Mechanical analysis of trapped field HTS-stacked ring magnets with and without HTS stack inserts

Trapped field high-temperature superconducting (HTS) magnets have zero resistance and can maintain strong magnetic fields without external power supplies once properly magnetized. HTS-stacked ring magnets fabricated with commercial HTS tapes have demonstrated the ability to trap large and stable fields with more flexible sizes. However, during field cooling (FC) magnetization, the Lorentz forces and corresponding mechanical stress may cause damage to the magnets. Therefore, in this study, 3D numerical models are established and verified to investigate the stress and strain in HTS-stacked ring magnets. The stress distribution in the HTS-stacked rings under FC magnetization is calculated and the influence of sample fixation methods on the stress concentration and strain is discussed. The study also reveals that HTS stack inserts, which enhance the central trapped field, are subjected to unbalanced Lorentz force during magnetization, causing asymmetric stress distribution in the HTS stacks due to the asymmetric trapped field of the HTS-stacked ring magnets. These findings offer important insights into the mechanical behaviour of HTS-stacked ring magnets, which can guide the optimization of their design for various applications, such as nuclear magnetic resonance, Maglev, and HTS machines.