An investigation of springback scatter in forming ultra-thin metal-sheet channel parts using crystal plasticity FE analysis

Springback is a difficult problem to solve in sheet-metal forming. It is more difficult in the forming of ultra-thin metal sheet (UTMS) parts. This is not only due to the lesser plastic deformation in the pure bending of UTMS but also due to their variations in microstructure. This research concentrates mainly on the understanding of the effects of grains, their sizes, and distributions on the amount of springback and to identify at which conditions the crystal plasticity finite element (CPFE) modeling technique has to be used for the process simulation. A simplified 2D FE analysis coupled with a crystal viscoplasticity model has been used in this study. Grains, their distributions, and their orientations are generated automatically based on probability theories using the developed VGRAIN system. For the same control parameters, average, maximum, minimum grain sizes, and distribution patterns were in either regular or non-regular distribution. Four microstructures of the UTMS are generated based on the gamma distribution. Up to six grain orientations are assigned randomly to each grain structure. Thus, a large number of FE analyses have been carried out based on the variation of grain structures and orientations. These are used to investigate the effect of grain size and orientation on the scatter of springback values in the forming of UTMS channel parts.