Mechanical Property Analysis Of Multilayer S-Shaped Bellows

Bellows expansion joints could effectively avoid the piping system from fracture by absorbing the mechanical deformation energy. They are widely applied on industry and laboratory to transport liquid material or exchange hot and cold gas. Extruded bellows expansion joints have many advantages, such as their simple processing, good tightness and long fatigue life, as a result they become the most widely applied expansion joints.Fatigue fracture of bellows is a common failure mode as the bellows undergo with the cyclic load. Fatigue life of bellows strongly depends on the stress of the structure. Therefore, it is important to calculate the stress distribution of the bellows under external load. The mechanical property of bellows is affected by many factors, for example, the dimension of corrugates, interaction between layers, extruding procedure, and so on. Using Finite Element Method (FEM), a series of researches are carried out on these problems of S-shaped bellows.This dissertation covers four aspects listed as follows:In chapter1, types and different applications of bellows are introduced.In chapter2, a simplified FEM model of single-layer S-shaped bellows is built with ABAQUS program. The stress distribution of single-layer S-shaped bellows is given under bending load and internal pressure. The influence of the dimension of corrugates on the bending stiffness and maximum bending angle of bellows is discussed in the following analysis.Chapter3builds a4-layers S-shaped bellows FEM model considering the nonlinear interaction between layers, and studies the stress distribution of4-layers S-shaped bellows under external load. Then, a comparison of FEM analyses using continuum elements and shell elements is given. The relationship between number of layers and the mechanical property of bellows is discussed using the continuum shell elements.In chapter4, a simulation of the extruding procedure of4-layers S-shaped bellows is made to study the residual stress and residual strain in the structure using axisymmetric model. It also calculates the three-dimensional model with continuum shell elements to study the influence of extruding procedure on the mechanical property of bellows.