Modeling and simulation of thermal fatigue crack in EB-PVD TBCs under non-uniform temperature

- Analytical stress calculation of TBC ceramic layer.
- Deriving plane-stress equation of a multi-layer circular solid disk under thermal fatigue and creep interaction.
- Finite element stress calculation of the disk by a half axisymmetric model.
- Analytical and finite element analysis of a pre-existing penny-shaped TBC crack.
- Calculation of stress intensity factor of the crack in the vertical and inclined directions.

Demand for enhanced jet engine efficiencies has led to a significant increase in the combustion temperature. Thus protecting components against the combustion products is necessary and is possible by using thermal barrier coatings (TBCs). In this research, thermal fatigue and creep interaction are studied via analytical and numerical finite element methods. Thermal stress and crack propagation analyses in the ceramic top coat are carried out based on plane stress condition and under inhomogeneous temperature distribution across the layers. The crack is assumed as a penny-shaped crack in both vertical and inclined growth directions. The study proposed that the creep-plasticity results in thermal stress alleviation and the tensile stress transforms into a compressive stress of − 200 MPa in forwarding cycles that will induce crack closure. In addition, the results confirmed that vertical cracks grow much faster than oblique ones due to single mode crack propagation and about 0.14 MPa√m greater values in stress intensity factor. The modeling and simulation results match together, and the obtained crack behavior is in compliance with other researcher's output.

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