Effects of pre-formed grooves and thermal barriers on the thermal response of ammunition under thermo-mechanical coupling

To address three limitations in current studies on ammunition thermal protection—insufficient design criteria for grooved weakening structures, fragmented optimization of thermal-insulation materials, and incomplete characterization of thermo-mechanically coupled failure mechanisms—this study developed a thermo-mechanically coupled simulation framework to evaluate two thermal-protection schemes for ammunition. First, to mitigate hazards associated with accidental internal energy release during storage and transportation, pre-formed grooves were designed using fragment dimensions obtained from simulated ignition and combustion of a Composition B charge measuring 25 mm × 105 mm in a cartridge with an outer diameter of 35 mm. Under slow cook-off, in which the temperature was increased at 3.3 K h -1 until ignition, and under fast cook-off, in which the flame temperature reached 823 K within 30 s and the average temperature was not lower than 1073 K, the grooved casing failed preferentially along the weakened paths, enabling early pressure relief. Second, a controlled-release thermal-protection strategy based on internal and external insulation was evaluated for a 19 mm × 76 mm charge with a length-to-diameter ratio of 1:8 under fast cook-off. Air gaps and single-layer/composite inert coating interfaces were introduced to examine the effects of charge amount, interface size, coating thickness, and heating direction on the thermal response. The results show that 6 mm × 13 mm pre-formed grooves can reduce the risk of violent post-ignition reactions. The optimal coating configurations were 4 mm inner GXTI and 2 mm outer HGN for bidirectional heating, 4.5 mm inner GXTI and 2 mm outer HGN for lateral heating, and 3.5–4 mm inner GXTI and 2 mm outer HGN for vertical heating. Compared with uncoated and single-layer coated cases, these configurations increased the ignition temperature by up to 14% and delayed ignition by up to 1648%.