Feasibility of measuring residual stress profile in different self-pierce riveted joints

The feasibility of measuring residual stresses in self-pierce riveted (SPR) joints by neutron diffraction technique was investigated. The main challenge involved dealing with the very small dimensions of SPR joints. Two different joints were examined: aluminium-steel and steel-steel. Even though small dimensions were involved, meaningful results were obtained. In the rivet head, tensile stress was observed for the steel-steel sample, whereas only compressive stress was observed for the aluminium-steel. The residual stress in the rivet head was higher at the centre and lower at the edge for both joints. Stresses in the sheet material beside the rivet wall and at a distance of three times the rivet radius from the rivet axis were not significant. For the SPR joints examined, the maximum value of residual stress was compressive and occurred in the rivet leg. The results are discussed according to the physical events involved during the process.