Critical current degradation behaviour in Bi-2223 superconducting tapes under bending and torsion strains

In this paper, we have investigated the I c degradation behaviours in Ag alloy sheathed Bi-2223 superconducting tapes under bending and torsion strains. In particular, we have examined the homogeneity of I c degradation along the longitudinal direction of tapes by adopting multiple voltage terminals. The bending modes influenced the I c degradation behaviour in Bi-2223 tapes. A gradual and consistent decrease of I c could be observed at all sections, which was a different behaviour from that under tensile loading. Up to ε irr , I c showed a nearly similar degradation at each section, due to a simultaneous initiation of cracks from defects indicating that uniform deformation occurred in tapes with bending. Over ε irr , some variations in the I c degradation occurred due to the difference of crack growth rates at each section. In particular, the behaviour appeared significantly with hard bending. The degradation of I c in Bi-2223 tapes by torsion occurred gradually when the torsion angle exceeded 150°. However, the I c degradation by torsion strain was small compared with other types of loading. Also, the I c degradation behaviour at each section along the longitudinal direction of tapes was gradual and consistent, representing a uniform torsional deformation in the tapes.