Coupled multiphysics modeling of the thermal-magnetic-mechanical instability behavior in bulk superconductors during pulsed field magnetization

Abstract

Magnetization is of great importance for the application of bulk superconductors. Flux jumps are frequently-encountered challenges during magnetization, leading to sharp temperature rises and material failure, and eventually affecting the field trapping capability of bulk superconductors. Intrinsically, the flux jumps and mechanical failure induced by thermomagnetic instability are coupled with each other, which makes the numerical simulation of the magnetization of bulk superconductors a challenging task. In this paper, a numerical simulation framework is developed based on my previous work (Jing 2020 Supercond. Sci. Technol. 33 075009), which further couples the H-formulation and the phase-field fracture model with the heat diffusion equation to simulate the flux jump and mechanical failure behaviors of bulk superconductors during magnetization. The experimentally observed features of the flux jumps are reproduced, and the corresponding mechanical failure is evaluated. The magnetic field, temperature, stress/strain, and mechanical failure within the bulk sample are presented. It is found that the varying ramp rate of the pulsed field significantly influences the flux jump behaviors of bulk superconductors. The optimum characteristic time of the pulsed field for the final trapped field is predicted through numerical simulations.