FEM analysis of coil support connections in the Wendelstein 7-X magnet system

The objective of the Wendelstein 7-X project is to test potential application of stellarator-type fusion reactor as a power plant. In this device the plasma channel is under the control of a magnetic field generated from and complicated magnet system, comprised of 70 superconducting coils symmetrically arranged in five identical modules. Each coil is connected to a central ring with two bolted connections which transfer the loads resulting from the electromagnetic field and gravity. m of this work was to analyse the mechanical behaviour of the connections by means of detailed 3D finite element models. All simulations were performed assuming elasto-plastic behaviour of the materials, and the assembly stresses and friction contacts between the different parts of the connections. The stress distribution, displacements and the forces acting on the bolts and welds were studied using standard methods. The results were subsequently used to optimise the design of the critical central support elements.