Transverse stress effects in Nb3Sn cables

The effect of transverse compressive stress on the critical current of solder-filled and unfilled Nb3Sn cables is reported. The conductor used in this study is a Nb3Sn Rutherford cable manufactured with a bronze-process wire of 0.92 mm diameter. Like epoxy-impregnated cables, solder-filled cables exhibit much less degradation than wire samples when subjected to the same stresses. On the other hand, unfilled specimens are irreversibly damaged at the thin edge when loaded to 160 MPa, and show significantly higher degradation than similar specimens of the solder-filled cable. A finite-element calculation of the stress state inside a particular composite superconductor indicates that more compressive stress is developed in the virgin wire than in a straight wire segment in a real cable environment