Abstract
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.
