Enhancement of Drucker-Prager yield model by adding corner points for pressure-dependent materials

To flexibly describe the pressure-dependent behaviors of materials, Drucker-Prager yield model is enhanced by introducing corner points. We call it piecewise Drucker-Prager (pDP) yield model. Constitutive model is derived by considering strain hardening with non-associative yield flows. Integration algorithm includes the return mapping to corner point. Consistent tangent operator is also formulated, and user material subroutine is written. It is demonstrated that the pDP model is effective in describing the pressure-dependent yield behavior of polymers.