Effect Of Metal Interlayer And Air Gap On The Shock Initiation Of Insensitive Explosives

Because shock initiation of explosives is a multidisciplinary study involving complex physics,chemistry and fluid dynamics,it is difficult to use a single theory to obtain a universal conclusion on the influence to shock initiation.We often get a qualitative analysis based on theory,and then get a quantitative result from theoretical analysis and design experiments.In the process of shock initiation,the shock wave passes through the metal interlayer and air gap,which increases the complexity of the shock initiation process.Not only does the metal interlayer and air gap attenuate the shock wave,but the metal interlayer has a large impedance and will reflect the shock wave.When the reflected shock wave is reflected again,it will cause a second compression of the explosive;secondly,the air gap will change the shock initiation state:Change from shock compression process to combined loading including quasi-isentropic compression and shock compression.These factors may cause the explosive to fail to form detonation or increase the detonation distance,so it is necessary to study the influence of the metal interlayer and the air gap on the shock initiation.However,in the case where the metal interlayer and the air gap coexist,we cannot quantitatively study their affect weight,so we carried out four experimental work:the experiment of the attenuation law of the shock wave of the metal interlayer,the experiment of the law of the influence of air gap on the shock wave.Air gap and metal interlayer shock initiation experiment and explosive under double shocks experiment.At the same time,a numerical simulation was carried out based on the experimental results.The specific work is as follows:1.Based on the artillery experiment platform,using PDV to measure the free interface velocity of 4mm,5mm and 6mm metal interlayers driven by C-type explosives and PBX-3 explosives(obtaining different incident pressures),calculated from the free interface speed of metal barriers based on shock wave theory The shock wave transmittance of the metal interlayer is obtained,and the shock wave attenuation law in the metal interlayer is characterized.The shock wave attenuation rules of metal barriers driven by two explosives and metal barriers of different thicknesses were obtained.2.The change of shock wave through air gap pressure reflects the influence law of air gap on shock wave.Because it is difficult to directly measure the pressure value after the shock wave passes through the air gap,the 5 mm metal interlayer is driven by the shock wave through the air gap of 0.3 mm and 0.57 mm thickness,and the free interface velocity of the metal interlayer is obtained.According to the free interface speed and the 5mm metal barrier shock wave transmittance,the pressure of the shock wave acting on the metal barrier after passing through the air gap is calculated,and the effect of the air gap on the shock wave is obtained.3.Due to the complexity of the factors that affect the impact initiation in the metal deflector and air gap impact initiation experiments,it is difficult to directly obtain the specific impact of secondary compression on the impact initiation characteristics of the explosive.Therefore,the flying disc impacted by Sapphire and Kel-F was used to detonate the D-type explosive,to simulate the secondary compression under the metal compartment,and the electromagnetic particle velocity meter was used to measure the velocity of the explosive particles at different depths,which was obtained from the particle velocity curve.The effect of secondary compression on the impact initiation characteristics of D-type explosives.4.The unreacted explosive HOM equation of state and the detonation product JWL equation of state.On the basis of the Euler equation are used to simulate the experiments,a simple conservative Lagrangian numerical scheme utilizing total variation diminishing interpolation,which uses the second-order Runge-Kutta method for time discretization,simulates the explosive-driven metal interlayer experiment and the secondary compression experiment,and better fits the experimental data.