Fatigue life prediction and stresses applicability of TBCs by the virtual <i>S-N</i> curve method

Abstract The application of thermal barrier coatings (TBCs) greatly improves the high-temperature resistance of aero-engine turbine blades, and the life prediction of TBCs has become a hot research topic, but what kind of mechanical parameters are favorable for the improvement of prediction accuracy has not been studied. In order to explore the applicability of stresses for TBCs life prediction, this study established the TBCs life prediction model by the virtual S - N curve method and an axisymmetric finite element model for circular tubes with TBCs. Then, the solution method for the morphology- related stresses at interface of the axisymmetric TBCs finite element model is derived. Finally, the errors of different stresses for TBCs life prediction are analyzed in conjunction with the particle swarm algorithm, and the stress with the best applicability is identified and verified experimentally. The results show that the TBCs minimum life area is located between the peak and middle obtained by equivalent stress, maximum principal stress and maximum shearing stress, and this area is experimentally verified. The minimum life area location for the morphology-related stresses is also located between the peak and middle. The maximum error in life prediction is minimized at 44.97% when the equivalent stress is used for life prediction of TBCs. Prediction accuracy improved by about 200% compared to previous studies. And under similar thermal fatigue test conditions for TBCs, the equivalent stress still has high life prediction accuracy, which indicates that the equivalent stress has the best applicability for TBCs life prediction. The conclusions provide new ideas for the fatigue and strength analysis of TBCs.