Dissimilar lightweight materials can reliably be connected by self-piercing riveting (SPR) in automotive manufacturing. In this work, the axisymmetric finite element model for formability analysis of dissimilar SPR joint of the B1500HS ultra-high strength steel/AA5052 aluminum alloy was developed and validated by experiments. The effects of design shape and dimensions of the rivet and die (rivet height, rivet hardness, die type, die groove diameter, die groove depth, and die pip height) on the formability characteristics of SPR joint were analyzed in detail. The results revealed that the undercut and effective thickness increase distinctly with the rivet height, while the remaining thickness and rivet head height decrease. The rivet hardness has an insignificant effect on the undercut, and the influence of rivet hardness on the other SPR quality indexes is similar to that of rivet height. The die type and dimensions has a prominent influence on the distribution of the bottom sheet and the forming quality indexes. The variation of rivet spread is directly related to the material flow of the sheets and the filling condition of cavities between the bottom sheet and the die. Before the cavity underneath the rivet tube was fully filled the rivet spread increases gently, and once the cavity underneath the rivet wall was fully filled the rivet spread presents a sharp increase. The tensile property of the SPR joint was significantly affected by rivet height, while the rivet hardness and die type have relatively smaller influence on the tensile property.
