Structural analysis and optimization of mechanical multi-pipe connection for DEMO Upper Port

This paper presents the structural optimization of a mechanical multi-pipe connection (MPC), which consists of multi-pipe flange connected with a threaded bolt connection, for use in DEMO Upper Port. Mechanical pipe connections are currently being researched in the fusion context as they offer faster operating time of the pipe connections compared to conventional welded connections. However, the main consideration is that the pipe connection must be sealed against a high vacuum at both room temperature and high temperature. To ensure the necessary tightness during the entire process, the metal seals required must be sufficiently preloaded in all operating conditions. In addition, strict space availability limits the overall shape and dimension of the MPC. For this purpose, a structural analysis and subsequent topology optimization of the flange connection is carried out using the commercially available FEA software Abaqus®. The result of the topology optimization, taking into account suitable boundary conditions, is a design for the flange which, in addition to achieving sufficient deformation of the seals throughout, also smoothed out the stress peaks present in previous designs. However, the design cannot yet be produced in its current form, as cavities have also been created within the flange. The manufacturability of the flange must therefore be investigated in a subsequent second step and the design adapted accordingly. In this paper, a design draft of a MPC for use in DEMO Upper Port is presented, which fulfills all the necessary boundary conditions, but still needs to be revised regarding its manufacturability.