Structural assumption on design of rounded rectangular bellows under pressure

Bellows is a flexible component whose volume can be changed by compression or expansion under pressure. Rounded rectangular type bellows is most applied where the internal space of application is strict. The Expansion Joint Manufacturers Association (EJMA) code is world-recognized code for design by formulas method. However, the calculation formulas of stress and deformation in EJMA code does not consider the shape of corner. Therefore, this study proposed a structural assumption of curved beam model to calculate the stress and deformation for rounded rectangular bellows under pressure load by formula calculation method. A parametric study by means of finite element analysis (FEA) was performed to assess the impact of different structural parameters and the applicable scope was investigated. The experimental and numerical results showed that the proposed method can obtain a suitable precision and safe result when ratio of wave height to corner radius is lower than 35 % and the ratio of length of short side length to corner radius is in range 5–20. This study will enrich existing bellows design code and help industry designers to accelerate the optimization iteration in preliminary design stage instead of FEA.