Analysis and discussion on launching mechanism and tactical electromagnetic railgun technology

This paper begins with a discussion on the significance of multi-physical fields in the research of railgun launching mechanism, followed by an introduction of research work about dynamic measurements and numerical simulations. The application of some measurement methods including the atomic emission spectrum, fiber-optic strain, optical level, pulsed X-ray, and high-speed video in observing the launching process was introduced. The models about the electromechanical dynamic processes and multi-physical fields in a railgun were developed. The mechanisms of the grooving, arc transition, and gouging were analyzed. These work provided a deeper understanding of launching mechanism of electromagnetic railgun. Some issues about the tactical railgun, such as the fiber composite overwrapped barrel, recoil,loading modes and eddy current loss were also discussed. Taking a medium-caliber launcher as an example, the basic process of design and analysis was introduced.

Research on proximity effect of electromagnetic railgun

The rails of electromagnetic railgun can be ablated by the temperature rise due to current concentration.The current distributions on the rails and armature are not only affected by the skin effect,but also influenced by the proximity effect which is rarely mentioned.This paper illustrated the difference between skin effect and proximity effect,and the influencing factors of proximity effect were investigated.Results show that the current is concentrated on the surface around rails due to the skin effect,and the proximity effect exacerbates the current density on the inner surfaces of rails.Decrease in distance from rails enhances the proximity effect,but has nothing to do with the skin effect,which also augments the rail resistance,resulting in temperature rise.It can explain the reason why the ablation is often detected in the small caliber railgun.Research results in this paper can provide support for design and optimization of electromagnetic railgun.

Numerical simulation of dynamic large deformation and fracture damage for solid armature in electromagnetic railgun

The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical,thermal and mechanical process in the interior ballistic cycle.In this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching process.Especially,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid armature.The results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric current.By the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.

Analysis of in-bore magnetic field in C-shaped armature railguns

In order to analysis the distribution characteristics of in-bore magnetic field for C-shaped armature electromagnetic railgun, a computational model considering dynamic contact pressure is established. By solving the dynamic equation, the in-bore motion characteristics of the armature are obtained. The distribution of current in the rail and armature is analyzed based on the magnetic diffusion equation and Ampere’s law. On this basis, three simulation models are proposed, which correspond to static state,motion state and motion state considering the velocity skin effect. The magnetic field of the investigated points along the central axes of the armature front end are obtained. The results show that, in static state,the peak magnetic flux density of each investigated point is greater than the other two states. Velocity skin effect leads to a decrease in peak magnetic flux density. The change of motion state has little influence on the peak magnetic flux density of the investigated point that far away from the armature. The calculated results can be used in the electromagnetic shielding design of intelligent ammunition.

Method of ballistic control and projectile rotation in a novel railgun

In order to realize the ballistic control of the railgun and the flight stability of the projectile, a new type of railgun is designed, which can control the muzzle velocity and rotation rate. The method of the muzzle velocity and overload control is to adjust the voltage or other parameters of pulse power supply. It would be easy to change velocity accurately in large wide. Another widespread concern problem is launching the spinning stability projectile by railgun. This paper designed a new structure of additional rails to generate an unsymmetrical magnetic field to produce rotational torque in armature. The structure is simple and can control the rotation rate by linear changing the barrel parameters. The calculation formulas of interior ballistic are derived by Biot-Safar law. The important parameter is the deflection angle of the additional rails relative to the symmetry plane of main rail. The larger the angle, the greater the rotation torque generated in the armature. To maintain the flight stability of the projectile, the barrel structural parameters should be proportional to the projectile structural parameters. When changing the muzzle velocity, the rotation rate will also be the equal proportion change. So that the gyro stability is the same. The experiment proves that the railgun designed in this paper can launch the projectile to rotate. And the rotational projectile may not cause the transition or much arcs. This method expands the application of the railgun.

