Nonlinear Deformation Analysis of Plasma-Sprayed Thermal Barrier Coatings

This paper presents the finite element formulation based on the nonlinear elastic constitutive equation of ceramic thermal barrier coatings. The finite element code that was developed herein was employed to analyze the problem of the coatings with surface-type and lamination-type cracks which was subjected to a tensile loading. The numerical result showed that the stress field around the tip of crack can be expressed as the multiplying form of stress singularity solution and angular function. However, the singularity orders were different between the crack shapes. The damage field, which is associated with micro crack initiation in splat structure, in lamination-type crack spread along the crack plane. The other damage field in surface-type crack was formed along the plane normal to the crack plane. The inhomogeneity in the damage field gives a physical explanation for TBC spallation which is known as serious damage observed in an actual gas turbine blade.