Wang Qinghua, Ri Shien, Tsuda Hiroshi
Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and Technology (AIST);
Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and Technology (AIST).
J Vis Exp. 2017 May 23(123):55739. doi: 10.3791/55739.
This work describes the measurement procedure and principles of a sampling moiré technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moiré method or the spatial phase-shifting sampling moiré method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moiré fringes are generated to reconstruct a multiplication moiré pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moiré method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moiré fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moiré techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.
这项工作描述了一种用于全场微纳尺度变形测量的采样莫尔技术的测量程序和原理。所开发的技术可以通过两种方式执行：使用重构乘法莫尔法或空间相移采样莫尔法。当试样网格间距约为2像素时，会生成2像素采样莫尔条纹以重构用于变形测量的乘法莫尔图案。在相同的宽视场中，位移和应变灵敏度都是传统扫描莫尔法的两倍。当试样网格间距约为3像素或大于3像素时，会生成多像素采样莫尔条纹，并结合空间相移技术进行全场变形测量。应变测量精度显著提高，并且易于实现自动批量测量。与传统莫尔技术一样，这两种方法都可以从单次拍摄的网格图像中测量二维（2D）应变分布，而无需旋转试样或扫描线。作为示例，在三点弯曲试验中测量了两个碳纤维增强塑料试样的二维位移和应变分布，包括剪切应变。预计所提出的技术将在各种材料的力学性能、裂纹出现和残余应力的无损定量评估中发挥重要作用。
