Nonlinear Elastic Finite Element Analysis of Ceramic Thermal Barrier Coatings

In this paper, finite element formulation based on the nonlinear elastic constitutive equation of ceramic thermal barrier coatings is presented. The finite element code that was developed according to the formulation is employed to analyze the problem of the coatings with surface-type and lamination-type cracks which are subjected to a tensile loading. By performing the numerical analysis, it is shown that the stress field around the tip of crack can be expressed as the multiplying form of angular function and stress singularity solution which is characterized by HRR singularity. The damage field, which is associated with micro crack initiation in splat structure, in a lamination-type crack spreads along the crack plane. The other damage field in a surface-type crack is also formed along the plane normal to the crack plane. The inhomogeneity of damage field developed ahead of the crack tip may give a physical explanation for TBC spallation which is known as serious damage observed in actual gas turbine blades.