Effects of Residual Stresses on the Fatigue Lifetimes of Self-Piercing Riveted Joints of AZ31 Mg Alloy and Al5052 Al Alloy Sheets

Abstract

During the self-piercing riveting (SPR) process, residual stress develops due to the high plastic deformation of the sheet materials. In this study, the effect of the residual stress on the fatigue lifetime of SPR joints with dissimilar magnesium AZ31 alloy and aluminum Al5052 alloy sheets was evaluated. The residual stress distribution was derived through a simulation of the SPR process by the FEA (finite element analysis). The measured values by the X-ray diffraction technique confirmed that the validity of the simulation has a maximum error of 17.2% with the experimental results. The fatigue strength of the SPR joint was evaluated at various loading angles using tensile-shear and cross-shaped specimens. It was found that the compressive residual stresses of the joint reduce the stress amplitude by 13% at 106 cycles lifetime, resulting in extension of its lifetime to approximately 3.4 million cycles from 106 cycles lifetime. Finally, it was confirmed that the fatigue life of SPR joints was appropriately predicted within a factor of three using the relationship between the fatigue life and the equivalent stress intensity factor. The fatigue resistance of the magnesium AZ31 alloy on the upper sheet was found to govern fatigue lifetimes of SPR joints of dissimilar magnesium AZ31 alloy sheets.

Mechanical performance and failure modes of self-piercing riveted joints between AA6061 and solution-treated TC4 alloy

“…Zhang et al [23,24] reported the fatigue property, crack growth mechanism, and performance of TA1 self-piercing riveted joints. Lee et al [25] found that the fatigue life was related to the amplitude of stress, and the smaller the amplitude of stress, the longer the fatigue life. Presse et al [26] studied the fatigue life of different combination SPR joints according to the stress-life curve.…”

Performance analysis of similar and dissimilar self-piercing riveted joints in aluminum alloys

“…22 At present, the method of evaluating the quality of riveting is mainly used through the tolerance band method of the force-displacement curve. 23 However, the tolerance band formed by the upward and downward displacement of the qualified joint force-displacement reference curve is not only insensitive to lateral displacement, but also cannot monitor rivet offset, button cracking, and joint cracking. Furthermore, there is a certain detection blind spot in the tolerance band.…”