Analysis of Reactive Hot Spot for Thermite under Shock Waves

Using laser scaners to measure the size of binary mixture of energetic materials thermite (Al+Fe2O3) and get the particle size distribution, the particle shape of aluminum powder, iron oxide and the contact status of the mixtures meeting the standard chemical proportion are observed under the electron microscope. Combined the raw material particle size distribution and the mass ratio of chemical reaction, the particle characteristic size (equivalent volume radius) and arrangement of aluminum and iron oxide particle were obtained. Based on the above conditions, the mesoscopic model for the thermite mixtures was established. The mesoscopic model can be guaranteed to get the statistical cavities structure consistent with that of the actual granular system. The features of hot spot for the thermite by impact were studied with the Smoothed Particle Hydrodynamics (SPH) method, under the condition of different particle arrangements and shock velocities. The result shows that the arrangement of three iron oxide particles closely contact each other is the basic one forming a single hot spot; the size of hot spot is determined by the initial size of the cavity; and the temperature of hot spot is controlled by the shock velocity. Finally, the thermite mixtures of different density and chemical ratio were impacted on the light gas gun, the qualitative regularities of experiments are well consistent with those of numerical simulation.