本文根據能量破壞準則探討以液壓鼓脹進行具有截面變化之零件外形的多道次製程，包括預成形管件以及模具幾何。並且發展出適合評估具有截面變化管件之預成形設計法則。
文中經由材料試驗取得材料破壞資訊，並且透過理論分析之成形極限圖和實驗結果比較，得知材料破壞條件符合能量準則所預測。同時，經由有限元素套裝軟體LS-DYNA針對鈷基超合金HA-188進行液壓鼓脹模擬分析，在後處理分析取得材料應變路徑得知接近線性。
本文利用具截面變化之管件為目標，根據體積不變，並且提出控制截面的概念設計初始管件外形，評估不同截面幾何管件的可成形性。對於模具幾何設計，首先進行道次規劃，並且使用有限元素分析軟體LS-DYNA進行初步分析，根據評估結果規劃出幾何參數組合，並且進行多道次的模擬分析，觀察管件於成形極限時的幾何外形。模擬結果得到道次數最少的模具幾何參數組合，並且有效減少原來製程的道次數量。

In this sttuy, an energy criterion was used for evaluating the forming limit of the components with variable cross-section shape in multi-stage tube hydroforming. A preform design rule was developing for assessing the tube with variable cross-section rule.
The material fracture data were obtained through material test. The experimental results were compared with forming limit diagram by theoretical analysis. The material fracture conditions agrees well with the prediction by fracture energy criterion. The finite element software LS-DYNA was applied to the cobalt-based superalloy HA-188 for tube hydroforming simulation analysis. By the post-processing analysis, the strain path obtained was nearly linear.
With variable cross-section shape as the goal, according to the constant volume, the concept of controlling the section of tube was proposed to design initial tube shape. Then, the formability of different cross-sectional tube shape was assessed. For the die geometry design, first perform the stage planning. Then, the initial result was obtained by the finite element simulation. According to the initial results, the geometrical parameter combination was planned, and then multi-stage simulation result was performed. The tube shapes with the forming limit were observed. The least number of stages was obtained in this study. It effectively reduced number of stages compared with original design in the industry.

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