Plasticity - Damage
I'm working on reinforced concrete joint behavior under cyclic effects. I have experienced convergence issues with solid65 - conc table combination and now I'd like to look for some alternatives now.
Using Menetrey-Willam plasticity (WM + HSD6) model, I had no problem obtaining good-matching results including the softening branch, however under cyclic loads, unloading stiffness is equal to elastic state of material since there is no damage formulation in this model.
I wonder if it is possible to introduce a cumulative damage formulation to reduce stiffness in each loading step. A simple damage parameter (or separate parameters for compression and tension) which is a function of plastic strains and reduces the elements stiffness in each step of reversal loading procedure would help me I think. A possible compression damage formulation is seen in the figure below.
So, I would like to keep solution in implicit scheme and tell to the code that it should calculate a damage scalar based on strain state and modify constitutive equations. Should I use usermats or a built-in feature may help in this issue? I would be really happy if you would suggest a solution for this problem.