Research On The Initiation Mechanism Of Moving Shelled Charge Under Jet Impact

In short-range anti-missile defense operations,to achieve successful interception,the incoming target must be detonated and disintegrated within a short period of time.Due to the demand for combating deep underground fortifications,earth penetrating weapons have always been the focus of ammunition research and development in various countries.For incoming targets with thick-walled shells and high terminal velocity,such as earth-penetrating weapons,it is difficult for traditional anti-missile warheads to penetrate the shell and initiation the internal charge,so there is currently no effective interception method.The shaped charge jet has strong penetration ability and high specific kinetic energy.If the shaped charge jet is used as the antimissile damage element,the anti-missile capability will be significantly improved.However,the initiation mechanism and damage efficiency of the jet on moving targets with thick-walled shell structure are still unclear.In view of the above problems,this paper studies the impact initiation of jet on moving shelled charges.The initiation process of the shelled charge under the impact of the jet is studied by theoretical analysis,numerical simulation and impact initiation test.The dynamic penetration of the jet and the influence law and degree of the explosive size,confinement type,shell material and jet shape on the initiation of the moving shelled charge are analyzed and discussed in detail.The relevant research results of this study can provide reference and basis for the development and application of shaped charge warheads for anti-thick-walled structure targets.The main work and contents are as follows:(1)Engineering model of critical initiation threshold for explosivesFirstly,the plastic flow field of the material in the metal cover plate during the jet penetration process is calculated by the upper bound method.According to the boundary conditions,a kinematically admissible velocity field is set.By minimizing the dissipation power,the velocity field,acceleration field and stress-strain field distribution in the plastic flow zone in front of the jet are obtained,and the compression depth of the explosive when the jet penetrates the cover plate is determined.Considering the compressed depth of the explosive,a critical initiation threshold engineering model including the influence of the explosive thickness is proposed,which can well reflect the relationship between the explosive thickness and the critical initiation threshold.Finally,the engineering model of critical initiation threshold is verified based on numerical simulation results,jet impact initiation test results and literature data.(2)Theoretical model of impact initiation of shelled charge under jet impactThe initiation process of the explosive under the jet impact is divided into two stages.The first stage is the evolution and development of the bow shock during the jet penetration process.Considering the mushrooming during the penetration process of the jet,the growth process of the bow shock wave during the penetration process is calculated according to the Pop curve of the explosive.When the bow shock reaches the bottom of the explosive and enters the second stage,the reflection of the bow shock on the shell or the attenuation of the rarefaction wave on the bow shock is calculated according to the boundary conditions,and the theoretical model of the shelled charge initiated by the jet impact is established.The pressure distribution in the explosive and the difference in the pressure growth of the bow shock under different constraints are studied by numerical simulation.Impact initiation tests of explosives under different constraint conditions were carried out using Φ40mm shaped charge.Combined with the simulation results and test results,the theoretical model of shock initiation is verified.Taking different explosives as examples,the influence of each factor is analyzed in detail through theory model.The influence rules and importance of the influence of the type of confinement,the size of the explosive,the material of the confinement shell and the diameter of the jet on the initiation process of the explosive under the impact of the jet are revealed.It is also proved that the critical initiation threshold engineering model is also applicable to confined explosives.The relevant conclusions lay the foundation for the research on the impact initiation of moving shelled charges by the jet.(3)Research on penetration characteristics of shaped jet on moving targetAccording to the infinitesimal element method and the virtual origin theory,parameters such as velocity,diameter,velocity gradient,and tensile fracture time during the movement of the jet element are obtained.On the basis of the hydrodynamic penetration model and the Szendrei/Held reaming model,a theoretical model of the shaped jet penetrating the moving thick target is established.In the model,the judgment criterion of jet interference by moving target plate and the judgment criterion of whether the disturbed jet has penetrating ability are given.On the basis of experimental verification,a Φ90 mm shaped charge is used for the theoretical calculation of the dynamic penetration of the jet,and the influence of the moving velocity and the strength of the target plate on the dynamic penetration of the jet is revealed.The effects of jet velocity and jet diameter on dynamic penetration are analyzed through the jets formed by shaped charges with the same charge diameter but different charge structures,and the variation law of the dynamic penetration depth of the jet with these factors is obtained.The relevant results can provide a basis and reference for the application and design of the shaped charge warhead.(4)Research on impact initiation of moving shelled charge by shaped charge jetCombined with the theoretical models in chapters 3 and 4,a calculation model for impact initiation of shelled charges is established.The dynamic impact initiation experimental study of the moving shelled charge is carried out using Φ90 mm shaped charge as the jet source.The thick-walled shelled charge is accelerated by the rocket sled,and the precise intersection of the shaped jet and the moving shelled charge is achieved through the detonation control circuit.In the test,the thick-walled shelled charge was successfully detonated by the jet.On the basis of test,numerical simulation and theoretical calculation are used to analyze the influence of the velocity of the shelled charge,the thickness of the target plate and the incident angle on the initiation of the moving shelled charge.The relevant results can provide technical support for the application of the shaped charge warhead for air defense and antimissile.