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题名 超导材料力-热-电-磁多场环境下的性能分析
姓名 景泽
院系 土木工程与力学学院
专业 固体力学
学位名称 工学博士
外文题名 Analysis on the properties of superconducting materials under mechanical-thermal-electromagnetic fields
第一导师姓名 周又和
关键词 超导体;应力;应变;Nb3Sn超导股线;YBCO;Ginzburg-Landau理论;磁通钉扎;微磁学;磁通崩塌;缺陷
外文关键词 superconductor;stress;strain;Nb3Sn superconducting strand;YBCO;Ginzburg-Landau theory;flux pinning ;micromagnetics;flux avalanches;defect
学科 工学
摘要 超导材料运行在力-热-电-磁等多物理场中,同时其超导性能与所处的磁场、电流、温度和应变等环境因素相关。因此,多场环境下超导材料的基本特性以及安全性、稳定性等问题是超导设备和器件应用过程中值得关注的基础性课题。本学位论文分别从宏观和微观角度研究超导材料在应用过程中的受力、变形及其对超导基本临界性能参数的影响。 首先,就目前具有广泛应用前景的两类超导材料(Nb3Sn超导股线和YBCO二代高温超导带材)在降温、电磁场以及外加机械载荷作用下的受力、变形以及临界性能进行理论建模和分析。基于复合材料细观力学理论中的Mori-Tanaka方法,建立了考虑Nb3Sn超导股线内部芯丝三维扭绞结构的理论模型,计算了股线在热应力以及外加机械载荷作用下的受力和变形。基于薄膜力学基本理论对YBCO二代高温超导带材在降温、外加磁场以及传输电流条件下的受力和变形进行力学建模和分析,给出了薄膜和基底材料物理参数、几何尺寸以及界面脱粘等因素对超导薄膜内正应力和界面剪切应力的影响规律。 其次,基于修正的Ginzburg-Landau理论从微观角度研究了变形对超导磁通涡旋凝聚以及超导临界性能的影响,讨论了耦合参数、外部压强以及几何尺寸等因素对超导体电磁行为的影响。此外结合微磁学理论及超导GL理论研究了超导/铁磁异质复合双层薄膜在外加磁场下的磁畴结构以及磁通涡旋演化过程。。 最后,从Maxwell电磁学方程、超导体的E-J指数模型以及热传导方程出发,研究了外加磁场作用下超导薄膜的磁热不稳定行为。给出了超导体发生磁热不稳定行为的临界磁场与外加磁场加载速率以及外界环境温度之间的关系。此外,通过直接数值求解耦合的Maxwell方程和热传导方程模拟了超导薄膜在外加磁场下的磁通崩塌过程。
外文摘要 Superconductors always operate under high electromagnetic fields at extremely low temperature, and the critical properties of witch depend on the transport current, the magnetic field, the temperature, and the stress (strain) state within the superconducting sample. Thus, investigations on the intrinsic properties and the safety-and-stability issues of superconductors are basic subjects for the application of superconducting devices. Starting from the macroscopic and microscopic perspective, the stress (strain) state and the intrinsic properties of superconducting materials under mechanical, thermal and electromagnetic field, the vortex dynamical behaviour and the flux pinning mechanism, the flux avalanche behaviours of the superconductors triggered by the themomagnetic instability are investigated in this thesis. Firstly, the mechanical behaviours and the critical properties of two promising candidates (the Nb3Sn superconducting strand and the second generation YBCO coated conductor) under mechanical-thermal-electromagnetic field are modeled and analyzed. A 3D theoretical model based on the Mori-Tanaka method in the micromechanics theory are proposed to analyze the stress (strain) state within the superconducting filaments and the overall effective properties of the Nb3Sn strand. Influences of the twisting of Nb3Sn filaments are considered in the simulation. In addition, the mechanical behaviours of the second generation high temperature superconducting coated conductor subjected to cooling and electromagnetic force are analyzed based on the thin film theory. The influences of the physical parameters and the geometry factors on the stress distribution in the film and at the film-substrate interface are discussed. Secondly, the vortex dynamics and flux pinning behaviour of the superconductors under magnetic fields are investigated within the Ginzburg-Landau theory. The coupling between lattice deformation and the superconducting electrons nucleation and its influences on the critical parameters of the deformable superconducting cylinder are investigated based on the modified Ginzburg-Landau equation. The effects of coupling parameters, the pressure and the geometry of the superconducting cylinder are considered in the analysis. The flux pinning effect of the secondary normal inclusion are also investigated. In addition, the magnetic domain patterns and superconducting vortices nucleation evolution in the superconductor/ferromagnet hybrid bilayer thin f...
研究领域 电磁固体力学与智能结构
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