Browsing by Author "Croessmann, Charles Luke (TTU)"

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Comparing pyrometry and thermography in ballistic impact experiments
(2022) Woodruff, Connor (TTU); Dean, Steven W.; Cagle, Colton (TTU); Croessmann, Charles Luke (TTU); Pantoya, Michelle L. (TTU)
Thermal analyses of projectile impact and subsequent combustion are investigated for aluminum projectiles using a high-velocity impact ignition system. Temperature measurements are compared using pyrometry and thermography. The implementation of these techniques is discussed, as well as their benefits and limitations in ballistic experiments. Results show pyrometry is best for measuring temperatures in the immediate vicinity surrounding the impact location, while thermography better quantifies temperature dissipation downstream from impact as the combusting debris cloud disperses. Temperatures comparable to the predicted adiabatic flame temperature are observed with the pyrometer. For thermography, emphasis is placed on the treatment of emissivity in temperature calculations. Three combustion stages are identified in the thermography data and attributed to 1) ignition and growth of the combustion front, 2) thermal dissipation due to initial particle burnout, and 3) a slower dissipation stage caused by reduced heat exchange between the burning debris cloud and surroundings.
Thermite and intermetallic projectiles examined experimentally in air and inert gas environments
(2022) Croessmann, Charles Luke (TTU); Cagle, Colton (TTU); Dube, Pascal; Abraham, Joseph; Altman, Igor; Pantoya, Michelle L. (TTU)
Intermetallic (aluminum and zirconium) and thermite (aluminum and molybdenum trioxide) projectiles were launched using a high velocity impact ignition testing system. The experiments were designed to simulate reactivity in high (argon) and low (air) altitude environments. The projectiles were launched into a chamber that included a steel target plate for projectile penetration before impacting a rear witness plate. The chamber was semi-sealed and instrumented for quasi-static pressure data. The results provide an understanding of energy release from the projectile materials and of the environmental influence on performance. The transient pressure traces provide insight into reaction kinetics. A bifurcation in transient pressure rise was an indication of a shift in reaction kinetics from the inherent reactive material to metal oxidation with the environment. The bifurcation was delayed by about 0.15 ms for the intermetallic relative to the thermite, evidence that the thermite reaction proceeded faster upon impact than the intermetallic. The two-step process (impact ignition of the reactive material followed by metal oxidation) was shown to produce higher energy conversion efficiencies than projectiles composed of pure fuel (i.e., aluminum) reported previously. Both reactive materials showed energy conversion efficiencies greater than 30% (for air) and 50% (for argon), and an explanation of underestimated efficiency and energy losses is provided. These results have implications for advancing formulations for ballistic applications. Structural reactive materials can be used to modify the effective reactivity of metal-containing formulations in varied atmospheric environments.