Predictive model of back-wall overpressure behind a cantilever wall

To reduce the hazards posed by blast shock waves, important potential targets are usually shielded by cantilever walls. The main factor that indicates whether there is damage is the back-wall overpressure, and of concern here is predicting the back-wall overpressure behind a rigid cantilever wall. This was measured in full-scale blast experiments using 20 kg of trinitrotoluene (TNT) located on the ground, and the experimental data reveal how the cantilever wall mitigates the shock wave. A 3D numerical model was established to determine how the wall size influences the diffraction of the shock wave and the peaks and attenuation of the back-wall overpressure. Based on the numerical results and dimensional analysis, a model is proposed that provides an effective means of predicting the back-wall overpressure rapidly from the TNT equivalent, the standoff distance, and the height of the wall

The thermal response of the ignition and combustion of high-energy material projectiles under the influence of heat

The thermal response of energetic materials involves processes of thermochemical mechanical coupling, which can lead to thermal damage in such materials both before and after ignition, thereby increasing ignition sensitivity and the level of danger. Many studies to date have either neglected or oversimplified the effects of thermal coupling, leading to significant discrepancies between simulated and experimental outcomes. This paper aims to examine the complex processes of ammunition ignition, combustion, and detonation. Employing finite element simulations in conjunction with Arrhenius dynamics and the ignition growth model theory under thermodynamic coupling analysis, it simulates the entire process from the thermal expansion of B explosive prior to ignition, through to combustion and detonation. It establishes the relationship between the damage and fracture state of the shell and the thermal response of the energetic material at varying heating rates. Findings indicate that the severity of the thermal response is determined by the balance between pressure accumulation and the loss of confinement leading to pressure release. Specifically, at heating rates below 0.25 K/min, the shell fractures before combustion of the energetic material; whereas, at rates exceeding 0.375 K/min, the shell fractures after combustion, significantly increasing the risk. The simulation outcomes of this study show strong correlation with experimental results reported in the literature, offering a valuable reference for simulating the ignition and combustion responses of ammunition with similar structural characteristics