A DAMAGE TOLERANT APPROACH TO HIGH CYCLE FATIGUE

摘要

Damage tolerance, commonly applied in low cycle fatigue (LCF) design, requires the capability to predict crack growth rates as well as inspect for initial or in-service cracks. High cycle fatigue (HCF), on the other hand, precludes the use of conventional damage tolerant design because of the small size of damage during the majority of life as well as the very rapid growth encountered near the very end of life because of extremely high frequencies. A damage tolerant approach for HCF requires the use of threshold concepts involving both fatigue limit stresses for large cycle numbers and crack growth thresholds corresponding to very low growth rates for parts which may contain or have developed cracks. The use of the Kitagawa diagram concept with a small crack correction is illustrated for HCF problems. Small cracks, while illustrating anomalous behavior using fracture mechanics, do not pose unusual problems when treated using fatigue limit stress concepts.