Measurement of displacement, velocity and deformation using Stereo Digital Image Correlation: Application to a large scale Pyrotechnic Experiment

Pyrotechnical experiments conventionally rely on discrete probes for quantitative data. In contrast, imaging diagnostics provide substantial spatial information and offer additional data on intrinsic material parameters. This study presents an attempt to measure displacement, velocity, and deformation of metallic free surfaces on a large field (200 mm²) using stereo digital image correlation (DIC) in pyrotechnical experiments. The studied object is composed of a roughly cylindrical explosive embedded in a 304L steel cover and initiated by a detonator at the top. Two Phantom TMX 7510 cameras were synchronized together at 308 820 fps. Random speckle patterns were applied on the surface and monitored with the software EikoTwin DIC. However during the expansion, ionization of air tends to modify the gray levels of the images. Correlation was calculated by comparing each image with its previous one. We managed to get displacement information with a precision lower than 200 µm. These results were compared with hydrodynamic simulations and two PDV probes that were implemented near the object. After comparing the results, we have found that the displacement measured by Stereo DIC is consistent. Overall, this technique also provides data about the deformation of steel.