3502 絞り比向上を目的とした振動ブランクホルダー力の最適軌道設計(OS3-8 設計と最適化VIII)

Abstract

Wrinkling and tearing are major defects in deep drawing, and blank holder force (BHF) plays an important role for the successful sheet forming. Variable blank holder force (VBHF) that the BHF varies through the punch stroke is useful for prevent these defects. On the other hand, the pulsing blank holder force (PBHF) is an attractive approach for the successful sheet forming. In this paper, both the VBHF and the PBHF trajectory are optimized, the formability window (FW) that represent the relationship between the BHF and the punch stroke is clarified. The identification of FW is one of the important issues to difficult-to-draw material. A design optimization problem is constructed to identify the FW and improve the limit drawing ratio (LDR). The object function is taken as the punch stroke. Several parameters in the VBHF and the PBHF are considered as the design variables. Numerical simulation in sheet metal forming is so numerically intensive that a sequential approximate optimization using a radical basis function network is used. In the numerical simulation, deep drawing of a cylindrical cup based on NUMISHEET2011 (BM1) is used. It is found from the numerical result that the proposed approach is useful for identifying the FW of a difficult-to-draw material. In addition, the optimum PBHF can reduce the maximum punch load that affects the tool life.