超导体力电特征及电磁行为可调性的研究

The superconducting magnets which are composed of superconductors have superior properties which normal magnets do not possess. With the development of the superconductors which can be used in large-scale applications,the superconducting magnets have been applied in many applications. As the superconductivity keeps developing,the mechanical behaviour also attracts attention of the researchers. Superconductors have complex nonlinear electromechanical behavior. The investigations of improving mechanical and magneto-thermal stability of superconductors and realizing the tunability of electromagnetic behavior with mechanical loadings have important scientific significance and application value. This proposed project will study the following problems: (1) The effects of inclusions on the mechanical and electromagnetic behavior will be analyzed so that the optimized distribution of inclusions which enhances the mechanical stability and improves the trapped field can be obtained; (2) We aim to investigate the flux jump in the superconductors by considering the electromechanical coupling behavior, analyze the impact of mechanical loadings on the magneto-thermal stability and the approach to improve the magneto-thermal stability; (3) The theoretical model which can describe interaction between the superconductor and ferromagnet will be established, the relationship between the mechanical loadings and electromagnetic behavior in Superconductor-Ferromagnet structure is studied and the tunability of electromagnetic behavior with mechanical loadings is realized;(4) The structure which can achieve magnetic cloaking will be designed by means of theoretical calculations and experiments, and the effects of deformation on the invisibility of cloaking structure in non-uniform field and time varying field are discussed.

由超导体构成的超导磁体具有常规磁体材料不具备的优越性能，随着大规模实用化超导体研究的不断发展和深入，超导磁体的应用范围也越来越广。超导体在不断提升超导电性的同时，其力学行为也引起了研究人员的重视。超导体具有复杂的非线性力电行为，提升超导体力学和磁热稳定性以及实现力学载荷对超导体电磁行为的可调性有着重要的科学意义和应用价值。本项目拟展开以下几个方面的研究工作：(1)分析超导复合材料中的夹杂对其力学行为和电磁行为的影响，寻求增强超导体力学稳定性并提升超导体俘获场的优化夹杂分布；(2)探讨力电耦合条件下超导体中的磁通跳跃行为，揭示力学载荷对超导体磁热稳定性的影响及改善磁热稳定性的途径；(3)建立超导-铁磁结构中相互作用的理论模型并研究力学载荷与超导电磁行为的关系，实现超导电磁行为的力学载荷可调性；(4)借助理论计算和实验设计合理的磁隐形衣，探讨不同变形时磁隐形衣在非均均和时变磁场中的隐身效果。

零电阻等特殊的物理性质使得超导材料在能源、交通以及大科学装置等领域具有显著的优越性。随着超导材料载流能力的不断提升，其在极端环境下的力学响应、热稳定性及电磁行为引起了研究人员的广泛关注。(1) 本项目首先研究了超导复合材料中的力电行为。基于临界态模型及有限元方法给出了电磁力作用下Bi2223超导带材、超导电缆及堆叠超导带材中的应力的变化规律。超导结构中的应力随着外加磁场增大而增大，但应力分布显著依赖于超导线材或带材的排布方式。此外，本项目研究了动态电磁力作用下超导块体中的断裂行为，借助Mori-Tanaka方法定量表征了Nb3Sn超导股线中的等效模量。(2) 本项目研究了超导材料及结构中的热稳定性。借助快速傅里叶变换的方法求解了Maxwell方程组及热传导方程，揭示了超导薄膜临界电流非均匀性和内部裂纹对磁通崩塌行为的影响。发现相比于均匀的超导薄膜，非均匀薄膜中的热稳定性较低，而内部裂纹位于薄膜中心时对热稳定性的影响最小。进一步建立了电-磁-热-力的多物理场耦合模型，揭示了无绝缘线圈失超及恢复过程中的温度、电流及应力的变化规律。(3) 本项目研究了超导结构中的交流损耗及临界电流。借助H方法给出了外加应变及铁磁材料对交流损耗的影响，发现外加磁场及传输电流条件下应变对交流损耗的影响并不一致，强磁性材料可以有效的降低超导线圈的交流损耗。此外，本项目建立了预测超导结构临界电流的多级等效模型并给出了超导电缆及线圈临界电流的变化规律，该模型在保证计算精度的基础上可以有效的减小计算量。