兰州大学机构库 >土木工程与力学学院
高温超导悬浮系统非线性动力特性实验与理论研究
Alternative TitleExperimental and Theoretic Investigations on the Nonlinear Dynamic Properties in High- Temperature Superconductors Levitation System
黄毅
Thesis Advisor周又和
2016-10-01
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword超导体 裂纹 YBCO 奇异性 超导悬浮 分岔 混沌 温度跳跃 磁热不稳定
Abstract

高温超导体与永磁体构成的悬浮系统具有悬浮力大、时间稳定性强且无需外界能量输入等优点,在能源、交通、材料科学等领域具有广泛的应用前景。研究超导体与永磁体之间的相互作用力及其在外界激励下悬浮体动态响应特征是该悬浮系统安全性与功能性设计的基石。目前已有大量研究针对高温超导悬浮系统准静态悬浮力,对系统在周期激励下的动态响应特性也有部分理论分析,但对系统在强激励作用下的非线性运动特征如混沌、分岔等现象都没有涉及,特别是悬浮体在非线性运动过程中自身的能量耗散及由此引起超导材料的温度变化这一关键科学问题一直没有得到研究。从实验研究的角度讲,主要难点在于当悬浮体呈现分岔、混沌等强非线性特性时,超导体表面温度的多点实时测量受到低温有限空间、感应电磁干扰等因素难以开展。从数值模拟的方面,高温超导体与永磁体之间相互作用力具有强的非线性,超导材料电磁本构关系同样具有强的非线性,超导材料表面热扩散过程也是具有强非线性特征,且均与悬浮体动力运动方程耦合,这些因素都给这个问题的解决带来了较大的难度。本博士学位论文针对高温超导悬浮系统在外界强激励作用下的动力响应问题开展实验和理论研究。自行研制高温超导材料表面温度、磁场实时测量的多点测试系统,对悬浮体动力运动过程中的悬浮力特性、表面磁场和温度特性进行了实验测量。在小组已有研究工作基础上,完成包含超导体温度扩散方程的数值求解程序,并进行验证。最后,实验验证了超导体内部裂纹尖端电流强度因子“-1”次幂的理论分析,为后续含有裂纹的超导材料电磁力及其变形特性研究提供了基础。主要研究工作如下:

自行设计并完成悬臂梁形式的高温超导悬浮系统动态测试系统的设备。主要功能包括:永磁超导之间悬浮力实时测量、悬浮体时间响应实时测量、外界激励幅值实时测量和超导体表面温度多点实时测量。该系统力分辨率为mN量级,温度和位移测试精度分别为±0.1K和±5μm。实验中根据不同的初始场冷却高度、外加激励频率和振幅,获得四种类型非线性运动:倍周期分岔运动、混沌运动、4倍周期分岔运动和拍现象。测量了永磁体直径变化对悬浮体动力运动过程中表面温度的变化,得到永磁体直径对超导体表面温度的影响规律。同时在倍周期分岔运动初始时刻发现超导体温度跳跃现象,温度跳跃的幅值远大于临界温度。其次,采用有限元方法计算高温超导体电磁场和温度场以及系统非线性运动,在小组已有研究工作基础上编译程序并验证程序的准确性。计算忽略温度效应和考虑温度效应的悬浮体响应特性,给出系统发生倍周期分岔运动时相应结果。分析悬浮体宏观分岔运动与超导体内微观磁通运动之间的关系。最后,研究超导体内部裂纹对感应磁场和感应电流分布影响。小组已有针对超导体内部裂纹尖端临界电流分布特性的理论分析均考虑裂纹处于超导体的中心,这给实验研究带来一定的难度。为此,本论文考虑裂纹处于超导体边缘,同样得到裂纹尖端临界电流分布具有奇异性,且奇异性的阶数仍为“-1”。采用自行研制的超导体多点磁热测试系统,在超导体表面,裂纹周围布置16路探头,实时同步测量了场冷磁化过程中裂纹周围的磁场分布,并计算出裂纹周围的电流分布。实验结果显示裂纹尖端临界电流分布有奇异性,奇异性的阶数为“-1.37”,分析理论和实验结果的差异。

