Thermal barrier coatings (TBCs) provide thermal insulation to high temperature superalloys.However,the interfacial crack caused by thermal loading at the bond coat/TBC is a fatal factor for TBC spallation and failure.The effects of voids or crack like flaw at the interface can be responsible for initiating debonding and accelerating the oxidation process.The effect of interfacial cracks should be studied by using the fracture mechanics approach.Due to different properties of bond and top coatings,stress intensity factor is complex.The paper presents two methods to evaluate the K factor by using numerical results of finite element method.One utilized crack flank displacement data,and another utilized the J integral.A plate with edge crack under thermal loading and tensile loading is chosen as an example to calculate the stress intensity factors.The variation of the properties as a function of temperature was used for the analysis.Both methods show consistent results,but the J integral method can not obtain the phase angle,whereas the other method uses the crack flank displacement data.The results of the experiments or other numerical methods can also be used for K evaluation.
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