Elastoplastic deformation and damage of REBCO insert coils induced by screening currents in ultra-high fields

Abstract The implementation of high-temperature superconducting (HTS) REBa2Cu3O7-x (REBCO) insert coils has become increasingly prevalent in ultra-high-field magnet technology. Nevertheless, the degradation of electromechanical performance caused by screening currents in REBCO insert coils remains a critical technological barrier for ultra-high-field HTS applications. This study proposes a refined electromagnetic-mechanical coupling model for REBCO insert coils in ultra-high field, fully considering the multilayer architecture of REBCO coated conductors (CCs) and the influence of co-wound stainless-steel tapes. The simulated screening-current-induced strains are in good agreement with experimental data. Numerical results reveal that interfacial damage occurs in the axial central region of the coil due to bending deformation caused by screening currents, which is mainly determined by the distribution of the interlaminar shear stress between the REBCO layer and Hastelloy substrate. Although the hoop strains in superconducting layers near the upper edges of the outer turns of the coil are more than the irreversible strain of REBCO CC, the current-carrying degradation of the coil is predominantly attributable to damage. Large hoop and axial stresses are respectively concentrated in the upper and middle sections of the coil, leading to plastic deformation in these zones. Moreover, the case of REBCO CCs bonded with stainless-steel tapes and the thicknesses of stainless-steel tapes have significant effect on the elastoplastic deformation and damage of REBCO insert coils in ultra-high fields. These findings could be valuable for the optimization design and analysis of ultra-high-field HTS insert magnets.