Coupled Mechanical and Electrical Modeling of Nb3Sn Strand Critical Current Under Bending

Strain dependence of Nb
₃
Sn superconducting properties is known to be responsible for the degradation of transport current capability of large steel jacketed cable-in-conduit conductors (CICCs). The mechanical deformations of the strands in the cables due to both cooldown after heat treatment and Lorentz force during operation are the main sources of strand-in-cable critical current degradation. The complete modeling of a CICC relies first on the modeling of the single strand with its superconducting filaments and then on the modeling of the strands in the cable. This paper reports on the description of the models and the analyses performed using coupled mechanical and electrical modeling. The key of this modeling lies in its ability to characterize the superconducting properties of the twisted Nb
₃
Sn filaments inside a locally bent strand from a global mechanical deformation map, taking into account possible current redistribution among filaments all along the strand length. In the same way, strands may experience local critical current degradation in a CICC, and current transfer between strands at their contact points must be modeled to predict cable performance. This work can be seen as the first stones of an integrated coupled mechanical-electrical modeling of large CICCs made with strain-sensitive strands.