Modelling the strain rate dependent hardening of constructional steel using semi-empirical models

Abstract

The importance of modelling the strain rate dependent material behaviour increases since structural components more and more have to be designed against extreme events. With growing usage of numerical programmes, good models become necessary. The goal of the ongoing research project is to find reasonable models for simulations concerning steel constructions. This paper discusses various models to describe the strain rate dependent hardening of mild steel. In this context, high speed tensile tests were performed and evaluated. Four commonly used material models and a new model were introduced and calibrated to the test results: The Johnson-Cook model, a modified Johnson-Cook model by Huh and Kang, the Cowper-Symonds model and a combined Johnson-Cook/Cowper-Symonds model. These four models do not describe the observed behaviour of constructional steels satisfactorily. Unlike these models, a newly introduced model is able to describe both a yield plateau and the slope of the strain hardening, both as a function of the strain rate. The quality of the approximations is discussed and further investigated by performing notched bar tensile tests and simulations. Finally, recommendations are given on the basis that the modelling of a yield plateau and the negative strain rate sensitivity of the strain hardening is necessary for modelling structural components under extreme events.