Abstract
To develop long-life welded bellows for use under different pressure conditions, that is, atmospheric pressure and a high vacuum applied to the inside and outside of the welded bellows, respectively, a deformation analysis of welded bellows (Hastelloy C-22, 460 mm in external diameter, 370 mm in internal diameter, 0.475 mm in thickness) is performed by elastoplastic finite element analysis. The simulation results are as follows. In a conventional welded bellows used in an external-vacuum and internal-atmospheric-pressure environment, the external straight portion forms a vertical opening due to the pressure difference. The opening angle decreases by forming a slope on the external straight portion. The stress amplitude that occurs during the compression of a conventional welded bellows reaches its maximum in the vicinity of the external weld. The maximum value also decreases by forming a slope on the external straight portion. Fatigue life testing is performed on bellows produced on the basis of the simulation results. It is confirmed by fatigue life testing that forming a slope on the external straight portion is effective for extending the life of the bellows.
