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**1. Homework Statement**

http://img683.imageshack.us/img683/7060/selection001l.png [Broken]

**2. Homework Equations**

[itex]\epsilon^{pl} = \epsilon - \epsilon^{el}[/itex]

[itex]\epsilon^{pl} = \epsilon - \frac{\bar{\sigma}}{E}[/itex]

[itex]r = \frac{\epsilon_w}{\epsilon_t}[/itex]

**3. The Attempt at a Solution**

I'm stuck trying to calculate [itex]\bar{\sigma}[/itex]. Can I just assume that [itex]\bar{\sigma} = \sigma[/itex] @ 10

^{4}s

^{-1}? If so, the axial plastic strain is calculated as follows:

[itex]\begin{align}

\epsilon_a^{pl} &= \epsilon_a - \frac{\bar{\sigma}}{E} \\

&= (0.10) - \frac{(66.1)}{(200*10^3)} \\

&= 0.09967

\end{align}[/itex]

and

[itex]\begin{align}

\epsilon_w^{pl} &= \epsilon_w - \frac{\bar{\sigma}}{E} \\

&= (-0.042) - \frac{(66.1)}{(200*10^3)} \\

&= -0.04233

\end{align}[/itex]

If this is correct I should be able to related the thickness by [itex]v[/itex], correct?

Also, as far as (b) goes, should I be using [itex]\sigma = k \epsilon^n \dot{\epsilon}^m[/itex]?

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