Numerical simulation of oxidation effect on fatigue crack growth behavior based on mesoscopic polycrystalline microstructure

• A finite element model for micro-polycrystalline structure is developed in conjunction with a fatigue-oxidation continuum damage model. • The effect of oxidation on fatigue crack growth behavior operating under different loading conditions is researched. • The proportion of fatigue damage component and oxidation damage component accounting for the total damage is controlled by load level and dwell time. In the high temperature service environment, oxidation can have an important effect on the fatigue mechanical properties of components and affect the crack propagation behavior, which poses an important challenge to the fatigue performance of components. In order to study the effect of oxidation on the crack propagation behavior of parts, a numerical simulation method for predicting the crack propagation behavior of Ti-6Al-4 V alloy under fatigue-oxidation interaction is proposed by developing a mesoscopic-scale idealized Voronoi polycrystalline microstructure modeling method, in which the difference of oxidation damage rate between grain and grain boundary is taken into account. Results show that the proportion of oxidation damage increases with the dwell time increases and the load level decreases, which leads to the decrease of crack initiation life and propagation life. In addition, the crack growth mode changes from transgranular fracture to mixed mode or even pure intergranular fracture, and the irregularity of crack fracture profile also increases. The evolution in crack growth mode is closely related to the change in competitive relationship between fatigue damage and oxidation damage. The crack growth rate curve obtained at serious oxidation damage condition is almost parallel to the crack growth rate curve obtained at pure fatigue condition in logarithmic coordinate system. The oxidation damage also promotes the formation and growth of secondary crack branches at the crack tip, which increases the dispersion of crack growth rate and changes the stress range as well as the maximum stress location during crack growth process.