Influence of Specimen Thickness on Fatigue Crack Growth at High Temperature Under Mixed-Mode Loading

The high-temperature components of aeroengines operate under high-temperature and fatigue-loading conditions, resulting in complex crack-related issues. This study presents fatigue crack growth (FCG) experiments under mixed-mode loading performed on compact tension shear specimens fabricated from a nickel-based superalloy, tested at 550°C under varying thicknesses. The influence of specimen thickness on FCG behavior under mixed-mode loading was analyzed through experimental investigations and finite element method simulations. The expanded FCG model, incorporating thickness effects based on closure theory, enables more precise predictions of crack growth rates under mixed-mode loading conditions. Additionally, the FCG da/dN − ΔK curve for nickel-based superalloys exhibits a vertical shift with varying specimen thickness, while the FCG angle under mixed-mode loading remains unaffected by thickness. These findings provide valuable insights for improving damage tolerance design in aircraft engines.