Efficient multiscale simulation for damage behaviors in Nb3Sn superconducting strands and cables

Abstract

The Nb₃Sn superconducting strands and cables are the most matured materials required for the next-generation accelerator magnets represented by the Future Circular Collider. However, the brittleness of the Nb₃Sn multifilament structures can cause severe critical current degradation when subjected to complex loading conditions, harming the stable operation of superconducting magnets. Considering the notable multiscale characteristics of Nb₃Sn materials and structures, this paper has proposed an efficient multiscale framework, which has combined the self-consistent analysis (SCA) and finite element method (FEM). Then, we have developed the brittle damage constitutive law for Nb₃Sn filaments and investigated the mechanical behaviors of PIT strands and ten-layered stack cables. The results of the PIT strands exhibit the ‘plateau stage’ phenomenon under uniaxial tension, which are explained by the random damage of Nb₃Sn filaments in microscale. Besides, the three-scale analysis of stack cables is also compared to existed experiments and simulations to validate the accuracy. The influences of the Weibull distribution parameters and compression, bending and torsion loading conditions are also discussed. The proposed efficient multiscale method can serve as a powerful tool for investigating the mechanical behaviors of Nb₃Sn superconducting materials and structures, which can be easily applied to other multiscale materials and structures.