One of the leading causes of critical current degradation in (RE)BCO tapes is the micro-cracks produced by mechanical slitting. In this paper, a tape model with multiple edge cracks is established. Under tensile loading, the effects of the Poisson ratio, crack length, crack angle, and geometric mutation between cracks on the stress intensity factor are investigated using the extended finite element method (XFEM). The stress intensity factor exhibits an evident jump characteristic when a geometric mutation occurs. The jump level strongly depends on the geometric difference. The jump location is the initiation site for crack propagation, which is consistent with the experiment results. The impact of cracks on the critical current degradation of the tape is also discussed.

In this study, the restoring force generated by the superconducting pinning phenomenon was examined in terms of the characteristic change caused by the concave-stage arrangement of the two superconductors. By analyzing the restoring force characteristics in each direction of a superconducting magnetic bearing created using two superconductors, we verified whether the restoring force characteristics change. As a result of the experiment, it was confirmed that the restoring force in each direction is increased by arranging the superconductor with a stepped shape. Experiments have shown the usefulness of applying a concave step arrangement to superconductors.