Strain characteristics of critical current in ISD/Dy-Ba-Cu-O coated conductors

The strain dependence of critical current I_c of ISD (inclined substrate deposition) Dy123 coated conductor tape has been studied by two kinds of bending and tensile testing apparatus at room (RT) and liquid nitrogen temperature (77K). In the continuous bending-tension tests by Goldacker type apparatus, in which a Dy123 layer was subjected to tensile strain, I_c began to decrease rapidly beyond the strain of 0.4% after initial moderate degradation. Bending back in the test deteriorated I_c intermittently and the reversible strain limit was reduced to less than 0.2%. In the bending-compression tests, however, the I_c was slightly increased up to the strain of 0.35 to 0.4% and then it decreased. In the discontinuous bending-tension tests by using FRP holders at RT, the reversible strain was smaller compared with that of the continuous bending tests at 77K due to the difference in thermal compressive residual strains. The strain characteristics of I_c obtained by tensile tests are almost the same as that by the bending tests.