Accounting Bauschinger effect in the numerical simulation of constrained groove pressing process

Abstract

Constrained groove pressing (CGP) is one of the severe plastic deformation techniques to achieve ultrafine grains in bulk sheet metals. The CGP process induces large plastic strain through incremental steps of shear and reverse shear using grooved and flat dies. The equivalent plastic strain distribution during CGP process can be correlated to the extent of grain refinement and the uniformity of ultrafine grains. The numerical analysis in the past have assumed isotropic hardening to model CGP process that does not consider the Bauschinger effect due to continuous change in deformation path between subsequent stages. In the present work, the effect of Bauschinger effect is considered using a combined isotropic-kinematic hardening model in simulation. The finite element model assuming isotropic hardening is validated with the results available in literature. Experiments on CGP were performed using three different materials and were modelled using both isotropic and combined hardening models. The maximum strain and the strain inhomogeneity predicted using combined hardening models were consistently greater than the isotropic hardening assumption.