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.

Microstructural Parameters in Large Strain Deformed Ni Polycrystals as Investigated by Synchrotron Radiation

“…In order to allow for suitable comparison of measured quantities with the same deformation, the nominal strains from torsion as well as from rolling were recalculated into resolved shear strain values g. As concerns the torsion experiments, values of torsional shear strains g H have been transformed into g, by the strain dependent Taylor factor Mg being calculated in [26] by means of the Taylor model. In order to find g in the case of rolling, the Taylor factor has been calculated by the Taylor model, too, but with respect to the (200) orientation of measured grains.…”

Some Physical Characteristics of Strain Hardening in Severe Plastic Deformation

“…The texture differences in turn led to differences in the Taylor factors [37] associated with the three types of straining. The texture differences in turn led to differences in the Taylor factors [37] associated with the three types of straining.…”

“…textures developed. The texture differences in turn led to differences in the Taylor factors [37] associated with the three types of straining. Here the Taylor factor is the coefficient linking the macroscopic (equivalent) flow stress to the current value of the average flow stress in shear on the operative slip systems.…”