A HARDENING ORTHOTROPIC PLASTICITY MODEL FOR NON-FRICTIONAL COMPOSITES - RATE FORMULATION AND INTEGRATION ALGORITHM

The rate formulation and an unconditionally stable integration algorit hm for a single-surface hardening anisotropic elastoplasticity model a re developed to obtain an effective medium constitutive model for a cl ass of periodic elastoplastic composites. Because the plasticity model features an intrinsically anisotropic failure criterion and hardening law, it requires more material parameters (15) than does its isotropi c analogue (2). To address this issue and to assess how well the new m odel serves as an effective medium constitutive model for a class of c omposites, results from numerical elastoplastic homogenization computa tions are utilized for free-parameter estimation. It is shown that the new model provides a good fit to the homogenization data. and the mod el's excellent performance in a two-dimensional finite element setting is demonstrated by performing computations involving in-plane loading of an elastoplastic masonry wall. The wall is modelled first as a het erogeneous medium with all of its microstructure, and subsequently as a homogeneous effective medium with the new plasticity model.