Influence of Fracture, Exfoliation, and Crack on Levitation Force Performance in YBCO High-Temperature Superconducting Bulk

High-temperature superconducting (HTS) maglev technology has currently been applied in fields such as flywheel energy storage and magnetic levitation. However, the specific mechanisms by which fractures in YBCO HTS bulks affect levitation performance remain unclear. To address this issue, experiments on the levitation force and trapped field of damaged HTS bulks have been conducted to investigate the effects of fractures. Furthermore, by applying appropriate magnetic field boundary constraints, the fracture, exfoliation, and crack of HTS bulks simulation method are developed. Both experimental and simulation results indicate that fractures along the a-c plane have a relatively minor impact on levitation force, with decay generally within 15%. For corner exfoliation, the maximum reduction in levitation force is around 5~8%. The influence of a-b plane crack, a-b plane fracture, and a-b plane exfoliation is fundamentally consistent, and the maximum reduction in levitation force remains below 13%, when the fracture height exceeds 6 mm and the depth ranges from 0 to 32 mm. This research can assess the visible surface crack to determine the usability of large-scale HTS bulk after damage, aiming to provide theoretical insights for the reliability of HTS bulks in practical applications.