Comparing pyrometry and thermography in ballistic impact experiments

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.