Study Of The Design Methods For Big Expansion Joints

As the elastic deformation compensation structure, bellows expansion joints are widely used in aerospace, petrol-chemical, electrical, automobile and other industries. With the enlargement of industrial production scales, bellows expansion joints are becoming bigger and bigger in size and more and more complicated in structure. To follow this trending, standards and codes for expansion joints should be updated and completed and the design or analysis methods should developed and practiced continuously. In this thesis, finite element analysis was performed on Ω-shaped bellows and U-shaped hinge type expansion joints used in pipelines. The main work and conclusions are as follows:(1) Design by rules and design by finite element analysis are employed for the design of a DN1100mm Ω-shaped bellows, The former is based on the standard of GB/T12777 and the later is carried out with the PLANE 182 element of the software ANSYS being used for meshing the finite element model. Stresses obtained from the finite element analysis well agree with those obtained from design by rules.(2) Stress classification method and limit-load analysis method are used to compute stresses and displacements of DN2200 and DN5500 single hinged expansion joints and DN2200 and DN6200 single gimbal expansion joints under specified loadings. In addition, light-weight analysis and stiffness reinforcement design are carried out based on limit-load analysis method together with the orthogonal experiment approach. Results show that limit-load analysis is more suitable for the design of the large hinged expansion joints.(3) Four main structure parameters of Ω-shaped bellows are optimized to minimize the weight of the bellows. To realize the optimization under the two working conditions, i.e. the action of the pressure and the action of the axial displacement, two independent models are created with the ANSYS optimization module. It is found that the weight of the bellows is reduced 54.97% after optimized.(4) An optimization software for the Ω-shaped and U-shaped bellows was developed with VB based on ANSYS software which can realize the light-weight design of the bellows.