Material-independent stress ratio effect on the fatigue crack growth behavior

It is well known that the fatigue life prediction for engineering structures with crack-like defects is a challenging issue, especially under variable amplitude loading. Although numerous models have been proposed, the intrinsic relationship between the stress ratio and fatigue crack growth (FCG) rate of materials is still unclear. In this study, we proposed a new FCG model containing a material-independent equivalent factor N through energy principle during crack growth, which could theoretically illustrate the effect of stress ratio on the FCG rate of metallic materials. The experimental verification indicates that the new model provides a more accurate relation between the stress ratio and FCG rate in various sorts of metallic materials. This model would be an effective strategy to the fatigue life prediction of cracked components under variable amplitude loading.