Study of the die design’s effects on self-piercing riveting of joint quality of aluminum and high-strength steel sheets

The research objective of this study is to enhance joint integrity and expand the design window of self-piercing riveting (SPR) process parameters for dissimilar joints between high-strength steel and Aluminum sheets, materials widely used in the automotive industry to achieve lightweight yet structurally sound assemblies. The methodology combines experimental trials and numerical simulations. A finite element model was developed using Qform to simulate the SPR process, reducing experimental costs while maintaining accuracy. The model was validated through cross-sectional analysis and tensile testing. Experimentally, various sheet thickness combinations and ten die geometries were examined. Key joint quality indicators—interlock and remaining bottom thickness—were precisely measured using Wire Electrical Discharge Machining (WEDM). Key findings demonstrate a significant enhancement in joint performance, with a maximum interlock of 0.72 mm and a remaining bottom thickness of 0.85 mm, both of which exceed previously reported values. The highest shear strength, 9872 N, was achieved using a 2.0 mm steel top sheet, a 1.2 mm Aluminum bottom sheet, and a 1.6 mm die depth (Die 8). The SPR processing window was substantially expanded: the d R /( t t + d d ) ratio increased from 0.95–1.05 to 0.75–1.35, and the t R / t t ratio from 0.2–0.28 to 0.28–0.6. The significance of this work lies in its contribution to a deeper understanding of SPR joint mechanics in dissimilar materials and in providing strength-based design charts that support faster, more reliable material and die selection in industrial applications.