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International audience; —An electromagnetic simulation of YBCO bulks was performed and the resulting trapped magnetic flux density was compared to Field Cooling experimental measurements for an applied magnetic flux density up to 3 T. The simulation relied on an axisymmetric problem implementing an A-formulation of the Maxwell’s equations solved by means of the Finite Element Method so that the time evolution of the magnetic flux density was computed over the cross section of the bulk. To derive its electrical conductivity, a classic power law was adopted that includes the dependence of the critical current density upon temperature and external magnetic field modelled on the basis of a Modified Kim-Anderson relation. It was found that this model tends asymptotically towards the critical state for which the n-value becomes a free parameter that should be then estimated experimentally. The experimental results could be fairly reproduced at different operating temperatures with the best trapping at temperatures below 77 K benefiting from an increasing critical current density.

International audience; Most of the latest models of HTS bulk magnetization take into account the thermal and electromagnetic coupling, but, they still lack the implementation of the mechanical deformation under strong magnetic fields. The following work tries to fill up partly the gap by proposing a model of the dependence of the electrical conductivity upon mechanical deformation during Field-Cooling magnetization. This dependence is carried out by the critical current density as a function of induced thermal and mechanical strain in the bulk. As a first approximation and bearing in mind the obvious discrepancies, a simple model inferred from HTS thin films and generic knowledge on ceramics is proposed. This first approach allows drawing some generalities on the expected thermal, magnetic and mechanical response of disk-shaped YBCO pellets during magnetization. The utter goal is to assess design parameters to insert those pellets in electrical rotatory machines.

International audience; A theoritical coupled thermal, mechanical and electromagnetic model of a YBCO disk under Field Cooling and Zero-Field Cooling magnetizations was implemented and the trapped magnetic flux density was computed as a function of the applied magnetic field. Due to the symmetry of the problem, an axisymmetrical model using Finite Element Method and the A-formulation of the Maxwell’s equations were implemented. One of the complexity of modelling superconducting bulks is the actual determination of the currrent path within the bulk which strongly depends on the chosen model of the critical current density. Assuming an isotropic material, the pure knowledge of the temperature distribution resulting from local Joule dissipation allows to define in first approximation the limitation of the intensity of persistent currents. However, the induced current in conjunction with large applied magnetic fields may lead to large mechanical stresses in addition to the pre-existing thermal induced ones. These effects mechanical in nature may well play a role in the local dissipation especially under intense magnetic field and pulsed magnetization. In the present work, the influence of the combination of both phenomena is qualitatively studied to determine how they may influence the magnetic behaviour of YBCO bulks and their ability to capture large magnetic flux densities.