Simulation of the Effect of Sub-Micron Interface Roughness on the Stress Distribution in Functionally Graded Thermal Barrier Coatings

In this research, a numerical modeling method was utilized to calculate the stresses occurring during the thermal cycling in a functionally graded thermal barrier coating (FG - TBC). The temperature – dependent material response of this protective material was taken into account and the effects of the thermal cycle and interface morphology of the ceramic /metallic layer in a functionally graded coating system was investigated. Sinusoidal mode of asperity with specific wavelength and amplitude was used to model the two dimensional geometry of interface profile between layers. A finite element model was used to model the effect of the thermal loading imposed on the thermo-mechanical response and stress distribution. In this regard, different observable facts were taken into account in the model such as: non- homogenous temperature distribution, periodic boundary condition and convective heat transfer. These phenomena depict the most real world situation in numerical simulation of multi- layer coating during cooling and thermal cycling, specifically near the ceramic/metal interface. In addition, regions which are potent to crack initiation and propagation in the system and the subsequent delamination places of the TBCs system were predicted.