Dear all!
For quite a long time (not full time though) I've been trying to get a multi-surface plasticity model running, without finally successing. Yet.
I am coding the algorithm Simo & Hughes give in "Computational Inelasticity" in Box 5.2a-c into an Abaqus-umat written in fortran. I apply it for perfect plasticity (at the moment), therefore it is simplified from the original.
Unfortunately, my code does not provide proper results even in a quite simple example (2 surfaces only) that can be more or less followed.
Nevertheless, the algorithm does work if only one surface is active.These results are verified by a single-surface model. I assume therefore, that the algorithm is OK in principle, only the combinatoric terms are somehow not working properly. I have also rewritten the code in mathematica which yields the very same results -wrong ones in case of multiple active surfaces.
Questions to the community are:
- is the algorithm given in Simo & Hughes working at all? I assume so, no worries!
- has someone experienced some troubles with this as well? Were there any minor/major/obvious/hidden misinterpretations or errors in understanding the procedure? Any hints what one can make wrong?
-since I'm not the most exerienced coder and material model expert, does anyone know of a similarly well-documented algorithm for multi-surfarce plasticity?
- any other information that may be helpful?
Regards
umat.