The effect of crystallographic textures on the formability of high-strength steel sheets

Abstract

The effect of crystallographic textures on the formability of high-strength steel sheets was investigated by using the elastic/crystalline viscoplastic finite element (FE) analysis. First, the preferred orientations, which correlate with the plastic anisotropy, were revealed by orientation fibers, skeleton lines and selected orientations in Euler angle space. Secondly, the mechanical properties such as R-values, yield loci and stress–strain relationships, and drawability were evaluated by crystallographic numerical analyses and experiments. It was confirmed that one of the reasons why high-strength steel sheets show low formability was due to lack of γ texture components. Then, a textural design method was proposed for improving the formability of high-strength steel sheets. An artificial γ fiber texture was specified in terms of a rotationally symmetric Gaussian distribution of misorientations with scatter widths along the given skeleton line. Traces of the artificial γ texture orientations in terms of volume fractions were randomly selected and assigned to the original high-strength steel model by using the orientation probability assignment method. Finally, from the standard limit dome height (LDH) test, it was found that there was distinct improvement on formability for the new high-strength steel sheets even with a little proportion of γ texture components.