Optimum Geometry of Welded Bellows under Tension and Compression

• Main Authors: Tz-Jie Lin, 林子捷
• Other Authors: Ching-Hwei Chue
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/19375942158290698292

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 91 === The objective of this paper is to determine the optimum geometry of circular waved diaphragms in welded bellows by performing static axisymmetric finite element analyses. For simplicity, 16 pairs of repeated diaphragms will be reduced to 2 pairs only. Based on linear elasticity associated with finite deformation, the stress distribution in diaphragm and the axial stiffness of the bellow can be computed subjected to tension or compression with or without internal pressure. The results show that there are six radii of curvature in diaphragms A and B are important in the optimum design. This paper modifies the size and geometry of the diaphragms offered by MIRDC according to the requirement of least effective stresses together with maximum compliance. The optimized sizes depend on the internal pressure, the material properties, and the contact area of the diaphragm during compression. Since the failure of the integrated structure always initiate at the weld spot of diaphragms, it is necessary to apply the fracture mechanics concept to predict the safety. The depth of the weld, which connects the diaphragms A and B, plays an important role in evaluating the fatigue life. The greatest stress intensity factor occurs at inner ring when tensile force is applied only. However, as the internal pressure involves, the greatest stress intensity factor may be shifted to the outer ring.