Simulation Of Electromagnetic Launching Environment,Design And Test For Projectile-borne Electromechanical Systems

Electromagnetic railgun is an advanced launch weapon driven by electromagnetic force to propel objects to reach ultra-high velocity.Through the power control of high-level power supply,it can achieve stable electromagnetic force and break through the muzzle velocity limit of conventional weapons.Nowadays,electromagnetic railguns are mainly equipped with kinetic energy projectiles.In order to achieve precision striking and expand damage effectiveness,the projectile-borne electromechanical system with intelligent chips is the future development direction of electromagnetic railguns to launch ammunition.However,for the case of electromagnetic rail launch,there will inevitably exist multiphysics environment such as electromagnetic field,mechanical field and thermal field,which will undoubtedly put forward higher requirements for the safety and reliability of projectile-borne electromechanical system.At present,the complexity of the in-bore environment during electromagnetic launch process,and the weakness of the existing projectile-borne electromechanical system design methods lead to the serious lag of the related research on the projectile-borne electromechanical system used in electromagnetic weapons.there is a lack of electromagnetic-mechanical-thermal coupling analysis model which can accurately describe the multiphysics environment of projectile-borne electromechanical system during electromagnetic launch process.Meanwhile,there is still a lack of in-depth understanding of the pulsed strong magnetic and high overload properties,and shielding principle.In addition,there are imperious demands for exploring the multi-physical field environment testing techniques and the equivalent test assessment method for projectile-borne electromechanical system during electromagnetic launch process with high energy level.Regarding the issues above,taking the projectile-borne electromechanical system of electromagnetic railgun as the research object,a systematic study on numerical simulation,experimental test,system design,and equivalent test for projectile-borne electromechanical system during electromagnetic launch process with high energy level was carried out in this dissertation.The main research contents are as follows.In order to break through the bottleneck in numerical simulation for multiphysics field environment of rail & armature during electromagnetic launch process,the numerical simulation method of coupling analysis between the equivalent circuit to model the pulsed power and electromagnetic launcher,and multi-physical field model of rail & armature during electromagnetic launch process is proposed.The electromagnetic-mechanical-thermal coupling analysis model is established by use of the relation between input parameters and output parameters,and the time discretization based iteration method.The equivalent circuit model is constructed for the pulsed power with high power and rail & armature during electromagnetic launch process,and the multi-pulse property of the input current generated by the capacitor bank of electromagnetic railgun is revealed.Based on electroresistive effect,skin effect,and thermal effect for conductivity,the relation between multiphysics field data and equivalent circuit parameters is constructed,and then the coupling analysis between the multiphysics field of electromagnetic launch and equivalent circuit is implemented by iteration method.The distribution law of electromagnetic field,force field and temperature field of key positions at rail & armature can be found out,which can provide with multiphysics field environment input for further investigation on electromagnetic-mechanical-thermal coupling properties at key positions of projectile mounted projectile-borne electromechanical system.With consideration of the influence of velocity skin effect on the current distribution inside the rail and armature,the calculation model is established for the electromagnetic field of key positions at the projectile-borne electromechanical system during electromagnetic launch process.Based on the adaptive algorithm for automatically changing the shape of the current distribution area of the rail,and contact length between rail and armature,the calculation error due to employing the mean current density instead of the actual one can be effectively reduced.The shielding principle under the lower frequency and high magnetic environment is studied by combination of numerical calculation and experimental test,and taking consideration with several schems including the single material and multi-materials.The detailed study results show that in the high energy level electromagnetic launch system,the conductive material is selected at the bottom of the projectile,and the magnetic material is selected at the warhead and the center of the projectile,and then the satisfied shielding effect can be achieved.Meanwhile,based on the stress wave transfer law and temperature diffusion principle,the mechanical field model and thermal field calculation model of key postions at projectile-borne electromechanical system during electromagnetic launch process are established.The stress shock with long pulse will affect the equivalent stress law of the key positions at the projectile-borne electromechanical system in the middle and later stage of launch,and the transmission of stress wave will be more obvious with increase of time.By contrast,the temperature of the projectileborne electromechanical system is mainly affected by the induction current heating of the shell,rather than by the high temperature of the armature.To meet the imminent demand of multi-physical field environment test for key positions at the projectile-borne electromechanical system during high energy level electromagnetic launch process,based on Hall effect and piezoresistive effect,a projectile-borne test system for measuring multi-parameters is designed and fabricated,and the synchronous test function of triaxial magnetic field and triaxial acceleration is realized.In order to reduce the test error of the storage test system,the linear Hall sensor is calibrated by using the pulsed strong magnetic field generator.Similarly,the peak value of the acceleration sensor is calibrated by using the Hopkinson bar.The dynamic recovery test of the high energy level electromagnetic launch is carried out by using the tested projectile and the developed test system.The spatial magnetic field data and acceleration data of the bottom position and the warhead position at the projectile are effectively recovered.The muzzle velocity obtained by integral of axial acceleration is consistent with the data from the high-speed photography test.The comparison between the test and simulation results verifies the credibility of the simulation model.The study shows that the shell of the projectile with high strength will gurantee the satisfied testing result,and during the electromagnetic launch process,the projectile-borne electromechanical system mainly undergoes the acceleration shock in the direction of the projectile axis,and with the increase of distance from armature,the magnetic field is distributed both in three axes.The method of utilizing magnetic environment information for projectile-borne electromechanical system during electromagnetic launch is studied,and the scheme of magnetic deprotection is designed for mechanical and electromechanical safty system.The calculation model of hysteresis effect is constructed for the permanent magnet used in mechanical projectile-borne system,and the demagnetization and inverse magnetization properties of permanent magnet are numerically simulated.The experiment of Hall switch and linear Hall sensor used in electromechanical projectile-borne system is designed.The experiments of response time of Hall switch subjected to different magnetic induction intensity and different shielding materials are conducted by use of pulse high magnetic field generator.A method of utilizing the magnetic environmental information based on passive sensor is proposed.The charging and discharging properties of the induction coil and its sensitivity are studied by finite elements analysis and circuit simulation.The study results show that the induction coil mode does not require energy excitation,and the stable voltage input can be generated at the bottom and middle position of the projectile,which can be used as an ideal induction component in the magnetic field environment.The methods of design of projectile-borne electromechanical system propotype used in electromagnetic launch ammunition,and equivalent test assessment are proposed.The projectile-borne electromechanical system used in electromagnetic launch ammunition is designed,and the test prototypes such as detector and safety system are developed.The safety test of projectile-borne electromechanical system components under high magnetic field and overload environment is carried out by using pulse high magnetic field generator and high overload test device.The reliability test of magnetic deprotection structure is conducted by using long pulse width magnetic field generator to verify the basic working performance of projectile-borne electromechanical system components.The results show that the new electromagnetic launching projectile-borne electromechanical system designed in this paper works normally under high magnetic field and high impact environment,and the magnetic release mechanism meets the requirements of in-bore release.