Thermal fatigue life predication of thermal barrier coatings by 3D hill-like model and GA

Abstract

In previous studies, the coating interface was simplified to a 2D axisymmetric model in order to solve the thermal stress of thermal barrier coatings (TBCs). But the 2D TBCs model ignored the circumferential roughness, which influenced the accuracy of thermal fatigue life predication. To solve the problem, a 3D hill-like TBCs model is established by cylindrical coordinate equation, and solved by finite element method (FEM). A life prediction method of the 3D TBCs is proposed by combining Manson-Coffin equation, linear cumulative damage theory and Genetic Algorithm (GA). The life prediction results of 3D hill-like TBCs model are compared with the 2D TBCs model. The result shows that the thermal stress distribution of the 3D hill-like TBCs model is similar to that of the 2D TBCs model. However, the circumferential positive stress is greater than the axial positive stress, which is hardly obtained by classical 2D TBCs model. The analysis of thermal stress in TC layer with 4 μm TGO thickness at different time shows that the thermal stress reaches 255.8 MPa (maximum value) at 1050 °C (maximum temperature in one cycle). Moreover, the maximum value of thermal stress is located at circumferential direction near the peak of the 3D hill-like TBCs model, and this phenomenon indicates that the risk point will appear in this area. The maximum fatigue life prediction error of 3D hill-like TBCs model is reduced by 153% compared with the 2D TBCs model, and all predicted fatigue results are located in ±1.66 scattering zone. The efforts of this study provide a framework for the thermal fatigue life prediction of TBCs.