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Tailor welded blanks offer an excellent opportunity to reduce manufacturing costs, decrease vehicle weight, and improve the quality of sheet metal stampings. However, tearing near the weld seam is a concern in Tailor Welded Blanks due to material changes in the fusion and heat affected zones of the weld. Therefore, data is required such as the potential strain of the material in these areas to use in the process design. For example, Cao and Kinsey proposed a modification to the deep drawing process where segmented dies with local adaptive controllers clamp adjacent to the weld line during the forming operation thereby reducing the strain in the material near the weld seam and in turn the concern of tearing failure. In order to aid in the design process for this modification, an understanding of the effects of the welding process on material changes near the weld seam is essential.

In order to effectively design sheet metal components using numerical simulations, an accurate means to predict tearing concerns is necessary. Currently, a strain based failure criterion is used to predict this type of failure in the automotive and aerospace industries. However, due to the strain path dependence of the strain based Forming Limit Diagram, accurate prediction is only possible for forming cases which possess a single linear strain path. Alternatively, a stress based failure criterion has been proposed and demonstrated analytically, experimentally in tube forming, and through numerical simulations. In this paper, further support for the stress based failure criterion is provided by demonstrating that the saturation of the stress level during plastic deformation is not the cause of the convergence of various strain based Forming Limit Curves to a single curve in stress space.

Tailor welded blanks offer a unique opportunity to reduce manufacturing costs, decrease vehicle weight, and improve the quality of stampings through the consolidation of multiple formed, then welded, parts into a single stamping. However, tearing near the weld line often occurs in this type of blank when formed with a traditional deep drawing process. Therefore, some adaptation to the existing sheet metal forming process must be developed in order to reap the numerous benefits available from tailor welded blanks. In this paper, numerical simulation are presented for a newly contrived tailor welded blank forming process where several hydraulic mechanisms apply distinct clamping forces along the weld line during forming. Excellent results demonstrate the effectiveness of the proposed method.