Fatigue response of electromagnetic riveted joints with different rivet dies subjected to pull-out loading

Electromagnetic riveting (EMR) as a green manufacturing and efficient process has extensive application prospect in engineering fields. In this study, the fatigue properties of electromagnetic riveted joints with different rivet dies under pull-out loading were studied. The results showed that rivet dies had a significant effect on the pull-out fatigue performance. The pull-out fatigue life of the electromagnetic riveted joints with special dies was higher than that with the flat die. The reason was that the special rivet dies restricted the radial flow of the material in driven head. More material flowed into the riveted hole and rivet shaft became larger. The joints were reinforced by larger interference fit. Particularly, the joints with 80 degrees rivet die had the best pull-out fatigue properties due to more uniform and moderate interference fit. Fracture analysis showed that there were two typical failure modes for the joints under pull-out loading: rivet manufactured head and upper sheet fracture. Due to the effect of cyclic impact and fretting wear damage, the joints with a flat die at high stress levels (194.8 MPa and 173.2 MPa) failed in rivet manufactured head, while the joints with special dies at all stress levels and with a flat die at low stress levels (151.5 MPa and 129.87 MPa) failed in upper sheet.