Non-intrusive measurement of inner bore temperature of small arms using integrated ultrasonic transducers

Management of thermal input to a small arms weapons system is a significant design and operational constraint. A collaborative project was initiated with the objective to measure non-intrusively the inner bore barrel temperature of a small arm during actual firing. The approach uses integrated ultrasonic transducers (IUTs) and the velocity temperature dependence of the longitudinal wave propagating through thickness. IUT is successfully implemented on a small arm at 3 locations and results from several firing tests are presented. The small but systematic increase in ultrasonic time delay of less than 1 ns after each firing shot is reliably measured, in agreement with a simple 1D model of heat conduction, and measured temperature rises are consistent with the thicknesses at the different locations. The evaluation of the peak inner bore temperatures using IUT and their validation using eroding surface thermocouples at the same locations in the barrel are discussed.