Wang Qinghua, Okumura Shigesato, Ri Shien, Xia Peng, Tsuda Hiroshi, Ogihara Shinji
Opt Express. 2020 Mar 2;28(5):7498-7514. doi: 10.1364/OE.387997.
In this study, we propose a second-order moiré method by performing digital sampling at two stages to realize high-accuracy deformation measurement in a wide field of view, where a grid image is recorded at a low magnification. Simulations have verified that this method has high strain measurement accuracy when the grid pitch is close to or even smaller than two pixels for both parallel and oblique grids with random noise. As an application, the two-dimensional microscale strain distributions of a carbon fiber reinforced plastic specimen when the grid pitch was about 2.1 pixels were presented. Shear strain concentration was detected before an interlaminar crack emerged, and tensile strain concentration was found prior to the occurrence of a transverse crack. The proposed method makes the two-step phase-shifting technique achieved indirectly, not only enlarging the field of view, but also maintaining the measurement accuracy.
在本研究中，我们提出了一种二阶莫尔条纹方法，通过在两个阶段进行数字采样，以在宽视场中实现高精度变形测量，其中在低倍率下记录网格图像。模拟已经验证，对于具有随机噪声的平行和倾斜网格，当网格间距接近甚至小于两个像素时，该方法具有较高的应变测量精度。作为应用，给出了网格间距约为2.1像素时碳纤维增强塑料试样的二维微观应变分布。在层间裂纹出现之前检测到剪切应变集中，在横向裂纹出现之前发现拉伸应变集中。所提出的方法间接实现了两步相移技术，不仅扩大了视场，而且保持了测量精度。
