Temperature, mechanical stress and induced current distribution in YBCO bulk during pulsed field magnetization
Résumé
A theoritical coupled thermal, mechanical and electromagnetic simulation of a YBCO disk during pulsed field magnetization was performed and the simulated resulting magnetic field was compared to experimental measurements. Due to the symmetry of the problem, a 2D axisymmetrical modelling using Finite Element Method was chosen, and A and T-formulations were compared. One of the complexity of modelling superconducting bulks is the actual determination of the currrent path within the bulk and how the micro-structure may play a role in limiting the intensity of induced current. Assuming an isotropic material, the pure knowledge of the temperature distribution resulting from the local resistivity of YBCO allows to define the limitation of the intensity of persistent current. However, the induced current in conjunction with the applied pulsed magnetic field in addition to thermal induced local stresses which is very little studied may play a role in the local dissipation as well. In the present work, the influence of one or the combination of both phenomena is studied to determne how they may explain early onset of local normal-zone transition and some of the experimental results reported hereinafter.