A damage-coupled constitutive model for superalloys accounting for creep–fatigue interactions and load variations

High temperatures and reusable environmental conditions cause the superalloys used in aircraft to experience significant creep–fatigue interactions. Research on the creep–fatigue interactions of superalloys still faces several issues, e.g., the incapability of life prediction models to adapt to diverse loading conditions, the lack of refinement in damage models, and the limited application scope in aircraft structural analysis. To solve the issues, this paper proposes a non-uniform damage-coupled constitutive model which encompasses a creep–fatigue damage model and a life prediction model. The life prediction model takes into account both the dwell time and the total duration of a single cycle, which effectively captures the creep–fatigue life with respect to different loading conditions. The creep–fatigue damage model considers the per-second damage accumulation. This enables the model to accurately reflect both the material and loading characteristics. The stress–strain predictions obtained from the damage-coupled constitutive model show excellent agreement with the experimental results. Finally, the key factors influencing the failure and service life of the aircraft nose cone structure are identified based on the proposed damage-coupled constitutive model. This constitutive model is readily applicable to engineering problems and can offer crucial support for the early-stage structural design of aircraft.