Murienne Barbara J, Nguyen Thao D
Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA.
Opt Lasers Eng. 2016 Feb;77:92-99. doi: 10.1016/j.optlaseng.2015.07.013. Epub 2015 Aug 15.
Three-dimensional (3D) digital image correlation (DIC) is becoming widely used to characterize the behavior of structures undergoing 3D deformations. However, the use of 3D-DIC can be challenging under certain conditions, such as high magnification, and therefore small depth of field, or a highly controlled environment with limited access for two-angled cameras. The purpose of this study is to compare 2D-DIC and 3D-DIC for the same inflation experiment and evaluate whether 2D-DIC can be used when conditions discourage the use of a stereo-vision system. A latex membrane was inflated vertically to 5.41 kPa (reference pressure), then to 7.87 kPa (deformed pressure). A two-camera stereo-vision system acquired top-down images of the membrane, while a single camera system simultaneously recorded images of the membrane in profile. 2D-DIC and 3D-DIC were used to calculate horizontal (in the membrane plane) and vertical (out of the membrane plane) displacements, and meridional strain. Under static conditions, the baseline uncertainty in horizontal displacement and strain were smaller for 3D-DIC than 2D-DIC. However, the opposite was observed for the vertical displacement, for which 2D-DIC had a smaller baseline uncertainty. The baseline absolute error in vertical displacement and strain were similar for both DIC methods, but it was larger for 2D-DIC than 3D-DIC for the horizontal displacement. Under inflation, the variability in the measurements were larger than under static conditions for both DIC methods. 2D-DIC showed a smaller variability in displacements than 3D-DIC, especially for the vertical displacement, but a similar strain uncertainty. The absolute difference in the average displacements and strain between 3D-DIC and 2D-DIC were in the range of the 3D-DIC variability. Those findings suggest that 2D-DIC might be used as an alternative to 3D-DIC to study the inflation response of materials under certain conditions.
三维（3D）数字图像相关技术（DIC）正被广泛用于表征经历三维变形的结构的行为。然而，在某些条件下使用3D-DIC可能具有挑战性，例如高放大倍数，从而导致景深小，或者是一个高度受控的环境，双角度相机难以进入。本研究的目的是在相同的充气实验中比较二维数字图像相关技术（2D-DIC）和三维数字图像相关技术（3D-DIC），并评估在不利于使用立体视觉系统的条件下2D-DIC是否可用。将乳胶膜垂直充气至5.41千帕（参考压力），然后充气至7.87千帕（变形压力）。一个双相机立体视觉系统获取膜的自上而下的图像，而一个单相机系统同时记录膜的侧面图像。使用2D-DIC和3D-DIC来计算水平（在膜平面内）和垂直（在膜平面外）位移以及子午线应变。在静态条件下，3D-DIC的水平位移和应变的基线不确定性比2D-DIC小。然而，在垂直位移方面观察到相反的情况，2D-DIC的基线不确定性较小。两种DIC方法在垂直位移和应变方面的基线绝对误差相似，但在水平位移方面，2D-DIC的基线绝对误差比3D-DIC大。在充气过程中，两种DIC方法的测量变异性都比静态条件下大。2D-DIC在位移方面的变异性比3D-DIC小，特别是在垂直位移方面，但应变不确定性相似。3D-DIC和2D-DIC之间平均位移和应变的绝对差值在3D-DIC变异性范围内。这些发现表明，在某些条件下，2D-DIC可能用作3D-DIC的替代方法来研究材料的充气响应。
