Multiscale modelling and numerical homogenization of the coupled multiphysical behaviors of high-field high temperature superconducting magnets

Ensuring the safe and stable operation of the high temperature superconducting (HTS) magnet has become a key problem to be solved currently. In this paper, we developed a numerical homogenization scheme to simulate the coupled electromagnetic-thermal-mechanical behaviors of the REBCO (REBa2Cu3Ox, where RE = rare earth) high field magnets. The homogenized T-A formulation is adopted to model the electromagnetics of HTS tapes. The representative volume element (RVE) based on the micromechanics is created to predict the homogenization properties of the magnets. The field dependences of the critical current density of HTS tapes on the magnetic field, magnetic field angle, the temperature and the strain are considered. The effectiveness and efficiency of the proposed numerical scheme have been well validated through comparisons with experimental results. Moreover, the effects of the anisotropic plasticity on the mechanical behaviors of the HTS magnets are also evaluated. Our results show that compared with the Hill's anisotropic model the commonly used isotropic von Mises plasticity model underestimates the plastic strain in the magnet. Under ultrahigh magnetic field, quench of the magnet is mainly triggered by the strain-induced degradation in the critical current of HTS tapes, which needs special attention in the design of high field magnets.