An investigation of the hot spot formation mechanism for energetic material

The shock-induced pore collapsing and hot spot formation processes of plastic bonded explosives are simulated by molecular dynamics. After shock loading, the temperature field, pressure field, particle velocity field, energy field, plastic work field, and plastic temperature field are calculated by using the virtual grid method. A set of microscopic parameters about the hot spot are evaluated, including the pore collapsing time, pore collapsing speed, plastic work, and hot spot radius. The physical models to describe the energy dissipation and temperature relaxation behaviors of the hot spot are developed. We find that the hot spot formation consists of three steps: pore collapsing, work-heat transition, and temperature relaxation. The pore collapsing speed is proportional to the piston speed, and the temperature relaxation time is proportional to the square of the hot spot radius.