Process metallurgy analyses for high bendability and springback property sheet design by using multi-scale finite element method

In this study, we develop bendability and springback prediction analysis code for an optimum crystal texture design scheme to generate ideal aluminum alloy sheet through the sheet rolling and heat treatment processes. To predict the relationships between the sheet metal formability and the crystal texture, we applied our multi-scale finite element (FE) procedure based on the crystallographic homogenization method for the bending process analyses. Our code employed two-scale method, such as the microscopic polycrystal structure and the macroscopic elastic plastic continuum by introducing the effect of crystal orientation distribution. It means that our code can predict the plastic deformation of sheet metal in the macro-scale, and the crystal texture evolutions in the micro-scale. Furthermore, we designed the polycrystal texture by asymmetric rolling (ASR) and annealing heat treatment processes to generate high bendability and low springback polycrystal material. Annealing heat treatment was modeled as the growth of Cube {001} orientation based on the Johnson-Mehl-Avrami’s equation. The design parameters, ASR ratio and annealing heat treatment time, were optimized by using a discrete multi-objective optimization algorithm to maximize the bendability and to minimize the springback angle. As the optimized result, the ASR ratio 1.16 and the annealing heat treatment time 13.5min were obtained.