汽車後搖臂管液壓成形灰關聯分析

隨著現代車輛輕量化、省能源、低成本與高性能的發展趨勢，管件液壓成形技術已成為國際間汽車產業主流製造技術之一。本文探討汽車後搖臂管件成形，由於後搖臂為一複雜3D幾何外形的汽車管件，成形過程需經過兩道預彎曲及一道液壓成形。本文首先採用有限元素法模擬後搖臂管件的成形過程，藉由製程參數的調整；如左、右端沖頭速度及內壓力等，檢視這些製程參數的改變，於此管件成形壁厚的影響趨勢、等效應力與等效應變的分佈情形及成形性等。接著使用田口法中的直交表與因子反應表，分別以最小壁厚及完整脹形成功的最大等效應力作為目標函數，以望目特性及望小特性求出個別品質目標的最佳參數水準組合。最後藉由灰關聯分析法，將上述各單一品質目標整合成一個多重品質目標，重新建立因子反應表，找出多重品質的最佳參數水準組合並與單一品質所得之結果進行比較。分析結果發現，由於本後搖臂管為一複雜幾何外型的管件，各部位管徑大小不同，其右側管徑大於左側，故右側沖頭補料速度必須大於左側，方可避免右側管壁因內壓力的鼓脹而破裂，此舉同時亦有助於成形成功。就單一品質變異數分析的因子貢獻率可看出，影響壁厚的主要製程參數為左沖頭速度，而影響等效應力值的主要參數為內壓力。單一品質所獲得之最佳最小壁厚比多重品質所求得之最佳最小壁厚大，且單一品質所獲得的最佳最大等效應力比多重品質所求得小。此乃單一品質只滿足單一目標所致，其無法同時兼顧其他品質之要求。而使用灰關聯分析可獲得兼具多重目標品質要求之最佳製程參數組合。

關鍵字

汽車後搖臂；預彎曲；田口方法；灰關聯；最佳最小壁厚

並列摘要

Along with the trend of development for weight reduction, energy-saving, low-cost, and high performance, tube hydroforming technique has become one of the major manufacturing technologies in the automotive industry worldwide. This work presents the tube forming of a trailing arm. The trailing arm is an automotive tube part in a complicated 3D geometrical shape. The process of forming should be performed pre-bending twice and a hydroforming. This work firstly utilizes the finite element method to simulate the forming process of the trailing arm. Through the adjustments of the process parameters, such as velocity of left and right punch, internal pressure, and so on, it examines the level changes of these parameters related to the influence trend of the wall thickness of the forming tube, the distribution of equivalent stresses and strains, and the formability. Secondly, by the orthogonal array and factor response table in Taguchi Method, take the minimum wall thickness and the maximum equivalent stress as the object functions, and obtain the optimal parameter combinations corresponding to each single quality object with nominal-the-best and smaller-the-best, respectively. Finally, by grey relational analysis, the above single quality objects are integrated as a multi-quality object. Re-establish the factor response table to figure out the optimal parameter combination fulfilling a multi-quality object, and compare the results with those obtained from the single quality object. From the analytical results, due to the complicated geometrical shape of the trailing arm, it found that the velocity of the right punch for billet material feeding should be higher than the left to prevent the bursting of the tube wall on the right side due to the bulging of the internal pressure since the tube diameter on the right side is larger than the left one. This is also helpful for the success opportunity of forming. From the factor contribution rate in analysis of variance for single quality object, it can be found that the major process parameter that affects the wall thickness is the left punch velocity, and the major process parameter that affects the equivalent stress is the internal pressure. The minimum wall thickness obtained from the single quality object is larger than that obtained from the multi-quality object; meanwhile, the optimal maximum equivalent stress obtained from the single quality object is smaller than the multi-quality object. This is because the single quality object only satisfies the single object and unable to match the other quality requirements at the same time. With grey relational analysis, the optimal process parameter combination of the multi-quality object can be obtained.

並列關鍵字

trailing arm ； pre-bending ； Taguchi methods ； grey relational analysis ； minimum wall thickness

參考文獻

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[1] J. B. Yang, B. H. Jeon, S. I. Oh, 2001, The tube bending technology of a hydroforming process for an automotive part, Journal of Materials Processing Technology, Vol. 111, pp.175-181

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汽車後搖臂管液壓成形灰關聯分析

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