Effects of bending on the superconducting critical current density of monofilamentary Nb3Sn wires

Variations in the superconducting current density J/sub c/ of the Nb3Sn wires upon bending were measured for a series of monofilamentary wires in which the ratio R/sub v/ of the matrix (Cu+Sn) to the core (Nb3Sn,Nb) was changed from 0 to 58. In most cases J/sub c/ was found to increase slightly until the bending strain exceeded a value of epsilon/sup irr//sub B/ , beyond which it severely and irreversibly degraded. For wires with intermediate values of R/sub v/ (approx.2 to 10), epsilon/sup irr//sub B/ , calculated by geometrical considerations, was substantially lower than the measured value of the tensile strain epsilon/sup irr//sub T/ which was required to irreversibly degrade the critical current. The influence of bending strains on J/sub c/ can qualitatively be described by considering residual prestrains in the matrix and the core