Determination and modeling of dynamic characteristics of automotive sheet metals for FE crash simulations

Vehicle crashes subject automotive sheet metals to multiaxial deformation and fracture across strain rates from 0.0001/s to 1000/s. This thesis examines the comprehensive effects of stress state, strain rate, and temperature on the yielding, hardening, damage, and fracture of H340 and DP1000 steels. High-speed tensile tests were conducted on specially designed specimens, eliminating system ringing and enabling accurate force measurements at strain rates exceeding 1000/s. Tests covered material orientations (0°, 45°, 90°) and temperatures (-30°C-280°C), tracking strain fields via DIC technique and capturing specimen temperature changes with thermal imaging. A new yield model, referred to as the YldSRH model, accounting for non-uniform strain rate hardening, was coupled with a strain-rate and temperature-dependent damage mechanics model (e²MBW) to predict anisotropic plasticity and fracture behavior of H340 and DP1000 under different loading conditions. The coupled YldSRH+e²MBW model was validated through experimental and FE simulation comparisons, offering enhanced accuracy for crash modeling.