热障涂层损伤机理及声发射特性的细观数值模拟研究

Some unpredictable cracks and flakes are easily happend in thermal barrier coatings for the bad environment and its complex structure, which leads to an important safety accident, therefore the thermal barrier coating faliure is the key problem needs to solve urgently. In this project, the thermal barrier coatings (TBCS) was the research object, numerical method and nondestructive testing was combined to establish the elastic and brittle damage evolution constitutive model of thermal barrier coating, basing on mesoscopic damage mechanics theory. The macroscopic nonlinear mechanical behavior of damage behavior of heterogeneous material in the failure process was revealed by the damage mechanism research. In the stage of macroscopic fracture and failure, the acoustic emission rules and the deformation distribution of internal micro cracks were observed, which establish a mapping mechanism with acoustic emission detection. We can get a deeper understanding of the coating damage mechanism, the damage degree and damage time of the coating were quantified, and the safety and reliability of the products were guaranteed.

热障涂层在恶劣的服役环境及自身复杂结构等因素影响下会发生不可预知的开裂、剥落导致涂层失效，引发重大安全事故，因此热障涂层的失效问题是目前急需解决的关键问题。本项目以热障涂层为研究对象，将数值方法与试验检测相结合，基于细观损伤力学理论，建立热障涂层的弹脆性损伤演化本构模型，研究含初始缺陷材料的损伤行为，揭示非均质材料破坏过程的宏观非线性力学行为，同时对热障涂层的宏观断裂、失稳和破坏的声发射规律与其变形时内部微裂纹的分布及微裂隙的产生扩展和贯通的力学本质进行研究，与声发射检测建立起映射机制，从而深入了解涂层损伤机理，对涂层损伤程度及损伤时间进行量化表征，为产品服役的安全性及可靠性提供保证。

航空发动机是国防科技水平和综合国力的标志，叶片作为航发关键性构件，始终是最核心的技术难点之一。本项目针对航空发动机叶片热障涂层的损伤失效问题，采用数值模拟的方法对热障涂层的微裂纹扩展行为及扩展过程中的声发射规律进行研究，为裂纹的定量评估及定位提供依据。利用数值模拟对涂层损伤破坏过程中的声发射特征进行研究，为声发射信号的辨识提供依据，从而克服了无损检测的局限性，使瞬变动力过程的研究从定性走向定量，取得结果主要有：（1）明确了微观尺度下热障涂层动态损伤中的表面及界面裂纹演化扩展及应变传递过程；（2）揭示了高温环境中热障涂层界面TGO的生长机制及对裂纹扩展的影响；（3）获得了稀土元素掺杂对热障涂层微观组织结构及力学性能的影响，以及稀土氧化物纳米颗粒对高温氧化物TGO成分及损失行为的影响；（4）利用声发射技术研究热障涂层的损伤行为，建立损伤变量和声发射信号之间的关系，实现零件裂纹的早期检测和评估。该项目工作为先进涡轮发动机的防护涂层损伤检测及监测解决现实难题，并奠定理论基础，对国防、航空、机械等领域对产品服役的安全性及可靠性具有重要的意义。