Understanding Fatigue Damage Under High-Cycle Random Fatigue on the Basis of the Actual Fatigue Process

In a previous paper, the present authors clarified that COD is a suitable parameter to interpret the fatigue damage on the basis of the fatigue crack growth in low-cycle random fatigue. Especially the COD parameter correlated well the fatigue damage counted using the rainflow method (RFM) with the crack growth life in LCF. To extend this idea to high-cycle random fatigue the present study has been done. The result showed that although the RFM is valid to evaluate total fatigue life, it is invalid to predict the crack growth life. This is due to the fact that the crack growth life is strongly affected by the effect of crack closure, which is more amplified in high-cycle fatigue than low-cycle fatigue