Thermal effects associated with the crack of high-temperature superconducting magnetic levitation system

Abstract

Based on the magnetic flux pinning characteristics of the non-ideal type II superconductor YBa2Cu3O7−x, the high-temperature superconducting magnetic levitation system has the advantages of self-stability in levitation and low energy consumption. Thermal stress, electromagnetic force, and other mechanical stress may cause the micro-cracks to expand and eventually lead to fractures in the application of superconducting materials, significantly affecting the superconductor’s ability to transmit current. The superconducting magnetic levitation system with low damping is prone to nonlinear vibration of large amplitude under external interference, which affects the system’s regular operation. Due to the limitations of experimental conditions, it is difficult to analyze complex physical phenomena with cracks and obtain the distribution characteristics of electromagnetic, heat, and force inside the superconductor in the nonlinear vibration process, as theoretical modeling can compensate for this deficiency. In this paper, we study the fracture behavior of the YBa2Cu3O7−x bulk superconductor under nonlinear vibration based on the flux creep and flow models. The temperature of the superconductor in the nonlinear vibration of the superconducting levitation system is calculated with center cracks. The flux flow phenomenon in the bulk superconductor for various cracks under the bifurcation vibration is presented. The results show that the temperature of the superconductor will dramatically rise in nonlinear vibration under thermal insulation conditions, and the distribution position is affected by the cracks. For the 15 and 12 mm center cracks, a large amount of heat is generated around the crack and causes the temperature to rise above the critical temperature.