Comparison of stereo vs 2D digital image correlation for wavefield reconstruction for damage imaging

This paper presents a feasibility study for the visualization of hidden damage using an integrated high-speed stereo-camera system. The reconstructed wavefields produced by the 3D-enabled stereo-camera system were compared to those from a single-camera system, which is limited to 2D sampling. To demonstrate this stereo-camera concept, guided waves were generated in a thin aluminum plate with surrogate damage using a surface-mounted piezoelectric actuator under continuous sinusoidal excitation. The resulting wavefield was captured with two calibrated high-speed cameras and reconstructed through stereo-digital image correlation. After signal or image filtering and processing, the reconstructed wavefield was produced. To overcome the limited data rate of state-of-the-art high-speed cameras, sample interleaving was implemented to effectively increase the sampling rate. For the single-camera 2D-DIC case, image stitching was needed to increase the field of view, which left artifacts in the damage image due to slight misalignments between samples. The implementation of two high-speed cameras for stereo-digital image correlation enables the full-field sampling of both in-plane and out-of-plane components of the wavefield displacement. Because the out-of-plane displacement is typically much larger than other wave modes due to the thin plate dimensions, this advantage of capturing out-of-plane vibrations unique to the stereo-camera setup lowered the required resolution and enabled the capture of a larger field-of-view without the need for image stitching.