Prediction of crack growth in polycrystalline XH73M nickel-based alloy at thermo-mechanical and isothermal fatigue loading

The importance of developing simple relationships for interpreting crack growth rate test results and a practical approach to predicting crack propagation under thermo-mechanical fatigue conditions based on readily available data is emphasised by many authors. In this study, a damage impact parameter was introduced to predict the crack growth rate and durability under isothermal and thermo-mechanical fatigue conditions. To validate the model, we used a single-edge notched specimen made of polycrystalline coarse-grained nickel-based alloy XH73M. The specimen was subjected to loading conditions that included in-phase and out-of-phase thermo-mechanical fatigue at a temperature range of 400-650 degrees C, as well as isothermal fatigue at 26 degrees C, 400 degrees C and 650 degrees C. A numerical analysis was used to simulate the material deformation behaviour at the crack tip according to a nonlinear kinematic hardening model. Numerical and experimental stress-strain state parameters based on strain energy density were used to formulate and estimate the damage impact parameter. Based on the correlation between the crack growth rate and the introduced damage impact parameter, a method for predicting crack propagation is proposed. The accuracy of the proposed method was experimentally validated.