Research progress on advanced rail materials for electromagnetic railgun technology

Electromagnetic railgun attracts more and more attention due to its advantage in speed,cost,and obscurity.It is found that the rail should withstand huge mechanical and thermal shocks during the launching operation.The forms of rail failure are accompanied by gouge,grooving,transition,and arc ablation,etc.The service life of the rail has become a bottleneck restricting the development of electromagnetic railgun technology.A series of researches are carried out to solve rail failure,including analysing the failure mechanism and using various advanced rail materials.This paper provides a comprehensive review of rail materials,including material composition,preparation,microstructure,and properties.We begin from a short background of the requirement of the rail material.Then a detailed investigation of rail materials is described,and the performances of those materials are introduced.Finally,further development prospect of rail material is discussed.

Modeling and simulation of muzzle flow field of railgun with metal vapor and arc

During the electromagnetic railgun launching process,there will be a complex flow field with high temperature in the muzzle area because of the high-speed friction,transition and seco ndary arc-ignition.This paper models the muzzle area of railgun when the projectile is far away from the muzzle,and the dynamic simulation of the flow field with secondary arc in the muzzle area is carried out based on the magneto hydrodynamic equations.Meanwhile,a multi-component plasma transport model is used to analyze the muzzle arc plasma flow process of the mixed gas of Al vapor and the air.Furthermore,the pressure boundary conditions are fitted by the dynamic mesh simulation results.The current and voltage of the muzzle are obtained through the emission experiment of the railgun experimental prototype.We load the current data into the simulation model and the voltage of experiments and simulations are compared,which proves the accuracy of the simulation.Then the plasma temperature and the composition of Al vapor in the muzzle flow process are analyzed in-depth.

Electrodynamic response study on railgun launcher based on electromechanical coupling model

The electrodynamic behavior of a medium caliber railgun launcher has been studied based on an electromechanical coupling model,which uses a unified modeling method for both electromagnetic and electromechanical field.This model adopts a material equivalent method to simulating the sliding contact behavior for the in-bore armature.An embedded node encoding program during field meshing operation provides good load transfer accuracy between electromagnetic field and mechanical field.Dynamic properties of in-bore magnetic field are firstly simulated and a subsequent dynamic analysis is conducted by mapping element results from electromagnetic analysis step to structure analysis step.The electromechanical-elastic response of the barrel is studied under the excitation current.The numerical model has shown reliability compared to experimental results.

Analysis of sliding electric contact characteristics in augmented railgun based on the combination of contact resistance and sliding friction coefficient

The contact resistance between the armature and rails is an important indicator of the contact characteristics in electromagnetic launches.As the contact resistance depends not only on the contact state but also on the contact stress and temperature,there are some limitations in analyzing the contact characteristics using only the contact resistance.In this paper,the contact characteristics of the augmented railgun are analyzed by the combination of contact resistance and sliding friction coefficient.Firstly,the theoretical calculation model of the contact resistance and friction coefficient of the augmented electromagnetic railgun is established.Then the contact resistance and friction coefficient are calculated by the measured values of the muzzle voltage,rail current and armature displacement.Finally,the contact characteristics are analyzed according to the features of the waveforms of the contact resistance and the friction coefficient,and the analysis conclusions are verified by experimental rail images.The results showed that:the aluminum melt film gradually formed on the contact surface reduces the contact resistance and the friction coefficient;the wear and erosion of the armature cause deterioration of the contact state;after the transition,the reliability of the sliding contact between the armature and rails decreases,resulting in an increase in contact resistance.

Ablation and geometry change study of solid armature in a railgun

Armature plays an important role in the electromagnetic launch process. Due to the skin effect, the current density distribution is neither uniform on the rail, nor on the armature. High current density centralization in one part could lead to a partial high temperature and make the armature material melt down and be ablated, especially at low velocity. In this paper we try to change the geometry of a Cshaped armature to improve the current density distribution and reduce the ablation. Four variants of C-shaped armatures are designed to study the specific features, including a conventional C-shaped armature （CCA）, a rounded leading edge C-shaped armature （LCA）, a rounded trailing edge C-shaped armature （TCA）, and a rounded incorporate edge C-shaped armature （ICA）. A novel low-speed experiment is constructed and tested. The armatures are ablated and recovered to compare the improved effects. Then finite element simulations according to the experimental results are performed to further analyze the experimental results. It is proved that the current density and hence the temperature distribution can be immensely improved by simply changing the armature geometry. LCA and ICA show that the erosion is more uniform on the contact surface due to the rounded leading edge. The curved trailing edge could improve the uniformity of the current on the interface. ICA which combinesthe effects of LCA and TCA is the best option in the four armatures. How much the leading edge and the trailing edge should be curved involves the geometry of CCA and the posture of the interface on the rail. A saddle shape is a good option to improve the current density and temperature distribution in the throat. Erosion mechanism is analyzed finally. The experiments and simulations support the erosion and transition mechanism. A detailed description of the experiments and simulations is also presented in this paper.

