Numerical modelling of mechanical stresses in bulk superconductor magnets with and without mechanical reinforcement
Numerical modelling of mechanical stresses in bulk superconductor magnets with and without mechanical reinforcement
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DOI：
10.1088/1361-6668/aaf851
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发表时间：
2019-02
影响因子：
3.6
通讯作者：
M. Ainslie;K. Huang;H. Fujishiro;J. Chaddock;K. Takahashi;S. Namba;D. Cardwell;J. Durrell
中科院分区：
文献类型：
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作者：
M. Ainslie;K. Huang;H. Fujishiro;J. Chaddock;K. Takahashi;S. Namba;D. Cardwell;J. Durrell
大块超导体的磁场俘获能力基本上由材料的临界电流密度Jc（B，T）决定。利用现有技术的体（RE）BCO（其中RE =稀土或Y）材料，很明显，超过20 T的捕获场是潜在可实现的。然而，在样品磁化过程中产生的大洛伦兹力FL = J × B会导致大的机械应力，从而导致机械故障。径向力是拉伸的，并且由于（RE）BCO材料的脆性陶瓷性质而不能很好地抵抗所产生的应力。当磁场超过17 T时，使用树脂浸渍和碳纤维包裹或收缩配合不锈钢对样品进行机械增强。在本文中，二维（2D）轴对称和三维（3D）有限元模型的基础上的H-制定，实现在商业有限元软件包COMSOL Multiphysics的，是用来提供一个全面的图片的机械应力在块状超导磁体与无机械加固场冷磁化。所选择的建模框架将电磁、热和结构力学模型耦合在一起，并且非常灵活，允许包含各种磁化过程和条件，以及所涉及材料的详细和真实的特性。的2D模型，一个更快的路线参数优化，首先用于调查的斜坡率的影响所施加的领域和任何热量产生的散装。最后，利用三维模型研究了大块超导体ab面附近Jc（B，T）的非均匀性对机械应力的影响。
The magnetic field trapping capability of a bulk superconductor is essentially determined by the critical current density, Jc(B, T), of the material. With state-of-the-art bulk (RE)BCO (where RE = rare earth or Y) materials it is clear that trapped fields of over 20 T are potentially achievable. However, the large Lorentz forces, FL = J × B, that develop during magnetisation of the sample lead to large mechanical stresses that can result in mechanical failure. The radial forces are tensile and the resulting stresses are not resisted well because of the brittle ceramic nature of (RE)BCO materials. Where fields of more than 17 T have been achieved, the samples were reinforced mechanically using resin impregnation and carbon-fibre wrapping or shrink-fit stainless steel. In this paper, two-dimensional (2D) axisymmetric and three-dimensional (3D) finite-element models based on the H-formulation, implemented in the commercial finite element software package COMSOL Multiphysics, are used to provide a comprehensive picture of the mechanical stresses in bulk superconductor magnets with and without mechanical reinforcement during field-cooled magnetisation. The chosen modelling framework couples together electromagnetic, thermal and structural mechanics models, and is extremely flexible in allowing the inclusion of various magnetisation processes and conditions, as well as detailed and realistic properties of the materials involved. The 2D model—a faster route to parametric optimisation—is firstly used to investigate the influence of the ramp rate of the applied field and any heat generated in the bulk. Finally, the 3D model is used to investigate the influence of inhomogeneous Jc(B, T) properties around the ab-plane of the bulk superconductor on the developed mechanical stress.