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立体数字图像相关(stereo-digital image correlation, stereo-DIC)方法因其非接触、全场测量等优点在结构振动测量和健康监测领域得到了广泛应用。然而，利用传统stereo-DIC系统测量结构离面振动位移时，易出现散斑制作困难、相机拍摄不同步，以及计算量大等问题，进而影响结构模态分析与损伤识别的效率和精度。借助投影散斑数字图像相关方法则有望解决上述问题。

西北工业大学曹善成副教授、念海波硕士和徐超教授，以及中国电子产品可靠性与环境试验研究所颜津玮助理工程师在《国际机械系统动力学学报（英文）》（International Journal of Mechanical System Dynamics, IJMSD）发表“基于投影散斑数字图像相关法的全场离面振动位移采集及其在损伤定位中的应用”研究论文。该文提出了一种借助投影散斑单目高速摄像测量系统对结构离面振动位移进行测量；并考虑结构损伤局部分布连续性和全局分布稀疏性的特点，提出了一种采用主成分分析方法提取模态振型中由损伤引起的局部畸变的结构损伤定位方法；最后，将投影散斑测量系统的模态分析和损伤定位结果与传统双目stereo-DIC测量系统的损伤定位结果进行对比。结果表明，借助所提出的投影散斑数字摄像测量系统能够准确地完成板类结构损伤定位，且其定位精度与传统双目stereo-DIC系统相当。

Stereo-digital image correlation (stereo-DIC) has been widely explored for modal analysis in plate-type structures due to its noncontact and full-field advantages. However, when the traditional stereo-DIC is adopted to capture the out-of-plane displacements, several challenging issues exist such as the development of surface speckles, asynchronous camera recording, and efficiency and accuracy degradation due to high computation costs. Moreover, with the captured out-of-plane displacements, effective and efficient evaluation of the high spatial resolution mode shapes and their application to damage localization are also critical problems. To tackle these issues, a speckle-projection DIC technique using a single high-speed camera is proposed to obtain the out-of-plane vibration displacements. Moreover, an enhanced peak-picking modal analysis method is adopted to enhance the estimation accuracy and efficiency of mode shapes. In addition, the low-rank property of mode shapes in an intact state and the spatial sparse property of damage locations are harnessed for the detection of damage positions without requiring reference data on the healthy state. Finally, the modal analysis and damage localization results based on the proposed speckle-projection DIC are compared with those of the traditional two-camera stereo-DIC technique to verify its feasibility and effectiveness. It is found that the differences in the identified resonant frequencies between these two methods are smaller than 1% for higher modes. Moreover, the proposed speckle-projection DIC has the same accuracy as the traditional two-camera stereo-DIC in terms of measurement accuracy, mode shape estimation, and damage localization.

Keywords:

damage localization, digital image correlation, low-rank property, modal analysis, out-of-plane displacement

DOI: 10.1002/msd2.12055

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https://onlinelibrary.wiley.com/doi/10.1002/msd2.12055

Cite this article: Cao S, Yan J, Nian H, Xu C. Full-field out-of-plane vibration displacement acquisition based on speckle-projection digital image correlation and its application in damage localization. Int J Mech Syst Dyn. 2022; 2(4): doi:10.1002/msd2.12055

该文亮点：

1. 借助投影散斑技术与单目相机实现了板类结构平面外全场振动位移的测量；
2. 提出了一种快速高效的基于频域分解的频率和高空间分辨率模态阵型辨识方法；
3. 提出了一种采用鲁棒主成分分析的板类结构局部损伤检测与定位方法。

Highlights:

1. A speckle-projection digital image correlation (DIC) technique via a single high-speed camera is proposed to obtain the out-of-plane vibration displacements.
2. An enhanced peak-picking modal analysis method is adopted to boost the estimation accuracy and efficiency of mode shapes.
3. A robust principal component analysis method is presented to realize the detection of damage positions in plate-type structures.

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