本文採用有限元素法中二維的軸對稱元素模型，將共16對膜片的銲接波紋管，透過其具重複性的特點，簡化成兩對膜片進行尺寸優化分析。

基於靜態及線彈性行為假設前提，分析銲接波紋管在各種不同的工作條件下之應力分布與伸縮剛性。藉由有限元素分析所獲得的計算結果，探討膜片各項幾何參數在力學行為上扮演的角色，以尋求膜片形狀與尺寸的最佳組合。接著導入破壞力學來分析銲道部分類似裂縫之結構，以了解銲道熔滲深度的影響，期望在形狀尺寸優化時，能有效提昇銲接波紋管之使用壽命。

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.

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