A mesoscopic reaction rate model for shock-to-detonation of PBX explosives having different mean particle sizes

In order to well predict mean explosive particle size effects on the shock-to-detonation transition (SDT) process of a plastic bonded explosive (PBX), some improvements to a previous three-term mesoscopic reaction rate model that consists of a hot-spot ignition term, a hot-spot growth term, and an overall reaction term are made: A set of new switch conditions, which depend on mean explosive particle size, is proposed for the operations of the three terms; a new expression is obtained for the hot-spot growth term by combining an ignition efficiency factor which depends on mean explosive particle size and replacing the original burning topology geometric factor, which merely describes the characteristic of the outward pore surface burning reaction, by a more reasonable one, which combines the characteristic of inward particle surface burning reaction and that of outward pore surface burning reaction. Furthermore, for verification, the improved reaction rate model is incorporated into the DYNA2D code to simulate numerically the SDT process of three formulations of PBXC03 having the same density but different mean particle sizes, and the numerical results of pressure histories at different Lagrangian locations in the explosive are found to be in good agreement with previous experimental data.