The effects of external reinforcement on the mechanical property and the axial tensile stress/strain dependence of the critical current Ic in Bi (2212) superconducting tapes were evaluated at a temperature of 4.2K and a magnetic field of 14T. The monocore and 19-core superconducting tapes with three kinds of sheath-Ag, Zr-reinforced Ag, and Ag/Zr-reinforced Ag double layer-were incorporated with reinforcing CuAg tape. As a result of this reinforcement, the 0.2% proof stress of superconducting tapes increased markedly without significant degradation of the Ic. The limiting value in strain for Ic degradation in Ag-sheathed tape was slightly improved, and that in stress was markedly improved. The improvement in the limiting value in strain or stress for the degradation was more evident in tapes with Zr-reinforced Ag sheath, compared with those with pure Ag sheath.
A new method is proposed to carry out numerical calculations on the shape of field-free core, current distribution, and AC transport losses in self-fields as a function of current amplitude I0 for high-Tc superconducting tapes with arbitrary cross-sectional geometry. Its validity can be confirmed by verifying that calculated results of AC losses for elliptic tapes agree with the prediction advanced by the theory of Norris. An application to rectangular tapes leads to the finding that the AC losses for them behave as a thin-strip superconductor in high I0 values near critical current Ic, but gradually deviate from this behavior with decreasing I0. A decrease in the aspect ratio of width to thickness for rectangles makes the deviation more remarkable. By using this method, the AC transport losses for two kinds of the 7-filamentary tapes with different filament arrangements are calculated, and the results are compared with the experimental behaviors of losses for tapes fabricated by a powder-in-tube method using the Ag sheath. The measured losses can be explained neither by the prediction for an elliptic tape nor by that for a thin strip based on the theory of Norris. Furthermore, the loss values depend on the filament arrangement, which is explained by the calculated results of loss-density distribution. The influence of filament arrangement on the loss behaviors is suppressed as the number of filaments increases to 37, from 7.