A novel numerical mechanical model for the stress–strain distribution in superconductingcable-in-conduit conductors

Abstract

Besides the temperature and magnetic field, the strain and stress state of the superconductingNb3Sn wires in multi-stage twisted cable-in-conduit conductors (CICCs), as applied inITER or high field magnets, strongly influence their transport properties. For anaccurate quantitative prediction of the performance and a proper understandingof the underlying phenomena, a detailed analysis of the strain distributionalong all individual wires is required. For this, the thermal contraction of thedifferent components and the huge electromagnetic forces imposing bending andcontact deformation must be taken into account, following the complex strandpattern and mutual interaction by contacts from surrounding strands. In thispaper, we describe a numerical model for a superconducting cable, which cansimulate the strain and stress states of all single wires including interstrand contactforce and associated deformation. The strands in the cable can be all similar (Nb3Sn/Cu) or with the inclusion of different strand materials for protection (Cu, Glidcop).The simulation results are essential for the analysis and conductor design optimization fromcabling to final magnet operation conditions. Comparisons are presented concerning theinfluence of the sequential cable twist pitches and the inclusion of copper strands onthe mechanical properties and thus on the eventual strain distribution in theNb3Sn filaments when subjected to electromagnetic forces, axial force and twist moment.Recommendations are given for conductor design improvements.