3-D Mechanical Finite Element Analysis of Impregnated Rutherford Cable Stacks

Low-temperature superconductors are widely used in high field accelerator magnets, mostly within Rutherford-type cables. Cables are multiscale composite structures including strands composed of superconducting filaments twisted in a metallic matrix. The magnet performance is driven by mechanical effects at the filament scale, especially with strain-sensitive superconductors such as Nb3Sn. During operation, the conductor is subject to a complex combination of axial and transverse loads. It is thus necessary to build three-dimensional (3-D) models at the cable scale. An approach to get the mechanical model of an impregnated lowtemperature superconducting Rutherford-type cable is presented. The process of the 3-D geometrical reconstruction of the cable, up to the scale of the strand, is described. Techniques to model and mesh the impregnation matrix are presented. The strand model is simplified by a bi-metallic description comprising a homogeneous superconducting filamentary region between the copper core and the copper outer layer. The geometrical reconstruction of cable stacks is finally demonstrated, under several configurations. In the second part of this paper, sensitivity analyses to model parameters such as cable compaction, cable configuration, and matrix stiffness are discussed.