Constitutive equations for twinning and slip in low-stacking-fault-energy metals: a crystal plasticity-type model for moderate strains

In the present paper, we propose an alternative description of twin-slip interactions by a crystal plasticity framework. Our analysis is limited to moderate strains occurring in many practical situations in metal-forming processes. Contrary to the previous models, we pay particular attention to the typical morphology developed during twinning within a single crystal. As a result and with the help of kinematic hypotheses, a distinction is made between the flow rules for twinning and slip by involving the appropriate couplings between the two inelastic mechanisms. Following a classical methodology, the constitutive equation of a single crystal is derived from the definition of the resolved and critical shear stresses related to slip and twinning. A self-consistent scheme is performed to account for the statistical disorder of a polycrystalline material. By direct comparisons with experimental measurements, the model reproduces correctly the principal features of low-stacking-fault-energy fcc metals.