High Strength/High Strain Tolerance DI-BSCCO Tapes by Means of Pre-Tensioned Lamination Technique

Excellent high tolerance on the yield stress and critical current of BSCCO-Bi2223 tapes was realized by the pretensioned lamination technique. The yield stress at room temperature and the stress to 95% I c retention exceeded 430 and 510 MPa, respectively. In order to make clear the potential of this technique, the influence of thickness of lamination sheet and degree of pretension was investigated in detail. The observed yield stress at which the macroscopic yielding starts due to the fracture of BSCCO filaments has been successfully evaluated by calculation as a function of stainless steel sheet thickness and pretension, which is useful as engineering data. The relaxation stress at which the local strain starts to relax due to filament fracture was expressed as a unique function of the thermal residual strain exerted on BSCCO filaments together with the residual strain induced by the pretension treatment. The force free stress at which the local stress exerted BSCCO filaments becomes zero was proportional in magnitude to the residual strain exerted on BSCCO filaments. The stress to 95% I c retention was elucidated to give a good indication, at which the critical current decreases abruptly due to the fracture of BSCCO filaments.