High speed image acquisition system and specimen heater for studies of high strain rate fragmentation of geomaterials
Abstract
The Funds received under grant # W911NF-17-0309 were used to purchase an ultra-high speed Shimadzu HPV-2 camera and mounting device, a non-contact specimen heater, and a 1 kHZ infrared thermometer for the investigation of brittle fragmentation under impulsive loads. The process of fracture in brittle geomaterials passes through a critical transition at strain rates of roughly 50-200s-1 at the earthÕs surface. Above these strain-rates, the predominant mechanism for brittle fracture transitions from discrete, continuous fracture to fragmentation and pulverization by distributed networks of tiny fractures. The proposed instrumentation will complement existing high strain rate testing tools, including a Split Hopkinson Pressure Bar apparatus. This DURIP purchase is designed to complement research being conducted under grant number W911NF-14-1-0276 (Experimental investigation of the micromechanics of rock damage during dynamic loading events (ARO Research Area 2.1: Terrestrial Sciences)), which has four primary objectives, including (1) constraining the fragmentation transition for crystalline rocks under near-surface conditions through dynamic compression tests; (2) quantitative characterization of damage in post-mortem specimens, with particular focus on fracture surface area and particle size reduction; (3) Evaluation of the work budget associated with the fragmentation transition, and the corresponding increase in failure strength; and (4) evaluation of the experimental data in light of micromechanical models for dynamic failure of brittle geomaterials. The purchased equipment will improve our data resolution and broaden the applicability of our results, including increasing our ability to pinpoint the exact time of macroscopic failure, allowing us to track particle trajectories during and after material failure to further kinetic energy terms and constrain a new fragmentation theory, and finally to investigate the role of plastic deformation and phase transformation under environmental conditions of elevated temperature.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 15, 2018
- Source ID
- W911NF1710309
Entities
People
- John Wickham
Organizations
- Army Contracting Command
- United States Army
- University of Texas at Arlington