Other Abstract

Levitation system is composed of high-temperature superconductors(HTSs) and permanent magnets with large levitation force, strong stability and no external energy input, has wide application prospect in energy, transportation, and materials science and other fields. The investigations of the interaction force between superconductor and permanent magnet and levitation system dynamic response characteristics is the cornerstone of security design. Now many studies on the quasi static levitation force system, part of the theoretical studies on dynamic characteristics under periodic excitation response, but the nonlinear motions caused by strong excitation such as chaos, bifurcation and so on are not involved, in particular the studies on the superconductor temperature change in the process of movement caused by energy loss has not been involved. From the point of view experimental investigation, the main difficulty is that when the levitation system show the bifurcation, chaos and nonlinear characteristics the superconductor surface temperature of multi-point real-time measurement limited by space in the low temperature, electromagnetic interference and other factors. From numerical simulation, high-temperature superconductors and permanent magnets relation strong nonlinear, superconducting materials and electromagnetic constitutive relation also strong nonlinear, superconducting material surface thermal diffusion process is strong nonlinear characteristics and coupling with the levitation dynamic equations of motion, which brought greater difficulty to solve the problem. In this doctoral dissertation, experimental and theoretical study the levitation system nonlinear motion in the external excitation, developed a real-time measurement system test superconducting material surface temperature and magnetic field. Experimental measurements levitation force characteristics and surface magnetic field and temperature characteristics in dynamic movement process. On the basis of the research work of the group completion the numerical solution procedure by add the temperature diffusion equation and to verify. Finally, experimental analysis of the crack tip current intensity factor “-1” power in the superconductor, provides a basis for the study of the electromagnetic force and deformation characteristics of superconducting materials with cracks.

Designed a HTSs levitation dynamic testing system with cantilevers. Main functions include: real-time measurement magnetic levitation force, levitation time response measurement, real-time measurement external excitation amplitude and multipoint real-time measurement the superconductor surface temperature. The system force resolution is mN order of magnitude, the temperature and displacement measurement accuracy is ±0.1K and ±5μm. According to different initial field cooling height and the vibration frequency or amplitude, obtain four types of nonlinear movement: period-doubling bifurcation motion, chaos movement, 4th period-doubling and beat phenomenon. The permanent magnets diameter changes effect on surface temperature of superconductors in the process of the levitation dynamic movement. The temperature of superconductor jump in the bifurcation movement and the temperature jump amplitude is much greater than the critical temperature. Secondly, numerical simulate HTSs maglev system nonlinear motion. Calculate the HTSs electromagnetic field and temperature by the finite element method, solve the system nonlinear movement, then verify the accuracy of the program. Consider with and without temperature influence in period-doubling bifurcation motion, analysis of the bifurcation motion with magnetic instability phenomenon. Analysis the relationship between macro bifurcation in system and micro flux motion in superconductor. Finally, analysis of crack in superconductor effect on magnetic field and current distribution. The group has been focused on the theoretical analysis of the critical current distribution characteristics of the crack tip in the superconductor, considered the crack is in the center of the superconductor, which was difficulty to the experimental study. Therefore, this paper considers that the crack is at the edge of the superconductor, the critical current distribution of the crack tip is singular and the order of singularity is still “-1”. In the superconductor surface, arranged 16 probes real-time measurement of the magnetic field around the crack in the field cooled magnetization process, calculated the current distribution around the crack with superconductor multi-point thermal magnetic testing system, the experimental results show that the critical current distribution of the crack tip is singular, and the order of singularity is “-1.37”,analysis the difference between the theory and the experiments.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226411
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
黄毅. 高温超导悬浮系统非线性动力特性实验与理论研究[D]. 兰州. 兰州大学,2016.
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