應用貼紙格線與影像處理軟體在鋁試片量測應變之評估

Assessment of Strain Measurements Using Grid Tab and Photo-image Management Software on Aluminum Specimens

陳文璟(Wen-Ching Chen) ； 張桓禎(Huan-Chen Chang) ； 吳嘉昌(Chia-Chang Wu)

《華岡工程學報》 18期 (2004/06) Pp. 35-43

https://doi.org/10.29987/CCUHKJE.200406.0006

摘要

紋身贴紙是一層延展性很好之透明薄膜（光面）披覆在另一層可以用水沾濕除去之背部紙面的覆層紙。本實驗以高解析度(5,760×1440 dpi)噴墨印表機在紋身貼紙之光面列印格線、裁下貼紙用氰胺乙酸乙脂熱固快乾膠將光面黏貼在鋁試片上、沾水除去背部紙面、將貼紙格線呈現在鋁試片上。然後在拉伸試驗過程，以5百萬畫素(2,560×1920 pixels)數位相機擷取一系列格線影像，輸入電腦以影像處理軟體量測各影像上貼紙格線之畫素座標，並以格線伸長除以格線原長計算各瞬時應變，然後與以應變片量測之應變和以刻痕量測之應變比較。結果顯示：當量測應變值大於0.0025(2500με)時，標準量測之格線應變之精確度在±10%之內。縱使格線伸長之量測誤差有±1畫素，只要量測應變值超過0.005(5000με)，格線應變之精確度仍然維持在±10%之內。因此，以格線量測應變正好可提供一精確之應變量測法，以克服應變片只能量測小應變量之量測限制，延續對較大應變之量測，直至試片破斷。

關鍵字

紋身貼紙 ； 格線 ； 鋁試片 ； 拉伸試驗 ； 影像處理軟體 ； 畫素點座標 ； 應變 ； 格線量測之應變 ； 應變片量測之應變 ； 刻痕量測之應變

並列摘要

The printable tattoo paper is a two-layer film-coated paper. A glossy, transparent and extensible film is coated on a backboard paper on the other side. The backboard paper can be removed by dampening the backboard. In this experiment, grids were printed on the glossy side of a tattoo paper using a high-resolution inkjet printer (5,760 × 1440 dpi). A grid tab was then trimmed and fastened (glossy side face down) on an aluminum specimen by using cyanoacrylate adhesive. The backboard paper was then dampened and removed, and the grids were shown on the specimen. A series of pictures of the grids were taken during the tensile test by using a 5-mega pixel digital camera (2,560 × 1920 pixels), and transferred to a computer. A photo-image management software was employed to measure the pixel-coordinates of the grids, and the strains were calculated by dividing the grid extensions by the original grid length. The strains measured by grids were then compared with those measured by strain-gage and those measured by scrape-lines. The results show that, if measured with standard procedures, the accuracy of grid strains is within ±10% when the measured strains exceed 0.0025 (2500με). Even if there is an error of ±1 pixel (the worst scenario) in the grid extension measurements, the accuracy of grid strains is still within ±10% when the measured strains exceed 0.005 (5000με). Therefore, the strain measurement using grid tabs can provide an accurate method for measuring large strains, which cannot be measured by strain-gages. This method overcomes the strain-gage limitations and can be used to succeed the strain-gage to continuously measure the large strains until the specimen breaks.

並列關鍵字

printable tattoo paper ； grid tab ； aluminum specimen ； tensile test ； photo-image management software ； pixel-coordinate ； strain ； strain measured by grids ； strain measured by strata-gage ； strain measured by scrape