The Bending Performance Study of Bridge-Type Butt Joint of REBCO Tapes

To meet the magnetic field design requirements of a new detector for the Circular Electron Positron Collider, a novel aluminum-stabilized stacked rare-earth barium copper oxide (REBCO) tape cable has been proposed and developed. Bridge-type butt joints are utilized to interconnect the REBCO tapes within the cable for the production of kilometer-scale cables. In this investigation, bridge-type butt joints of the REBCO tape were fabricated using soldering techniques, and their bending performance under various bending diameters at 77 K and self-field conditions was examined through finite-element analysis and bending tests. The simulation and experimental results showed a gradual degradation in the critical current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub>) of the bridge-type butt joint under bending strain. Enhanced bending performance was achieved by positioning the joint gap at the lower side and increasing the gap between joints. When the gap distance is 10 mm, the critical bending radius threshold may lie between 25 and 20 mm. Finite-element analysis revealed a notable degradation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> when the equivalent strain surpassed 0.4%, indicating uneven stress distribution during bending, leading to localized areas experiencing elevated stress levels that could result in potential damage and degradation.