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ENSC 3313, Spring 2006
TEST 2  KEY
Name_________________________
Answer all 10 questions, show all work, 2points each
1.
Cartridge brass (C26000) has the following properties: E=16
×
10
6
psi,
ν
=0.35, TS=58 ksi, YS=46 ksi, and
%elongation = 35%.
Assume that you performed a tensile test on a C26000 sample with a 0.25 in diameter
and 2 in gage length.
Label the load elongation curve (not stressstrain) with the relevant values.
Cross sectional area is:
05
.
0
4
)
25
.
0
(
A
2
=
π
=
Yield load = 46,000*0.05 = 2300 lb
Max load = 58,000*0.05 = 2900 lb
Yield strain = YS/E = 46/16
×
10
3
= 2.9
×
10
3
Yield elongation = 2*2.9
×
10
3
= 5.8
×
10
3
in
Failure elongation = 0.35*2 = 0.7 in
2.
Calculate the resolved shear stress (
τ
r
) relevant for dislocation motion in the primary slip system of a copper
crystal (FCC) if a tensile stress of 30 ksi is applied in the (001) direction.
Recall the cosine of the angle
between two vectors is:
2
1
2
1
v
v
v
v
cos
⋅
=
θ
The primary slip systems in FCC are the {111} planes
and <110> directions.
As sketched, the relevant plane
and direction are (111) and [
01
1]
3
1
cos
;
2
1
cos
=
φ
=
λ
Hence,
ksi
2
.
12
6
r
=
σ
=
τ
elongation (in)
0.7
0.0058
2900
2300
load (lb)
x
y
z
(111)
[101]
[001]
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3.
Tell about the 2 issues that caused this problem.
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This note was uploaded on 01/10/2012 for the course ENSC 3313 taught by Professor Staff during the Fall '11 term at Oklahoma State.
 Fall '11
 staff

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