Bachelor of Mechanical Engineering 2nd Year 2nd Semester Examination, 2021
Mechanical Engineering Department
Jadavpur University
Design of Machine Elements I
Full Marks: 70
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Instructions to be followed:
a.
b.
c.
d.
Put your full signature and examination roll number on each page
Put page number
Answers should be handwritten and questions should be answered in sequence
For uploading the answer script, scan the pages and make a single file in pdf format and
rename it as your class roll number_your name_your section.
e. An assignment is created in Google Classroom; please upload the same using the link.
f. Total allotted time: as decided in Faculty Council Meeting, FET
g. Any missing dimension, data may be reasonably chosen.
h. Please remember during the evaluation, the similarity of the answer scripts may be checked.
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1. Justify the following:
03x10=30
a) Maximum shear stress theory is conservative in nature, b) Flow curve is essential in selecting
manufacturing processes, c) Machining of outer surfaces of cast components is to be minimized,
d) Factor of safety in brittle material is more than ductile material, e) Endurance limit is a material
property, f) Tolerance is a tool to control the cost of the product, g) Increasing the size of a product
may not increase the endurance limit, h) Fatigue stress concentration factor is less than or equal to
theoretical stress concentration factor, i) Type of material, type of loading and environment will
influence selection of Factor of Safety. j) Miner’s rule is based on linear cumulative damage rule.
2. Design and draw a cotter joint subjected to an axial load of (last three digits of your
examination roll number + 100) kN. Select the material, factor of safety with proper justification.
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3. a) Briefly state the design procedure of a machine component subjected to low cycle fatigue.
b) Design a shaft subjected to an alternating torsional moment which varies from -300 N-m to
+600 N-m and at the same time shaft is subjected to a bending moment that varies from (last three
digits of your examination roll number + 50) N-m to (last three digits of your examination roll
number + 200) N-m. Select the material with proper justification.
03+12
4. A mild steel shaft of 40 mm diameter is subjected to a bending moment of (last three digits of
your examination roll number + 50) N-m and torque, T. If the yield point of the steel in tension is
300 MPa, find the maximum value of torque T without causing yielding of the shaft according to
von-Mises and Tresca failure theories.
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