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, which lead to sharp temperature rises and material failure and eventually affect the field trapping capability of bulk superconductors. Intrinsically, flux jumps and mechanical failure induced by thermomagnetic instability are coupled with each other, which made 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 Z 2020 Supercond. Sci. Technol. 33 075009), which further coupled 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 t0 of the pulsed field for the final trapped field is predicted through numerical simulations.

R-z plane spatial critical current inhomogeneity-induced mechanical response of GdBCO superconducting bulks during field cooling magnetization

“…where Γ 1 , Γ 2 , Γ 3 are set to the stress-free boundary condition, and the displacements in z direction of bottom surfaces Γ 4 , Γ 5 are constrained to zero [23].…”

“…Subsequently, according to strain measurement results, Takahashi [7] and Namba [17] constructed 2D and 3D numerical models to analyze the fracture behavior of HTS bulk and further considered the effect of the real structure of the mechanical support apparatus. Recently, apart from the FEM, the extended finite element method (XFEM) [18,19], peridynamics (PDs) [20,21], and phase-field method [22,23], the theories of fracture mechanics, were also gradually employed in the structural failure analysis of bulk materials caused by crack propagation.…”

“…Zhang [30] applied Trillaud's model to analyze the electromagnetic-mechanical coupled behavior of a staggered-array homogeneous bulk HTS undulator during FCM and the final simulation results show excellent agreement with the experimental data. In addition to the correlation between mechanical strain and J c , Jing [23] analyzed the coupled electromagnetic-mechanical fracture behavior of homogeneous HTS bulks during PFM by introducing a phase-field fracture variable f into the traditional J c model. Given that the above models utilized a homogeneous J c distribution, it is necessary to reconsider the electromagnetic-mechanical coupled behavior under the r-z plane inhomogeneous J c model.…”

Mechanical effects: challenges for high-field superconducting magnets

“…Recently, Zhou et al . [ 7 ] reported a new phenomenon of mechanical perturbation-induced quench. Jing et al numerically simulated the thermal-magnetic-mechanical properties in bulk and films.…”

Fast time-varying current triggering flux jumps of multi-filamentary Nb3Sn wire exposed to oblique magnetic field

“…This scheme was further validated in work considering the effects of strain and field slope on the magnetothermal instability of composite multifilamentary Nb 3 Sn wires within superconducting coils [46,47]. Moreover, for the bulk superconductors, Zhang [48] and Jing et al [49] successively simulated the flux jump of bulk superconductors during magnetization accompanied by thermal and mechanical strains. Nevertheless, numerical simulations for the analysis of thermal-magneto instability of complex superconducting magnets with oblique magnetic fields and excitation currents are still far less explored.…”