Fracture analysis of a central crack in a long cylindrical superconductor with exponential model

Abstract

The fracture behavior of a long cylindrical superconductor is investigated by modeling a central crack that is induced by electromagnetic force. Based on the exponential model, the stress intensity factors (SIFs) with the dimensionless parameter p and the length of the crack a/R for the zero-field cooling (ZFC) and field-cooling (FC) processes are numerically simulated using the finite element method (FEM) and assuming a persistent current flow. As the applied field [Formula: see text] decreases, the dependence of p and a/R on the SIFs in the ZFC process is exactly opposite to that observed in the FC process. Numerical results indicate that the exponential model exhibits different characteristics for the trend of the SIFs from the results obtained using the Bean and Kim models. This implies that the crack length and the trapped field have significant effects on the fracture behavior of bulk superconductors. The obtained results are useful for understanding the critical-state model of high-temperature superconductors in crack problem.

Influence of CeO2 on microstructure, cracking and trapped field of TSIG YBCO single-grain superconductors

“…Defects which are introduced into the melt-grown YBCO bulk superconductors during the solidification process influence the overall superconducting and mechanical properties of the fabricated monoliths. In the case of YBCO bulk single-grain samples prepared by TSMG process, a number of reports describe the microstructural behaviour during the fabrication such as chemical phases present in the material, the size and the orientation of the crystal, growth front and growth mechanisms, subgrain formation [8][9][10][11][12][13][14][15][16][17], the size and volume fraction of Y211 particles [18][19][20][21][22][23][24][25][26][27], or crystal defects which arise after oxygenation such as cracks, twins, stacking faults [28][29][30][31][32][33][34][35], oxygen-deficient regions etc, and their impact on superconducting properties. The most important thing is to achieve high criticall current density by introducing effective pinning centres into the single-grain phase of YBa 2 Cu 3 O 7 (Y123).…”