Strain effect of YBCO coated conductor on transport characteristics

YBCO coated conductor is commercially available now and will be widely used in various practical power applications. In these applications, the conductor will be subjected to different kinds of mechanical stresses and strains. To achieve an optimal design of the devices, the transport characteristics under tensile, bending and torsional strains were investigated at 77 K and self-field. It is observed that the critical current Ic increases initially with applied strain, reaches a peak at emax and then decreases with further increases of strain. The improvement of Ic at emax can be attributed to the residual compressive strain and the shield of plastic deformation produced by the laminate layers. In AC cases, the induced Ic degradation causes an increase of transport loss, which can be described by the Norris model with a non-uniform current distribution. The torsion of the conductor can decrease the AC loss by field decoupling. The fluctuation of the n-value and the almost constant slope of the AC transport loss curves at applied strains in the measured range indicate the possibility of plastic deformation without the influence of the current distribution and the changes of the pinning potentials in the weak-link areas of the conductor.