Effect of hard-way bending strain on the current-carrying properties of the REBCO tape

Abstract

REBCO superconducting tapes possess high critical temperature, large engineering critical current density, and high critical magnetic field, making them essential for winding high-field magnets above 20 T. Layer-wound coils offer advantages such as fewer joints and reduced Joule heating but involve inevitable hard-way bending, which induces strain that degrades critical current and can cause irreversible damage at high strain levels. This study investigates the effect of hard-way bending radius on the current-carrying properties of REBCO tapes with different structures. Critical current measurements were conducted in liquid nitrogen, combined with theoretical calculations and finite element simulations to characterize strain distribution. The simulation accuracy was verified by the distributed optical fiber technique. Results reveal a nonlinear relationship between strain and hard-way bending radius, with strain concentrated at the tape edges. At a hard-way bending radius of 200 mm, the critical current of copper-plated tape decreased to 20 %, multi-filament tape to 18 %, while stainless steel-encapsulated tape retained 70 % of its critical current. These findings provide a theoretical basis for optimizing layer-wound coil fabrication.