|Alternative Title||AC losses and mechanical properties of complex high temperature superconducting structures
|Place of Conferral||兰州
|Other Abstract||AC 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.|
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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