Zhu Feipeng, Gu Jian, Lu Runzhi, Bai Pengxiang, Lei Dong, Kang Xin
Appl Opt. 2020 Dec 1;59(34):10813-10825. doi: 10.1364/AO.405419.
A conventional optical extensometer realized by a single common camera and two-dimensional digital image correlation (2D-DIC) often provides unsatisfactory strain results owing to the out-of-plane motion of the specimen. In this work, we propose an improved optical extensometer based on two parallel cameras and 2D-DIC. In the proposed extensometer, the gauge points are selected at the image centers of two cameras, which are negligibly affected by the out-of-plane translation and rotation, leading to higher accuracy of strain measurement as compared with the conventional optical extensometer. A rigid out-of-plane translation experiment and four repeated uniaxial tensile tests were conducted to verify the feasibility, reliability, and accuracy of the proposed method. Experimental results indicate that the proposed method has a strong ability to resist the effect of out-of-plane motion and experimental vibrations. Moreover, the strain measurement results obtained with the proposed method were found to be in excellent agreement with those obtained with a strain gauge, and the strain errors between them were only a few microstrains. Given that no compensation method is required, the proposed method is easy to implement with 2D-DIC and can be used for specimens of different sizes by adjusting the distance between the two cameras.
由单个普通相机和二维数字图像相关技术（2D-DIC）实现的传统光学引伸计，由于试样的面外运动，常常提供不尽人意的应变结果。在这项工作中，我们提出了一种基于两个平行相机和2D-DIC的改进型光学引伸计。在所提出的引伸计中，应变片选在两个相机的图像中心处，面外平移和旋转对其影响可忽略不计，与传统光学引伸计相比，这使得应变测量具有更高的精度。进行了刚性面外平移实验和四次重复单轴拉伸试验，以验证所提方法的可行性、可靠性和准确性。实验结果表明，所提方法具有很强的抵抗面外运动和实验振动影响的能力。此外，发现用所提方法获得的应变测量结果与用应变片获得的结果非常吻合，两者之间的应变误差仅为几个微应变。鉴于无需补偿方法，所提方法易于用2D-DIC实现，并且通过调整两个相机之间的距离可用于不同尺寸的试样。
