The study of the influence of load amplitude on the fatigue behavior of Al 7075-T6 double-lap bolted joints

Abstract To investigate the influence of varying load amplitudes on the fatigue behavior of 7075-T6 aluminum alloy bolted joints, a series of fatigue tests and finite element analyses were conducted across a broad load range of 8 kN to 20 kN, with a constant tightening torque set at 10 N·m. The experimental results indicated no significant wear or fatigue damage was observed in the bolted joints under low load amplitudes. However, as the load amplitude increased, wear was exacerbated at the bolt joint, leading to a transition in failure mode from fretting fatigue to ordinary fatigue. Finite element analysis results revealed that stress amplitude and slip amplitude within the bolt joint increased with rising load amplitudes. Furthermore, the location of maximum stress shifted from the periphery of the hole towards its edge. This shift elucidated why failure modes in bolt joints transition from fretting fatigue to ordinary fatigue as loading conditions change.