requirement for plastic card in Calculix?

I have did one simple test in Calculix, as a start point.

The simulation cannot start after factoring the system of equations if I inserted plastic card.

However, when I use elastic properties, it runs well.

If I change one example with elastic properties into plastic one, it can continue, even with some warnings.

So I was wondering if there is any prerequisite for plastic cards, such as element type. I am using hybrid mesh. What surprised me is that the elastic card only works but plastic card does not.

Thank you.

Hello

I'm using ccx 2.12 with beams and plasticity. Results are reasonably good. Now I would ask you about the integraton of the stresses on the cross section. Which is the algorithm? Does the code consider a fiber model? Is it possible to size it? I didn't find it in the docs. Thank you very much indeed for every help.
Bruno