Analysis of joint formation mechanisms for self-piercing riveting (SPR) process with varying joining parameters

By combining experimental SPR tests with a finite element (FE) model, the influences of top sheet thickness (Tt), bottom sheet thickness (Tb) and rivet length (L) on the joint formation mechanisms were systematically investigated in this study. Single factor experiments were firstly conducted to uncover the three joining parameters’ effects on the joining results. Interrupted SPR tests were also performed to confirm the prediction accuracy of the FE model on the joint formation process. Then, the joint formation mechanisms were analyzed by numerically inspecting the events during the riveting process, including the sheet deformation behaviours, rivet shank flare behaviour and formation of quality indicators. The results revealed that the joining parameters affected the interlock formation by directly altering the positions of two interlock boundaries. The rivet shank flare behaviour was apparently affected by the Tt and Tb, but less influenced by the L. The formation of remaining bottom sheet thickness at the joint centre (Tc) was significantly affected by the Tt and Tb. Rapid reduction of the Tc occurred before the top sheet was penetrated and after the rivet cavity was fully filled. Meanwhile, it is highlighted that the FE model is an excellent tool to analyse SPR joint formation