Question

The flow stress (in MPa) of a material is given by $\sigma =600{ϵ}^{0.15}$ where $ϵ$ is true strain. The mean flow stress $\left({\overline{\sigma }}_0\right)$ of material is 200 MPa. What is the maximum stress value corresponding to maximum strain value during deformation___

• A. 200
• B. 230
• C. 350
• D. 400

Answer 1

The correct option is B 230

$\text{Mean flow stress}\left({\overline{\sigma }}_0\right)$ = $\frac{k{ϵ}^n}{1+n}$

$k=600MPa$
$n=0.15$

$200=\frac{600\times {ϵ}^{0.15}}{1+0.15}ϵ=1.67\times {10}^{-3}$

$\sigma =600(1.67\times {10}^{-3}{)}^{0.15}$

$\text{True stress,}\sigma =230MPa$