SimScale CAE Forum

Plastic material stress-strain definition


#1

What stress-strain definition should be used in Plastic material csv file.
Engineering stress or true stress?
Engineering strain or true strain or true plastic strain?


#2

Hi @Thorbjorn and thanks for your question!

I would say true stresses (cauchy-stresses) because the FEM also describes the real geometry which is the current cross-section.

\sigma_{true} = \sigma_{eng}*(1+ \epsilon_{eng})

\epsilon_{true} = ln (1+ \epsilon_{eng})


Maybe my colleagues @ahmedhussain18 & @rszoeke as well as the @PowerUsers_FEA can give you some additional information or correct me if I am mistaken here.

All the best!

Jousef


#3

Hi @Thorbjorn @jousefm, sorre for the late replay.
Jousef is right, the stress-strain data has to be given in “true” stresses and strains.
Also not that the first point in the curve should not be (0, 0), but the yield point (\epsilon_{yield}, \sigma_{yield}) and that the Young’s Modulus should be consistent with that:
E = \sigma_{yield} / \epsilon_{yield}

Best,
Richard