With the rapid development of lightweight automobiles, the clinching joint technology of ultra-high-strength steel with aluminum alloy sheets have been paid more and more attention. However, due to significant differences in plastic deformation capabilities between the two metals, particularly the difficulty of steel sheet deformation, conventional clinching processes often result in insufficient joint interlocking or fracture issues. Although the preliminary use of clinching processes with preforming methods has shown some effectiveness in connecting two types of sheets, the bond strength is not high. This study employs finite element simulation and orthogonal optimization methods to investigate the impact of relevant process parameters on joint morphology in clinching processes with preforming. Under the condition of optimizing process parameters, a clinching punch with an added pressure-step structure was proposed to compact the joint and further enhance joint quality. Experimental verification demonstrates the feasibility of the improved clinching processes with preforming for bonding ultra-high-strength steel and aluminum alloy sheets.

In recent years, with the rapid advancement of automotive lightweight technology, the mechanical clinching process between aluminum alloy and ultra-high-strength steel sheets has received extensive attention. However, the low ductility of ultra-high-strength steel sheets often results in conventional mechanical clinching processes producing joints that either fail to establish effective interlocks or cause the steel sheets to fracture. To address this issue, a novel mechanical clinching process is presented, called center-punching mechanical clinching (CPMC). This innovative process employs a method of punching, flanging, and bulging gradation to achieve the mechanical clinching of aluminum alloy and ultra-high-strength steel sheets in a single step. In order to determine the effects of different parameters on the quality and strength of the joint, an experimental study was carried out for various die depths and diameters based on the condition of constant punch size. Based on tensile and shear tests, the static strength and failure modes of CPMC joints were analyzed. The results indicated that the CPMC process significantly enhances the connectivity of joints for AA5052 aluminum alloy and DP980 ultra-high-strength steel. Optimal tensile and shear strengths of 1264 and 2249 N, respectively, were achieved at a die depth of 2.2 mm and a diameter of 10.4 mm. The CPMC process provides new ideas for the mechanical clinching of aluminum alloy and ultra-high-strength steels.

As research on new, lightweight energy vehicles continues to develop, the application of high-strength steel sheets with tensile strength greater than 1 GPa and their mechanical clinching technology, which is associated with aluminum alloys, has emerged as a new research focus. However, due to the challenges associated with the cold deformation of high-strength steel, conventional mechanical clinching processes often fail to establish effective joint interlocking, resulting in weak connections. This study proposes a center-punching mechanical clinching process for connecting DP980 high-strength steel to AL5052 aluminum alloy. The mechanical evolution during the forming process was analyzed via finite element simulation. An orthogonal experimental design was employed to optimize key geometric parameters of the punch and die, yielding the optimal configuration for the mold. Mechanical testing of the joint demonstrated average pull-out force and pull-shear forces of 1124 N and 2179 N, respectively, confirming the proposed process’s ability to successfully connect high-strength steel and aluminum alloy.