先進高強度鋼板沖壓成形之回彈分析

Analysis of Springback in the Stamping Process with Advanced High Strength Steel Sheets

10.6342/NTU.2008.02840

劉士維

先進高強度鋼板 ； 沖壓成形 ； 特徵造型 ； 回彈現象 ； 回彈機制 ； CAE模式 ； 模面設計 ； advanced high strength steel (AHSS) ； stamping ； springback compensation ； springback mechanism ； CAE method ； tool design

國立臺灣大學機械工程學系學位論文

2008年

碩士

陳復國

繁體中文

由於日益嚴苛的環保要求，以及能源價格的不斷上升，因此如何提高燃油的效率，是汽車製造以及相關產業所面臨的最大課題，汽車輕量化的需求也就由此產生，而因輕金屬價格仍然居高不下，故對於汽車鋼構件之應用，仍然以使用鋼材為主，進而促使先進高強度鋼之研究開發。由於先進高強度鋼之強度較傳統鋼板為高，故使用先進高強度鋼取代傳統強度之鋼板時，可使得載具所需之厚度較使用傳統鋼板時為低，而能夠達到汽車減重之目的。然而由於高強度鋼板強度的提升，使得其經過沖壓成形所產生之回彈現象，亦較傳統鋼板來得嚴重且難以解決，而造成模具開發時間與成本之耗費。 為了提升模具設計之正確性與時效性，電腦輔助分析(computer aided engineering, CAE)技術已被廣泛地應用於模具設計階段，然而目前針對先進高強度鋼板沖壓之模擬準確性，仍有許多問題待克服與解決，因此如何建立最佳之CAE技術，亦是相關產業與學界所刻不容緩進行研究的議題。本論文首先選定使用先進高強度鋼板之實際載具，並定義可反應回彈現象之幾何造型為回彈參數，以各載具第一道次之成形工程，再以專業之沖壓分析軟體PAM-STAMP，探討製程及模擬等二大類參數對於回彈現象之影響，並建立最適當之先進高強度鋼板沖壓成形CAE模式。 對於先進高強度鋼CAE模式之驗證，本論文針對實際業界載具-前保險桿內板與車側門檻件成形之全工程，首先利用逆向工程照相掃描技術，獲得載具成形工程之模具表面資料，其次定義載具中反應回彈現象之幾何造型為回彈參數，使用分析軟體PAM-STAMP進行模擬分析並與掃描實際板件所獲得之資料比對，其中於車側門檻件之比對中，由分析結果修正了模擬沖壓速度之設定，最後完成確認預測回彈參數之準確率。 對於實際案例之模面設計，本論文以完成建立與驗證之CAE模式，選定前保險桿內板與門檻件之模面設計，針對所定義探討之造型參數，使用模擬技術輔助分析回彈現象，以造型參數的回彈結果來討論載具之模面設計，確認並修正回彈補償量後決定模面造型參數之設定值，經反覆設計分析使板件成形後達到成品設計所需之目標。 先進高強度鋼板於汽車之應用，目前主要以安全與強度之結構件為主，為了提升先進高強度鋼載具開發之時效與效益，因此有必要針對常見之載具造型，定義特徵造型並探討其回彈現象與機制，以提供模具設計之參考依據。本論文針對汽車鋼構件常見之造型，定義具代表性之隧形樑特徵造型，並對於其普遍使用之成形工法進行分析，包含一次彎曲及二次彎曲之工法，探討其分別對應之回彈現象與回彈機制。

Along with the intensifying of energy crisis and environmental problems, energy saving and safety have become the most important issues for auto-making and related industry. To achieve these goals, weight reduction is most effective, which leads to the fast development and application of advanced high strength steels (AHSS). However, due to the increasing strength, the use of advanced high strength steel has encountered the springback issue, which is more serious and hard to be solved than that occurs in the stamping of conventional steel sheets. Computer aided engineering (CAE) technology has been widely adopted for assisting the development of stamping tools in the design stage. Nevertheless, the accuracy of springback prediction of CAE technology in the sheet metal stamping of advanced high strength steel is yet to be improved. Therefore, this thesis begins with the study of the effects of the simulation parameters on the accuracy of the springback prediction. The finite element code PAM_STAMP was employed and the dimensions of production automotive parts such as side sill were measured to validate the CAE simulations results. An optimum set of simulation parameters was thus determined and the accuracy of the springback prediction by the CAE simulations was then improved. With the use of the validated CAE model, the stamping die designs for two automotive parts, front bumper inner plate and side sill part, were studied. The multi-stage forming process used to manufacture the parts was designed and simulated by the proposed CAE model. The design concept of springback compensation was applied to reduce the springback on the production parts. With the aid of the CAE technology, optimum stamping die designs for the two automotive parts were proposed and the sound production parts with dimension variations within the design tolerances confirm the validity of the CAE simulations. Due to the applications of advanced high strength steel in automobile are usually the structural parts. The tunnel-beam shape bears the characteristic geometry for these structural parts. In order to study the springback properties in this characteristic geometry, two common forming processes, single bend and double bend, were simulated in the present study. The mechanism of springback was analyzed and the effects of different forming process on the reduction of springback were examined with the aid of the proposed CAE model.

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