FACULTY OF ENGINEERING SCIENCE AND TECHNOLOGY
Hamdard University
Assignment-2
ME-122 Engineering Materials
Announced Date: May 18, 2023
Due Date: May 24, 2023
nd
Semester: 2 /Spring-23
Program: B.E. (Mechanical Engineering)
Total Marks = 4
Marks Obtained =
(CLO-2): (Cognitive Level C3 (Applying)) (PLO_2, i.e., Problem Analysis)
Question#1
(a) Zirconium has an HCP crystal structure and a density of 6.51 g/cm3.
(i) What is the volume of its unit cell in cubic meters?
(ii) If the c/a ratio is 1.593, compute the values of c and a.
(b) Calculate the energy for vacancy formation in silver, given that the equilibrium number of vacancies
at 8000C (1073 K) is 3.6 x1023 m-3. The atomic weight and density (at 8000C) for silver are,
respectively, 107.9 g/mol and 9.5 g/cm3.
(c) Determine the Miller Index of the planes A and B shown in the figure below.
Question#2
(a) A large tower is to be supported by a series of steel wires. It is estimated that the load on each wire will
be 11,100 N. Determine the minimum required wire diameter assuming a factor of safety of 2 with yield
strength of 1030 MPa.
(b) A cylindrical rod of copper (E = 110 GPa) having a yield strength of 240 MPa is to be subjected to a load
of 6660 N. If the length of the rod is 380 mm, what must be the diameter to allow an elongation of 0.50 mm?
(c) A cylindrical rod 380 mm (15.0 in.) long and having a diameter of 10.0 mm is to be subjected to a tensile
load. If the rod is to experience neither plastic deformation nor an elongation of more than 0.9 mm. When
the applied load is 24,500 N, which of the four metals or alloys listed below in the following table are possible
candidates? Justify your choice(s).
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FACULTY OF ENGINEERING SCIENCE AND TECHNOLOGY
Hamdard University
(d) An FCC iron-carbon alloy initially containing 0.35 wt% C is exposed to an oxygen-rich and virtually
carbon free atmosphere at 1400 K (1127°C). Under these circumstances the carbon diffuses from the alloy
and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface
position is maintained essentially at 0 wt% C. (This process of carbon depletion is termed decarburization.)
At what position will the carbon concentration be 0.15 wt% after a 10-h treatment?
The value of D at 1400 K is 6.9 x10-11 m2/s.
(e) Nitrogen from a gaseous phase is to be diffused into pure iron at 700°C. If the surface concentration is
maintained at 0.1 wt% N, what will be the concentration 1 mm from the surface after 10 h? The diffusion
coefficient for nitrogen in iron at 700°C is 2.5 x 10-11 m2/s.
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