Simulation experiment on ignition response of fragmented explosive under gap extrusion loading

Modeling powder is used to simulate the highly fragmented state of pressed explosives resulting from collisions, and the gap extrusion ignition behavior of PBX modeling powder is studied. Experiments were designed based on the way of projectile impact method. To ensure that no flow space exists except the designed gap, the surface of the sample was covered with cushion and coated with grease for sealing. The movement and reaction of molding powder squeezing into the gap were recorded by high-speed photography. By changing the ratio of gap area to sample cross-sectional area, the influence of compaction on ignition was studied. The results show that in the absence of grease seal, PBX molding powder undergoes particle crushing and compaction, and then the compacted molding powder is extruded from the clearance near the cushion, and ignition occurs in the extrusion process. The ignition position is at the interface between explosive and cushion. In the case of grease seal, PBX molding powder does not ignite for a period of time after compaction. When the indenter moves halfway, a wedge-shaped slip zone is formed, and a slip-dead zone interface could be seen in high-speed camera photos. Then the deformation mode evolves from single-wedge slip zone to double-wedge slip zone, and the shear effect of slip-dead zone interface does not cause ignition. At the later stage of loading, the indenter travels close to the gap surface, and the wedge-shaped slip zone disappears. Before and after the collision between the indenter and the gap, the explosive ignites once in each instance. Compaction effect has an important influence on ignition behavior. After compaction, the threshold value of ignition speed is obviously reduced, with the impact speed required to cause ignition being merely 4.5 m/s.