Characterization and Modeling of Anisotropy in Plastic Deformation and Damage of Titanium Materials

Abstract. At room temperature, titanium materials display deformation and failure properties that are quite different from that of typical materials with cubic crystalline structure (aluminium, steels, etc). Rolled or extruded products exhibit a strong anisotropy and very pronounced difference in yielding and work-hardening evolution between tension and compression loadings. In this paper, a macroscopic elastic/plastic model that accounts for the key features of the plastic deformation of Ti, in particular the distortion of the yield surface induced by texture evolution is presented. Comparison with data demonstrates that the model predicts with accuracy the plastic response for a variety of loading conditions. Furthermore, it is shown that the model can be extended such as to incorporate damage. In contrast to existing approaches, the plasticity-damage couplings are deduced and not postulated. Hence, all material parameters have a clear physical significance, being related to plastic properties that can be determined from few simple mechanical tests. The new model predicts that in titanium materials damage accumulation is strongly influenced by the anisotropy and asymmetry in plastic flow. Moreover, it is shown that under uniaxial tension, the porosity evolution should be much slower than in materials with plastic flow obeying the classical von Mises criterion, and that the succession of damage events leading to failure should also be markedly different.