ABSTRACT
Basic high cycle fatigue (HCF) characteristics are discussed in chapter, but the emphasis is put more on the effects of various externally or internally inflicted damages such as foreign object damage, dwell and prior creep strain damage. It is shown that the Tanaka-Mura-Wu model is also applicable to HCF to describe the S-N behavior with a microstructure-dependent fatigue limit. Cold dwell and prior creep damages arise by different mechanisms, because of the temperature effect. The former accumulate as Zener-Stroh-Koehler dislocation pile-ups, whereas the latter accumulate as creep voids/cracks even during steady-state creep. Both cold and hot dwell-fatigue life is governed by the same ICFT damage equation. Metallurgical evidence is presented to support the theory. Again, the linear damage rule does not work in the cases of dwell-fatigue and fatigue with prior creep strain.
