Approach to Heterogeneous Strain Distribution in Cable-In-Conduit Conductors Through Finite Element Simulation

The ITER Cable-In-Conduit Conductors are submitted to high thermal and electromagnetic cyclic loadings responsible for conductivity loss in the strain-sensitive Nb₃Sn strands. The complex mechanical phenomena occurring at the local scale of the strands make the final performances of the CICC difficult to predict from single-strand properties. In order to assess the amplitudes of the local strains that drive the conductor electrical behavior, a nonlinear finite element simulation code is used. The successive stages of the conductors´ service life, from the forming of the cable to its thermal cool down and Lorentz force loading, are simulated. Each strand is individually modeled along with the great number of contacts-friction interactions between the strands. This paper presents the simulation results obtained for 144 strand cables of two different designs. It is shown that the various loadings result in a heterogeneous distribution of strains along and across the strands with occurrence of extreme tensions and compressions. The use of simulation would eventually help to better characterize the influence of conductor design parameters.