Ultra-High Speed Imaging for DIC Measurements in Kolsky Bar Experiments
Full-field, stereo DIC were applied to measure the dynamic deformations for a series of compression Kolsky bar experiments at strain rates from 102/s to 103/s. A pair of Specialised Imaging’s Kirana cameras were configured in a stereo configuration which helps to account for the large radial deformation. Key specifications for these CMOS-based cameras are the ability to record at a max frame rate of two million frames per second at full sensor resolution of 924 × 768 with a total of 180 frames. Common challenges that are associated with high speed imaging are adequate lighting throughout the duration of test and accurate triggering to ensure the event is properly captured in the allotted record time. In our setup, continuous, high-intensity LED lighting provided the needed light source. Combination of location of the strain gages and knowing the incident bar wave speed, the trigger is established by a delay time until the loading pulse reaches the test sample. In this work, the DIC methodologies and results for two class of materials, a set of formulated epoxy blends and steel alloy FeMnAl, are presented and discussed.
KeywordsDigital image correlation Kolsky bar Strain-rate Ultra-high speed imaging