Nonlinear Finite Element Analysis Of Bellows And Its Software Development

Bellows expansion joints are important compensating components, which are usually used to compensate the axial displacement, transversal displacement and angular displacement caused by changing temperature, mechanical motion or vibration. It is widely applied in the fields of petrochemical industry, metallurgy, electric power, ship, nuclear industry, space flight, etc. Because the properties of bellows belong to material nonlinearity and geometry nonlinearity, its mechanical analysis is very complex. Therefore, it is an important work in this field that analyzing its stress field by using numerical analysis method, namely nonlinear FEM(finite element method). At the same time, developing a special FEA(finite element analysis) software of bellows has become the urgent matter. With developed successfully, it will impel Chinese bellows study a higher level.In or to analyze bellows by nonlinear FEM and develop a corresponding software, which can be applied in practice of bellows stress analysis, following research work has been carried out in this paper.In the first, according to the theory of nonlinear finite element, this paper analyzes the nonlinear properties of bellows from two aspects of material nonlinearity and geometry nonlinearity, and deduces the balanced equations of bellows FEA. Moreover, numerical solutions of these nonlinear equations are discussed. On this base, according to the method of finite element programming, the finite element equations and their numerical solutions as mentioned are realized by computer program. The nonlinear FEA program of bellows is developed in Fortran.According to the features of structure and loads of bellows, an automatic model-built program is developed, which can fulfil the data preparation works such as dividing elements, building boundary constrains and applying loads. By the model-built program, the proper FEA model can be built and the fore treatment process of FEA is simplified greatly.By studying the interface technology among different programming languages, especially the mixed languages programming technology of Visual C++ and Fortran, the Fortran process of FEA is inserted into the Visual C++ process. Therefore, the FEA technology and the object-oriented software developing technology are unified.With the use of object-oriented software developing technology of Visual C++, the customer interface is made, by which the user can call the model-built block andthe FEA block. Moreover, by using all sorts of programming technology of Visual C++, many functions are realized, such as interactive data, files operating, graph manipulation, etc. Therefore, the special FEA software system of bellows is made.By compared, the calculating result of the software approximates the experimental result relatively. It is showing that the calculating result of FEA can be used as the foundation of design and application of bellows.