Strain Hardening Behavior Exercise - Solution Procedures

General Concepts: For a material with stress-strain behavior that can be described by

s = K en
a measure of the material strength is given by K and n describes how quickly the flow stress changes with strain.

What is the value of flow stress at strain = 1?

On the stress-strain plot a value of n can be set and different values of K tried. It will be seen that the value on the stress axis for strain = 1 is equal to the value of K chosen.
A more easily seen answer can be obtained by by setting a value for K and trying various values of n.
Which material parameter, K or n, has a larger effect on material strength?
Answering this question requires defining "strength" and deciding on a method for comparing values of strength. One possibility is to define strength as the flow stress at a particular value of strain and ask, does doubling the value of K or n have a larger effect on flow stress?

If the value of K is doubled, by how much does the flow stress change?

Since the flow stress depends on K, n and e, values of n and e have to be selected to determine the change when K is doubled? Several values of n and e have to be used to get a full picture of the effects.
If the value of n is halved, by how much does the flow stress change?
Again, flow stress depends on K and e as well as on n so the answer will vary with the values of K and e at which the comparison is made.

Example answers are provided HERE

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© 2001 by Barney E. Klamecki. All rights reserved