Investigation of the Evolution of Plastic Anisotropy and Pile-up of Al Single Crystal in Nanoindentation Using Different Crystal Plasticity Models

The nanoindentation test is a widely adopted technique for characterizing the mechanical properties of materials. In this study, a dislocation density -based and a phenomenological crystal plasticity hardening model are employed to investigate the evolution of plastic anisotropy and pile-up of a single -crystal aluminum specimen with varying crystallographic orientations during nano -indentation. Utilizing crystal plasticity finite element (CPFE) simulations, we delve into the influence of crystal orientations on key factors such as depth -load curves, stress distributions, shear strains across different slip systems, and dislocation density evolution. Our analysis highlights the plasticity anisotropy inherent in the material, elucidated through the evolving shear strain exhibited by activated slip systems. Furthermore, we gain insights into the pileup phenomenon by examining the evolution of shear strains within slip systems and the associated dislocation density, employing various modeling approaches. The height of pile-up evolution is determined by the localized cumulative shear strains and evolution of dislocation density.