Plasticity Model for Transversely Isotropic Materials

Abstract

The most frequently used approach for representing the constitutive relations for anisotropic materials is Hill's incremental plasticity model. However, a fundamental difficulty with the use of Hill's plasticity model is the need to select a unique effective stress‐effective strain relation when none truly exists. Recently, an alternative model based upon stress invariants that does not require definition of an effective stress‐effective strain relation has been proposed. In this study, the invariant‐based model and Hill's model are implemented in a general finite element system. The invariant‐based model is reviewed and a modification is proposed that improves performance for certain multiaxial stress states. Performance of the modified invariant‐based model relative to Hill's model is measured. Comparisons are based upon finite element micromechanics analysis and experimental test results. The invariant‐based model is shown to be superior to Hill's model for a variety of uniaxial and multiaxial loading conditions, but this model is limited to predicting inelastic behavior of transversely isotropic materials.