Effects of bending and torsion behavior on Ic degradation and microstructure of ReBCO coated conductors

Abstract

The performance degradation caused by bending and torsion is crucial for the application of superconducting coated conductors. In this study, we investigated the critical current (Ic) degradation of four kinds of conductors under bending and torsion. With 1 mm resolution, the critical bending radius of STT236μm (Shanghai Superconductor Technology) conductors is 6–7 mm, and that of STT380μm conductors is 4–5 mm, and that of SAMRI (Suzhou Advanced Materials Research Institute) conductors is 4 mm. With better bending tolerance, SAMRI conductors also have a less critical twist pitch of 82–87 mm. Considering the residual thermal stress during fabrication, the longitudinal strain corresponding to 5 % Ic degradation is 0.484 %. Further, to figure out the failure mechanism of coated conductors, the micromorphology of the ReBCO layer was observed after chemical etching. The crack distribution not only verified the cause of Ic degradation under mechanical behaviors, but also helps to develop a crack-based Ic prediction method.