A new approach to the analysis of polycrystal plasticity

When a polycrystal is subjected to inelastic deformation, there inevitably exist residual microstress fields in a polycrystalline material due to its nonhomogeneous morphology. The energy stored in these microstress fields may partly be released and influence the material behavior during subsequent inelastic deformation. Correspondingly, a simple mechanical model is introduced to formulate the constitutive equation for a slip system and the hardening law for single crystal. The corresponding approach for the analysis of polycrystalline materials is obtained based on KBW's self-consistent theory. The proposed approach employs no yield criterion and the corresponding numerical analysis is greatly simplified because it involves no additional process for determination of the activation of slip systems and slip direction. A mixed averaging approach is used in polycrystalline plasticity analysis. The response of 316 stainless steel subjected to typical biaxial nonproportional plastic strain cycling is described and the validity of the proposed approach is demonstrated by the satisfactory agreement between the calculated result and experimental observation.