Development of a Modified Gurson–Tvergaard–Needleman Damage Model Characterizing the Strain-Rate-Dependent Behavior of 6061-T5 Aluminum Alloy

It is of vital importance to improve the lightweight and crash safety of automobiles to accurately characterize the fracture features of automotive aluminum alloys under complex working conditions. This study starts with mechanical tests of 6061-T5 aluminum alloy under different stress states and strain rates, the results of which show obvious strain rate sensitivity in such a material. Then, the parameters of the Gurson–Tvergaard–Needleman_Johnson–Cook (GTN_JC) damage model are calibrated based on the test data under different stress states. In view of the fact that the GTN model cannot reflect the strain rate effect, the yield stress is introduced into the strain rate term to modify its hardening stage; in addition, the relationships among \({f}_{c}\),\({f}_{F}\) and the strain rate are established to modify its fracture stage. The modified GTN model can accurately predict the plastic and fracture features of 6061-T5 aluminum alloy at different strain rates. Finally, the modified GTN damage model is programmed as a UMAT in LS-DYNA for simulation analysis. The results of the simulation and the test agree with each other very well, proving the superior reliability of the UMAT.