INITIATION IN THE GIGACYCLE FATIGUE REGIME

摘要

SEM observations have shown that initiation in the gigacycle fatigue is often related to defects and flaws located beneath the surface, according the probability to find a defect. An estimating model for sub-surface and internal initiations has been developed according experimental observations made in steels, aluminum and nickel base alloys. In some cases, the internal initiation is studied, using thermal dissipation during the test, in order to confirm the theoretical approach. The conclusion of this work emphasizes the role of micro-plasticity around the defect in gigacycle fatigue and explains the formation of fish eye in terms of short crack initiation.