Calculation of stress tensors in Nb3Sn multifilamentary wires

We present stress tensor calculations for the internal prestress in Nb3Sn filaments of binary Ta and Ti alloyed and internal steel reinforced multifilamentary wires at 10 K derived from experimental data for the strain tensors and elastic parameters. Strain tensors were determined from the tetragonal distortion of the A15 crystal structure relative to the stress free cubic A15 structure measured by neutron and x-ray diffraction. The influence of ternary alloying reduced the distortion components and enhanced the hydrostatic compression components of the strains. The stress-strain analysis correlated with the change in superconducting properties attributed the major effect to the lattice distortion and a non-negligible contribution to the hydrostatic compression of the filaments