1
VK 250 Summer 2008
Homework 1
(Due on Friday, July 4, 2008)
1.
Engineering stress-stain data are plotted in the figure below. For the initial
portion of a tension test on 7075-T651 aluminum. Note that data points A and B
are labeled with their stress-strain coordinates.
(a) Obtain an approximate value of the elastic modulus
E
.
(b) If a sample of this material is strained to point B and then unloaded, what is
the plastic (permanent) strain that remains after unloading?
(c) If a bar of this material 150mm long is strained to point A and then unloaded,
what is its length at point A and also after unloading?
(d) Repeat (c), but with the bar loaded instead to point B.
2.
Callister (Textbook, 7
th
edition), Page 170, Question 6.28. (only solve (a)~(e))
3.
Callister (Textbook, 7
th
edition), Page 171, Question 6.37.
4.
Show that when a material deforms by conserving its volume (
i.e.,
A
0
l
0
=
Al)
, the energy absorbed per unit volume is the same whether expressed
in terms of nominal or true stress and strain;
i.e
.,
σ
n
d
ε
n
0
ε
n
∫
=
˜
σ
d
˜
ε
0
˜
ε
∫

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