Practical Considerations for High-Speed DIC

Digital image correlation (DIC) is an imaging technique that enables full-field measurements of a material motion and deformation (displacement, velocity, strain, and strain rate). Advances in high-speed (HS) and ultra-high-speed (UHS) camera technology have driven widespread adoption of HS and UHS DIC especially when sampling rates in the kHz to MHz are required. A common challenge in the application of DIC to high- rate material loading are issues with the applied speckle pattern failing during high-rate loading. A primary requirement of DIC is that the applied speckle pattern follows the underlying surface. When materials of interest are subjected to high-velocity impact, the applied pattern can debond or otherwise fail to follow the motion and deformation of the material surface. This work will evaluate common speckle pattern preparations for both distributed loading and localized deformation. The study will outline unique challenges associated with characterization high-rate material testing and describe a laser-based methodology for probing time-resolved pattern integrity. Photonic Doppler velocimetry will be used to study the effectiveness of the various patterns in tracking the surface deformation including woven composite panels and thin metal plates. The technique offers a simple, objective means of quantifying pattern integrity at selected measurement points and directly comparing different pattern techniques.