The combined research of ultra-high vacuum CF flange joints' sealing parameters considering plastic properties of materials

Computer simulation and experimental research of the tightening processes of ultrahigh vacuum CF flange joints have been carried out. Finite element analyses were carried out considering the plastic properties of materials. The analysis variable parameters are flanges' knife edge angle between the shelves (Wheeler's and CERN's models), tip rounding radiuses, and gasket material state (annealed and hard). Curves of changes in the stress and strain intensities of the edge nodes of the flanges' knife edge were obtained. Essential sealing parameters of the ultrahigh vacuum system were also studied, such as the height of the knife edge, the length of the knife-edge trace on the gasket (in the radial direction), and the gap between two flanges. The mentioned sealing parameters' measurements were carried out by the combined method. The latter is a parameters' measurement of both computer simulation and experimental samples and a comparison of the obtained results. It should be noted that the sealing parameters were studied for several tightening cycles of the flanges to research their changes in case of multiple uses. The vital value of this research is obtained empirical functions for calculating the height of the flanges' knife edge based on the tightening cycles.