Influence of bending and torsion strains on critical currents in YBCO coated conductors

A YBCO coated conductor is expected to be a next generation high performance superconductor. To design superconducting machines using YBCO conductors, evaluation of not only superconducting properties but also mechanical properties is very important. Hence, we applied bending and torsion to the YBCO conductor and measured degradation of the conductor against the strain. To compare with the YBCO's data, a Bi2223 conductor was also tested under the same experimental condition. From the bending test, degradation of the Bi conductor was faster than that of the YBCO conductor and the critical current gradually decreased with increasing bending strain. The YBCO conductor kept better performance than the Bi conductor, and degradation suddenly occurred. And when the superconducting layer in the YBCO conductor was subjected to compressive strain in the bending test, the critical current hardly decreased at approximately one percent of the bending strain.