Modeling of fracture of functionally graded thermal barrier coatings under high heat fluxes

高热通量下功能梯度热障涂层断裂的建模

• 批准号: 397980451
• 负责人: Professor Dr. Siegfried Schmauder
• 金额: --
• 依托单位: Institut für Materialprüfung, Werkstoffkunde und Festigkeitslehre (IMWF)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/397980451?language=en
• 关键词: Modeling; fracture; functionally; graded; thermal

Functionally graded thermal barrier coatings (FGCs) are used in energy producing engineering and aircraft applications in the hottest parts of gas-turbine engines, and they protect the inner metallic parts from overheating and melting. Increasing the capacity of these engines requires increasing the operating temperature, and this relies on further improvement of FGCs with respect to improvement of temperature durability and fracture resistance. During manufacturing and service small defects appear in FGCs and then the cracks can initiate from these defects; the defects and cracks change both the thermal conductivity and fracture resistance of FGCs. In this context, a study of thermal fracture of functionally graded coatings on a homogeneous substrate (FGC/H) under the influence of high heat fluxes is of great demand.The main goal of the project is to develop a computational semi-analytical model for the fracture analysis of functionally graded coatings on a homogeneous substrate FGC/H (with an additional oxidation layer between the coating and substrate which is formed as a result of oxidation processes) under thermal and mechanical loading. A number of new issues arising with increased temperatures and with high heat fluxes will be addressed, such as, thermal conductivity problems for FGC/H with pre-existing systems of interacting cracks; the cracks will be considered as partially thermal permeable due to the thermo-conductivity of gas inside the cracks. The material properties vary significantly with temperature and this will be accounted for in the model. The thermal and elastic properties of FGCs will be modeled from the point of view of its practical application to the specific problem of cracks in FGCs under thermal and mechanical loadings. The thermal problem and thermo-elastic (plastic) problems will be formulated by means of integral equations. The solution will be obtained numerically, using special quadrature formulae for the integrals. Besides, new approximate analytical solutions will be obtained for some special cases, e.g. for the interaction of thermally permeable cracks. This semi-analytical approach allows to correlate the structural material parameters (material gradation, crack parameters) and the thermo-mechanical loading parameters with the main fracture characteristics. The model in combination with a detailed parametric analysis can help to optimize the gradation of the FGCs and their structure in order to improve the fracture resistance of FGC/H systems operating under elevated temperatures. In this regard, potentially desirable thermal and mechanical properties of FGCs will be analyzed as well as available real material combinations for advanced thermal barrier coating applications.

功能梯度热障涂层（FGC）用于燃气涡轮发动机最热部件的能源生产工程和飞机应用中，它们保护内部金属部件免受过热和熔化。提高这些发动机的容量需要提高操作温度，这依赖于FGC在提高温度耐久性和抗断裂性方面的进一步改进。在制造和使用过程中，FGC中会出现小的缺陷，然后裂纹可以从这些缺陷开始，缺陷和裂纹改变FGC的热导率和断裂阻力。在这一背景下，本项目的主要目标是建立一个用于均匀基体上功能梯度涂层断裂分析的半解析计算模型，并对该模型进行了数值模拟（在涂层和基底之间具有作为氧化过程的结果而形成的附加氧化层）。随着温度的升高和高热通量的增加而产生的一些新问题将得到解决，例如，FGC/H的导热性问题与预先存在的相互作用的裂纹系统;由于裂纹内气体的导热性，裂纹将被认为是部分热可渗透的。材料特性随温度变化显著，这将在模型中考虑。FGCs的热性能和弹性性能将从其实际应用的角度来模拟FGCs在热载荷和机械载荷下的裂纹的具体问题。热问题和热弹性（塑性）问题将通过积分方程来表述。将使用积分的特殊求积公式数值求解。此外，对于某些特殊情况，如热渗透裂纹的相互作用，将得到新的近似解析解。这种半分析方法允许相关的结构材料参数（材料级配，裂纹参数）和热机械载荷参数的主要断裂特征。该模型结合详细的参数分析可以帮助优化FGC的级配及其结构，以提高高温下运行的FGC/H系统的抗断裂性能。在这方面，潜在的理想的热性能和机械性能的FGC将进行分析，以及先进的热障涂层应用可用的真实的材料组合。