利用數位影像相關法於先進高強度鋼板應變場量測

近年來隨著環保意識之復甦，節能減碳已成為未來全球工業界製程發展之趨勢與目標，因此汽車界已積極投入可降低油耗之輕量化車體結構開發。但現今車廠常用之先進高強度鋼，於常溫沖壓下成形性低且回彈量高，不利於產品之設計開發，熱沖壓成形製程即因應而生。透過此製程中之模內淬火方式，可使工件顯微組織轉變為高強度之麻田散鐵，其抗拉強度可高達1,500MPa以上，而該強度已漸成為現代汽車產業之基本技術指標。在沖壓成形的製程當中，使用成形極限圖可以有效地分析和預測材料破裂或著是頸縮的情形。但在高溫的環境限制之下，無法使用傳統的網格量測法做手工的接觸式量測，因此，使用非接觸式的即時量測有其必要性。而數位影像相關法(Digital Image Correlation Method, DIC)即是一種非接觸、非破壞性的光學即時量測方法，本研究應用於數位影像相關法中最常見使用皮爾森積差相關係數(Pearson product-moment correlation coefficient)來進行相關性匹配運算來編寫MATLAB程式碼。並藉由一個簡單的位移方程式配合牛頓法理論進行此位移方程式之優化，最後透過迭代運算進而求得物體表面於變形後位移，進而計算應變場。本研究所建立的數位影像相關法於材料試驗的實驗設備主要為兩大部分:常溫三維的成形試驗與高溫二維的板材拉伸。藉由實驗完成後數位影像相關法程式讀取值與手動量測蝕刻網格變形量的比較，證實數位影像相關法與傳統方法所取得的數據有一致性，並藉此證明使用數位影像相關法於三維高溫應變場的可行性。藉由應變場的量測，應用所獲得的數據分析，本研究建立了2015年新世代590級和1180級高強度鋼板的第一象限極限成形曲線、驗證了在800oC、不同應變率之下使用數位影像相關法量測應變場的可行性，並同時建立了中鋼公司15B22錳硼鋼材的應力-應變曲線。

關鍵字

數位影像相關法；應變場量測；高溫沖壓成形

並列摘要

In recent years, automobile industries have being dedicated to improve the fuel efficiency by using advanced high strength steels in vehicles structural parts. However, increasing the strength steels leads to a limited formability and high tendency to springback. On the other hand, the hot stamping process becomes an effective solution. Because of the transformation of microstructure to martensite during the die-quenching process leading to an ultimate strength up to 1,500 MPa. Forming Limit Curve(FLC) is an important material property for CAE simulations of hot stamping. However, the traditional grid method is not applicate in high temperature environments. Digital Image Correlation (DIC) is a non-contact method for strain measurement. Therefore, this study aim to explore the application of 3D Digital Image Correlation (DIC) method to establish FLC. Advantages of DIC is the simplicity of experiment setup and providing accurate full field strain distribution. In this research, the self-developed DIC code on Matlab is also developed to find the displacement and strain fields. Experiments in this thesis are divided to two parts: using DIC to obtain 3D Forming Limit Curve in room temperature and using DIC to obtain 2D strain field in 800˚C tensile deformation. By using DIC, the FLD of the 590Y and 1180Y high strength steel and the stress-strain curve of the 15B22 coated steel strips in high temperature are established.

並列關鍵字

hot stamping process ； digital image correlation ； strain field measurement

參考文獻

[2] 戴暘, "熱沖壓成形高溫摩擦特性分析," 2013.

[3] A. Korhonen, "On the theories of sheet metal necking and forming limits," Journal of Engineering Materials and Technology, vol. 100, pp. 303-309, 1978.

[6] J. Xavier, A. M. Sousa, J. J. Morais, V. M. Filipe, and M. Vaz, "Measuring displacement fields by cross-correlation and a differential technique: experimental validation," Optical Engineering, vol. 51, pp. 043602-1-043602-12, 2012.

[7] O. Lokberg and K. Hogmoen, "Use of modulated reference wave in electronic speckle pattern interferometry," Journal of Physics E: Scientific Instruments, vol. 9, p. 847, 1976.

[8] W. Peters and W. Ranson, "Digital imaging techniques in experimental stress analysis," Optical engineering, vol. 21, pp. 213427-213427-, 1982.

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利用數位影像相關法於先進高強度鋼板應變場量測

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