This paper reviews the stress/strain characteristics of some typical highly strengthened bronze-processed practical Nb
3Sn superconducting wires examined in the HFLSM, IMR of Tohoku University up to the magnetic field of 14.5 T at a temperature of 4.2 K. Internal reinforcement of the superconducting composite wires using the materials with high strength and high electrical conductivity such as
in situ processed or jelly rolled Cu-Nb microcomposite, Ta, and recently developed Cu-Nb-Ti compound was proved to be promising, although the stability of the wire is decreased to some extent. Although the intrinsic axial tensile strain sensitivity of
Ic was not markedly changed, the reinforcements changed not only mechanical properties such as the 0.2% proof stress but also the parameters relevant to the tensile strain characteristics of
Ic, the strain corresponding to the
Ic peak, ε
m, and reversible strain limit, ε
irr, where permanent damage such as cracking starts to take place in the Nb
3Sn filaments. Furthermore, the transverse compressive stress sensitivity of
Ic decreased and the reversible stress limit increased. The effect of parameters on the Cu-Nb composite reinforced bronze-processed Nb
3Sn wires and the strain characteristics are intensively discussed.
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