IE 215
HOMEWORK CHAPTER 18
18.1.
The strength coefficient = 550 MPa and strainhardening exponent = 0.22 for a
certain metal. During a forming operation, the final true strain that the metal
experiences = 0.85. Determine the flow stress at this strain and the average flow
stress that the metal experienced during the operation.
Solution
: Flow stress
Y
f
= 550(0.85)
0.22
=
531 MPa.
6.
For a certain metal, the strength coefficient = 700 MPa and strain
hardening exponent
= 0.27. Determine the average flow stress that the
metal experiences if it is subjected to a stress that is equal to its strength
coefficient
K
.
Solution
:
Y
f
=
K
= 700 =
K
ε
n
= 700
.
27
must be equal to 1.0.
= 700(1.0)
.27
/1.27 = 700/1.27 =
551.2 MPa
10. The following stress and strain values were measured in the plastic region
during a tensile test carried out on a new experimental metal: (1) true
stress = 43,608 lb/in
2
and true strain = 0.27 in/in, and (2) true stress =
52,048 lb/in
2
and true strain = 0.85 in/in. Based on these data points,
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 Fall '08
 Groover
 Materials Science, Stress, Tensile strength

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