Virtual tryout of stretch flange type parts in tailored blank stamping

In the forming of TB (Tailored Blank) side outer panel, splits frequently occur in the stretch flange areas. Most splits in these areas are categorized as two different types - one at the end of weldline in blank corner due to the local concentration of deformation on thinner or weaker material resulting from different material gauges or strengths and the other at the die corner due to the lack of draw-in of blank during stamping. Therefore, the proper design of blank shape, weldline placement and drawbead in the stretch flange area is crucial for the successful forming of TB side outer panel. In this paper, the design practice of TB stretch flange forming was investigated. The effects of the selected design parameters such a blank corner radius, weldline position and drawbead restraint forces were examined separately and the optimal TB stretch flange design was examined with respect to the several design parameters. The orthogonal array experiment plan was adopted for the optimization of TB stretch flange forming. CAE was used for the experiments and the forming analyses were done with the incremental explicit FEM code. The results are promising, i.e., the virtual tryout reproduces the tendency observed in real TB panel tryout good enough.