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  • 學位論文

大圓扁頭鉚釘之多道次冷鍛成形模擬分析

A Simulation Analysis of Multi-pass Cold Forging for Rivet with Large Pressed Semispherical Hea

指導教授 : 許源泉
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摘要


以往台灣坊間扣件業生產所製作的流程,皆以傳統的試誤法與實務經驗法作為依據,往往造成人力、物力上的浪費及開發日程上的延遲。因應現今全球化且各種數位化的快速發展,為了搶先商機並保有優勢,在數位電腦的快速崛之際增強運算能力,電腦輔助工程應用(Computer-aided Engineering ,CAE)為未來各項產業的發展趨勢,因此希望透過電腦輔助工程應用的方式,使其各項加工方式皆有理論依據,進而作為研究觀察、最佳化與討論,讓扣件產業技術日益精進不斷向上提升,也不會因人員流動面臨技術流失及斷層現象。 本研究利用有限元素軟體DEFORM-3D,針對SAE1006低碳鋼線材製作為大圓扁頭鉚釘的製程進行分析模擬與實際試驗進行探討。透過實際環境的條件套入模擬程式的參數及材料塑流應力、摩擦係數等,探討實際各道次鍛造成形與模擬相關數據差異性,包含胚料成形的流動變形分析、成形負荷分析、應力分佈、應變分佈及相關的模具應力分佈、磨耗分析等狀況。再將模擬結果與實物實驗做其驗證比對,觀察其各項加工道次的變化及關聯性;進而利用其結果檢證所規劃的各項道次和模具相關設計,是否符合扣件量產性的條件。 由模擬各項分析所得結果,胚料流動變形以第一道次所產生之縮徑現象最為明顯,其過程中流動速度來到最大值32.2mm/sec;第二道次鍛壓與沖孔具有些微時間差;第三道次為鍛大圓扁頭形狀,頭部流動狀況較為明顯。在成形負荷上第一道次負荷為2.829tons,第二道次為5.41tons,第三道次為6tons。最大等效應力與等效應變分佈方面,第一道次發生於縮徑變化處,第二道次發生於尾端沖孔處,第三道次則發生於大圓扁頭頭部中心處。模具等效應力方面,第一道次形成的地方為成形沖棒的前端,第二、三道次由於頂針設計為縮頸外形,故應力集中於縮頸根部。針對磨耗的狀況,以第二道次磨耗最為嚴重,其磨耗位置為頂針前端上。而尺寸的比較誤差,以第三道次大圓扁頭之頭部直徑差異較大,最大誤差值為5%。 經過實物實驗與模擬分析比較後,本研究模擬分析狀況與實物外型尺寸具有對應性及可參考性,故可將透過模擬分析數據作為扣件相關的準備和模具初期開發設計參考,讓扣件鍛造成形設計開發上,能導入相關開發概念,使模具設計開發上可透過模擬的方式預知問題點,進而於設計初期排除可能發生問題點,設計出最佳化的冷鍛加工方式;且在往後新材料的特性上的掌握,亦可透過有限元素軟體DEFORM-3D,在短時間即可應用於製程上。

關鍵字

鉚釘 冷鍛 有限元素法 鍛粗 擠伸

並列摘要


In the past, the production process of fastener industry in Taiwan was customarily based on traditional trial and error approach as well as practical experience methods. By the experiences, these methods consume not only plenty of labor power and material resources, but also put off the production schedule. Response to the effects of globalization and a variety of rapid digitized developments, and to preempt opportunities and possess advantages, assisted engineering application of Computer-aided Engineering (CAE) will be considered as the trend for various industries in the near future. We hope that CAE would be the theoretical basis of research, observation, optimization and discussion of each processing method, then improve the technique of fastener industry gradually and avoid technology vanish and the gap caused from brain-drain. Because of above mentioned reasons, we hereby use the Finite Element Software DEFORM-3D to make simulation analysis and realistic trials to get the further validation test regarding the production process with the large pressed semispherical head made by SAE1006 low carbon steel thread material. We apply the actual environmental conditions to parameter of simulation program, material flow stress, and friction coefficients to explore the differences between each pass of forging forming and simulation related data, including the analysis of billet forming flow deformation, forming load, stress and strain distribution, the related die stress distribution, wear analysis and other conditions; then, make the comparison and validation along with the simulation results and realistic experiments to observe the variation and connection from each pass. In addition, we can also use these results to inspect and validate whether each pass and die design corresponds to the requirements of mass production for fastener or not. According to the results of simulation analysis, the necking phenomenon which arises from billet the flow deformation on the first pass is most conspicuous. The flow speed goes to the maximal value of 32.2mm/sec within this pass. There are only slight differences between the forging and punching on second pass. The third pass is the shape of large pressed semispherical head, and flat head shape is more significant than other passes. The forming load- the first pass is 2.829 tons, the second is 5.41 tons, and the third is 6 tons. Then, for the maximum effective stress and strain distribution, the first pass occurs in necking change; the second comes about at the end of punching; the third happens in the center area of large pressed semispherical head. In case of the die effective stress, the first pass is formed in the front of the forming punch, the stress of the second and the third concentrate on constriction roots because of the thimble designed to constriction shape. Concerning of the situation of wear, the second pass is most obvious, and the wear position is on the front end of the thimble. As for the comparison error of size, diameter difference for the head of large pressed semispherical head on the third pass is large, and the maximum error is 5%. After the analysis and comparison of the physical experiment and simulation, we found that the simulation analysis status and physical dimensions are with the correspondence and reference. We could esteem them as the reference of fasteners preparation and die initial development and design. Therefore, the related developing concepts can be imported to the design and development of fastener forging forming, anticipate potential problems that may occur at the beginning of development, then excludes them from initial design stage and to devise optimization cold forging. On that occasion, we can control the character of the new material in the future as well as apply the Finite Element Software DEFORM-3D to the production process in short period.

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