FATIGUE CRACK INITIATION MECHANISMS AND FATIGUE LIFE IN HIGH-CYCLE AND IN ULTRAHIGH-CYCLE FATIGUE

摘要

An account of fatigue crack initiation mechanisms that are important in high-cycle fatigue (HCF) and in ultrahigh-cycle fatigue (UHCF) is given. In addition to the cyclic strain localization phenomena which occur most prominently in persistent slip band (PSBs) and that have been studied extensively in the past, other forms of fatigue crack initiation that have attracted interest only quite recently will be addressed. In particular, the following topics will be dealt with: 1) Cyclic strain localization and fatigue crack initiation in PSBs. 2) Macroscopic shear banding and fatigue crack initiation in ultrafine-grained (UFG) metals. 3) Fatigue crack initiation at near-surface pores and cavities in cast (and powder metallurgical) alloys. 4) Subsurface fatigue crack initiation at inclusions in high-strength steels in the UHCF regime: multistage fatigue life diagrams.