Dimensional Analysis And Finite Element Simulations On The Erosion Process Of Plasma Sprayed Thermal Barrier Coatings

Thermal barrier coatings(TBCs) with the high temperature durability and excellent heat insulation can reduce the metal surface temperature, which results in a significant improvement in performance and high efficiency of gas turbine engines. TBCs have been developed as a key heat protection technique. During flight, TBCs are unavoidably impacted and then eroded by particles from combustion chambers or foreign objects. Erosion of TBCs has become a severe problem of service performance and reliability. As one of the main preparation methods of TBCs, plasma spraying thermal barrier coatings contains are full of tiny pores and cracks. With the complex geometry structure, the erosion performance of plasma spray coatings is particularly difficult to study. In this thesis, by simplifying the defects of plasma sprayed coatings, setting up the geometrical model of it which contains a random distribution of pores or cracks. And using three different methods of ABAQUS, a software of finite element analysis, to simulate different Erosion failure modes of plasma spray coatings. Finally, this research is focus on the analysis of the relationship between the relevant parameters and the erosion performance of TBCs, and setting up the model of TBCs which contains a uniform distribution of pores as comparison. The main contents of this thesis are as follows:First, setting up the finite element models of plasma sprayed TBCs which contains a random distribution of pores. By analyzing with its microstructure and the erosion process, These defects are composed of cavities and micro-cracks, whose locations, orientation and size are random variables. Setting up the finite element models simply and quickly, by combining the characteristics and advantages of relevant softwares: such as MATLAB, which is Easy to code, ANSYS, which is easy to operate by order flow, and ABAQUS, which is better at study of structural mechanics and the related fields.Second, using three different methods of ABAQUS to simulate different Erosion failure modes of plasma spray coatings, and find out the most appropriate method by contrasting them. Because of there is no constitutive relation of ceramic materials in ABAQUS, we have to rely on other ways to simulate erosion destruction of plasma spray coatings. Then we discovered this: the Extended Finite Element Method(XFEM) adapted to simulate the crack propagation,and the method of Brittle Cracking could be used to simulate the whole damage process of coatings. By contrasting them and thinking about parameters which related to fabrication process, it was sum up that we could use the Brittle Cracking do more further researches.Third, we studied the influence of the porosity of the ceramic layer on erosion performance with the method of dimension analysis, by changing the parameters of porosity. Parameters(for example porosity, pore size, the velocity of eroded particles) were converted to dimensionless, and we analyzed their effects on erosion performance of plasma spraying TBCs, such as stress, energy, the mass loss rate, crack length, etc.Fourth, setting up models of plasma sprayed TBCs containing uniformdistribution pores in order to comparison with the TBCs containing randomdistribution pores. In the case, the interference of pores distribution was eliminated, and we studied the impacts of pore radius, porosity and pore spacing on the erosion rate of TBCs.This paper studied the erosion destruction of plasma sprayed TBCs by using the finite element simulation and dimensional analysis, found related parameters’ effects on the mass loss rate and degree of damage of it, thus provided guidance for predicting its service life and optimize the preparation process of plasma sprayed TBCs.