To learn about User subroutines, the best starting point is to refer to Abaqus User Manual at: Abaqus > Verification > User Subroutines > User subroutine verification > UMAT and UHYPER > User subroutine for isotropic Mises plasticity model Here is a direct link to the above page: help.3ds.com/2022/english/dssimulia_established/SIMACAEVERRefMap/simaver-c-umatuhyper.htm?contextscope=all&id=33e823641d2945689bb88bd7db06e975#simaver-c-umatuhyper-t-UserSubroutineForIsotropicMisesPlasticityModel-abqversubsect1
