Finite Element Analysis for Optimization of Jacketing Process for Manufacturing of SST-1 CS CICC

Abstract

SST-1 is steady state tokomak under operation at Institute for Plasma Research, Gandhinagar. SST-1 has superconducting magnet system having 18 toroidal field coil with central solenoid coil at center bore. Under up gradation of SST-1, superconducting central solenoid (CS) based on Nb3Sn CICC has been designed and its assembly sequence with SST-1 has been finalized. The design calculations with required technical parameters for Nb3Sn CICC has been completed. Cable in conduit conductor (CICC) for CS consists of superconducting cable wrapped with SS316L foil, jacketed in SS316LN tubes. The manufacturing of Nb3Sn CICC for CS will carried out by adopting pulled through methodology which involve insertion of superconducting cable in jacketing tube and cold forming in required dimensions. The shaping and sizing of CICC is done by application of cold work (compaction and swaging), which generates stresses in SS316LN tubes. The appropriate cold forming schedule considering dimension accuracies, stresses, material flow, strain hardening, damages to superconducting cable needs to be prepared. With this motivation, to optimize jacketing process for CICC manufacturing, simulation approach with appropriate material models is adopted to minimize the trials and to investigate effect of various operating parameter. The basic analytical calculation has been performed to calculate percentage of cold work and stress generated for various dimension considering elastic-plastic material properties. With inputs from basic calculation, FE analysis in commercially available ABAQUS 6.13 software to simulate shaping and sizing for Nb3Sn CICC has been done for suitable dimensions to achieve final size of 15 mm × 15 mm. The process optimization for manufacturing of SST-1 CS CICC considering critical process parameters such as initial tube size, feed velocity and compaction scheme has been carried out by FE analysis. The proposed SS316LN jacket tube for different sizes (20 mm OD, 21.3 mm OD) along with compaction and swaging die with their actual dimensions has been modelled and meshed using appropriate element. During this investigation various compaction scheme (19.5 mm OD, 19.0 mm OD, 18.5 mm OD) with different feed velocities (20 mm/s, 15 mm/s, 8 mm/s) has been explored to evaluate their feasibility observing stresses generated and their distribution. The effect of mentioned parametric variations has been investigated in details and stress distributions are presented for each cases. The results of 27 different cases for circular compaction and 6 different cases for square swaging have been discussed in this thesis. On the basis of these investigations, four different feasible scheme for manufacturing of SST-1 CS CICC has been identified and presented.