Identification technique of constitutive model parameters for crashworthiness modelling

This paper deals with a parametric identification technique, based on the c onjugate gradient methods. As part of this research, compression tests are performed on a XC48 steel (AFNOR norm 1048AISI), which is strain rate sensi tive. Two kinds of specimens, tubular and cylindrical "dumbbell", are teste d at different strain rates, from 10(-3) to 130 s(-1) and for impact veloci ties ranging from 5 mm/min to 6 m/s. The parameters of the Johnson-Cook con stitutive model are evaluated directly from the XC48 steel compression stre ss-strain diagrams expressed in terms of true stress and strain measurement s. These parameters are next used as input data for a FE crash simulation o f the tubular specimen. Comparison with experimental results prove the vali dity of the identified parameters. (C) Elsevier, Paris.