Identification technique of constitutive model parameters for crashworthiness modelling

This paper deals with a parametric identification technique, based on the conjugate gradient methods. As part of this research, compression tests are performed on a XC48 steel (AFNOR norm 1048AISI), which is strain rate sensitive. Two kinds of specimens, tubular and cylindrical "dumbbell", are tested at different strain rates, from 10(-3) to 130 s(-1) and for impact velocities ranging from 5 mm/min to 6 m/s. The parameters of the Johnson-Cook constitutive model are evaluated directly from the XC48 steel compression stress-strain diagrams expressed in terms of true stress and strain measurements. These parameters are next used as input data for a FE crash simulation of the tubular specimen. Comparison with experimental results prove the validity of the identified parameters. (C) Elsevier, Paris.