MET 205W Material Sclence (Fall 2017) Dr. Calvo Page 3 of 10 5· T s-strain curve
ID: 699221 • Letter: M
Question
MET 205W Material Sclence (Fall 2017) Dr. Calvo Page 3 of 10 5· T s-strain curve for a nonlinear, perfetly elastic material is shown below. A sample of material is nt deformation) in the material is loaded until the stress reaches the value at point b unloaded to zero stress. What is the approximate permanent set the material? (A) o (B) 0.001 (C) 0.002 (D) 0.003 . Then, the (permanen (MPa) 125 100 75 - 50 25 A 5 10 15 20 25 30 35 40 (× 10-4) 6. A cylindrical test specimen with a 15 mm diameter is tested axially in tension. A 0.20 mm elongation is recorded in a length of 200 mm when the load on the specimen is 36 kN. The material behaves elastically during testing. What material could the specimen be made of? (A) aluminum (B) magnesium (C) polystyrene (D) steel The movement of defects through a crystal by diffusion is described by which of the following? (A) Boyle's law (B) Fick's law (C) Dalton's law (D) Gibbs' rule 7.Explanation / Answer
5)
Draw a line parallel to linear part of elastic region curve passing through B. This line intersects the x-axis at 10 x 10-4
Permanent set of material, = 1 x 10-3 = 0.001
Option B)
6)
Diameter of specimen = 15 mm
Cross sectional area = d2 /4 = 3.1416 * (15 x 10-3)2/4
= 1.77 x 10-4 m2
Stress = Force/Area
= 36 x 103 N / 1.77 x 10-4 m2
= 2.037 x 108 Pa
Strain = Elongation / Initial length
= 0.2 / 200 = 0.001
Young’s Modulus = Stress / Strain
= 2.037 x 108 Pa / 0.001 = 2.037 x 1011 Pa
For steel Young’s Modulus = 2 x 1011 Pa
The specimen could be steel
Option D)
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