Experimental Investigation And Numerical Modelling Of Non-shock Ignition Mechanism In PBX Explosives

Non-shock ignition in explosives is the concept that explosives ignite undesirably due to undergo low amplitude long duration loading(0.01~1.0GPa, 102μs), which will cause the killing and injuring of person and loss of economics during manufacture, storage, and transport of explosives, and failure of the explosive weapon during attack or defense. Therefore, safety research of explosives under non-shock loading has become important and imminent. The investigation of explosive ignition and hot-spot mechanisms involves in the couple of mechanical, thermal, and chemical processes, and spans mesoscale and macroscale, which makes the problem become more complex and challenging.This study concerns on the experiments and numerical modelling of non-shock ignition and hot-spot mechanisms of the typical heterogeneous solid explosive, PBX. Visco-SCRAM constitutive model, which fit to describe the dynamic mechanical behavior of PBX, is analysed thoroughly, and a method for obtaining the parameters of the model is proposed. The model parameters of PBX are obtained by fitting the results of the mechanical experiments. Three apparatuses which provide PBX under low amplitude long duration loading, such as hybrid SHPB-anvil test, shear punch test based on small SHPB apparatus, and combined pressure shear test based on drop weight apparatus are designed and performed for PBX ignition experiments. In order to obtain the ignition threshold of PBX, the loading force and the bulk temperature are measured, combined with high speed photography. The forming processes of hot-spots due to two mesoscale hot-spot mechanisms, pore collapse and crack friction, and the influences of the important parameters, are analysed thoroughly. The heating source and efficiency of hot-spot due to the two mesoscale hot-spot mechanisms which lead the temperature of hot-spot increase until PBX ignite, are presented. The Visco-SCRAM constitutive model combined with pore collapse and crack friction hot-spot mechanisms are implemented in LS-DYNA codes, forming a user defined model which could reveal both the macroscale mechanical behaviour and the mesoscale physical mechanisms of PBX. Validation of the model is conducted by the simulation of the PBX ignition experiments. Finally, a numerical modelling method which could exhibit the mesoscale physical mechanisms clearly and predict the safety of explosives under macroscale loading effectively is established.