Validation of constitutive models for experimental stress-strain relationship of high-strength steel sheets under uniaxial tension

Abstract

The constitutive relationship between stress and strain is one of the important issues in numerical simulation of metal forming. For steel, there are two kinds of constitutive models wildly used. One is power law like Ludwik and Swift. The other is saturation models like Voce and Hockett-Sherby. It is necessary to determine the most appropriate model and parameters for newly developed high strength steels. In order to describe the ultra-high strength dual phase and quenching and partitioning steels, uniaxial tensile tests with the aid of digital image correlation techniques were performed to analyse the strain field over the whole gauge section as well as the element close to the necking point. Through experimental data analysis and numerical fitting, the validity of different models have been confirmed. It shows that equation of Hockett-Sherby model has the best fitting accuracy and high strength steels require a model with more parameters. The extrapolated weighting coefficient of combined Swift and Hockett-Sherby models is characterized, which is proved to improve the accuracy of the numerical simulation of forming of ultra-high strength steels based on the conventional tensile tests.