| In this thesis, a three dimensional and nonlinear finite element analysis model that integrated equivalent tubesheet, bolts, two gaskets and two flanges is established for the flange-tubesheet joint in U-tube heat exchanger considering nonlinear properties and hysteresis effect of the gasket material. With this model, the deformation and stress distributions of the flange joint are analyzed using ANSYS FEM software, and the influences of gasket properties, tube side pressure and shell side pressure, bolt pre-loading for gasket sealing as well as bolt size (diameter) on tightness (distribution of compressive stress on gasket) of the model are investigated under gasket sealing and operating conditions, respectively. In the above model, the central perforated region of the tubesheet, according to ASME Code, is simplified to be an equivalent plate. The results of tubesheet stress distribution are calculated by FEM software ANSYS and compared with the results from formulas of China...
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