Density effects resulting from polymer bonded explosives pressing parameters

Abstract

Shaped charges are used when a focused force is required to penetrate a target. They have dominated the weaponry market in the recent past due to their ability to penetrate targets. Shaped charges have become more potent and reliable as their technology has improved. However, the problem of uneven density distribution during the pressing stage of the manufacturing process remains. This is due to uneven particle sizes and ineffective pressing techniques, which affect the jet performance of the shaped charge. The aim of this study, therefore, was to predict the density distribution of a pressed polymer-bonded charge in an 85-mm casing. This was achieved via a numerical modelling technique that used a discrete element method (DEM). This study employed DEM to model the pressing process of shaped charges. The experimental procedure involved the calibration of material input parameters (particle size, shape distribution, static friction coefficient, and bulk density). Calibration of the static coefficient was done using the angle of repose test. The experimental and numerical results were compared to determine the differences between the procedures and verify the calibration procedure. The numerical procedure used to model the experiments was DEM using AutoCAD and imported into Rocky® software. DEM, which was chosen because the consolidation process involved granular interactions, was used to simulate the pressing process system model. The results showed that the density distribution in the casing had regions of low-density distribution, medium-density distribution, and high-density distribution. The regions close to the casing wall and the base of the bottom rammer exhibited medium density, while the regions closer to the wall (and in contact with the wall) had low density. Simulation results were verified and showed agreement with experimental result of Seloane (2018). Based on the outcomes of this project, DEM was successfully used to predict the density distribution in shaped charges. Future studies should focus on investigating DEM using different explosive materials and calibres. Consideration of future work should also include the incorporation of the particle distortion.