永磁体运动致使有限尺度非均匀超导薄膜断裂特性研究

Because it can work in liquid nitrogen environment, the high temperature superconducting thin films have great prospect. Inhomogeneity and Cracks inevitably appear in this kind of material because of the special production and manufacturing process.Although some researches on fracture mechanics of superconducting thin films havebeen made, all of the theory study, numerical analysis and experimental characterization are not enough. In particular, the research on fracture mechanics of inhomogeneous superconducting thin films has just started. This project is going to study the fracture behavior of superconducting thin films with finite size caused by electromagnetic force due to the permanent magnet moving parallel to the film in three ways of theoretical analysis, numerical simulation and experiment. The research contents include several aspects.Firstly, considering the effects of crack and material inhomogeneity on shielding current and magnetic field in superconducting thin films, a theoretical model for shielding current and magnetic field distribution in inhomogeneous superconducting films under permanent magnet action willbe established, and the corresponding numerical solution method will beput forward. Then, the application of coupling method of extended equal geometric analysis with multiple isoparametric element in fracture mechanics ofsuperconducting film will be studied, and the crack tip behaviors of several crack models on inhomogeneous superconducting film will be further numerically analyzed. Finally, model experimental study will be carried out for somecrack problems of superconducting film. The ultimate purpose of this project is to obtain reasonable degree of the crack models of inhomogeneous superconducting films based on these theoretical, numerical and experimentalresults, and further to lay the theoretical foundation for both design andmanufacturing of superconducting thin film components.

高温超导薄膜因可在液氮环境下工作，具有巨大应用前景。由于制造工艺的限制超导薄膜常含裂纹且是非均匀的。目前尽管人们对超导薄膜断裂力学问题做了一些探讨，但无论理论研究、数值分析还是实验表征都远远不够，特别是关于非均匀超导薄膜断裂力学研究才刚刚起步。本项目拟从理论分析、数值模拟和实验三种途径研究有限尺度非均匀高温超导薄膜在永磁体平行于薄膜运动时由电磁力造成的超导薄膜的断裂特性。研究内容包括：考虑裂纹和材料非均匀性对超导薄膜内屏蔽电流和磁场的影响，建立永磁体作用下相应的关于有限尺度非均匀超导薄膜内屏蔽电流和磁场分布的模型，研究其数值求解方法；探究扩展等几何分析与多等参元耦合方法在非均匀超导薄膜断裂力学中的应用，数值分析超导薄膜中各种裂纹模型的裂尖性态；开展相关问题的模型实验研究。研究的最终目的是根据理论、数值和实验结果，得到非均匀超导薄膜裂纹模型的合理度，为超导薄膜器件的设计与制造奠定理论基础。

高温超导薄膜凭借较高的临界转变温度和优异的磁电性能在超导智能器件领域具有广泛的应用前景。然而由于制造工艺的限制超导薄膜常含裂纹等缺陷，因此开展相关断裂问题的研究具有重要价值。项目组通过四年的努力：深入研究了含缺陷超导材料结构在永磁体运动或外加磁场作用下的断裂特性并取得实质性突破；对由永磁体和超导材料构成的超导悬浮系统的电磁特性及力学行为的研究取得新的进展并将研究成果应用至以超导轴承为核心的飞轮储能系统；对超导或磁电薄膜/板的屈曲、波动和弯曲等力学问题进行了系统研究，取得了系列成果；对于银基氧化物电接触材料断裂以及大电流接触线与相对高速运动下的受电弓之间的离线放电等问题也开展了一些研究并取得了新的进展。截止到2022年12月31日，已发表SCI收录论文23篇，授权国家发明专利3项。尽管本项目取得诸多成果，但受限于时间和精力，本项目在超导薄膜内部裂纹动态扩展机理及实验测试方面的研究仍有不足，而这也正是项目组接下来的工作重点。相信本项目的研究可以为超导材料的抗断裂设计及相关器件的可靠性分析提供理论指导和技术支撑。