Fretting fatigue analysis and strength evaluation for swage-locking pinned aluminum alloy–steel connections under tension loading

Given the early stages of widespread adoption of swage-locking pinned connections in rail vehicle structures, research on their fatigue failure behavior remains scarce. This study investigates the fretting fatigue behavior of aluminum alloy–steel connections fastened by swage-locking pins through experiments and numerical analysis. It involved fatigue experiments under tension loading, fretting wear and fatigue analyses, followed by fatigue crack initiation prediction. Results show that the contact surface of clamped plates can be divided into the stick, slip, and open zones, with fretting wear occurring within the slip zone of aluminum alloy plate. Fretting fatigue cracks typically initiate within the slip zone near the stick-slip boundary, specifically at wear scars edges. A finite element model was developed to analyze contact status and stress states of test connections, with the friction coefficient at the aluminum alloy-steel interface optimized based on measured stick zone sizes. Results show the fatigue crack initiation of test connections is predominantly influenced by tensile stresses. Consequently, the SWT multiaxial fatigue criterion, combined with the critical plane method, can be used to predict crack initiation. The predicted crack initiation sites, angles, and fatigue strengths closely matched experimental results, with errors below 20 %, 5 %, and 7 %, respectively.