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標題: | 汽車板金沖壓成形之缺陷分析與改善研究 Analysis and Elimination of Forming Defects in the Stamping Process of Automotive Parts |
作者: | Meng-Syun Tsai 蔡孟勳 |
指導教授: | 陳復國(Fuh-Kuo Chen) |
關鍵字: | 先進高強度鋼,包辛格效應,變壓料力,可調式阻料條,有限元素法, advanced high strength steels,Bauschinger effect,variable blank holder force,adjustable drawbead,finite element analysis, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 在全球暖化日益嚴重下,節能減碳已是一個主要的議題,因此國際各大汽車產業均以輕量化為目標,為了達到輕量化之目的,目前各大車廠主要使用先進高強度鋼(Advanced High Strength Steel),藉由先進高強度鋼的使用來減輕車身重量。但先進高強度鋼其沖壓成形都面臨到之破裂、皺褶以及回彈等成形缺陷,相較於一般傳統軟鋼更為嚴重。
其先進高強度鋼之沖壓成形困難,在試模時需花費大量的金錢及時間成本,因此導入Computer Aided Engineering(CAE)分析技術,希望藉由CAE之分析,以達更精確的模具設計,可以大幅減少開模成本。而材料模型亦是其CAE分析中非常重要的一環,先進高強度鋼有著明顯包辛格效應(Bauschinger effect),考慮包辛格效應之加工硬化準則以及考慮雙軸向受力之降伏準則,在瞭解材料塑性變形行為,提升先進高強度鋼之成形特性分析與回彈預測能力。 本論文首先針對目前常用之Hill48、Hill90、Barlat89、Barlat91和Yld2000-2d等降伏準則進行探討,探討可以描述材料包辛格效應之之Yoshida-Uemori材料模型,並執行建立降伏準則以及加工硬化準則所需之實驗,有單軸拉伸實驗、反覆拉伸壓縮實驗以及塑性應變比值實驗,建立有限元素分析所需之Hill48以及Barlat91降伏準則以及加工硬化準則材料模型之參數。 本論文參考車側門檻件,提出一個基本造型以及兩個特殊造型的U形帽狀載具探討車側門檻件成形缺陷,主要成形缺陷為皺褶缺陷以及破裂缺陷,利用變壓料力以及阻料條兩種方式可以有效改善皺褶缺陷以及回彈缺陷。並針對阻料條改善回彈部分,設計一組實驗模具,用墊片方式改變阻料條作用深度,用在實際之U形帽狀引伸模具設計,且以實際之沖壓成形進行實驗驗證,並用等向性加工硬化準則以及Yoshida-Uemori 材料模型搭配Hill48以及Barlat91降伏準則進行模擬分析,比較實驗之厚度與回彈結果,其結果顯示Barlat91降伏準則結合Yoshida-Uemori 材料模型與實驗結果最為接近。並利用機構設計一套可調式阻料條可快速調整阻料條之高度。 Energy conservation and carbon reduction have become a major issue in the face of increasing global warming. Therefore, all major international automotive industries aim for lightweight. In order to achieve the goal of lightweight, major automakers mainly use Advanced High Strength Steel (AHSS) to reduce the weight of the car. However, advanced high strength steels are subject to forming defects such as crack, wrinkle and springback, which are more serious than mild steel. The advanced high-strength steel forming is difficult, and it takes a lot of money and time cost to test the mold. Therefore, Computer Aided Engineering (CAE) analysis technology is introduced, and it is hoped that CAE analysis can achieve more accurate mold design. Significantly reduce the cost of mold opening. The material model is also a very important part of its CAE analysis. The advanced high-strength steel has a significant Bauschinger effect, the work hardening rule considering the Bauschinger effect and the yield criterion of considering the biaxial force. Understand the plastic deformation behavior of materials, improve the forming characteristics analysis and springback prediction ability of advanced high-strength steel. This paper first discuss the commonly used yield criteria such as Hill48, Hill90, Barlat89, Barlat91 and Yld2000-2d, and explore the Yoshida-Uemori material model which can describe the material Bausching effect, and implement the establishment of the yield criterion and the work hardening rule. The required experiments include uniaxial tensile experiments, tensile-compression experiments, and plastic strain ratio experiments to establish the parameters of the Hill48 and Barlat91 yield criteria and the work hardening rule material model required for finite element analysis. With reference to the side sills of the automotive, this paper proposes a basic shape and two special-shaped U-hat shape to discuss the forming defects of the side sill parts. The main forming defects are wrinkle defects and springback defects, using variable holder force and drawbead. Variable holder force and drawbead can effectively improve wrinkle defects and springback defects. In order to improve the springback part of drawbead, a set of experimental molds is designed. The drawbead height can be adjusted by changing the gasket. The drawbead design has been used in the U-hat shape drawing die. The isotropic work hardening rule and the Yoshida-Uemori material model were simulated with Hill48 and Barlat91 yield criteria. The thickness and springback results of the experiment were compared. The results show that the Barlat91 yield criterion combined with the Yoshida-Uemori material model is the closest to the experimental results. And use the mechanism to design an adjustable drawbead to quickly adjust the height of the strip. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/72202 |
DOI: | 10.6342/NTU201803706 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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