Research On Influencing Factors Of Fatigue Life Of U-shaped Bellows Based On Finite Element Method

The bellows expansion joint is an axisymmetric tubular shell composed of one or several bellows and components,because of its characteristics such as compensation of thermal displacement,vibration reduction and noise reduction,and protection of equipment,it is widely used in aerospace,petrochemical,pipeline connection,nuclear industry,automobile manufacturing and other industries.When the bellows work,it needs to absorb vibration displacement under pressure,so it has high requirements for many of its performances.The traditional method based on various physical tests to ensure the performance of the bellows requires multiple repeated tests,which has disadvantages such as a long design and development cycle and excessive expenditure.Therefore,it has high research value to simulate and calculate the performance of multi-layer bellows by finite element method.In this paper,a finite element model is established for the actual state of a multilayer bellows.Based on ANSYS software,the influence of the structural parameters of the multilayer bellows on its axial stiffness,stability and fatigue life is explored.A new method for optimizing the structural parameters of multi-layer bellows is explored through design orthogonal experiment combined with finite element simulation.The main contents of this article are as follows:Through the establishment of an elastoplastic model of the multi-layer U-shaped bellows and the simulation analysis under the conditions of considering the contact relationship and large deformation,it is found that the fatigue failure of the bellows is caused by the accumulation of its plastic strain,and the peaks and troughs are the dangerous points of fatigue failure.Comparing the results of theoretical calculation and finite element analysis,the results of the two have a certain error.Because many influencing factors are considered in the finite element analysis,it is believed that the finite element analysis result is closer to the actual state of the multilayer bellows than the theoretical calculation;and it is more economical than physical test method.The control variable method is used to analyze and calculate the performance changes of the bellows under the same working conditions and different structural parameters.It is found that changing the structural parameters will change the axial stiffness and stability of the bellows,thereby affecting the fatigue life of the bellows.The analysis and calculation results show that the change of wave height and wall thickness has a greater impact on the performance of the multi-layer corrugated pipe.The changes of wave height,wave distance and wall thickness have the same influence on the axial stiffness as the stability,contrary to its fatigue life influence law.Starting from the structural factors of multi-layer corrugated pipe in terms of wave height,wave distance and wall thickness,orthogonal experiments are designed,combined with finite element simulation and calculation to obtain the performance data of each combination scheme,analyze the results of the orthogonal test,comprehensively consider the stiffness and stability to meet the work requirements,and obtain a structural parameter combination scheme that is better than the performance of the initial model.The result proves that this method of optimizing the structural parameters of the multi-layer U-shaped bellows is feasible and can improve the efficiency of product design and development.