A simple but effective model for characterizing SPR joints in steel sheet

A simple and effective model has been developed to determine rivet flaring in self-piercing riveted (SPR) joints. Both interrupted and un-interrupted SPR experiments were performed with recording of force and punch displacement data. Based on the analysis of experimental SPR process data and the examination of cross-sections of SPR samples, two key points of the force–displacement curves were identified that mark the start (d0) and end (dmax) of rivet flaring, respectively. It was found that these two events were able to be related to the path of the tip of the flaring rivet and hence the internal characteristics of the SPR samples via a simplified geometric approach. A linear relationship between the rivet flaring and (dmax–d0) was thus established. The study shows that in the absence of a finite element model, the experimental characteristic force–displacement curve can be used directly to estimate the rivet flaring without having to cut the SPR joint.