Unifying the crystal plasticity, neuber/glinka and elastic follow-up frameworks to evaluate creep-fatigue in gas turbine single crystal nickel superalloys

A local strain method is developed to estimate creep-fatigue life at hot spots based on linear elastic FE analysis. The method combines the concepts of Crystal Plasticity, Neuber/Glinka and elastic follow-up factor and predicts cyclic plastic-creep deformation at the hole of a Nickel-based single crystal plate under temperature cycling between 20 °C and 1100 °C. The results agree with Crystal Plasticity Finite Element (CPFE) simulations and indicate that: (a) Neuber/Glinka rules apply to single crystal cubic metals, (b) the increase of Young’s modulus on shutdown drives excessive residual stresses and low cycle fatigue, (c) the elastic follow-up factor $Z$ increases during non-local creep at high temperature, but room temperature plasticity on unloading resets $Z$ to low values. The competition between hot creep and cold plasticity controls whether local strain-ratchetting occurs in compressive or the tensile direction and cannot be captured by Neuber/Glinka rules alone. However, the combination of Glinka and Neuber suffices to predict reasonably well the cyclic strain range related to low cycle fatigue. These results extend the understanding of fatigue-creep-ratchetting failure to leverage industrial/academic research on the structural integrity of high temperature technologies, including fusion/fission reactors, hydrogen gas turbines, re-usable space vehicles.