Li Wei, Wang Yongzhe, Zhou Xingui, Xu Jingchao, Zhang Ruyue, Zeng Yi, Miao Hong
CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China.
The State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050, China; Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Ultramicroscopy. 2023 May;247:113697. doi: 10.1016/j.ultramic.2023.113697. Epub 2023 Feb 6.
High-resolution electron backscattering diffraction (HR-EBSD) was used to measure rotations and elastic strains by matching diffraction patterns based on cross-correlation. However, the subset-based phase correlation algorithm was unable to determine pattern shifts accurately when large rotations occurred. In this paper, a new matching algorithm was proposed to measure pattern shifts and recover the elastic strain and lattice rotation with finite deformation theory. The algorithm was implemented in two steps: (a) Integral pixel matching: The pixel-related information of the Kikuchi patterns was mapped to the original three-dimensional sphere to obtain the image projected in parallel by using the feature points as the pattern center through the transformation of its spatial coordinates. The correlation between the images projected in parallel before and after deformation was then obtained. The locations of the integral pixels were determined by the peaks of the surface of correlation obtained by traversing all pixels in the search area. (b) subpixel refinement: the locations of subpixels were obtained by FAGN with an appropriate shape function involving rotation and translation. The algorithm was applied to dynamic simulated test sets, and its results were compared with those of the first-pass cross-correlation and the second-pass cross-correlation method with remapping. The proposed method was more robust in the case of rotation and solved the problem that displacement vectors could not be accurately measured when a larger lattice rotation occurred. The mean errors of the measured displacement, rotation, and strain components were 0.02 pixel, 0.5×10rad, and 1×10, respectively. Compared with the second-pass cross-correlation method, the angle of rotation was more precisely extracted.
高分辨率电子背散射衍射（HR-EBSD）通过基于互相关匹配衍射图案来测量旋转和弹性应变。然而，当发生大角度旋转时，基于子集的相位相关算法无法准确确定图案偏移。本文提出了一种新的匹配算法，利用有限变形理论来测量图案偏移并恢复弹性应变和晶格旋转。该算法分两步实现：（a）积分像素匹配：将菊池图案的像素相关信息映射到原始三维球体上，通过其空间坐标变换，以特征点为图案中心获得平行投影图像。然后得到变形前后平行投影图像之间的相关性。通过遍历搜索区域内所有像素得到的相关表面峰值来确定积分像素的位置。（b）亚像素细化：通过具有包含旋转和平移的适当形状函数的FAGN获得亚像素的位置。该算法应用于动态模拟测试集，并将其结果与首次互相关和重新映射的二次互相关方法的结果进行比较。所提出的方法在旋转情况下更稳健，解决了大晶格旋转时位移矢量无法准确测量的问题。测量的位移、旋转和应变分量的平均误差分别为0.02像素、0.5×10弧度和1×10。与二次互相关方法相比，旋转角度的提取更精确。
