Bending Strain Dependence of Critical Current in BSCCO and REBCO Tapes

Abstract

Applying BSCCO and REBCO tapes to various engineering purposes, three modes of tensile and edgewise- and flatwise- bending are essential to deform the tape in pancake and spiral windings as well as twisting. Both kinds of tape consist of brittle superconducting (SC) oxide and several metallic components. Fine SC filaments are embedded in Ag matrix in BSCCO tape while single SC layer is put on the metallic sheet in REBCO one. These texture difference influences clearly on the bending dependence of critical current (I_c). The I_c of BSCCO tape decreased up to 95% of I_c0/I_c00 when the tape is bent to ∼53 mm diameter by flatwise bending and 1325–1682 mm by edgewise one. The equivalent flatwise bending strain was 0.29% –0.39% when the critical current degradation starts, while the critical edgewise strain was 0.29% –0.31%. In the case of REBCO tape, the I_c did not decrease up to 10 mm flatwise bending while it decreased by 405 mm edgewise bending. The degradation was observed to start from 1.04% edgewise bending strain while the flatwise bending did not give degradation up to 0.92% . The fracture behavior induced in BSCCO and REBCO tapes was discussed. The degradation starts from fracture of BSCCO filaments, while it originates to a delamination between the oxide and the metal interface in REBCO tape.