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Description
High field magnet technologies are supported by the development of advanced superconducting (SC) cable constructed from the composite SC tape. The SC tapes in the helically wound composite cable experience flatwise as well as edgewise bending load together with tensile one. We analyzed precisely the influence of uniaxial tensile load to critical current (Ic) of BSCCO tapes, where the reversible stress / strain limits (R95 / A95) for critical current degradation up to 95% of Ic were defined.
In the helically wound cable, a complicated bending load including flatwise and edgewise components generates in the SC tape. For clarifing quantitatively the degradation of Ic due to bending load, it is efficient to investigate separately the degradation behavior from each flatwise and edgewise bending. In the present study, we designed two types of sample holder applying flatwise or edgewise load to the tape for Ic measurement at 77 K.
The critical currents measured by changing flatwise sample holders with different diameter (D). When bending the tape wire up to Dc = 60 ~ 80 mm, the critical current decreased up to 95%. On the other hand, when the Ic was measured by using the edgewise sample holders, Ic decreased up to 95% for Dc = 1000 ~ 1600 mm. This difference of critical diameters is caused relating to the maximum strain experienced by SC filaments locating at the most outside position. When calculating those strains equivalent to the critical diameters, they were in the same strain range between 0.25 ~ 0.28 %. So we concluded that the degradation of Ic due to both flatwise and edgewise bending originates from the same reason.
