Degradation Due to Flatwise and Edgewise Bending on Critical Current of BSCCO Tapes

K Osamura,T Kato,S Yamade

doi:10.1109/tasc.2022.3153752

Abstract

In order to clarify the influence of edgewise and flatwise bending as well as tensile load to critical current of DI-BSCCO tapes, the critical current measurement was carried out under those external loads. Both flatwise and edgewise bending gave a degradation of critical current. The reversible strain limits ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵb, 95 ) resulted in 0.36 – ∼0.41 and 0.28–0.32% the aforementioned bending modes, respectively. Even though the bending diameter giving the degradation of critical current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I c ) up to 95% of the original one ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I c00 ) was in the range of ∼45–55 and 1200–1750 mm for the flatwise and edgewise ones the reversible strain limits were close to each other. This suggested that the position reaching the maximum bending strain (ϵ b ) acts as a starting point of degradation. The critical current decreased gradually up to 95% of original value, of which strain (stress) is assigned as ϵ 95 (σ 95 ). When the strain exceeds ϵ 95 , the critical current decreased rapidly. During this process, the upper part <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ BSCCO,T + <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ b reached the fracture strain ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ f ) at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ 95 and σ 95 , where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ BSCCO,T is the residual strain induced in BSCCO filament under non external stress. The large <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ b resulted in the small <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ 95 and σ 95 .

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