Fatigue damage in polycrystals – Part 1: The numbers two and three

The fundamental difference between the cyclic yield stress and the fatigue limit is scale. The basic rate of slip mismatch towards a saturated condition, representing polycrystalline behaviour, is a material property embedded into the grain size distribution. Deviations from its basic rate will depend on the shape of the crack and the selected crack path. This work concludes that during the first loading cycle, and for stresses equal and above the fatigue limit, the surface will always been deformed plastically.