Reshaping, performance optimization and failure mechanisms of self-piercing riveted joints in 5083 aluminum alloys under axial compressive loads

Abstract

In consideration of the drawback of self-piercing riveting (SPR) technology, where the protruding bottom of SPR joint is highly susceptible to be squeezed in practical applications, which subsequently alters the internal forming structure and mechanical performances, the effects of axial compressive loads on SPR joints were investigated through a combination of experiments and numerical simulations systematically. The results indicated that the forming feature of the rivets and sheets could be accurately predicted by the FE model. The compression process may potentially promote the initiation of cracks within the rivet, and the remaining bottom would become a potential weak point in practical applications. The typical cross-sectional parameters were improved apparently with the compressive loads of 60 and 80 kN. The protruding joint bottom was strongly affected and the original coarse grains fined to fibrous structures, which resulted in further plastic deformation and work hardening on the rivet tail and bottom sheet. The compression process can effectively enhance the joint strength, but has a negative impact on the stability of the joint performance and complicates the failure modes. The rivet tail pulled out was the main failure mode for all the joints. The rivet head pulled out and rivet fracture could also occur due to the aggravation of forming defects under higher compressive loads.