稳态热载荷作用下热障涂层结构界面断裂研究

针对陶瓷层与黏结层构成的双层热障涂层结构存在单边界面裂纹的情况,利用虚拟裂纹闭合技术(VCCT)计算了稳态热载荷作用下结构的能量释放率,根据计算结果研究了单边界面裂纹的扩展行为.给定结构的温度边界条件求解得到稳定温度场,并以此作为结构的热载荷,计算能量释放率时采用随温度变化的材料参数.计算结果显示,在给定条件下,界面裂纹起裂后结构总的能量释放率大于界面断裂韧度,裂纹将进行失稳扩展;在裂纹扩展至接近自由端面时总能量释放率迅速减小并降到界面断裂韧度以下,裂纹不扩展.分析表明,处于高温稳态热载荷条件下的热障涂层系统,不会发生陶瓷层彻底剥落的失效现象.

Fracture analysis of thermal barrier coating structure with interfacial crack under steady-state thermal loading

Considering unilateral interfacial crack in thermal barrier coating(TBC),virtual crack closure technique(VCCT) was used to calculate strain energy release rate of the structure under thermal loading,and unilateral interfacial crack propagation behavior was studied according to the results.During calculation,the stable temperature field was obtained by the given temperature boundary conditions,and taken as the thermal loading in the structure.The temperature-dependent material parameters were adopted.The results show that,in the given conditions,the total energy release rate is greater than interfacial fracture toughness during crack initiation stage,indicating that once the unilateral interfacial crack appears,the unstable propagation will occur subsequently under thermal loading.When the crack extends close to the free end,the total energy release rate decreases rapidly and drops below the interface fracture toughness,leading to stop of crack propagation.The analysis shows that,for the structure of TBC with unilateral interface crack under high thermal loading,the ceramic coat won't flake-off completely.