Finite polycrystalline elastoplasticity and damage: multiscale kinematics

A physically realistic macroscopic decomposition of the deformation gradient for metallic polycrystals should explicitly account for all relevant sub-macroscopic kinematic processes, including lattice deformation, plastic flow, and evolution of damage, that significantly contribute to the homogenized deformation at the macroscale. The present work suggests such a decomposition, based on principles of volume averaging and focusing upon elastoplasticity and a variety of damage modes including intergranular fracture, void growth and coalescence, and shear discontinuities. This decomposition, of hybrid additive–multiplicative form, captures precisely the kinematics of arbitrarily anisotropic damage and also offers insight into mesoscopic distributions of residual elastic lattice strain attributed to heterogeneity of local deformation occurring at both intergranular and intragranular scales.