非均匀高温超导体的磁-热-力耦合分析及其失超研究

Since the discovery of the high temperature superconductors(HTS), superconducting materials have been widely used. The superconducting material is characterized by three basic parameters, namely, the critical temperature Tc, critical magnetic field Bc and the critical current density Jc. If any of the three basic parameters exceeds its critical value, the superconducting materials will lose its superconductivity, thus resulting in quench. When a superconductor in the mixed state is subjected to a time-varying magnetic field or transport current, its quench is caused by the magnetic flux move under the effect of the thermal activation and the electromagnetic force. Therefore, this project studies the interaction of magnetic-thermal-mechanics of nonlinear electromagnetic physics and multi-field coupling of inhomogeneous HTS under the alternating magnetic field to conduct research on such basic subjects of the high temperature superconductor as the electromagnetic response, mechanical response, quench conditions and quench speed. Numerical modeling, quantitative analysis, and basic experimental measurement are also involved in the project. The research provides the basic analytical framework and methodology for the application of inhomogeneous HTS to materials engineering.

自高温超导体发现以来，超导材料就得到了广泛的应用，超导材料的性质可由三个基本参量来表征，即临界温度Tc、临界磁场Bc和临界电流密度Jc。只要超导磁体在运行过程中有一个基本参量超过临界值，超导材料的超导性质就会消失，从而发生失超。由于超导体处于混合态且在交变外磁场和交变电流的作用下，超导体内部的磁通由于热激活和电磁力的作用会产生运动导致超导体内部温度超过临界温度而发生失超，本项目针对非均匀高温超导体的非线性电磁物理与多场耦合问题，开展交变磁场作用下超导体材料属性非均匀变化时磁-热-力耦合作用下的电磁响应、力学响应、失超条件以及失超速度等高温超导体中的基础性课题展开理论与数值建模、定量分析、基本实验测量研究，为非均匀高温超导材料工程应用中的力学设计提供基本的分析框架和方法。

本项目研究了非均匀高温超导体的非线性电磁物理多场耦合问题，建立了一个能够很好模拟超导体磁-力-热耦合特性的模型。在这个模型的基础上， 开展了交变磁场作用下非均匀超导体的电磁响应、力学响应及由于内部缺陷及裂纹引起的超导安全运行问题，对于超导体的失超条件和失超速度，重点研究了裂纹引起的失超，对于这一问题，我们计算了时变磁场中动态裂纹扩展对失超的影响及非均匀高温超导体中的裂纹问题，动态裂纹问题采用有限元法编程计算，超导本构采用Bean本构关系，非均匀高温超导体的裂纹问题采用基于实数基础解法，将这一问题解析的推导为奇异积分方程，然后数值的求解奇异积分方程得到这一问题的解。本研究实现了理论建模、定量分析及数值计算相结合的模式，对非均匀高温超导体的电磁特性及失超问题进行定量的计算，为超导材料在工程应用中的安全设计提供基本的分析方法。