Identification of fully coupled non-associated-Ductile damage constitutive equations for thin sheet metal applications: Numerical feasibility and experimental validation

Developing an efficient non-associated plasticity criterion fully coupled with isotropic ductile damage is the main contribution of the current research. Two ductile degradation functions with variable degradation exponents are considered in this model, one for elasticity and the other for plasticity. Mixed (isotropic/kinematic) hardening rule and Hill’48 quadratic yield criterion are adopted to describe the elastoplastic material behavior. For this contribution, a VUMAT subroutine including the proposed model has been adopted and implemented in Abaqus/Explicit finite element code. Various experimental tests and finite element simulations are carried out to validate the current model and to predict the damage evolution in notched tensile specimens. In the validation part of this investigation, the quality of the numerical simulation results is assessed by comparison with the experimental ones taking into account the fully coupled non-associated-damage model. The effectiveness of the developed approach is evaluated through comparisons with experimental measurements and numerical models (Hill_S and Hill_R) and show good agreements. This fact indicates that the current model is a useful virtual tool to estimate the formability of anisotropic sheet metals. Numerical prediction is performed in order to reveal the stress triaxiality distributions for single point incremental forming (SPIF). The mentioned study is intended to give a guideline for 5083-aluminum alloy sheet forming.