Plastic internal parameter definition

[Jensoulou]

Hi,
I would like to define a multi-model plastic surface (SolidMechanics) by defining these plastic surface in UserObjects and making the synthesis of those with the « ComputeMultiPlasticityStress » material. Some of the parameters of the plastic surfaces would be SolidMechanicsHardeningModel.
To my understanding, there is one internal parameter defined per plastic surface. There is therefore a vector of internal parameters defined in ComputeMultiPlasticityStress.

How these internal parameters are computed? And how could I modify their definition?

From what I could find, it looks like the internal parameters are always directly linked to J2 but as I want to model a compressive cap behavior I would like to be for example defined on the trace.

[GiudGiud]

@WilkAndy

[Kavan-Khaledi]

The existing plasticity models in MOOSE use different internal variables for the shear and volumetric components. If I’m not mistaken, index 0 in plastic_internal_parameter stores the internal variable for shear, index 1 is for tensile, and index 2 is for the compression cap.

[Jensoulou]

Hi,

Thank you for your response! 😊

I looked deeper into the code, and it seems that there should be one plastic_internal_parameter per plastic surface. Based on my investigation, the internal parameter (intnl) appears to be modified by dintnl, which is assigned in MultiPlasticityLinearSystem within the Utils folder—rather than in the material definition, as one might expect.

However, I’m still struggling to fully understand how all the parameters affecting plastic_internal_parameter are updated and where I could modify them 😕