Hot stamping of patchwork blanks: modelling and experimental investigation

Hot stamping of patchwork blanks is flexible to adjust the mechanical properties of the component by applying patched blanks with different thicknesses and at different locations. Efficient process analysis needs a sophisticate finite element (FE) model for numerical simulation. A novel thermal–mechanical coupled FE model for hot stamping of patchwork blank was developed considering the thermal dependent failure of welding spots. The failure of the welding spots was evaluated by shear strength, which was characterized by tensile shear tests under different temperatures. Furthermore, the welding current and the arrangement of welding spots were determined to produce the patchwork blank. The locations and causes of forming defects, e.g. wrinkling and crack in hot stamping of a B-pillar with patchwork blanks, were analyzed. With numerical simulations and experimental investigations, the optimum process parameters were obtained. For predicting the thickness of typical sections and temperature distributions on the B-pillar for patchwork blank, the errors between numerical and experimental results were less than 10% in thickness distribution, and the maximum error was only 14.5% in temperature distribution. Experimental and simulation results show that the developed FE model is reliable and can be used to predict the results and improve the hot stamping process of patchwork blank.