Effect of Load Sequence on Fatigue Damage Accumulation of a Low Carbon Steel under Rotating Bending and Cyclic Torsion

Abstract

Fatigue damage accumulation induced by rotating bending (RB) and cyclic torsion (CT) is examined on a low carbon steel. The effect to the load sequence on fatigue damage accumulation was investigated microscopically as well as macroscopically. The loading type of RB-to-CT switching strengthened the fatigue life of the second stress cycle, while the fatigue damage accumulated linearly in the case of CT-to-RB loading. This trend of load sequence effect on the fatigue damage accumulation is clarified through microscopic observation of the fatigue process. The fracture mechanics-aided interpretation of the microcrack growth behavior from the slip band cracking to visual crack also supports this tendency.