In-phase thermomechanical fatigue lifetime prediction of nickel-based single crystal superalloys from smooth specimens to notched specimens based on coupling damage on critical plane

Abstract

A lifetime prediction method is proposed to predict the in-phase thermomechanical fatigue (IP TMF) lifetime of notched nickel-based single crystal superalloy by combining continuum damage theory and the critical distance theory in the present study. Firstly, an IP TMF lifetime prediction model considering both fatigue damage and creep damage is developed based on continuum damage mechanics for smooth specimens of the nickel-based single crystal superalloy, in which material constants are identified through experimental data under creep loading and fatigue loading. The accuracy of the lifetime model is validated by performing stress-controlled tests of IP TMF with dwell times on smooth specimens. Secondly, the IP TMF experiments on notched specimens with different orientation film-cooling hole are conducted to investigate the effect of film-cooling hole orientation on IP TMF lifetimes. Based on the slip-based constitutive model, the stress distribution nearby the film-cooling hole is simulated. Finally, a lifetime prediction method for the notched specimens is proposed by combining the critical distance theory and damage-based model. Predicted results show good agreement with the experimental data.