Analysis of interfacial cracks in a TBC/superalloy system under thermomechanical loading
- Wayne State Univ., Detroit, MI (United States)
In thermal barrier coatings (TBC) residual stresses develop during cool down from processing temperature due to the thermal expansion mismatch between the different layers (substrate, bond coat, and TBC). These residual stresses can initiate microcracks at the bond coat/TBC interface and can lead to debonding at the bond coat/TBC interface. The effect of voids or crack-like flaws at the interface can be responsible for initiating debonding and accelerating the oxidation process. Effect of oxide layer growth between bond coat and ceramic layer (TBC) can be modeled as volume increase. In this work the authors represent the change in volume as an induced pressure across the interface. Mixed-mode fracture analysis of a thin circular delamination in an-axisymmetrically multi-layer circular plate is developed. Geometrical nonlinearity is included in the analysis, since they have a large deflection case. The elastic deformation problem of a circular plate subjected to a clamped boundary condition at the edge of the delamination, an out of plane pressure load, and a compressive stress due to thermal mismatch between different layers, was solved numerically using a Rayleigh-Ritz method. The strain energy release rate was evaluated by means of the path-independent M-integral. The numerical results of this problem based on the energy method were verified using finite element method. Both methods correlate well in predicting the energy release rate for Mode I and Mode II, deflection, and postbuckling solutions. The energy release rates G, for both Mode I and Mode II using virtual crack extension method, were evaluated. The specimen was cooled down from processing temperature of 1000 C to 0 C. The variation of the properties as a function of temperature was used for analysis. It was found that the use of temperature dependent properties in contrast to constant properties provides significantly different values of J-integral and G.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 316151
- Journal Information:
- Journal of Engineering for Gas Turbines and Power, Vol. 120, Issue 4; Other Information: DN: Paper presented at the international gas turbine and aeroengine congress and exhibition, June 2--5, 1997, Orlando, FL (US); PBD: Oct 1998
- Country of Publication:
- United States
- Language:
- English
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