Incorporation of deformation twinning in crystal plasticity models

A new constitutive framework, together with an efficient time-integration scheme, is presented for incorporating the crystallography of deformation twinning in polycrystal plasticity models. Previous approaches to this problem have required generation of new crystal orientations to reflect the orientations in the twinned regions or implementation of "volume fraction transfer" schemes, both of which require an update of the crystal orientations al the end of each time step in the simulation of the deformation process. In the present formulation, ail calculations are performed in a relaxed configuration in which the lattice orientation of the twinned and the untwinned regions are pre-defined based on the initial lattice orientation of the crystal. The validity of the proposed constitutive framework and the time-integration procedures has been demonstrated through comparisons of predicted rolling textures in low stacking fault energy fee metals and in hcp metals with the corresponding predictions from the earlier approaches as well as through qualitative comparisons with the measurements reported previously. (C) 1998 Elsevier Science Ltd. All rights reserved.