Influence of cracks on nonlinear motion of high-temperature superconducting magnetic levitation system

The magnetic levitation system of a high-temperature superconductor (HTSC) has nonlinear vibration under external excitation, in which the HTSC is subjected to a sizable electromagnetic force. The high-temperature superconducting block is a brittle material, which will crack when subject to heavy pressure. Microfracture of superconductors is inevitable, especially in superconducting magnetic levitation systems. Our paper studies the fracture behavior of a YBaCuO superconducting magnetic levitation system under a large electromagnetic force based on nonlinear bifurcated motions. The E − J constitutive model and the current vector T method are applied to obtain the electromagnetic force of the bulk superconductor during vibration. We analyze the effects of five lengths of the central crack on vibration displacements, the electric field distribution, and the electromagnetic force of superconductors. Without damages, the system does not have apparent bifurcation motion. For the inner cracks, the system has obvious bifurcation motions. The results show that the cracks have a meaningful influence on the nonlinear vibration of the superconducting magnetic levitation system. The displacement of the suspended permanent magnet in bifurcation motion increases with the increase in the crack length, and the collision occurs when the crack length reaches 15 mm.