Material characterization and constitutive modelling of ductile high strength steel for a wide range of strain rates

This paper presents results of a research program in progress to describe the behaviour of 35NiCrMoV109 high strength steel over a wide range of strain rates for numerical simulations of dynamic events. In the low strain rate regime tensile tests in combination with a numerical stress state correction in terms of necking have been carried out. In comparison to the common Bridgeman-analysis this procedure allows to determine reliable necking-corrected stress-strain curves in a shorter time with a high accuracy as well. These data have been linked to high strain rate data from a novel modified Taylor-impact test using VISAR technique and data from planar-plate-impact-tests. The yield-stress strain-rate dependency covering a strain rate range of 11 orders of magnitude (5 x 10(-5)-1.78 x 10(6) s(-1)) have been measured. A bee --> hcp phase transition could be observed at pressures exceeding 13 GPa. A phenomenological material model including a strength model and an equation of state has been developed. The validation of the material model has been performed by numerical simulations of the modified Taylor-impact tests and the planar-impact-tests. In addition to common analysis by comparison of sample deformation, an enhanced model validation has been made by comparing the measured and calculated VISAR-signals while this technique is normally used for plate impact-test only. Agreement between the numerical simulations and the experimental results is found for the comparison of the deformation and the characteristic profile of the VISAR-curves. (C) 2004 Elsevier Ltd. All rights reserved.