High speed circular hemming; a novel joining process for thin and low- ductile sheets

摘要

A new joining process, named high speed circular hemming (HSCH) is presented. The metal sheet is positioned on a pressure chamber and austenitized. The electrical energy stored in a pulse generator is suddenly discharged between the electrodes submerged in a fluid such as water and initiated a shock wave in the fluid. The shock wave propagates through the fluid and forms the austenitized sheets to the die cavity and creates a joint between them. The joining process is performed within a few microseconds without any phase transformation in the sheet during forming. Immediately after forming, the joint area directly quenches by the water and takes a martensitic microstructure with high strength. To investigate the capabilities of the presented method, the HSCH process was applied for the joining of 0.5 mm thickness AISI1070/AISI1070 and AISI1070/AA3105 sheets. The metallurgical and mechanical properties of the joints were investigated by optical microscopy, shear test, and peel test. According to the accomplished results, the utilization of this joining process increases the shear strength and energy absorption capacity of the joint.