Combined Tension-Torsion Effects on 2G REBCO Tapes for Twisted Stacked-Tape Cabling

One method of cabling flat REBCO tapes for high-current, high-field magnet applications is the twisted stacked-tape cable (TSTC) which stacks REBCO tapes between copper stabilizing strips and twist them along their axis. During fabrication and operation these TSTC conductors are subjected to various loading states including combined tension-torsion. To better characterize the electromechanical characteristics of the twisted stacked-tape cables the effect of tension on single twisted REBCO tapes was studied. A detailed structural finite-element analysis using ANSYS was done to investigate the stress-strain behavior, torque characteristics and axial elongation of REBCO tapes under pure torsion and tension-torsion loadings. The numerical strain results were combined with an analytical model to predict the critical current performance of these tapes. In addition to the numerical investigation, measurements of torque and critical current dependence on the axial load of twisted REBCO tapes at 77 K and in self-field were performed. A SuperPower sample with a 200-mm twist pitch saw 10% reversible critical current reduction under 700 MPa of tensile stress. Overall, a good agreement between the measurements and the finite element analysis was found validating the capability of the model to capture the electromechanical characteristics of REBCO tapes.