Investigation of self-pierce riveting (SPR) process data and specific joining events

This paper describes a methodical study of the self-piercing riveting (SPR) process. The force-displacement curve is typically used in most investigations of SPR, but in this study, additional SPR process data are examined in details. Specifically, the characteristic pressure-displacement, displacement-time, force-pressure as well as force-displacement curves are analysed and correlated with cross-sections of interrupted joints obtained at different positions to determine the key different physical events that occur during SPR joining. The study shows that it is possible to identify the exact point when the rivet starts piercing the top sheet, finishes piercing the top sheet and starts flaring in the bottom sheet. It was found that all of the characteristic curves can be segmented into three distinctive stages (bending, piercing and flaring). However, the die filling event which is embedded within the piercing stage can be identified only by examining the pressure-displacement and force-displacement curves. This study also shows that it is possible to identify when the bottom sheet touches the die bottom surface.