Extracting High Frequency Operating Shapes from 3D DIC Measurements and Phased-Based Motion Magnified Images

Abstract

The three-dimensional digital image correlation (3D DIC) method in conjunction with a stereo-vision system can provide the full-field dynamic displacements of a structure with sub-pixel accuracy. However, stereo-photogrammetry systems are limited by camera resolution and intrinsic noise of the acquired images. Thus, in order to use optical sensing techniques to identify dynamic characteristics of a structure at high frequencies, the signal-to-noise ratio (SNR) in the sequence of images taken with a stereo-vision system needs to be improved. Within this paper phase-based video magnification, in conjunction with 3D DIC are used to visualize the high frequency operating shapes of a cantilever beam. The magnified sequence of images using motion magnification technique are post-processed using 3D DIC to quantify infinitesimal deformation that is not recognizable using only digital image correlation. The results obtained within this paper reveal the great potential of extracting 3D operating shapes of a high frequency structure using the motion magnification and stereo-photogrammetry techniques. Moreover, results of this paper indicate that using the motion magnification technique increases the SNR of the measurements, and could be used as a new approach to extract more information about the structure than previously possible compared to using 3D DIC alone.