A comparative study on self-piercing riveting and pre-holed self-piercing riveting of high-strength steel and aluminum alloy

High-strength steel materials play a crucial role in improving automotive crash safety and reducing vehicle weight. However, the high hardness and strength characteristics of high-strength steel make it challenging to be joined by the conventional self-piercing riveting (C-SPR) process. In this study, the C-SPR and pre-holed self-piercing riveting (PH-SPR) processes are employed to join high-strength steel DP590 and aluminum alloy AlSi10MnMg-T7 sheets. The forming quality, microstructure, mechanical properties, and failure behavior of the PH-SPR joint are investigated and compared with the C-SPR joint. The effects of rivet strength, rivet length, sheet thickness, and sheet material on the forming quality of the two types of joints are compared systematically and numerically. The results show that the forming quality of the PH-SPR is sensitive to rivet parameters while not to the material of the top sheet. The rivet with lower strength and larger length can improve the forming quality of PH-SPR joints. the PH-SPR process reduces the riveting force and energy consumption by 12.1% and 46.3%, respectively, compared with the C-SPR process. The presence of the top steel sheet in C-SPR joint brings an increasing hardness of both the rivet leg and aluminum sheet during the riveting process. The mechanical responses of the PH-SPR joint are superior to those of the C-SPR joint. Specifically, the peak force of the C-SPR joint is 4.8% lower than that of the PH-SPR joint, while the energy absorption of the PH-SPR joint is 3.18 times higher than that of the C-SPR joint.