No strain rate dependency- then?

[svishal03]

i,

I'm attaching a file which have the stress strain curves of same material at quasi static and high strain rates.


See materials on page 1 and page 2.

Both are same materials.

The curve on page 1 is obtained at quasi static strain rate and the curve on page 2 is obtained at high strain rate.

Both have almost the same ultimate stress indicating that material is not strain rate dependent.

However, there is some change in elastic limit. Material at high strain rate has a lower elastic limit than one at high strain rate as well as there is some difference in slopes at quasi static and medium strain rates.

What can we infer why- changes in slope and elastic limit are occurring?

 

[Navin A S]

The change in slope and elastic limit can be attributed to the fact that materials behave differently at different strain rates. At high strain rates, the material deforms more quickly and hence more energy is dissipated as heat resulting in lower elastic limit and changes in slope. This is due to the higher rate of plastic deformation at high strain rates which results in the material not being able to return to its original shape or dimensions.