Damage Mechanisms and Fatigue Lives: From the Low to the Very High Cycle Regime

The primary cause of fatigue damage is usually intimately related to some form of cyclic slip irreversibilities. Depending on material and details of the loading conditions, various types of fatigue crack initiation are observed. Here, typical examples of fatigue damage evolution in low and high cycle fatigue (LCF, HCF) and ultrahigh cycle fatigue (UHCF) will be discussed. Various forms of fatigue damage and life-controlling microstructural mechanisms in different metals and alloys will be illustrated. In particular, the fatigue properties of ultrafine-grained (UFG) materials will be discussed, and the microstructural mechanisms and the question of the existence of a fatigue limit in the UHCF regime will be considered.