CORD, a novel numerical mechanical model for Nb3Sn CICCs

The strain state of the superconducting Nb3Sn strands in multi-stage twisted ITER Cable-In-Conduit Conductors (CICCs) strongly determines the transport properties. For an accurate prediction of the performance and a proper understanding of the underlying phenomena, a detailed analysis of the stress and strain distribution along all individual strands is imperative. Also during the cabling process, the axial stress of the individual strands must be well controlled to avoid kinks, in particular when mixing different strands, e.g., Nb3Sn and copper strands. A mechanical model for a superconducting cable (CORD) was developed, which can predict the strain and stress states of all single strands including interstrand contact force and the associated deformation. The simulation results are not only important for analysis but can be used for optimization of cable manufacturing and conductor design optimization. We discuss the influence of the sequential cable twist pitches and the inclusion of copper strands on the mechanical properties.