Development of an anisotropic constitutive model for single-crystal superalloy for combined fatigue and creep loading

A unified anisotropic viscoplastic constitutive model for single-crystal superalloys is developed based on a modification of a phenomenological isotropic model. Orientation-dependent viscoplastic behaviour was observed in experiments. The model is used to simulate the orientation and cyclic mechanical response of single-crystal SRR99 under combined fatigue and creep conditions at 950°C. The results from the simulations are then used to estimate the fatigue-creep lives of the single-crystal nickel-base superalloy SRR99 using a new life prediction methodology. The predicted fatigue-creep lives are in good agreement with the experimental results.