Study on the hot stamping simulation and experiment of A-pillar patchwork blanks

Hot stamping patchwork blanks technology can flexibly adjust the mechanical properties by designing different thicknesses and profiles of the main blank and the patched blank. Due to the spot welding connection between the main blank and the patched blank, the material flow between them is uneven and crack defects easily occur. To investigate the influence of the forming parameters, especially welding spot arrangement, on the formability, a high-temperature welding spot failure damage model was established through high-temperature tensile shear and cross-tension experiments. Subsequently, the thermal–mechanical coupling finite element model (FEM) of A-pillar patchwork blanks in hot stamping process was established. The results indicated that the strength of the welding spots satisfied the forming requirements, and the forming defects were mainly caused by the excessive thinning of the base material around the local welding spots. By analyzing the causes of the cracking and then optimizing the welding spot arrangement, the thinning rate of the base material around the welding spot decreased from 33% to less than 12%. The thickness distribution of different sections was compared with the simulated and the experimental results and the error was less than 10%.