A New Three-Parameter Model for Predicting Fatigue Crack Initiation Life

Based on the idea that the fatigue damage is caused by the cyclic damage strain, a concept of the critical damage quantity is introduced and a new three-parameter model is developed. The model contains three material performance parameters, i.e., the fatigue ductility coefficient, the fatigue ductility exponent, and the theoretical strain endurance limit. The fatigue ductility coefficient reflects the existence of the critical damage quantity. The fatigue ductility exponent shows the damage resistance ability of the material. And the theoretical strain endurance limit represents the existence of the critical cyclic strain. By using the proposed model, the fatigue crack initiation life of metallic materials can be predicted.