Effect of twisting on strain tolerance of Bi-2212 multifilamentary round wires

Abstract

Silver sheath Bi2Sr2Ca1Cu2Ox superconducting multifilamentary round wires having various twist pitch lengths and an untwisted one were fabricated by the oxide powder-in-Ag-tube method. The twisting process to a pitch length of 4.5 mm at a diameter of 1.45 mm did not influence the superconducting critical current density Jc whose value was about 90 000 A/cm2 at 4.2 K, 0 T. The Jc of the twisted wires is less sensitive to bending strain as twist pitch length becomes shorter. This phenomenon is explained by the calculated results that the filament’s curvature, which is added by the bending, becomes less as pitch length becomes shorter.

Intrinsic limits ofJcin composite metallic/Bi(Pb)-2223 multifilamentary tapes with twisted filaments

“…This model, which accounts for the intrinsic reduction of the effective cross section, cannot explain the presence of a plateau of I c against the twist pitch for large t p values. This is because we have assumed the same local J c values independent of t p and this condition needs to be revised in the light of new experimental findings [21]. The strain tolerance of Bi-2212 multifilamentary round wires improves by twisting the filaments.…”

“…The strain tolerance of Bi-2212 multifilamentary round wires improves by twisting the filaments. This is ascribed to the increase of the crack resistance of the spiral filaments [21]. Accordingly, the bending strain tolerance is improved for shorter twist pitches and the propagation of cracks is more difficult.…”

Study of a bi-system superconducting wire with an oxide barrier using the strand and formed method

“…This achieves reduction in both of coupling loss of wires and hysteresis loss. It is suggested that multifilaments and strand bundling the wire structure may contribute to an improvement of strain tolerance [9,10]. The strand bundle of wires is considered to be one of a number of means for resolving the challenges listed in figure 1.…”