Prediction of corrosion fatigue crack initiation life of pits in engineering structures

In order to study the essence of the difference of corrosion fatigue crack initiation locations in the pit and predict the corrosion fatigue crack initiation life, the pit morphology was described by the two-parameter model and the stress concentration at different pit morphologies was analyzed based on the three-dimensional finite element model. Then, the influence laws of pit parameters (e.g. depth, depth-diameter ratio and location) on the stress concentration at different positions were investigated. Finally, a three-dimensional two-parameter pit-corrosion fatigue crack initiation evaluation model was established according to the phenomenology of corrosion fatigue, and the critical value of corrosion fatigue crack initiation corresponding to different pit morphologies was analyzed. It is shown that the factors controlling the corrosion fatigue crack initiation include the depth and shape of the pit. The critical values of the corrosion fatigue cracks initiating at different locations in the pit can be expressed by the critical pit depth. The validity and rationality of the proposed model are verified effectively. The research results provide a feasibility method for predicting the corrosion fatigue initiation life of the structures that are damaged by corrosion fatigue in engineering practice.