Influence of local surface texture by tool impression on the self-piercing riveting process and the static lap shear strength

Abstract

To increase fuel efficiency and reduce emission, aluminium alloys have been increasingly used in automotive body-in-white structures for lightweighting. Due to its advantages over some of the more traditional joining technologies, self-piercing riveting (SPR) has been widely used for these lightweight structures. Research has showed that friction is a very important factor that influences both the riveting process and joint strength for SPR, but these influences have not been fully understood. In this paper, an innovative method was used to modify the local surface of the top sheet around the rivet piercing location with different impression tools (the central pin, the small ring, the medium ring and the large ring) and garnet particles to study the influence of local frictions on rivet inserting process, joint features and static lap shear strength. The results showed that the local surface textures on the aluminium sheet did not have significant influence on the rivet inserting process based on displacement-force curve analysis. The local surface textures could slightly change the joint features, especially the rivet head height, but overall this influence was not significant. The lap shear tests showed that ring impressions with garnet particles and central pin impressions on the bottom surface of the top sheet increased the static lap shear strength of the SPR joints. The results confirmed that the critical location for local friction influence on the lap shear strength was around the rivet leg piercing location.