兰州大学机构库 >土木工程与力学学院
复杂高温超导结构的交流损耗和力学特性
Alternative TitleAC losses and mechanical properties of complex high temperature superconducting structures
黄晨光
Thesis Advisor周又和
2015-06-05
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword高温超导体 热-磁耦合 临界态模型 幂定律模型 交流损耗 退磁效应 磁致伸缩 最小磁能方法 超导磁悬浮运输系统 超导-铁磁耦合
Abstract高温超导体的交流损耗和力学特性是当前超导应用中关注的基础性课题。在考虑热电磁耦合作用的基础上,本论文从理论和数值上展开了复杂高温超导结构的交流损耗和力学特性的研究。 首先,基于热-磁耦合模型,数值分析了超导圆柱线材和板材内温度场和电磁场的时间演化规律。研究发现,若外磁场幅值小于或大于完全穿透场,频率的增大分别会减少或增加交流损耗。仅当传输电流幅值较大时,热-磁耦合作用才会明显地影响交流损耗。 其次,基于临界态模型和最小磁能方法,研究了外磁场作用下二维任意形状超导薄膜和三维轴对称超导块体的电磁力学特性,结果表明在任意形状超导薄膜内,裂纹缺陷出现后其尖端附近的感应电流密度急剧增大。而在轴对称超导块体内,空洞缺陷的存在使得超导壁厚在超过某一临界值后出现了奇特的磁致伸缩曲线“翻转”现象。 最后,将最小泛函方法应用于不同含铁磁材料的高温超导系统的力学性能分析。对于导轨中含铸钢等铁磁材料的超导磁悬浮运输系统,结果显示在大多数磁悬浮运输系统中,特定尺寸和位置的铁磁材料才能较大程度地提高系统的悬浮性能。对于以镍钨合金等铁磁材料为基底的超导涂层导体,提供了一些理论指导来有效减小涂层导体断裂与撕裂脱层的风险。
Other AbstractAC losses and mechanical properties have become the fundamental subjects in currently superconducting applications. Based on the thermal electromagnetic coupling properties, the AC losses and mechanical properties of complex high temperature superconducting structures are theoretically and numerically investigated in this thesis. Firstly, based on the thermal-magnetic coupling model, the time evolutions of temperature and electromagnetic fields in superconducting cylinder and slab can be obtained. It is found that when the amplitude of magnetic field is less than or greater than the full penetration field, the AC losses will be respectively decreased or increased with increasing frequency. Only when the current amplitude is relatively large, the thermal-magnetic coupling will significantly affect the AC losses. Secondly, based on the critical state model and the magnetic energy minimization method, the electromagnetic mechanical properties of two-dimensional arbitrary shaped superconducting films and three-dimensional axisymmetric superconducting bulks in external magnetic field are systematically studied. Results show that in arbitrary shaped superconducting films, when the crack is appeared, the induced current density around crack tip is sharply increased. In axisymmetric superconducting bulks, a flipping behavior of the magnetostriction curves is observed in the magnetization process when the wall thickness changes through a critical value. Finally, the functional minimization method is applied to analyze and improve the mechanical performance in different high temperature superconducting systems containing ferromagnetic materials. For superconducting magnetic levitation transportation systems with guideway containing ferromagnetic materials, such as iron or steel, results show that in most configurations the soft ferromagnet contributes to effectively improve the levitation performance only when they have particular locations and dimensions. For superconducting coated conductor containing ferromagnetic substrate, such as Ni-W alloys, some theoretical guidance is provided to effectively reduce the risk of fracture and delamination in coated conductors.
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226499
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
黄晨光. 复杂高温超导结构的交流损耗和力学特性[D]. 兰州. 兰州大学,2015.
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