Strain characteristics of critical current in RABiTS/Y-Ba-Cu-O coated conductors

The strain dependence of critical current I_c of a commercial RABiTS (Rolling-Assisted Biaxially Textured Substrates) YBCO coated conductor tape with Cu stabilizing layers on both surfaces has been studied by two kinds of bending apparatus and a tensile apparatus at 77 K and 293 K. According to the voltage measurements using multi-taps in the longitudinal direction, local I_c degradation was also observed. In the continuous bending-tension test at 77 K, in which YBCO layer was subjected to the tensile strain, I_c began to decrease rapidly beyond the strain of 0.6% after initial moderate degradation. In the continuous bending-compression tests, the I_c began to decrease rapidly beyond the strain of 0.4%. The strain for the beginning of degradation of I_c obtained by tensile tests at 77 K was almost the same as that by the bending-tension tests. Bending test at RT using FRP holders showed I_c degradation not so different from that by the continuous bending tests at 77 K. In all tests, the I_c initially degraded locally irrespective of the position in the specimens. Furthermore, I_c degradation by repeated bending was also studied.