- 學位論文
汽車結構件之管件液壓成形製程分析
An Analysis of Tube-Hydroforming Process for Automobile Structural Parts
摘要
管件液壓成形技術在汽車產業中對於改善結構的輕量化以及高強度化是人們所關注的。本論文針對汽車後懸吊系統之拖曳臂，進行管件液壓成形技術之研究。 管件液壓成形技術包含截面分析、彎管、預成形、液壓成形。本研究以一簡單模型為案例，在做截面分析之過程中同時提出成品面設計的參考點，包含了可製造性及強度需求；然後再探討不同彎管方式之缺陷，並利用有限元素法PAM-STAMP分析缺陷對成形的影響。最後從局部膨脹與軸向側推補料著手，研究局部膨脹所造成之成形性問題。 由於彎管後管材並非全然能放入模穴，而必需用預成形來避免夾料之影響。本研究藉由實際開發案例，設計兩種預成形模具，使其對管材產生不同的變形模式，探討預成形設計對管材的影響，提供未來設計預成形的參考。 對於複雜形狀工件，需以軸向側推方能提供足夠的材料給膨脹率較高的位置。在液壓成形時的軸向側推，適當的液壓壓力負載路徑是工法設計的基礎。然而在實際生產時，簡單的液壓壓力負載路徑始終是工法設計的首選。本文對於在固定軸向側推量之情況下恆壓的負載路徑進行研究，探討不同之負載路徑對成品之影響。藉由上述的研究，可提升管件液壓成形技術，同時可提供未來開發汽車後懸吊拖曳臂之參考。
並列摘要
The application of tube hydroforming technology to improve the structure property in lightweight and high strength has drawn much attention from the automotive industry. In the present study, the hydroforming process for producing a trailing arm was examined. A tube hydroforming process usually consists of three forming operations: tube bending, pre-forming and hydroforming. In the present study, the analysis of cross-sections was conducted first to examine the manufacturing feasibility according to the part shape design. The tube-bending processes were then investigated using the finite element analysis. The tube may be pre-bent by a bending machine or bent in the pre-form die, called die bending, depending on whether the centerline of the bent tube is planar or not. The effect of the tube bending method on the formability of hydroforming was analyzed. It is found that the tube bent in a die is apt to causing local expansion that may lead to fracture in the final product. However, most of the local expansions which appear near the tube ends could be formed without fracture with the assistance of axial feeding. For a bent tube not being properly placed into the hydroforming die cavity, an additional pre-forming operation is required to avoid pinching at die closing. Two types of pre-forming dies were proposed in the present study to cope with the pinching problem. The efficiency of these two different pre-forming dies was also evaluated with the use of the finite element simulations. For a part with complex shape, axial feed is usually required to provide sufficient material at the position where the expansion ratio is much higher. In the hydroforming process with axial feeding, an appropriate loading path of hydraulic pressure is fundamental to the process design. However, in an actual production process, a simple loading path is always preferred. In the present study, the effect of various loading path on the formability of hydrofoprming a trailing arm was also discussed. The finite element simulation results show that the trailing arm with complex part shape could be produced with a constant hydraulic pressure during the axial feeding. The results obtained in the present study could be valuable references to the future research in hydroforming a complex-shaped part with advanced technology.