Analysis for the residual prestress of composite barrel for railgun with tension winding

Based on the elastic theory of cylindrical shells and the theory of composite laminates,a prediction model for the residual prestress of the simplified round composite barrel for railgun is established.Only the fibre pretension is considered in this model.A three dimensional numerical simulation for the residual prestress in the railgun barrel is carried out,by combining the temperature differential method with the element birth and death technology.The results obtained by the two methods are compared.It reveals that the distribution trends of residual prestress are consistent.And the difference for residual prestress in the filament wound composite housing of barrel is relatively small.The same finite element method is used to analysis the residual prestress in the non-simplified composite barrels for railgun,which are under different control modes of winding tension.The results mean that the residual prestress in barrel will increase while the taper coefficient for winding is decreasing.Therefore,the sealing performance in bore is improved,but the strength of the filament wound composite housing drops.In addition,the axial and circumferential residual prestress in the filament wound composite housing with constant torque winding are close to the ones in iso-stress design for barrel.

Research on momentum transfer in simple railgun

In this paper,the momentum conservation equation in the longitudinal direction for simple railgun was deduced.Then,a three-dimensional model was established and the finite element method was utilized to simulate the problem.Based on the simulation,some results such as the surface force on the electromagnetic field,the electromagnetic force on the conductor in the longitudinal direction were obtained.Besides,the surface force density on different longitudinal section of railgun was analyzed and discussed in details.The results showed that the momentum of the railgun system was conserved when the surface force of the electromagnetic field was contained.Moreover,large amount of longitudinal force was transmitted to the breech by the electromagnetic field in the form of surface force.The exact position and distribution of recoil were related to the current input device.

A Measurement System for Railgun Test

A measurement system was designed to measure the railgun's parameters in launching process,which includes Rogowski coil sensor for measuring rail's current,B-dot probe for obversing projectile's velocity in bore,net target for catching muzzle velocity,signal condition circuit and high-speed data acquisition card for analyzing and storing data.Its software was also developed in WINDOWS operational environment via modularized design.The designed sensors and test software were successfully used in a practical electromagnetic railgun system to monitor the process of launching.The test results indicate that the state of launching can be intuitively observed and the parameters are accurately acquired and recorded.The software design method can shorten the development cycle,enhance the system's flexibility and provide the interface for the secondary development.The system shows great reliability.It is an effective and practical measurement platform for further research on the electromagnetic launch system.

Three dimensional simulation of electromagnetic railgun's exterior ballistics

In order to evaluate the electromagnetic railgun＇ s practical combat capability as well as its tactic application prospects, a three dimensional simulation model of electromagnetic railgun＇ s exterior ballistics is presented. On the hypothesis of the Earth＇ s being round and ignoring the influ- ence of rotation, the railgun＇ s atmospheric environment and its motion equations are established by the Simulink Module of Matlab. And the railgun＇ s characteristics of exterior ballistic under different muzzle energy and emission inclinations are discussed. Results show that its incomparable superiori- ty in improving range and lethality to conventional artillery under the same launch condition based on railgun＇ s range and variation of velocities. It is useful for the efficacy evaluation of railgun＇ s combat capability and its practical applications in fields such as ground war, missile interception and so on.

