Abstract

Tailor-welded blanks (TWB) are widely used for stamped auto panels because of their great benefits such as weight and cost reduction. However, the weld line in a tailor-welded blank causes serious concerns in formability because it induces material discontinuity and additional inhomogeneous stress/strain distribution. This paper proposes a blank holding force (BHF) control strategy to control the weld line movement, distribute the deformation more uniformly and improve TWB formability. The control methodology is developed based on a simplified 2-D sectional analytical model that estimates the stress/strain distribution and the required BHFs for each side of flange with dissimilar materials. The model can be further extended to 3-D by superimposing the 2-D sectional analysis results around the entire binder ring and thus determining required BHF for the whole panel. Finite element simulations are performed to study the effects of forming parameters on the weld line movement. Experiments have been conducted to verify the analytical model and partial finite element simulations. Both analysis and experiments demonstrated that a lower BHF should be applied on the thicker blank side to allow more metal to flow in for obtaining more uniform strain distribution. The proposed BHF control is proven to be a good solution to enhance TWB formability.

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