Bending strain characteristics of critical current in REBCO CC tapes in different modes

The influences of bending strain on the critical current, I c in stabilized YBa 2Cu 3O 7− δ (YBCO) and SmBCO coated conductor (CC) tapes in different modes of easy and hard bending were investigated at 77 K and self-field. Under easy bending, the influences of the compressive and tensile bending strains on the I c in REBCO (rare earth element, Barium and Copper oxide) CC tapes were investigated. Under tensile bending strain, when the I c was plotted against the strain on the YBCO film layer, the 95% I c retention strain limit under bending was comparable to the value obtained in the axial-tension test. Under the hard bending of YBCO CC tape, I c started to degrade when the bending strain exceeded 0.6% and the recovery of I c did not occur when the bending strain applied was released. This might be a result of the generation of a new type of damage such as local buckling during hard bending which is different from the damage type experienced in Bi-2223 tapes. The n-value behavior showed a good agreement with the I c degradation behavior. On the other hand, the SmBCO CC tape showed a superior strain tolerance under hard bending resulted from its flexibility to in-plane deformation due to thin geometry compared to other copper stabilized YBCO CC tapes.