Electromechanical degradation of REBCO coated conductor tapes under combined tension and torsion loading

Abstract

In this study, the electromechanical and critical current degradation behaviors of rare earth–barium–copper–oxide (REBCO) coated conductors (CCs) under uniaxial tension, torsion, and tension–torsion deformations were experimentally and theoretically investigated. A self-designed apparatus was established to provide a 77 K cooling environment incorporated with a mechanical loading fixture to determine the critical current (Ic) under different deformation modes. The effects of the deformation and mechanical properties of REBCO CCs on the Ic and its degradation were addressed. Uniaxial tensile tests demonstrated that the irreversible Ic degradation was mainly related to the plastic failure of the conductor. A comparative analysis of the electromechanical behavior of the three deformation modes indicated that the longitudinal strain in the REBCO superconducting film was responsible for Ic degradation, unifying the characterization of different deformation modes. Furthermore, the degradation modeling of the strain dependence of Ic based on the Ekin power-law formula and Weibull distribution function was extended to examine the influence of different deformation modes. The phenomenological model can predict Ic degradation behavior effectively, including reversible and irreversible processes in the combined tension–torsion deformation mode.