Abstract
A finite element analysis code was developed to accurately predict stress and damage fields in thermal barrier coatings (TBCs) systems subjected to thermo-mechanical loadings. An inelastic constitutive equation for TBCs, and a Chaboche-type viscoplastic constitutive equation for Ni-based super alloys (IN738LC) were employed to simulate high-temperature creep and cyclic deformations at a high-temperature condition. Additionally, fatigue crack propagation under thermo-mechanical loadings was performed by eliminating the stiffness matrix ahead of crack tip if the associated damage parameter is larger than the critical value. It was confirmed that stress-strain response and crack initiation/propagation simulated by the developed FE code was matched to the high-temperature tensile test results at all temperature conditions. The thermo-mechanical simulation showed that the crack initiation life in in-phase condition was shorter than one of out-of-phase condition. However, it was revealed that the crack in out-of-phase condition was initiated and propagated along the interface between top and bond coats in TBC multilayered structure, which may overlook the damages occurred in TBC in the gas turbine (GT) inspection service.
Published Version
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