UMAT/VUMAT for linear, bilinear and piecewise Drucker-Prager models

These are the user material subroutines (UMAT/VUMAT) in Abaqus for linear, bilinear, and piecewise Drucker-Prager models, where strain hardening can be considered. The UMAT/VUMAT are created separately for each case where the finite element model is two-dimensional and three-dimensional.