Grant: Discovery Grants Program - Individual

The behaviour of heterogeneous high explosives (HHEs) at engineering scales is governed by the quantity and type of heterogeneous inclusions in the HE. Examples of HHEs include: explosives containing large fractions of dense, inert particles (steel or tungsten), or mixtures which react at the interface between fuel and oxidizer phases. HHEs are the primary type of explosive used in mining and civilian blasting, and are increasingly important in military ordnance. While the extreme conditions encountered in explosions are outside everyday experience, understanding phenomena associated with detonation and explosion of HHEs is critical to their safe, effective, and efficient use. The engineering output of explosives used in mining and civil engineering applications is indirectly felt by all citizens through consumption of material goods and use of public infrastructure. The proposed research program focuses on four sub topics that investigate the behaviour of HHEs at different scales of effect: 1) Impact initiation of HHEs: Impact by a high velocity projectile transmits a shock wave into the impacted material. If the material is energetic, chemical reaction will occur, possibly resulting in transition from fast burning to detonation. Explosive initiation by projectile impact is quantified by the shock pressure and volume of explosive material that is shocked with little curvature of the shock front. The presence of large fractions of heterogeneities modifies the sensitivity to shock, such that more of the shock front may produce detonation. Experimental ballistic impact tests are required to extend existing scaling laws to HHEs. 2) Detonation structure of HHEs: Ideal explosives detonate with a structure known as the Zel'dovichvon NeumannDöring (ZND) detonation: a strong inert shock that initiates chemical reaction, which progresses for a discrete amount of time and then stops. Solid explosive is converted into high temperature, high pressure gas that accelerates to sonic and then supersonic velocities soon after reaction completes. The large quantity and extreme mismatch of heterogeneities in HHEs can modify the detonation structure. Experimental measurements will be performed using time resolved free surface velocity measurement and impedance matching. 3) Modelling of particles in donation product flow: A critical factor governing the ability of HHEs to accelerate material is the energy transferred between the gaseous detonation products and solid particles in the flow. Multiphase simulations will be performed to elucidate this transfer. 4) Blast from HHEs: The presence of particles in the blast generated by an HHE historically complicated measurement of the impulse imparted at a distance from the charge. Novel laser velocimetry and spectroscopy techniques permit measurement of the complete impulse and enable correlation with exothermic reaction of the particles in air.