Corrosion fatigue crack growth mechanisms in welded joints of marine steel structures

This paper presents a model of fatigue crack growth in a welded joint and a two-dimensional model of anodic dissolution based on Donahue model and anodic dissolution mechanism, respectively. In addition, a model for predicting the corrosion fatigue crack growth rate in welded joints of steel marine structures is established and crack growth mechanisms are analyzed. The results show that during early stages of crack growth, corrosion fatigue crack growth rate in welded joints is mainly controlled by corrosion action, whereas cyclic loading becomes more influential during the later stage of crack propagation. Loading frequency and effective stress ratio can affect rupture period of protective film at the corrosion fatigue crack tip and the length of corrosion crack increment, respectively, which changes the influence of corrosion action on crack growth rate. However, the impact of stress amplitude on crack growth rate is only significant when crack propagation is caused by cyclic loading. Welding residual stress not only improves the effective stress ratio of cyclic loading, but also promotes crack closure and increases corrosion fatigue crack growth rate in welded joints. Compared to corrosion action, welding residual stress has a more significant influence on crack growth caused by cyclic loading.