A numerical scheme of convex yield function with continuous anisotropic hardening based on non-associated flow rule in FE analysis of sheet metal

Abstract

A non-associated flow rule (NAFR) model is developed by adopting the convex function YLD-2004 as the yield stress function and the plastic potential function. The yield stress function coefficients are continuously updated which are associated with the change of directional uniaxial yield stress and biaxial yield stress to simulate the anisotropic hardening behaviour. That was achieved by implementing the numerical identification procedure of coefficients into stress integration procedure. The coefficients of plastic potential function are constant and identified by the uniaxial and biaxial r-value. This constitutive model is capable of describing anisotropic hardening and yield behaviour of strongly textured aluminium alloy sheet metal. In this paper, the model was implemented into the FE code via ABAQUS subroutine to predict the deep drawn cup earing and directional flow stresses of the AA5042-H2 aluminium alloy. The new anisotropic hardening model shows better agreement with experiments compared with the isotropic hardening model.