Computer Simulation and Experimental Analysis of Ultrahigh Vacuum Cf Flange Joints Applied in the Accelerator and Space Technology

Abstract

Computer simulation and experimental research of ultrahigh vacuum CF flange joints are widely used in accelerator and space technology have been carried out. The computer simulation was carried out in the automated software environment "ABAQUS", which allowed to study the stress-strain state in the sealing zone. The novelty of the work lies in taking into account the certified (real) hardening curve of the flange material during simulation since the work carried out before that was performed for an ideal rigid (nondeformable) flange, which introduces significant inaccuracies in calculations. Two of the most famous CF flange designs of Wheeler and CERN are simulated. Zones of distribution of intensity of stresses and strains, as well as components of the stress state are obtained. The experiments were carried out in four cycles of assembly and disassembly of the flange joint (with a change of the copper ring after each cycle) using standard flanges and gaskets. Also, to eliminate statistical inaccuracies, each experiment was carried out repeatedly to clarify all the measured parameters. A comparative analysis of the results of simulation and experiments is performed. The obtained data are close both qualitatively and quantitatively, which makes it possible to use them both for practical and research purposes.

The analysis and experimental research of ultrahigh vacuum ConFlat-type flange joints applied in accelerator and space technology

“…The same pattern is observed in Wheeler's model (figure 6) [14] (the gap increases with increasing radius of rounding at the tip of the knife edge), but obviously, the gap is much larger compared to the CERN's model. From figure 5 and figure 6, it can also be seen that the maximum stress intensity concentration is at the tip of the knife edge, but in Wheeler's model, a large stress concentration is also formed at the base of the knife edge (marks).…”

“…Figure 5 to the right shows enlarged fragments of the knife-edge of the flange and the sealing ring to clearly demonstrate a gap (the angle: 𝛿) that appears during the tightening of the bolts inside the system (from the vacuum side). You can see simulation results for 𝑟 = 0.05 and 0.2 mm tip radius in [14] workshop presentations. It is obvious from [14] that the gap increases with an increasing rounding radius at the tip of the knife edge.…”

“…You can see simulation results for 𝑟 = 0.05 and 0.2 mm tip radius in [14] workshop presentations. It is obvious from [14] that the gap increases with an increasing rounding radius at the tip of the knife edge.…”

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

“…The analysis and calculations in [7] were carried out for the two most common models of knife edges and two states of gasket (annealed and 1 4 hard). The stress-strain state zones' distributions of the tightening process for various dimensions of knife edge geometry are demonstrated in [12]. It is revealed [7,12] that from the stress-strain state perspective, the CERN's model is much better than Wheeler's model.…”

“…The stress-strain state zones' distributions of the tightening process for various dimensions of knife edge geometry are demonstrated in [12]. It is revealed [7,12] that from the stress-strain state perspective, the CERN's model is much better than Wheeler's model. The latter is subjected to crumpling and also plastic bending.…”