Propagation Lifetime from the Surface and Internal Defects in the Ultra High Cycle Fatigue Regime~!2008-03-10~!2008-05-06~!2008-07-03~!

Abstract

Ultra High Cycle fatigue leads to a failure initiated in the bulk material of a material. Some results on the nodular cast iron are presented: initiation occurs from the defects, located at the surface or in the bulk. It has been shown that environment plays a major role that could explain the difference between fatigue lives, for the surface and internal initiation. The influence of the defect size and crack growth law is discussed and, the importance of fatigue crack initiation stage is revealed, in the ultra high cycle regime

Cracking simulation‐based fatigue life assessment

“…Fatigue cracks initiate from the most favorable surface or subsurface sites, eg, geometrical imperfections, favorably oriented grains, nonmetallic inclusions, or brittle precipitates. In design against fatigue, linear elastic fracture mechanics (LEFM) approach is considered inherently conservative since a crack of a considerable size is assumed to preexist, and so the initiation life can be neglected.…”

Cracking simulation‐based cumulative fatigue damage assessment

“…The common view that fatigue life of a component is divided into crack initiation phase, and a subsequent crack propagation phase has witnessed over the last two decades several relaxations, 6 specifically with the initiation period being subdivided into initiation plus microstructurally short crack growth phases. Fatigue cracks initiate from the most favorable surface or subsurface sites, for example, 7 geometrical imperfections, favorably oriented grains, nonmetallic inclusions, or brittle precipitates. Below the fatigue limits of steels, cracks are frequently observed propagating but subsequently arrested.…”

Cracking simulation-based cumulative fatigue damage assessment

“…Fatigue cracks initiate from the most favorable surface or subsurface sites, e.g. 7 , geometrical imperfections, favorably oriented grains, non-metallic inclusions or brittle precipitates. Below the fatigue limits of steels cracks are frequently observed propagating but subsequently arrested.…”