Nb₃Sn超電導多芯線材の多重破断現象

抄録

The multiple fracture phenomenon of the Nb₃Sn layer in multifilamentary Nb₃Sn superconducting composite wires prepared by the bronze method was studied theoretically and experimentally. The results of the present work can be summarized as follows. (1) The stress distribution of Nb₃Sn segment varies with the length of the Nb₃Sn segment. When the Nb₃Sn segment is long, the tensile stress distribution as a function of distance is trapezoidal and when it is short, it becomes triangle. (2) The smaller the volume fraction of Nb₃Sn layer, the higher becomes the tensile stress exserted on the Nb₃Sn layer, resulting in shorter segments. (3) When the multifilamentary composite is loaded, the Nb₃Sn layer is not broken before the apparent yield point in the stress-strain curve, but it shows multiple fracture beyond this point. (4) The length of the broken Nb₃Sn segment descreases rapidly in the early stage of multiple fracture, but it remains nearly constant for high applied strain.