High-Speed Photography and Digital Optical Measurement Techniques for Geomaterials: Fundamentals and Applications

Abstract

Geomaterials (i.e., rock, sand, soil and concrete) are increasingly being encountered and used in extreme environments, in terms of the pressure magnitude and the loading rate. Advancing the understanding of the mechanical response of materials to impact loading relies heavily on having suitable high-speed diagnostics. One such diagnostic is high-speed photography, which combined with a variety of digital optical measurement techniques can provide detailed insights into phenomena including fracture, impact, fragmentation and penetration in geological materials. This review begins with a brief history of high-speed imaging. Section 2 discusses of the current state-of-the-art of high-speed cameras, which includes a comparison between Charge-Coupled Device (CCD) and Complementary Metal-Oxide-Semiconductor (CMOS) sensors. The application of high-speed photography to geomechanical experiments is summarized in Section 3. Section 4 is concerned with digital optical measurement techniques including photoelastic coating, Moiré, caustics, holographic interferometry (HI), particle image velocimetry (PIV), digital image correlation (DIC) and infrared thermography (IRT), in combination with highspeed photography to capture transient phenomena. The last section provides a brief summary and discussion of future directions in the field.

Recent Milestones in Unraveling the Full-Field Structure of Dynamic Shear Cracks and Fault Ruptures in Real-Time: From Photoelasticity to Ultrahigh-Speed Digital Image Correlation

“…In addition, when processing digital images with DIC algorithms, the noise level of the camera needs to be extremely low, as it affects the quality of the displacement fields and especially the fields obtained through temporal and spatial differentiation, such as velocities and strains. These are very stringent requirements for a high-speed camera, since cameras in the ultrahigh-speed range (0.5 million frames/s and above) were traditionally based either on gateintensified technology (which produces noisy images) or rotating mirror systems (which can produce operational challenges at highframe rates due to the elevated rotating speeds) [77,[95][96][97]. On the other hand, cameras that have low noise levels typically are in the low range of frame rates, below what is needed for highly dynamic ruptures [77,96,97].…”

“…These are very stringent requirements for a high-speed camera, since cameras in the ultrahigh-speed range (0.5 million frames/s and above) were traditionally based either on gateintensified technology (which produces noisy images) or rotating mirror systems (which can produce operational challenges at highframe rates due to the elevated rotating speeds) [77,[95][96][97]. On the other hand, cameras that have low noise levels typically are in the low range of frame rates, below what is needed for highly dynamic ruptures [77,96,97]. In addition, the high-speed systems acquire images via the presence of multiple sensors, which can introduce further complications in the process of correlation [77].…”

Study on Roof Breakage-Induced Roadway Coal Burst in an Extrathick Steeply Inclined Coal Seam

“…e maximum height of the pendulum in the first 6 slice tests is 0.5 m (6.50 × 10 6 J), and the pendulum in the 7 th slice test rises step by step until the coal and rock are destroyed. e test monitoring system included a DH960 superdynamic signal test and analysis system, a PIC-2 AE system, a Memrecam GX-3 high-speed camera, and pressure cells [26], and the layout is shown in Figure 5.…”

Full-field Ultrahigh-speed Quantification of Dynamic Shear Ruptures Using Digital Image Correlation

“…The stress components are computed using linear elastic plane-stress constitutive equations with the dynamic Young's modulus of Homalite to account for its strain-rate dependent behavior cameras with a frame rate above 1 million frames/s, referred to as ultrahigh-speed cameras, can achieve a high spatial resolution (in the megapixel range) but typically have a low record length and rather high electronic noise levels, while cameras that can attain a large number of recorded frames can do so at a low sampling rate. Recent advances in high-speed camera technologies have enabled a higher number of recorded frames in the ultrahigh-speed range [44]. While the spatial resolution of these cameras is still limited, their low noise level makes them good candidates for DIC [32,35].…”