Large-strain hardening curves corrected for texture development

Abstract

The paper is concerned with the problem of constructing equivalent stress-equivalent strain curves at large strains. For the equivalent strain, the average accumulated crystallographic shear is used, while for the equivalent stress, the resolved shear stress is employed. The latter is obtained from the work conjugacy condition. In such a construction of the hardening curve, the Taylor factor appears to be the major factor that can be calculated from polycrystal deformation texture models. In this paper, the viscoplastic Taylor and self-consistent approaches are employed to calculate the Taylor factors. The self-consistent model was calibrated on the torsion texture development which is the most sensitive to the polycrystal model parameters at large strains. The obtained Taylor factors show important variations in torsion, compression and rolling. They have been used to convert experimentally measured work hardening data on copper into resolved shear stress-resolved shear strain curves. The effect of the Taylor factor on the absolute hardening rate was found to be significant at a large strain range of deformation. The simulation textures were markedly different from the measured textures at very large strains where both polycrystal texture deformation models fail to predict the correct texture evolution. For this reason, the textures were measured at increasing strains at 11 points in rolling, at 12 points in compression and at four points in torsion from where the Taylor factors were calculated by both of the models in order to construct the equivalent stress-equivalent strain curves.