A Combustion Model for Explosive Charge Affected by a Bottom Gap in the Launch Environment

Abstract

Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world as launch situation of ammunition becomes consistently worse. However, the existing numerical models have different defects. This paper formulates an efficient computational model of the combustion of an explosive charge affected by a bottom gap in the launch environment in the context of the material point method. The current temperature is computed accurately from the heat balance equation, and different physical states of the explosive charges are considered through various equations of state. Microcracks in the explosive charges are described with respect to the viscoelastic statistical crack mechanics (Visco-SCRAM) model. The method for calculating the temperature at the bottom of the explosive charge with respect to the bottom gap is described. Based on this combustion model, the temperature history of a Composition B (COM B) explosive charge in the presence of a bottom gap is obtained during the launch process of a 155-mm artillery. The simulation results show that the bottom gap thickness should be no greater than 0.039 cm to ensure the safety of the COM B explosive charge in the launch environment. This conclusion is consistent with previous results and verifies the correctness of the proposed model. Ultimately, this paper derives a mathematical expression for the maximum temperature of the COM B explosive charge with respect to the bottom gap thickness (over the range of 0.00-0.039 cm), and establishes a quantitative evaluation method for the launch safety of explosive charges. The research results provide some guidance for the assessment and detection of explosive charge safety in complex launch environments.