Modified Johnson-Cook model for vehicle body crashworthiness simulation

Dynamic response prediction of vehicle bodies is important for vehicle cras hworthiness evaluation. The dynamic behaviour of vehicle body materials is dependent on material strain rates. One of the typical high strain rate ten sile tests is the split Hopkinson bar test. In this paper, experiments have been conducted based on a new split Hopkinson bar apparatus specially desi gned for the dynamic tensile test of sheet metals. Results from both quasis tatic and dynamic tests show that the strain rate hardening effect for shee t metals cannot be described by the original Johnson-Cook constitutive rela tion. This relation has been modified to include a higher-order term for th e hardening effect. The modified constitutive relation represents a more ac curate simulation than the original model for the dynamic behaviour of vehi cle body structures.