Strength Design And Forming Process Numerical Simulation Of Bellows Based On Finite Element Analysis

Bellows expansion joint is a kind of elastic compensation element which is widely used in many fileds such as petro-chemical, mechanical industries. With the increasing demends, higher and higher necessities are needed for the design and manufacture of bellows. In this thesis, numerical simulations were performed on bellows to research its strength and hydro-forming. The main work and conclusions are as follows:(1) Mechanical models about calculation formula of stresses at bellows expansion joints in the code of GB16749-1997 were reviewed. Stresses at a super-large expansion joint with the inner diameter of the straight edge being 4216mm were calculated based on the conventional design code of GB 16749 and finite element method. Results demonstrated that stresses in the two methods are close, meaning that GB 16749 code can be applied to large and even super-large bellows expansion joints even though the stress calculation formulas are based on some simplifications.(2) Finite element analysis was performed on three-layer ?-shaped bellows, single-layer ?-shaped bellows and ?-shaped bellows with thinned reinforced structures and strength check was completed based on the standard of GB/T12777-2008. By comparing the analysis simulations, it is showed that three-layer ?-shaped bellows are more suitable for the conditions with cyclic loadings; The strength and stiffness of ?-shaped bellows with thinned reinforced structures can also meet the requirements of GB/T12777.(3) Numerical simulation of the hydro-forming process for U-shaped bellows was carried out and compared with the actual manufacturing forming. The results show that the deviations of bellow height, bellow weight, length of bellows busbar and thickness thinning ratio at peak are all less than 5%, which means that bellows hydro-forming can be calculated by finite element method exactly.(4) A lot of numerical simulations were performed on the hydro-forming of bellows. Based on the simulation results, the weight, height, meridian length, thickness thinning ratio of bellows were formulated as the functions of the independent variables diameter and thickness. Finally in this thesis, operating parameters such as bulging pressure, forming pressure and axially compressive force were also investigated for their influences on the waveform of bellows during bellows forming process.