Forming Qualities and Mechanical Properties of AA5052 Aluminum Alloy Self-piercing Riveted Joints Connected by Tubular and Semi-tubular Rivets

As a plastic deformation connection technology, self-piercing riveting (SPR) has wide applications in the reliable joining of lightweight alloy sheets in the automotive industry. The deformation behavior and mechanical property of SPR structure are significantly dependent on the geometric structure and dimension of rivets. In this paper, the three-layer AA5052 aluminum alloy SPR samples are fabricated with tubular rivets and semi-tubular rivets of different heights. The forming qualities as well as mechanical properties of SPR samples under different joint configurations are characterized using cross-section parameters, and tensile and axial tension-tension fatigue tests. The joint failure modes of the SPR samples under tensile and cyclic loads are also investigated. The results evidence that as the rivet height increases, the undercut and the rivet spread are increased, while the remaining bottom thickness is decreased. High-strength AA5052 aluminum alloy SPR joints can be obtained using the tubular rivet. The tensile strengths of SPR samples with 8 and 9 mm height tubular rivets are superior to the semi-tubular rivet joints, and the optimal tensile strength can be obtained using the 9 mm tubular rivet. The tensile failures of the three-layer AA5052 sheet SPR samples are the complete detachment of rivet tails from the bottom sheets. The fatigue life of the tubular rivet joints increases with the increased rivet height. The formation of macroscopic cracks in the bottom sheet is the main fatigue failure mode of the joints, and the macroscopic cracks are generated in the fretting wear areas between the rivet foot and sheets.