Formability and Dynamic Energy Absorption of Tailored Blank with High Strength Steel Sheets

Both the laser welding and the mash seam welding are prevailing welding methods in tailored blanks. In applying these methods to the tailored blanks, however, the forming limits of welded sheets of DP and TRIP steels, which show fairly good formability in high strength steels with the tensile strength of 590MPa, are sometimes found to be lower than those of non-welded sheets of DP and TRIP steels depending on welding methods and sheet thickness. In the high speed deformation, dynamic absorbed energy for the welded sheet of DP steel is remarkably lowered as compared with that for the welded sheet of TRIP steel, and it is also found that forming limit is strongly affected by the sheet thickness ratio, and the absorbed energy is larger in the case of laser welding than that in the case of mash seam welding. These results clearly show that careful selection of steel, welding methods and sheet thickness ratio are important to get the desired shapes and characteristics in the tailored blank parts. Furthermore, experimentally derived data for tailored blank in the present research may help to improve the accuracy of the analyses in CAE and/or numerical simulations.