Influence of mechanical properties of HTS cable to its critical current

Mechanical properties of HTS cable cores have been experimentally investigated. As is well known, HTS tapes with Ag-sheathed Bi-2223 have weak mechanical properties. Most attention to the weakness have been concentrated on the tape itself. However for realizing HTS cables, it is necessary to examine mechanical properties of the cable, because the performances of HTS cables are affected by stresses during cable production and their final uses. Three mechanical tests were performed; (1) a thermal cycle test, (2) a bending test and (3) a tensile test. In the thermal cycle test, Ic was not influenced. In the bending test, Ic depended on a bending radius, and a bending radius of less than 500 mm caused a significant problem to the conducting and shielding layers of the cable. It was also found that a flexible former was more suitable for the HTS cable than a copper pipe former, although its pressure drop was higher for liquid nitrogen. The tensile test indicated that tensile strains of up to 0.3% did not decrease Ic, and at 0.5% tensile strain Ic decreased to 10% of the initial Ic. These results are useful for HTS cable design.