Role of Small Cracks for Discussion of Fatigue Damage in Low Cycle Fatigue of Metals

摘要

The role of small cracks on fatigue life and loss of ductility are discussed to understand the reality of fatigue damage in low cycle fatigue. The series of low cycle fatigue tests were carried out paying attention to the role of small cracks and its influence on ductility loss. These tests showed that the fatigue lives were pronouncedly extended by removing surface cracks. Also, it was quantified that the loss of fracture ductility was correlated with crack length but not with the number of fatigue cycles. From those results, it is elucidated that the behavior of small cracks is crucial to explain the mechanism of low cycle fatigue damage rather than the crack initiation process and change in bulk material properties.