Formula to obtain engineering stress for Elastomers

[evilalibertad]

So, After uniaxial tests We all use the conventional formulas to obtain engineering stress and strain:
Strain=L-Lo/Lo
Stress=F/A

But my advisor told me of a different formula to calculate engineerig stress for elastomers due to the fact that the response is not linear anymore.. He mentioned it but I am not able to find it anywhere.. It may be something like this:
Stress=TF^-1

Any reference or someone please correct me?

[Jorgen]

Your first equation should be: strain = (L - L0) / L0

There may be different ways to calculate the engineering stress and strain. What type of experimental data do you have (uniaxial, torsion, shear?)

-Jorgen

[maria]

Excellent post I must say.. Simple but yet entertaining and engaging..