Experimental determination and numerical prediction of the dynamic forming limits of a press hardened steel

Abstract

Material characteristics such as yield strength, failure strain, strain hardening and strain rate sensitivity parameter are affected by loading speed. Therefore, the strain rate dependency of materials for plasticity and failure behavior is taken into account in crash simulations. Moreover, a possibility for consideration of instability at multi-axial dynamic loadings in crash simulations is the use of dynamic forming limit curves (FLC). In this study, the dynamic FLC of the press hardened automotive steel Usibor 1500 (AlSi coated 22MnB5) is investigated. The experimental results are obtained from a unique high-speed Nakajima setup. Two models are used for the numerical prediction. One is the numerical algorithm CRACH as part of the modular material and failure model MF GenYld+CrachFEM 4.2. Furthermore, the extended modified maximum force criterion considering the strain rate effect is also used to predict the dynamic FLC. The comparison of the experimental and numerical results are presented and discussed.