신축이음용 벨로우즈의 구조해석 및 최적화에 관한 연구

Abstract

The bellows is installed with expansion joint or pipe to absorb axial displacement, lateral deflection, angular displacement and vibration. There are many kinds of bellows such as Ω-shaped bellows, U-shaped bellows, S-shaped bellows etc. Among them, U-shaped bellows is often used in all of mechanical industry, because it is cheap and works well when subjected to pressure and forced displacement. Bellows can also be classified by the number of ply. In EJMA standard, the number of ply of bellows leads to different behavior each ply. Therefore, it is necessary to study about stress characteristic as changing plies of bellows. Since the performance of bellows is determined by fatigue life controlling stress, it is important to increase strength. Bellows has some parameters to control strength. So, it is necessary to conduct optimization in order to increase strength of bellows considering production cost. In this study, finite element analysis of bellows for 100A specified in bellows manufacturer standard was carried out in order to obtain stress characteristics and optimal solutions. Optimization was also carried out to find optimal shape of bellows and reduce stress. First, using three cases of bellows (1ply, 2ply, 3ply bellows), stress variation and characteristic were investigated as changing inner pressure and displacement, then compared with theoretical formula of EJMA in order to assure reliability of the results. Second, optimization was conducted to answer whether production cost of bellows is reduced, reinforcing strength of bellows. Volume is chosen to design variable to deal with problem of cost when conducting optimization, inner pressure and displacement were fixed to design pressure and maximum forced displacement. As a result, 3-ply bellows is the highest strength one among three models in FEA case. In case of optimization, 1-ply and 3-ply bellows models were optimized to wide variation about stress and volume. But 2-ply bellows models were optimized little about stress and volume.