Abstract:The grain statistics effect was investigated through asymmetric rolling of pure copper foil by a realistic polycrystalline aggregates model and crystal plasticity element finite model. A polycrystalline aggregate model was generated and a crystal plasticity-based finite element model was developed for each grain and the specimen as a whole. The crystal plasticity model itself is rate dependent and accounts for local dissipative hardening effects and the original orientation of each grain was generated based on the orientation distribution function (ODF). The deformation behaviors, including inhomogeneous material flow, decrease of contact press and roll force with the increase of grain size for the constant size of specimens, were studied. It is revealed that when the specimens are composed of only a few grains across thickness, the grains with different sizes, shapes and orientations are unevenly distributed in the specimen and each grain plays a significant role in micro-scale plastic deformation and leads to inhomogeneous deformation and the scatter of experimental and simulation results. The slip system activity was examined and the predicted results are consistent with the surface layer model. The slip band is strictly influenced by the misorientation of neighbor grain with consideration of slip system activity. Furthermore, it is found that the decrease of roll force and the most active of slip system in surface grains are caused by the increase of free surface grain effect when the grain size is increased. The results of the physical experiment and simulation provide a basic understanding of micro-scaled plastic deformation behavior in asymmetric foil rolling.

Key words: foil rolling; grain heterogeneity; crystal plasticity; finite element; deformation behavior