Three-directional analysis of thermally-induced strains for Nb/sub 3/Sn and oxide composite superconductors

Composite superconductors like Cu/Nb/sub 3/Sn and Ag/Bi-oxides are subjected to thermally-induced residual strain by other component materials due to the around 1000 K temperature difference between the high temperatures where the superconductor is formed and the cryogenic temperatures where they are operated. To clarify especially the radial (r) and (/spl theta/) tangential strain behaviors, we analyzed elastic-plastically two models, the concentric core model (single-core model) and multi-core model and used two analysis methods, calculation of the force balance equation for the former model and computing of FEM for the former and the latter models. Strains in r and /spl theta/ directions varied with combination of component materials having large and small thermal expansion coefficients; the superconductor sandwiched by high thermal expansion materials is subjected to larger tensile r-strain and larger compressive /spl theta/-strain, as compared with superconducting core only embedded in the matrix. Furthermore it was found that there was a strain distribution by the core location at the inner or the outer. Finally, a better combination of the superconductor with other materials was obtained.