A modified Ehlers model for the description of inelastic behavior of porous structures

This paper describes a modification of Ehlers' model for the inelastic behavior of granular media. The modified model can be applied for describing the inelastic behavior of porous media. The key feature is a subtle change of the yield potential, which allows the correct orientation of the triangular-shaped yield surface cross sections depending on the hydrostatic stress state. The model is incorporated into a general framework for isotropic plasticity. An elastic predictor/corrector algorithm is employed to solve the constitutive equations. The necessary derivatives for a Newton update are also given in detail. The model is calibrated using stress, and strain data obtained from finite element simulations of a generic highly porous open-cell Wheire-Phelan foam.