed 63MPa and twist in a length of 3 meters not to
exceed 1.4 degrees .find the external diameter of the shaft, if the internal
diameter to the external diameter is 3/8. Take modulus of rigidity as 84GPa.
6.
A Machine component is subjected to fluctuating stress that varies from 40 to
100N/mm2. The corrected endurance limit stress for the machine component is
70N/mm2. The ultimate tensile strength and yield strength of material are 600
and 450N/m2 respectively .find the factor of safety using: (a).Gerber theory;
(b) Soderberg line; (c). Goodman line; and (d). Also, find factor of safety
against static failure.
7.
A Pulley is keyed to a shaft midway between two anti-friction bearings. The
bending moment at the pulley varies from -170Nm to 510Nm as the torsional
moment in the shaft varies from 55N m to 165Nm.The frequency of variation of
the loads is the same as the shaft speed. The shaft is made of cold drawn steel
having an ultimate strength of 538Mpa and yield strength of 400Mpa. Determine
the required diameter for an infinite life. The stress concentration factor for
the keyway in bending and torsion may be taken as 1.6 and 1.3 respectively. Use
design factor N=1.5
8.
A bolt is subjected to a tensile load of 25 KN and to a shear load of 10KN. suggest
a suitable size of a bolt according to various theories of failure. Take
allowable yield stress is 300N/mm2, Poisson’s ratio is 0.25
9.
A 50 mm diameter shaft is made from carbon steel having ultimate tensile
strength of 600Mpa. It is subjected to a torque which fluctuates between2000
N-m to -900N-m. Using soderberg method calculates the factor of safety.
10.
(i) What are the factors influencing machine design? Explain it.
(ii) Write short notes on the following:
a. interchangeability b.
tolerance c. allowance
