# Thermal Fatigue Life Prediction of Thermal Barrier Coat on Nozzle Guide Vane via Master-Slave Model
## 5 Conclusions  
The target of this paper was to propose an efficient master-slave model for the thermal fatigue life (TFL) prediction method of a nozzle guide vane (NGV) with a thermal barrier coat (TBC), with respect to flow-thermo-structural coupling, oxidation damage, and thermal fatigue damage. The modeling and simulation methods and life molding processes were first investigated and validated. Then, the TFL prediction method of the NGV with the TBC was performed with respect to the proposed master-slave model in the foundation of the temperature filed analysis, temperature test, and matching of the master and slave models. Through these studies, some conclusions and findings can be summarized as follows:  
(1) The adopted SST \(\gamma\)-\(\theta\) turbulence model effectively predicted the convective heat transfer coefficient by thermal-elastic simulation, and the temperature field solved by the fully coupled solid 226 element agreed well with the test data of the aircraft engine. This revealed that the fully coupling solid 226 element is promising to improve the accuracy of the temperature field calculation. Compared with the traditional method, the accuracy of the temperature field calculation was improved by over 5%. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Number**} & \multicolumn{2}{c}{**Life Cycle**} & \multicolumn{2}{c}{**Thermal Fatigue Life**} \\ \cline{2-5}  & **Leading Edge, N** & **Trailing Edge, N** & **Leading Edge, H** & **Trailing Edge, H** \\ \hline Case 1 & 1892 & 1558 & 40 & 33 \\ Case 2 & 1345 & 870 & 279 & 180 \\ Case 3 & 1419 & 916 & 30 & 20 \\ Case 4 & 1310 & 704 & 28 & 15 \\ Case 5 & 1126 & 558 & 24 & 12 \\ Case 6 & 895 & 536 & 19 & 11 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Thermal fatigue life of the TBC on the NGV. (2) Based on the volume element intersection mapping algorithm, the boundary conditions of the temperature and displacement were successfully transferred from the master model into the slave model with high precision. The simulation results of the master model and slave model showed good agreement, indicating that it is possible to link macro- and micro-scales with the master-slave model presented in this paper. (3) The ranges of the axial and shear strains in the TC layer were affected by the thickness of the TGO layer, but the trends of the two kind strains were almost the opposite. With the increase in the thermal cyclic number, shear strain plays a dominant role in the life model because it seriously effects the TFL prediction of the TBC on a NGV for an aero engine. (4) Based on the developed master-slave model, the TFL of a typical NGV was precisely predicted with minor errors when compared to the test data, and the life variation also met the actual usage of the NGV. The proposed method comprehensively considers the physical characteristics of heat transfer boundaries, macro-scale and micro-scale to reflect the coupling failure of oxidation damage and thermal fatigue. In short, the developed master-slave model was validated to be highly-computationally precise and efficient with regard to TFL prediction for a NGV with a TBC by comparing the temperature and the life cycle of the key points at the leading edge and trailing edge with the experiments. The efforts of the study provide a promising modeling strategy (master-slave model) for the integrated TFL prediction design of thermal structures other than NGV in engineering. Conceptualization, Y.A. and P.G. ; Methodology, P.G. and Y.Y. ; Software, P.G. and Y.Y. ; Validation, P.G. and C.F. ; Formal Analysis, P.G. and C.F. ; Investigation, P.G. and C.F. ; Resources, Y.A. and C.F. ; Data Curation, P.G. and C.F. ; Writing-Original Draft Preparation, P.G. ; Writing-Review & Editing, C.F. ; Visualization, P.G. ; Supervision, Y.A. and C.F. ; Project Administration, Y.A. and C.F. ; Funding Acquisition, Y.A. and C.F. This work was sponsored by the National Natural Science Foundation of China (Grant nos.