Numerical optimization of blank shape and sloped variable blank holder force trajectory for an automotive part

Abstract

Sheet metal forming is one of the important manufacturing technologies to produce metal parts. Tearing and wrinkling are major defects in sheet metal forming, and they should strongly be prevented for the high product quality. A constant blank holder force (BHF) is conventionally used for successful forming, but the variable blank holder force (VBHF) that the BHF varies during the forming process has attracted attention and has been recognized as one of the advanced manufacturing technologies. However, it is difficult to determine the VBHF trajectory for successful sheet forming without defects. In other words, a trial-and-error method is so widely used to determine the VBHF trajectory. In addition, blank shape also affects the product quality. In this paper, the blank shape and the sloped VBHF trajectory are optimized simultaneously. To determine them, a multi-objective optimization is performed. Numerical simulation in sheet metal forming is so intensive that sequential approximate optimization is adopted to determine them, and the Pareto-frontier is then identified. An automotive part provided from NUMISHEET2011 (BM3) is selected for the application of the proposed approach. The optimal blank shape and the optimal sloped VBHF trajectory is determined through the numerical simulation. It is found from the numerical result that the optimal blank shape minimizing earing without tearing and wrinkling can be obtained.