The 77-K Stress and Strain Dependence of the Critical Current of YBCO Coated Conductors and Lap Joints

The electromechanical performance of commercially available YBCO high-temperature superconductor (HTS) is characterized in support of the 32T all-superconducting magnet program at the National High Magnetic Field Laboratory. Accurate characterization of the HTS coated conductors mechanical properties are essential for the aggressive high-field magnet design. Here, we report the 77-K stress-strain behavior of a series of conductors with varying thickness coatings of copper. The electromechanical performance of the conductors is determined in tests to measure the critical current as a function of applied axial strain, at 77-K in self field. Available conductor lengths necessitate a magnet design with soldered lap joints and the subsequent evaluation the lap joint performance reported here. Reports of low transverse strength and conductor delamination due transverse (
c
-axis) tensile stress prompted tests to measure the conductors' electrical performance in the presence of transverse stress that are also reported.