Numerical Study On Shock Initiation And Detonation Of PBX Explosive

It is very important to study the short initation response behavior and propagation behavior of heterogeneous explosives to improve the numerical simulation ability of detonation in both commercial and military fields.In particular,the influence of initial state difference of explosives at different tempertatures and densities on initiation and detonation propagation,and the special response behavior of explosives under multiple shock response are the focus of current academic research.In this paper,theoretical detonation modeling and numerical simulation of single shock response and multiple shock response of two HMX based and TATB based PBX explosives,which are commonly used in China.The research contents and achievements are as follow:(1)The D-u relation was extracted by analyzing the experimental data of electromagnetic particle velocity in shock initiation,combined with the data of shock adiabatic line from other experiments,two kinds of hugoniot relation were given,and the parameters of unreacted explosive JWL equation were developed.Based on the empirical relationship between detonation velocity and initial density,and according to CJ theory,the CJ states at different initial densities wree given.We calibrated the parameters of equation of state of detonation products by simulating the cylinder test.The difference of simulated wall expeansion in the cylinder experiment with different initial densities is consistent with the experiment.(2)The distance to detonation and time to detonation of double shock impact initiation of Ex1 explosive are longer than that of singer impact by analyzing the experimental datas.It is desensitization on the explosive when impacted by low-pressure pre shock.Based on Lee-Tarver three term ignition growth reaction rate model,the entropy function was added and the ignition term form was modified to expand the reaction rate model applicable to simulate the double shock desensitization problem.The parameters of the reaction rate model were calibrated by numbers of singer impact initiation experiments.The simulated growth behavior of single shock to detonation at different pressure loading is basically in accordance with the experimental results.The double shock impact initiation experiments were simulated.When the speed of the composite fliers is low,before the main shock catches up with the front of the pre-shock,there is no reaction growth behavior,and when the speed of composite fliers is high,before the main shock catches up with the front of the pre-shock,there is a slight reaction growth behavior.It is well agree with the double shock impact experiments of Ex1 explosive.The comparison between numerical simulation and experimental results of double shock desensitization problem shows that the modified ignition growth model can be applied to the pre shock desensitization of PBX explosive.(3)The parameters of WSD model were calibrated by simulating the shock to detonation and detonation propagation experiments,and there are some shortcomings of WSD model in simulating some specific problems.On the basis of WSD model,the compression ratio was replaced by the relative entropy represented the hot spot density by the shock.The form of ignition term was modified,which has some correction effect on the non initiating element at the edge of explosive when simulating the propagation of unconfined cylindrical explosive charges.The entropy function was added to ignition term and growth term of WSD model to expand the reaction rate model applicable to simulate the double shock desensitization problem.In addition to the ignition term,the parameters of the WSD model can be basically not calibrated again.The double shock initiation experiments were simulated by using WSD-M model,before the main wave catches up with the front driving wave,there is on obvious burning behavior after the main wave,which is in good agreement with the experiments,but the WSD model cannot simulate the phenomenon.(4)The WSD-M model was used to simulate the experiment of propellant flying decentralized detonation with different explosive thicknesses and different initial densities.The simulation results show that in the range of 5mm-25mm explosive thickness,the growth of detonation wave head increases with the increase of the thickness of the explosive,the wave head pressure also increases with the increase of initial density of the explosive.The simulated expansion velocity curve of the flying disc is in good agreement with the experiment.The different of work ability between high and low density explosive EOS,and the different between high and low density experiments are in good agreement after considering the size deviation of experiment device.To simulate the corner effect problem of the two-dimensional propagation of Ex2 explosives,when the WSD-M model simulates the detonation wave passing the 90°corner,the explosive near the corner has a desensitization effect under the pre-compression condition,leaving a stable non-reacted or partially reacted material region,which called 'Dead Zone',consistent with the experimental and simulation results of relevant literature.While the WSD model simulates the detonation wave passing the corner,the detonation wave can be continuously generated near the corner,and no dead zone can be formed.