Finite Element Analysis of Multiaxial Fatigue and Mixed-Mode Crack Growth in Inconel 600

This study investigates the fatigue life prediction of Inconel 600 under multiaxial loading conditions as well as fatigue crack growth under mixed mode (I and II). Finite element simulations based on critical plane criteria were performed for fatigue analysis under combined tensile and shear loading in different non-proportional modes (i.e., phase difference between tensile and shear loads). To achieve this, fully reversed tensile stress with a maximum value of 480 MPa (mean stress: zero) was considered. Subsequently, a constant shear stress of 28 MPa was applied at different phase angles ranging from 0° to 90° in 10-degree intervals (i.e., 0°≤θ≤90°,∆θ=10° ). For all modes, hysteresis stress diagrams were extracted to investigate the cyclic behavior of the material. Furthermore, various fatigue damage models, including Fatemi-Socie, SWT, normal strain, and shear strain, were employed to assess the fatigue life of the samples under different loading modes using MSC software. The results showed that the Fatemi-Socie and shear strain criteria predict the shortest fatigue life for phase difference in the ranges of 0°-30° and 40°-90°, respectively. Therefore, selecting a more conservative criterion is not feasible as it depends on the loading conditions. Additionally, it was found that the most critical conditions occurred at phase difference of 50° and 60°. Next, in order to numerically investigate the crack growth behavior, a semi-Arcan fixture model was used. Simulations were performed for four different loading modes (i.e., fixture settings), considering variations in the loading angle with respect to the longitudinal axis of the crack (0°, 30°, 60°, and 90°). Eventually, crack length graphs were extracted in terms of loading cycles. The results indicated that the lowest and highest crack growth rates occurred when the angle between loading and the longitudinal axis of the crack was 0° and 90°, respectively.