Monday  |  Salon 13  |  09:40 AM–10:00 AM

#16052, 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 has driven widespread adoption of HS and UHS DIC especially when sampling rates in the kHz to MHz are required. Two common challenges in the application of DIC to high-rate material loading are (1) the tradeoff between resolution, record time and sampling rate, and (2) issues with the applied speckle pattern failing during high-rate loading. HS cameras are limited by data transfer rates so the user must balance necessary imaging resolution with frame rates in the kHz range. Due to large memory buffers, seconds of data is possible. UHS camera have fixed resolution and yield sampling rates in the MHz range, but are limited by very low number of images (i.e., 100s). At 5 MHz this may only yield approximately 25 microseconds of data. Thus, HS cameras are best up to around 100 kHz with long record times and UHS are useful at 100 kHz and greater rates with 100s of images. From a practical point of view there is a significant need for greater flexibility in the imaging rate and number of images for DIC. A potential solution offered by a select number of HS and UHS cameras is image interpolation which can boost the available frame rate and number of images. By acquiring images using a fraction of the pixels and filling in the gaps with image interpolation, the cameras can return “full-resolution” images at higher frame rates and record increased number of images. Due to limited work exploring image interpolation this study will evaluate the effects of interpolation on DIC data and offer insight into the resulting measurement error. Another challenge of DIC applied to dynamic loading is a requirement that the applied speckle pattern follow 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 and unique challenges associated with impact testing. DIC results will be compared with PDV to study the effectiveness of the pattern in tracking the composite surface during testing.

Phillip Jannotti   U.S. Army Research Laboratory
Nicholas Lorenzo   U.S. Army Research Laboratory
Samantha Cunningham   U.S. Army Research Laboratory