Explosives Whitepaper
6Pages

Precision Explosives Analysis Using High-Speed Imaging Written By Dr. Vilem Petr, Colorado School of Mines Technical Contributions by:Philip Taylor and Gene Nepomuceno, Vision Research hether explosives are being used to clear land for construction and digging deeper mines, or are being encountered by the military and police, it is important to understand how various chemical mixtures and detonators affect the power of an explosion. High-speed imaging can be used to quantitatively capture explosions, the resulting damage, and to measure other important parameters of the explosion. The data collected can provide information to aid in the understanding and characterization of a detonation, which can then lead to the creation of better and more precise explosives. THE POWER OF HIGH-SPEED IMAGING Explosions were historically analyzed by manually observing the scene before an explosion and then looking at the resulting debris field. Advanced imaging techniques, such as shadowgraphy or Schlieren imaging can be combined with high-speed imaging technology to provide relevant measurements including the fast, radial expansion of the shock wave and the velocity of fragments eminating from the explosion. Explosions are thermochemical reactions that produce extremely bright light and often cause large, high-velocity, and vision-obscuring debris fields. Since a shockwave moves from 400 to 600 meters per second, the imaging area needs to be large enough to capture those changes — an area of around 50 X 50 centimeters is typically required. It is also important that the highest resolution possible be used to ensure high-quality data for post-processing of the images. If the camera is going to be placed close to the explosion, choosing a camera that is rugged will offer protection from the strong explosion shockwaves and the powerful air movements that follow the shockwaves. Advanced techniques ... can be combined with high-speed imaging to provide relevant measurements.

Precision Explosives Analysis Using High-Speed Imaging HIGH-SPEED IMAGING OF FLUID DESENSITIZED DETONATORS The Advanced Explosives Processing Research Group (AXPRO) at the Colorado School of Mines used high-speed imaging to study fluid-desensitized detonators used in oil and gas applications, more specifically for well perforation. These detonators contain holes that cause them to deactivate in the presence of any liquid, offering an additional precaution against liquid that might enter the perforating gun.1 Erika Nieczkoski, an undergraduate researcher at AXPRO, sought to determine if a...

Precision Explosives Analysis Using High-Speed Imaging were causing the desensitization to fail, and concluded that the cleaning fluids, diesel, and mineral spirits, did indeed affect detonator performance, causing the detonator to become desensitized when applied directly to the secondary explosives. Additionally, it was observed that the detonators do not become desensitized when fully submerged in fresh water up to 200 cm. Figure 3 shows images from the one of the experiments testing result with water. A NEW WAY TO MEASURE BLAST WAVE ENERGY The Institute of Makers of Explosives (IME)...

Precision Explosives Analysis Using High-Speed Imaging mirror, and a retro-reflective screen. Figure 4 shows the birds-eye view of the shadowgraph experimental set-up. Capturing extremely fast phenomena, like explosives, requires the use of a short exposure time and large (f/4.5) lens aperture. Explosives generate bright light that can saturate images, however this typically affects only the initial few frames. To mitigate this, the researchers made use of the camera's extreme dynamic range (EDR) mode. The 'EDR' function permits the end-user to expose for darker areas in the subject and...

Precision Explosives Analysis Using High-Speed Imaging brightness of the explosion, additional lighting is not always needed for imaging. In fact, a more important consideration may be limiting the light emitted by the explosion. A neutral-density filter can be helpful because it reduces the intensity of all wavelengths of light equally, which allows the use of combinations of lens aperture, exposure time, and sensor sensitivity that would otherwise produce overexposed pictures. Using the minimum aperture, short exposure times, and a camera's EDR mode, can also be useful for reducing light....

Precision Explosives Analysis Using High-Speed Imaging Figure 8: Phantom v2512 image at 25,000 fps, 1 μs exposure, 5 μs EDR complicated setup, and because electric light sources are easily obtained (for example, the MegaSun illumination system can replace argon candles for high-speed imaging photography). In conclusion, the high-quality data obtained with high-speed imaging combined with the right imaging approach and lighting setup can help scientists study explosives and their detonation systems in ways not previously possible. References 1. Pioneer Energy Services- Recommended Safety...