acuum vessel of the HT-7U is a fully welded toroidal structure with a nonicrcular cross-section nested in the bore of the TF coils.According to the requirement of the physics design,sixteen horizontal ports on outboard mid-plane and thirty-two vertical ports on the top and bottom are designed for diagnostics,plasma heating ,current driving,vacuum pumping and gas puffing,Bellows on these port necks are used for flexible components to absorb the relative displacement in radial and vertical directions due to external load,thermal expansion or contraction and assembly tolerance,and also used for isolation of mechanical vibration.For the support system of vacuum vessel it should be not only strong enough to withstand forces acting on the vessel interior components and the vessel itself due to the dead weight and electromagnetic interactions during plasma disruption.but also sufficiently flexible to be suited to thermal expansion during baking In order to solve this contradiction a new kind of low rigid support has been designed,which has a perfectly rigid in vertical direction and perfectly soft in radial direction. Some three-dimension finite element COMSMOS models were performed to analyze their structural strength,stiffness and fatigue life,with an emphasis on the static stress analysis.The load spectra during vacuum vessel operation were also simulated on these models in the view of fatigue design.It was confirmed that the bellows and support had sufficient strength in the designed range of the load conditions.The results showed that the peak stress on bellows was 87MPa and on the support system was 97MPa.Now all kinds of bellows and support system have been designed.In order to accumulate some engineering,experiences and probe into some molding die and welding technologies,prototypical bellows and support system have been fabricated.At the same time a mechanical testing apparatus was designed for proof tests on the prototypical bellows and support to verify their functional and structure capability.The experimental data indicated that he results of finite element analysis were coincident with experimental test results.It has been proved that the present vacuum vessel's bellows and support system are reasonable and feasible.
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