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Description
The toroidal field (TF) coil system is one of the most mechanically stressed system in a tokamak. Structural integrity of the system must be maintained on the global and on the local scale, where the stress state in each conductor jacket as well as in insulation is to be within structural allowables. Solving this task head-on leads to very high computational demands. In this work a methodology for a FE detailed analysis of a graded TF coil winding pack (WP) for EU DEMO is presented.
The procedure relies on the submodeling approach. In the global model the WP is approximated by smeared material properties. The cut boundary displacements are transferred to the submodel which consists of a piece of the TF coil case with the detailed WP geometry. Operational electromagnetic loads are applied as hydrostatic pressure to the conductor jackets and the superconducting cable is omitted from the submodel for additional computational savings. The contact interaction between the case and the WP is taken into account as well. The procedure is implemented parametrically using ANSYS APDL macro language and allows automatic generation of the submodel geometry, meshing and recalculation for faster assessment of new design iterations.
A graded WP design option was analyzed in several critical locations of the coil, which were identified by an approximate, but very fast approach [1] developed earlier. A comparison with the said approach was made to verify its applicability and limitations. Convergence studies were conducted to find the required length of the submodel cut piece.
The presented procedure proved to be accurate requiring only moderate computational efforts. The parametric approach allows fast implementation of design changes into the model. The procedure can be used to speed up the assessment of future design iterations of the DEMO TF coil system.
