基于内聚力单元热障涂层体系失效过程有限元模拟分析-材料科学与工程专业论文.docxVIP

Abstract Thermal barrier coatings (TBCs) have been widely applied in nuclear technology and aircraft engine due to their excellent wear resistance, corrosion resistance, and thermal insulation as engine components. However, most of TBC systems, frequently used in turbine blades and vans, have complex and irregular geometrical structures, it is inconvenient and difficult to use experimental methods and theoretical models to estimate their reliability and durability under severe environments. Thus, we have to resort to numerical analysis such as the finite element method (FEM). In this paper, finite element analysis and experimental verification were used to determine numerical model parameter in predicting the damage, cracking and spallation of TBCs system. The obtained material properties in this work would play a crucial role in predicting the reliability and durability of TBCs with irregular geometry in future. The main research contents are summarized as follows. Firstly, with the help of a digital image correlation technique, fracture strength and fracture toughness of freestanding 8wt% Y2O3-ZrO2 (8YSZ) coatings were directly measured by single edge notched bending (SENB) tests. An extended finite element model (XFEM) was established to simulate the fracture process of notched 8YSZ samples. Its energy release rate was estimated by the known fracture strength and Young’s modulus. Within the linear elastic brittle fracture, the calculated energy release rate was transformed into the corresponding fracture toughness, which is in good agreement with the experimental results by SENB. The obtained material properties of XFEM in this work would play a crucial role in predicting the reliability and durability of TBCs with irregular geometry in future. IISecondly, a two-dimensional finite element model with cohesive zone element was developed to predict cracking in TBC system that is subjected to residual stresses and external tensile loads. In the first, the residual s