热/力/辐照环境下颗粒增强型核燃料的跨尺度断裂分析方法研究

Particle reinforced nuclear fuel has a wide application prospect. The fracture behavior of this fuel is extremely complex due to the effect of fission reaction and thermal-mechanical-irradiation environment. On the meso-scale, the propagation and growth of micro-cracks in fuel particles, and the ductility fracture of matrix are two key issues. Because of the cross-scale behavior between the meso-scale fracture behavior and macro-scale failure, it is difficult to simulate the failure behavior of particle reinforced nuclear fuel. At the same time, the traditional multi-scale mechanical simulation method cannot balance the accuracy and efficiency. In present project, the nuclear fuel under thermal-mechanical-irradiation environment is the research object. The meso-scale model is constructed by using the brittle fracture model based on the cohesive theory. Meanwhile, the continuation fracture model based on the progressive damage theory, and the micro-crack generation and the extended behavior in different components are analyzed in detail. At the same time, in order to solve the limitation of traditional multi-scale method, a data-driven cross-scale fracture mechanics analysis method is proposed based on the data mining theory. The research results of the project are of great significance to the study of the cross-scale fracture behavior of nuclear fuel, and also provide a new way of thinking for exploring the combination of data mining theory and multi-scale method.

颗粒增强型核燃料具有广泛的应用前景，由于裂变反应和热/力/辐照环境的作用，该型燃料的断裂行为极其复杂。在细观尺度上，燃料颗粒中具有微裂纹生成、扩展现象发生，基体具有辐照损伤及延性断裂现象发生。由于细观断裂行为与宏观破坏之间的跨尺度行为，目前针对颗粒增强型燃料的断裂失效行为难以准确模拟。同时，传统多尺度力学模拟方法存在难以兼顾精度与效率的问题。本项目热/力/辐照环境下的核燃料为研究对象，利用基于内聚力理论的脆性断裂模型和基于渐进损伤理论的延续断裂模型构建精细化细观尺度模型，细致分析微裂纹生成及在不同组分中的扩展行为。同时，为解决传统多尺度方法的局限性，基于迅速发展的数据挖掘理论，构建数据驱动跨尺度断裂力学分析方法。项目研究成果对核燃料的跨尺度断裂行为研究具有重要意义，也为探索数据挖掘理论与多尺度方法的结合提供了新的思路。

本项目研究获得了适用于颗粒增强型核燃料的细观尺度精细化力学行为模拟方法及跨尺度分析方法。针对颗粒增强型燃料建模方法，完成了细观尺度基于数字图像和统计规律的两种有限元重构方法的研究并开发了自动建模程序。基于内聚力单元方法建立颗粒材料脆性断裂的模拟方法，通过双判据损伤模型建立基体材料延性断裂和剪切带破坏的模拟方法。提出了基于非正交周期性边界条件与实时均匀化方法的数据挖掘的层级跨尺度方法，利用复杂变形数据库对RVE模型进行加载并建立了切线模量数据库。具有网格划分简单、计算量小等优点。本项目为我国先进核燃料设计提供了精细化的力学分析工具，具备细观尺度及跨尺度的燃料失效行为模拟能力，对有效释放设计裕量，提高核燃料性能起到促进作用。