Birla Institute of Technology & Science, Pilani
Work Integrated Learning Programmes Division
First Semester 2022 -2023
Comprehensive Examination
(EC-3 Regular)
Course No.
Course Title
Nature of Exam
Weightage
Duration
Date of Exam
Note to Students:
1.
2.
3.
4.
: ENGG ZC232
: Engineering Materials
: Open Book
: 40%
: 2 ½ Hours
: 26/11/2021 (FN)
No. of Pages
=3
No. of Questions = 8
Total marks = 40 Marks
Please follow all the Instructions to Candidates given on the cover page of the answer book.
All parts of a question should be answered consecutively. Each answer should start from a fresh page.
Assumptions made if any, should be stated clearly at the beginning of your answer.
Please answer precisely to the point and do not drag around.
Q.1. (a) Explain the main reason why aluminum and its alloys are widely used in motor vehicles?
What are the advantages of using aluminum alloys compared to conventional steel materials
for the production of parts and vehicle assemblies?
[2.5 M]
(b) What is specific strength? Why fibers have very high specific strength?
[2.5 M]
Q.2. (a) Compare the linear densities for the (1 0 0), (1 1/2 1) and (1/2 1/2 1) directions for the
Iron (Fe) crystal structure below 723 °C with help of diagrams.
[2.5 M]
(b) Determine the miller indices for the unit cells shown in the figure below.
[2.5 M]
Q.3. (a) Sketch an isomorphous phase diagram of AB alloy and determine the weight fraction of
liquid in an alloy of 73% B, if α of 82 % of B and liquid of 57 % B are in equilibrium. What
would be the degree of freedom in such a case?
[3 M]
(b) Explain briefly the concept of true stress and strain against engineering stress and strain
with a help of stress-strain diagram.
[2 M]
Q.4. (a) Mention the enabling materials properties for each labelled item in the figure given
below.
[2.5 M]
(b) Briefly describe the importance of temperature, corrosion, fatigue, and strain rate
behaviour of materials in engineering design applications.
[2.5 M]
Q.5. State the treatment processes must be performed on eutectoid steel to obtain transformation
from:
[2 M]
(a) Martensite to Pearlite
(b) Pearlite to Bainite, and
(c) Austinite to Ferrite
Q.6. (a) Sketch and explain the iron-iron carbide equilibrium diagram, and show their salient
feature. Indicate the significance of this diagram for the heat treatment of steel.
[4 M]
(b) For a brass alloy, the stress at which plastic deformation begins is 345 MPa, and the
modulus of elasticity is 103 GPa.
[4 M]
i.
What maximum load may be applied to a specimen with a cross-sectional area of
130 mm2 without plastic deformation?
ii.
If the original specimen length is 76 mm, what is the maximum length to stretch
it without causing plastic deformation?
Q.7. Draw the tensile stress-strain diagram of the following materials in Table below and locate the
yield and ultimate stress value. Also compare and make a ranking on the following
mechanical properties, Toughness, Hardness, Ductility, Ultimate Tensile Strength and
Plasticity of these materials. [5 M]
S.No.
Materials
1
2
3
4
5
Pure Copper
Steel
Pure Aluminum
Magnesium
Diamond
Q.8. Explain the following BRIEFLY to the point:
S.No.
1.
2.
3.
Fatigue
Define it
Discuss the mechanism of fatigue
failure
Suggest methods to improve the
fatigue life of materials
[5 M]
Creep
Define it
Discuss the mechanism of creep
failure
Suggest methods to improve the
creep life of materials
***********