Experimental Investigations And Numerical Simulations Of Granular Explosive Impact Mechanics

Drop-weight impact experiments of energetic crystals and inert particles wereperformed to investigate their mechanical response using high-speed photography. Themorphology of the collected samples has been observed based on an optical microscope.Numerical simulation of individual and multiple particles under low-velocity impact wasthen carried out based on experimental results.(1) Under low drop-height impact, granular explosives mainly underwent deformation,fracture, fragment, pulverization, compaction, partial melting leading to translucency, andcooling with vanishing of translucency. Size of localized melting region is strongly relatedto size and morphology of the particles. RDX is more prone to melt than HMX and inertsalt of the same dimensions.(2) High speed photography observations indicated that speed of crack generation isdependent on particle size and morphology. The larger the particles are, the slower thecrack generates and propagates. Duration of fragmentation became longer with the increaseof particle size. Central region of the sample is easy to be pulverized much finer and morecompacted.(3) High speed photography and optical microscope analysis of collected samplesprovided us with large number of photos on crack surface interactions and stronglyfragmentation. These observations inspired us to establish better theoretical model takinginto account free surfaces due to large scope of fragementation. Such model can be used todescribe mechanical coupled with chemical responses of these explosives since it’s notenough without considering interactions among cracks.(4) Numerical simulation of individual and multiple explosive particles underlow-speed impact was performed using brittle cracking model and elastic-plastic damagemodel respectively based on software code ABAQUS. Loading durations simulated withbrittle cracking model are in good agreement with experimental results.(5) Frictional heat and heat conduction between particle and particle, particle and anvilhave been included in the simulation of multiple particles. Temperature rise mainly derivesfrom plastic work and frictional heat. Evolution of deformation, stress and temperaturedistribution in particles were obtained, which help to predict those dangerous localizedsites.