Strain Softening Material

[uwcomposites]

Hello,

I am having problems performing a non-linear static analysis with strain softening.
I cannot use any Structural -> Nonlinear -> Inelastic -> Rate Independent material models because they are all hardening models, and I get an error if I input a negative slope for one of the segments.

So I tried the Structural -> Nonlinear -> Inelastic -> Cast Iron material model and I included strain softening this way, but I ran into a convergence problem.

Then I tried a Structural -> Nonlinear -> Elastic -> Multi-Linear Elastic and I ran again into convergence problems: the model crushes when it reaches the softening region.

I need to validate a theory, and for that I would need to observe the behavior of the material when it reaches softening. I am not bound to any particular material and I am dealing with any unloading, so elastic or inelastic will work with me for now.

Has anybody performed a non-linear analysis with softening before? If so, could you please point me in the right direction? I would highly appreciate it.

Thank you in advance for any help you will be able to provide me.

Best Regards,

-Francesco