Degradation Due to Flatwise and Edgewise Bending on Critical Current of BSCCO Tapes

In order to clarify the influence of edgewise and flatwise bending as well as tensile load to critical current of DI-BSCCO tapes, the critical current measurement was carried out under those external loads. Both flatwise and edgewise bending gave a degradation of critical current. The reversible strain limits (
ϵ_b,
95
) resulted in 0.36 – ∼0.41 and 0.28–0.32% the aforementioned bending modes, respectively. Even though the bending diameter giving the degradation of critical current (
I
_c
) up to 95% of the original one (
I
_c00
) was in the range of ∼45–55 and 1200–1750 mm for the flatwise and edgewise ones the reversible strain limits were close to each other. This suggested that the position reaching the maximum bending strain (ϵ
_b
) acts as a starting point of degradation. The critical current decreased gradually up to 95% of original value, of which strain (stress) is assigned as ϵ
₉₅
(σ
₉₅
). When the strain exceeds ϵ
₉₅
, the critical current decreased rapidly. During this process, the upper part
ϵ
_{BSCCO,T +}

ϵ
_b
reached the fracture strain (
ϵ
_f
) at
ϵ
₉₅
and σ
₉₅
, where
ϵ
_BSCCO,T
is the residual strain induced in BSCCO filament under non external stress. The large
ϵ
_b
resulted in the small
ϵ
₉₅
and σ
₉₅
.