Influence of transverse compressive stress onI_cdegradation of Ag alloy sheathed Bi-2223 tapes

Abstract

In order to investigate the degradation of critical current (I c ) in the Ag alloy sheathed Bi-2223 tapes due to a transverse compressive stress introduced during manufacturing and operation of the HTS systems, a sample holder consisting of the upper block made of Ti alloy and the lower support plate made of glass fibre reinforced plastic was prepared. A shorter spacing of voltage taps caused large degradation of critical current with respect to compressive stress. It was found that the extent of the I c degradation is proportional to the initial critical current density of the tapes. Through the experiment optimizing the shape of voltage terminals and the pressing load for the continuous contact type 4-probe I c measurement system, it was found that the conical shape tip with large curvature radius was effective in suppressing the I c degradation in Bi-2223 tapes during the I c measurement. A hard alloy sheath of Ag-0.6wt%Mn was found to be quite tolerant to the I c degradation against the pressing load of voltage terminals.

Finite element models for thermal stress, axial tension, bending, and transversal compression of filamentary Bi-2223 tapes

“…Suitable experiments to confirm transversal compression models were not found because the tape is usually compressed only over a very short length in measurements [35][36][37]. Then, the edges of the compressed region are subjected to large shear forces and the tape damages more easily than in the lengthwise homogeneous compression described by the model.…”