Recent progress on improvement to mechanical properties of DI-BSCCO wire

Abstract

To improve the mechanical properties of silver-sheathed BSCCO wire, the laminated BSCCO wires with stainless steel were made under some experimental conditions. The dependence of the stainless steel thickness and the dependence of the pre-tension of stainless steel tapes on the laminated BSCCO were investigated by mechanical tests (tensile test at 77 K and RT and double-bending test at RT) using short samples. Due to the difference of the coefficient of thermal expansion (CTE) and the relaxation to equilibrium after removing the total pre-tension of no laminated BSCCO (insert tape) and stainless steel tapes, the residual axial compressive strain applies to an insert tape after the lamination process. A high compressive strain up to the compressive yield of the silver-alloy is so useful for improvement of the mechanical properties of BSCCO wire. Measurement results were approximately the same as the simple model calculated from the residual strain applied to an insert tape by the difference of CTE and pre-tension. The stainless-steel-laminated BSCCO wire ‘Type HT-SS’ has been able to be achieved over 500 MPa at 77 K by increasing stainless steel thickness and the residual axial compression for an insert tape. The developed tough DI-BSCCO has a higher hoop force to compare with YBCO-coated conductor using Hastelloy substrates under the same circumstances such as magnetic field, winding diameter and transport current.

Drastic Improvement in Mechanical Properties of DI-BSCCO Wire With Novel Lamination Material

“…This value is comparable to the performances of all the pre-tensioned Type HT-SS wires [9]. The new Type HT-XX showed I c retention of more than 95% even at the bending diameter of 30 mm.…”

“…These values are higher than the maximum of Type HT-SS wire in our previous work, 510 MPa [9]. Considering the Type HT-SS wire had 100 μm-thick stainless steel tapes and pre-tensions of 161 N, the Type HT-XX wires, which were produced with only 35 μm-thick Ni-Cr tapes and pre-tension of 140 N demonstrated their superior mechanical performances.…”

“…Our previous study revealed the pre-tension technique was also effective for improvement in the mechanical properties of Type HT-SS wires [9], [11]. Basically, the mechanical strengths of the laminated wires increased with higher pre-tension unless the filaments fracture.…”

High temperature superconducting axial field magnetic coupler: realization and test

“…In fact, the tape is exposed to various mechanical, thermal and chemical stresses like bending, tension and welding [9,10,11], from which a reduction of the critical current is expected.…”

Theory analysis of critical-current degeneration in bended superconducting tapes of multifilament composite Bi2223/Ag

“…In practical applications, the HTS tapes always experience different stress/strain, such as bending, pulling, and/or torsion, which can significantly degrade the superconducting properties. The mechanical properties are among the most important parameters for HTS tapes [1][2][3]. The relation of deformation and fracture behavior of multi-filamentary Bi2223/Ag composite tapes to the superconducting property has been studied widely [4][5][6][7][8][9].…”