Tensile strain transverse compressive stress dependence of critical current in Ag-sheathed Bi(2212) 7-core superconducting wires

The mechanical properties and tensile strain/transverse compressive stress dependence of the critical current I-c in Ag-sheathed Bi(2212) 7-core superconducting wires of different constructions were evaluated at a temperature of 4.2 K and a magnetic field of 14 T. The increase in the volume fraction of the superconductor shifted the stress-strain curves upwards. The tensile strain for I-c degradation onset was in the range 0.14-0.27%. This strain depends upon the residual compressive strain and the thickness of the superconductor layer. On the other hand, the transverse compressive stress for I-c degradation onset was in the range 9-20 MPa. Wires with a thin Ag-sheath layer showed a remarkably low stress for I-c degradation onset. There was no well-defined correlation between the onset stress for degradation of I-c caused by the tensile stress and that caused by the transverse compressive stress.