Tensile stress applied to NbTi, Nb3Sn, Bi-2223 and MgB2 composite superconductors at room temperature

Axial tensile stress was applied to four different composite wires containing the superconductors NbTi, Nb3Sn, Bi-2223 and MgB2 at room temperature. The basic mechanical properties obtained from the stress-strain characteristics of these wires are compared and discussed. The wire samples were then tested by transport critical current measurements at 4.2 and 77 K. The results obtained show that the critical current degradation of all composite wires occurs at the stress value corresponding to the beginning of the plastic deformation. These data have important implications for the technological application of such superconducting wires.