Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2307
標題: 應用電腦視覺於金屬薄板成形的線上應變量測
On-Line Strain Measurement by Sheet Metal Forming Using Computer Vision
作者: 蔡兆益
Tsai, Chao-Yi
關鍵字: Computer Vision;電腦視覺;Strain Measurement;Grid Analysis;Sheet Metal Forming;應變量測;網格分析;金屬薄板成形
出版社: 機械工程學系
摘要: 
金屬板材的成形極限會隨成形過程的應變路徑而有所變化,然而在量測板件應變時,均需中斷成形過程,而使應變路徑無法確實描述。為正確量測其成形極限與應變路徑,本研究應用電腦視覺法建立金屬薄板成形線上板面應變非接觸式量測系統,主要以電化學蝕刻方式塗敷方形網格於原始金屬平板上,藉架設於成形機台旁的二數位攝影機,擷取金屬成形過程中的影像,由2D平面影像重建3D影像,經計算處理後,取得各網點的空間座標,並藉網格網點間拓樸關係的形成,勾勒出板件的幾何形狀,再依均勻變形的假設,計算各網點的應變量。此線上應變量測技術可即時取得板件於成形過程中的影像,並能直接描繪出成形板件的幾何圖形,與顯示成形板件的應變分佈,同時也可點繪出網點的應變路徑。本文以單軸拉伸、平面應變拉伸及平面應變狀態的張伸成形試驗,展示非接觸式線上應變量測方法在金屬薄板成形應變量測的應用。

Abstract
The strain path of sheet metal influences its forming limit diagram. However, by measuring the strain on the sheet metal, the forming process must be interrupted, then the strain path can not correctly be described and consequently the forming limit can not properly be defined. In order to measure the forming limit and strain path, this study presents apply computer vision to set up On-Line Non-contact measuring the strain on the sheet metal system. The main processing sheet metal is initially printed with square grids pattern by an electrochemical etching method. During the forming process the sheet metal is sequentially photographed with two CCD (Charge Couple Device) cameras mounted on the forming machine. We can use a pair of two-dimensional images to reconstruct a three-dimensional image. When images processed, the coordinates for each node of the grids can be determined, the skeleton of the part can also then be constructed with the topology identification, and then the strain at the node can be calculated under the postulation of homogeneous deformation. The developed on-line measurement technique can catch the sheet metal images during the forming process, which can be used not only to illustrate its geometry but also to display its strain distribution, especially to follow the strain path at the grids. This study presents the Non-contact On-Line strain measuring method applying to sheet metal forming by the following experiments: uniaxial tension sheet metal in tension strain state, uniaxial tension sheet metal in plane strain state, and stretching sheet metal in plane strain state.
URI: http://hdl.handle.net/11455/2307
Appears in Collections:機械工程學系所

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