Electromechanical Behavior of Bronze $\hbox {Nb}_{3} \hbox {Sn}$ Strands Under Wide Range Pure-Bending

A series of experiments to study the electromechanical performance of Nb₃Sn superconducting wires under large pure bending strain has been performed. Based on the previously developed pure-bending sample holder beam for applied strains up to 0.8 %, an improved beam was designed to cover the entire range up to nominal bending strains of 1.25% on the strand surface. Critical current measurements as a function of bending strain are discussed for bronze strands from EAS and Hitachi. The samples were mainly tested at 15 T. High deformation and Lorentz load effects were studied through a finite element model structural analysis. Good agreement between finite element model and experimental results was found. Full range bending strain and reversed current tests were performed and it was found that for Lorentz loads below 3 kN/m the sample holder design could be appropriately used to cover a bending range from 0.6 % to 1.25% nominal strain on the surface of a 0.81-mm-diameter strand.