Bending Strain Effects on the Critical Current of Bi-2223 Superconducting Tapes by Pure Bending Method

The effects of bending strain on the critical current of 19-filament Ag/Bi-2223 and 121-filament AgMg/Bi-2223 tapes produced by powder-in-tube method have been studied by a pure-bending method at 77K. The Icn(epsilon) curves are of two regimes, Icn does not decrease until bending strain increases to a limit epsilonirr. The epsilon0.9 values of 19-filament Ag/Bi-2223 and 121-filament AgMg/Bi-2223 tapes are 0.32% (negative bending), 0.64% (positive bending) and 0.30%, respectively. The Icn(epsilon) curves are fitted by the formulae Icn =1-(epsilon/a)b, where a and b is the material parameters. The strain dependences of the Icn values for the pure-bending, modified RRT and bending-rig methods were nearly identical up to epsilonirr.