Effect of Mean Stress on Fatigue Crack Initiation Life and Fatigue Crack Propagation Rate

Abstract

Effect of mean stress caused by cyclic creep on fatigue crack initiation life and crack propagation rate was derived quantitatively for mild steel. As a result, using one S-N diagram for arbitrary stress ratio being from-1 to 1, the method of obtaining S-N diagrams of another stress ratio was given as to the crack initiation life of structural members and mechanical components with stress concentration factor K, where a definition of stress ratio is the ratio minimum stress to maximum stress. Main factors of means tress which affect the crack propagation rate are phenomena of cyclic creep and crack closure, in this paper, the method of appreciating the quantitative influence of cyclic creep was presented.