Cohesion yield stress?

[Mohamedsayed]

Hello,

To define the hardening or softening of a material using Mohr-Coulomb criterion, i need to define the variation of cohesion yield stress with Abs. plastic strain.

The question is, how can i define the variation of the cohesion yield stress with plastic strain? I know that, i can find the cohesion from the shear test, however, i have no idea how can define the yield stress as a function of the plastic strain.

Thanks