三通管件液壓成形製程之有限元素分析

Abstract

管件液壓成形技術應用在輕量化且高強度的零組件方面有越來越多的趨勢，然而對於三通管件(T形管件)而言，在成形過程中所施予的負載路徑(Loading Path)常是決定管件成形優劣的關鍵。而為了降低實際試模所需花費的時間與成本，有限元素法(Finite Element Method)常被用來模擬分析液壓成形製程以得到最佳之成形條件。然而對於實際生產廠商而言，最有助益的莫過於提供一參考指南，使其能快速判斷產品之成形可行性與設計出合適之製程參數。 因此本論文針對負載路徑提出新的設計，該負載路徑設計準則簡單容易計算，且在此負載路徑下所得到之管件成形結果均較一般線性負載路徑優越。同時亦針對三通管件液壓成形製程之影響參數進行探討分析，利用統計學迴歸分析之方法以比較模具幾何外型與製程參數對於成形結果之影響性大小，利用該分析方法亦可建立一預測模型，以快速預測不同參數條件下所能得到之凸柱高度大小，作為判斷產品是否能順利成形之參考。 由上述分析結果得知管件長度是影響凸柱成形高度很重要之因素，故本論文亦針對不同凸柱高度要求下所需之管件長度進行分析探討，將可行之管件長度定義於某一範圍，以供設計人員作參考。另一重點則是針對管件成形圓角半徑與所需之液體壓力之間的關係做一探討分析，並找到一合適且可供設計人員參考之公式。 本論文針對三通管件液壓成形製程之設計，包含管件之選擇、負載路徑之設計、不同圓角半徑下之最大壓力決定等參數做了完整之分析，透過本論文可清楚的了解到三通管件液壓成形製程參數之計算與選擇，利用該參數而設計出之負載路徑，不僅可以利用最小之管件長度順利成形所欲之凸柱高度，亦可達成近淨型(Nearly Net Shape)產品之要求。而該設計方法可作為液壓成形業者進行製程規劃以及設計時的參考。

The application of tube hydroforming technology to improve the structure property in lightweight and high strength has drawn much attention from industry. For a part with complex shape, such as T-shaped part, axial feed is usually required to provide sufficient material to the position where the expansion ratio is much higher. In the hydroforming with axial feed, an appropriate loading path of hydraulic pressure is fundamental to the process design. In the present study, an optimum loading path for hydroforming a T-shaped part is proposed based on the finite element analysis. Compared with other loading paths published in literature, which are mainly linear paths, the proposed loading path provides better performance in the hydroforming process. The effects of process parameters, such as die shape and friction condition, on the formability in hydroforming were also studied in the present study. The major process parameters that affect the formability most were identified using a regressive analysis with the help of the finite element simulations. The hydraulic pressure required to form a minimum part corner radius was investigated in the present study, and an appropriate formula that gives the relations between hydraulic pressure and corner radius was found. The effect of tube length on the formation of protrusion was examined as well using the finite element analysis. In conjunction with the studies of loading path and process parameters, a design guideline was developed. With the use of the developed design guideline, not only the protrusion in the T-shaped part can be successfully formed with an initial tube of a minimum length, but also a nearly net shaped part can be obtained. The design guideline developed in the present study provides a relevant reference for the related research and a useful tool for the hydroforming process design.