Research On The Coupling Characteristics Between The Strong Magnetic Field And The Shaped Charge

The technology of the strong magnetic field coupling with shaped charges(SCs)is a non-traditional technology for enhancing the penetration capability of SCs,in which the magnetic field can be loaded at different periods of the inertial stretching stages of shaped charge jets(SCJs).The intial energy is provided by a capacitor which is loaded into the solenoid to generate a low-frequency magnetic field to couple with the SCJs based on basic electromagnetic laws.The state of the stress-strain inside SCJs would be improved under the coupling effect of the external magnetic field,which can extend the inertial stretching stage and delay the breakup of SCJs effectively.The rotation of particles after the breakup of the SCJ is inhibited due to the presence of the magnetic field produced by the solenoid,which can guarantee that particles remain aligned with the jet axis.The effective length of SCJs is increased on basis of action mechanisms mentioned above,which is beneficial to improve the penetration ability of the SCJ.In addition,the accelerating effect of the electromagnetic force on axial motion of the SCJ is explored based on X-ray experiments.The increase of the SCJ axial velocity due to the presence of the magnetic field is also conductive to enhance its penetration capability.It is of important theoretical value and guiding significance to carry out mechanism research on this technology at the present time,and this work would also promote the development of the new and powerful shaped charge.The following aspects are included in this work:(1)Research on theory of the effect of magnetic field on delaying the SCJ breakup.On basis of the model of a uniformly stretching cylindrical incompressible perfectly plastic rod and the law of electromagnetic induction,the radial velocity of a SCJ coupling with the magnetic field can be calculated.According to characteristics of the discharge current of the coupling system and the theory of the magnetic field distribution of a solenoid,the magnetic induction intensity can be calculated when a jet element arrives at any position in the solenoid.The equivalent circuit model,the model for describe the magnetic field and deformation model of a SCJ inside the magnetic field are used in succession,so the model for describing the magnetic field delaying the breakup of a SCJ is established.(2)Research on influence of a strong magnetic field on the stretching coefficient of SCJ.The stretching coefficient of a SCJ is a critical parameter to evaluate the stretching level and breakup characteristics for a SCJ.The theoretical model used for calculating the stretching coefficient is given based on the equation of motion for the SCJ material and the conditions of plastic instability.By comparison,the theoretical reults show a good agreement with the experimental.This work provides guidance for a follow-up research about the magnetic field coupling with a SCJ.(3)Research on inhibiting effect of the magnetic field on rotation of particles after the breakup of the SCJ.The particles do not remain aligned with the jet axis after breakup of a SCJ,but start rotating.The inhibiting action of the magnetic field on rotation of particles after the breakup of the SCJ is studied in detail by means of theories,simulation and experiments.Under the hypothesis of rotation with small angle of a SCJ particle,the equation of rotational motion is obtained based on magnetic-charge theory.In addition,using Ansoft Maxwell software,the force bearing state and the torque of SCJ particles with different materials and different rotational angles due to presence of the magnetic field is simulate,in which the mechanics regularity of particles under different conditions is obtained.(4)Research on the axial acceleration effect of the magnetic field on a SCJ.The magnetic field produced by the solenoid was analyzed by considering both the longitudinal and radial components of the field.Based on the Gauss's law,the expression of the radial component of the magnetic field was proposed.Following the law of electromagnetic induction,the electromagnetic force of the SCJ with the overall influence of the magnetic field was analyzed.Therefore,a comprehensive theoretical model was developed to describe the acceleration mechanisms of the SCJ in the magnetic field.(5)Related experimental research of the magnetic field coupling with a SCJ.In the research process,DOP and X-ray experiments are carried out to comprehensively evaluate the coupling properties between the magnetic field and a SCJ,which include principle experiments and system optimazition experiments.In the principle experiments,technical concepts are identified,the feasibility is determined,and some macroscopic phenomena are recognized.Based on system optimazition experiments,coupling system timing is optimized,which is beneficial to make full use of the magnetic field to couple with a SCJ,and the theoretical model and simulation model are systematically identified.In addition,DOP tests of 056mm shaped charge under different standoffs are carried out with and without the effect of magnetic field,which provides experimental data to plot DOP vs.standoff curve for different conditions.