Abstract
This paper presents novel U-bending setups in order to investigate the effects of the curvatures created on the punch, die, or both on the spring-back/spring-go of the two-layer aluminum/copper sheets. Comparison of the new U-bending setups with the regular ones showed that the curvatures had important roles in reducing the spring-back/spring-go in the U-bending process. The results further indicated the good agreement between spring-back/spring-go and finite element simulations. Moreover, through finite element simulations, the effects of three effective parameters on reducing the spring-back/spring-go, including the curvature radius (r) of the punch, the distance between curvature center and the fillet center (d) in the punch, and the curvature radius at the end of the die (R) were investigated. In achieving the desired state (90°), the results showed that the distance of curvature center from the fillet center (d) was a more important parameter compared with the curvature radius at the end of the punch (r) and the curvature radius at the end of the die (R). This paper also focuses on the thicknesses of copper and aluminum as well as the stacking sequence of layers. Concerning the thicknesses of the implemented copper and aluminum change, the minimum angle of the spring-back/spring-go relative to the desired state was 75% Al/25% Cu thickness. Furthermore, the spring-back of aluminum/copper was lower than the copper/aluminum layer sheet. The effects of both thickness changing and stacking sequence of aluminum/copper layers on the spring-back/spring-go amounts of different sheets were due to the relocation of the neutral axis.
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