Iím trying to simulate a material behaviour that reacts different in tension and compression.
At the moment I am trying to develop the compression behaviour for the material that should be an elasto- plastic one. Additionally it is an anisotropic material and solid 3D elements are used.
I am using the plastic Hill yield criterion for anisotropic materials. Such kind of behaviour can be modeled with Abaqus itself, so that I can compare the stresses and strains with the Abaqus results.
For testing the Umat, I modeled a cubus and in a STATIC general step this cubus the forces are applied via boundary conditions, so that this is displacement controlled. (I attatched the input file)
As it can be seen from the plots (attached jpg), the material starts to yield, stresses are kept constant, but strains, too. Does anyone has some hints or does anybody have such kind of UMAT? I guess I have problems with my Jacobian Matrix. It would be great if somebody could help me.
Thank you very much in advance.