An optimization method for passive muzzle arc control devices in augmented railguns

In this paper,a passive muzzle arc control device(PMACD)of the augmented railguns is studied.By discussing its performance at different numbers of extra rails,a parameter optimization model is proposed.Through the calculation model,it is found that the PMACD works well in the simple railgun,which refers to the gun that there is only one pair of rails in the inner bore.The PMACD may decrease the simple railgun’s armature peak current and muzzle arc,but affect its muzzle velocity not much.However,in the augmented railguns it has different characteristics.If the parameters of the PMACD are not selected suitable.It may increase the armature peak current and muzzle arc,but greatly decrease the velocity.The reason for this problem is that the extra rails generate a strong magnetic field in front of the armature,which induces a large current to change the armature current.It is also found that when the resistance and inductance parameters of the PMACD satisfy with the optimization formula,the PMACD can also play a good role in arc suppression in the augmented railguns.Experiments of an augmented railgun with a stainless steel PMACD are carried out to verify this optimization method.Results show that the muzzle arc is obviously controlled.This work may provide a reference for the design of the muzzle arc control device.

Metallurgical analysis of multiple launch railgun materials

Railgun materials play an important role in electromagnetic launch,and its performance has great effect on the shot-efficiency and lifetime of the launcher.In this paper,the effect of shots number on the performance of multiple launch railgun material under high current conditions is studied by metallurgical analysis.The metallographys of kinds of rails'surface at various locations are observed,and the details of damage zones at different positions are analyzed.The results indicate that molten aluminum from the armature deposits on the rail surface to form a thin film.The deposited film becomes thicker and multi-layered with the increase of shots number.When the velocity is greater than 2 km /s,the gouge phenomenon always appears.The gouge volume of material is measured by 3D laser image and the qualitative observations of the damage are obtained.The evidences show that gouge phenomenon mainly causes by the kinetic energy of the armature and it is related to the shear strength of rail materials closely.By the addition of nano-sized ceramic powders,the shear strength of rail materials increases,the volume of gouge decreases during multiple launches.

Numerical simulation of interior ballistic process of railgun based on the multi-field coupled model

Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural fields. Some characteristics of railgun shot, such as velocity skin effect, melt-wave erosion and magnetic sawing, which are generated under the condition of large-current and high-speed sliding electrical contact, were demonstrated by numerical simulation.

3D numerical simulation and analysis of railgun gouging mechanism

A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the rail gouging phenomenon. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface, obliquely extruded into the rail when accelerating the armature to a high velocity, can produce gouging. Both controlling the bulge size to a certain range and selecting suitable materials for rail surface coating will suppress the formation of gouging. The numerical simulation had a good agreement with experiments, which validated the computing model and methodology are reliable.

电磁轨道发射器能量转换过程

为提高电磁轨道炮发射效率,探讨电磁轨道发射器的能量转换过程及规律,依据电路和电动力学理论,构建了由动生阻抗、轨道电感、轨道电阻和枢轨接触电阻等组成的发射器非线性数学模型,搭建了耦合结构力、速度、位移等因素的发射器仿真模型,在分析动生阻抗、轨道电感、轨道电阻和枢轨接触电阻特性的基础上,揭示了发射器的脉冲电源激励、脉冲电源和轨道电感共同激励、轨道电感主激励三阶段能量转换规律,得到某次试验发射器能量转换过程和各负载消耗能量占比,其中轨道电阻消耗能量占比52.73%最高,降低轨道电阻、轨道电阻梯度和摩擦系数等仿真参数后,发射器效率由27.27%提升至60.87%。

大口径轨道炮弹药运用中多物理场环境表征

当前轨道炮相关研究主要集中于小口径轨道炮,对于大口径轨道炮发射过程中弹药的多物理场环境表征缺乏认知。针对该问题设计了一种大口径轨道炮发射一体化弹丸的动态仿真模型,充分考虑了组件之间的接触特征、材料属性变化以及结构变形等实际因素,讨论了发射过程中发射组件的电磁场、温度场以及结构场的时空分布特性。基于仿真结果,对发射过程中弹药运用的可靠性进行了评估。研究结果表明,该型130 mm轨道炮能够将26 kg弹丸加速至1 023 m/s,最大过载约为6 700g。此外,在发射组件出炮口的瞬间,引信感应电流以及TNT药柱所受应力会急剧增大,导致弹药运用存在安全隐患,而温度场对弹药的影响较小。