Modelling fatigue crack initiation life

Abstract An accurate formula for the fatigue crack initiation (FCl) life, correlating it with the geometry of notched speciments, the cyclic loading conditions, the behaviour of metals and the tension overloading effect, has been developed based on the hypothesis of the widely used local strain approach, and checked by test results on the FCl life of aluminum alloy notched specimens. In addition, the overloading effect factor z has been defined. It can be used to characterize quantitatively the interaction between larger load and smaller loads in the load spectrum. Taking into account the interaction between loads, Miner's rule can be used to calculate the cumulative damage in the FCl phase. Based on the work mentioned above, a new model has been developed and substantiated for accurate prediction of FCl life under variable amplitude loading. Further work is needed to increase the FCl life prediction accuracy.