Prediction of Propellant and Explosive Cook-Off for the 30-mm HEI-T and Raufoss MPLD-T Rounds Chambered in a Hot MK44 Barrel Advanced Amphibious Assault Vehicle - AAAV

摘要

An analytical thermal study was conducted of the 30-mm MK44 barrel and two high-explosive rounds to determine the relationship between the number of rounds fired and the time to initiate propellant and explosive cookoff in a misfired round that remains in the barrel. The barrel temperature distribution during firing was calculated using the FDHEAT finite difference heat-transfer program, with film coefficients and gas temperatures being supplied by the XNOVAKTC interior ballistics program. Heat transfer between the barrel, projectile, and the environment during a simulated misfire event was modeled using the ABAQUS finite element program with the initial barrel temperature distribution, associated with a particular number of rounds fired, being supplied by FDHEAT. Propellant cook-off calculations were made by assuming that cookoff would occur when the transient temperature profile at the inside of the case, in the shoulder region, exceeded an experimentally based cook-off curve developed for M2 double-base propellant Explosive cook-off calculations were made by assuming that cook-off would occur when any small volume of explosive material in the finite element model experienced thermal runaway. In order to be able to simulate the initiation of explosive cook-off in the finite element model, it was necessary to include an Arrhenius-type heat generation equation as part of the explosive's material definition. Two rounds were considered in the study, the High Explosive Incendiary with Tracer (HEI-T) and the Raufoss Multi- Purpose, low Drag with Tracer (MPlD-T), each containing PBXN-5 explosive. The Raufoss round also contained the Comp-A4 explosive that was also considered an explosive cook-off candidate. Predicted barrel and projectile temperature profiles showed good agreement with barrel and instrumented round thermocouple test data generated during a 20,000 round wear and performance test conducted by Boeing Ordnance in 1999.