Strain analysis of I-c(epsilon) characteristic of YBCO coated conductor measured by a Walters spring

Abstract

lc-strain characteristic of YBCO coated conductor was measured using a Walters spring (WASP). In this technique, additional bending and thermal strains induced to the YBCO layer should be considered. In order to produce different initial bending strain to the YBCO layer, the conductor was wound around the springs with different diameters and in the different bending directions. The clear evidence was obtained that -strain curves using a WASP strongly depend on the initial bending strain state. However, when -strain curves were normalized by a maximum value, all of the curves even including the data measured by uniaxial strain method for a short sample fall on to the same curve. Strain analysis based on the rule of mixture probes that the shift along the strain axis for each -strain curve can be explained by the bending and thermal strain during soldering. This result suggests that combined strain of bending and tensile strains can be regarded as simple summation in the present YBCO coated conductor.