Effect of riveting process parameters on the local stress field of a T-joint

Rotorcraft airframes are complex structures designed to satisfy different goals; fatigue life represents one of the most critical issues, which must be guaranteed throughout the design and the construction phase. In this scenario riveted joints play an important structural role especially because of the variable loads they are subjected to. Their fatigue behaviour is strictly influenced by the local stress fields left very near to the holes during riveting manufacturing operations. Therefore, with the aim to improve design awareness, the effects of the different parameters involved during the riveting process are herein investigated. The effects of the squeeze force, the clearance, the rivet length and the clamping angle in the stress field of the joints are considered by means of numerical models. Detailed finite elements models (including rivet forming formation) are validated through experimental tests. These models are aimed at obtaining an accurate stress–strain field in the most stressed zone including the residual stress in the holes. Finally, using the literature fatigue data of Al8090-T81 and the Crossland multiaxial fatigue criterion, the influence of the riveting parameters on the fatigue strength is evaluated for optimisation purposes.