Electromagnetic projectile launch uses electromagnetic force. After the armature exits the barrel, the leftover energy in the launch system is released via the muzzle plasma arc. This high-energy arcing can harm the launch system. To grasp the muzzle plasma arc’s development and its impact on the muzzle environment, this paper employs fluid simulation software. For a 16 mm-caliber launch system, combining magnetohydrodynamics with user - defined functions (UDF), a 2D fluid - structure interaction model is built, achieving multiphysics coupling of electromagnetic, flow, and thermal fields. The simulated potential difference between the guide rails matches experimental data, showing the simulation’s reliability. Results indicate that the muzzle plasma arc gradually transfers from the plasma arc circuit to the guide rail circuit, and it has a relatively stable phase. Its high temperature and shock waves expand inward and outward. The outward shock wave alters the initial muzzle flow field, while the inward expansion causes reverse airflow and blowback. After briefly reversing, the internal airflow moves outward again. This aligns with experiments where molten metal is ejected as the plasma arc fades. These findings offer theoretical support for muzzle material/structure selection, dynamic launch experiments, protection design, and electromagnetic launch interior ballistics research.

The geometric shape of the convex track has a significant impact on the sliding electrical contact characteristics in electromagnetic orbit launch devices. This article uses finite element software to establish a bidirectional coupling simulation model of structural field and electromagnetic field for a 20 mm diameter launch device, and studies the influence of convex track arc surface on pivot rail contact pressure and current distribution under different curvature radii. The simulation results show that as the curvature radius of the track arc increases, the contact pressure between the pivot and the track gradually shifts from the center to the edge, and the high current density area also moves from the center of the contact surface to the edge. In a 20 mm caliber launch device, when the curvature radius of the curved surface is 10 mm, the efficiency of the launch device is the highest and the current density distribution is the most uniform. By studying the variation of current density at the contact interface of the pivot rail with the curvature radius, a theoretical basis is provided for optimizing the geometric shape of the convex rail.

Deposition occurs on the rail surface during the start-up stage of the launching process. These phenomenon influence the velocity of the armature, the acceleration of the armature and the launching stability of the launcher. In this article, 15 experiments with the linear current density of 19 kA/mm were carried out. The morphology of the rail surface at the armature start-up stage and the start-up time of the armature were measured by a 3-D laser profilometer and a high-speed camera, respectively. Three conclusions are obtained: 1) the morphology of the deposition layer on the surface of rails is high at the edges of armature-rail interface and low in the middle of interface because of nonuniform contact pressure and temperature; 2) as the number of experiments increases, the thickness of the deposition layer on the rail surface increases and then tends to stabilize; and 3) the start-up time of the armature increases rapidly, and then tends to stabilize. Moreover, to analyze the reason for the distribution of deposition layer on the rail surface observed during start-up stage in experiments, the contact pressure, current density and Joule heating were calculated. Results show that the contact pressure of the edges of the armature is relatively high, and these areas are also where high temperature is concentrated on the surface of the armature.

The armature-rail interface of the electromagnetic launchers conducts the current with megamperes in the milliseconds. This extreme condition results in the rapid melting of the metal at the armature-rail interface, followed by the outward ejection of molten metal. The molten metal with high-velocity and high-temperature impacts rails and insulators, causing serious grooving damage and metal pollution, which limits the performance and service life of the launcher. To study this phenomenon, a 3-D electro-magnetic-thermal-mechanical-fluid multiphysics coupling model was established, taking into account dynamic contact resistance, velocity skin effect, development trend of the liquefied layer, and fluid pressure. The calculation results show that the liquefied layer initially appears at edges of the front of the armature. And rapidly expands toward the center of the tail. The maximum liquid pressure occurs neartheinterface between solid and liquid. Due to the degradation of the armature material properties caused by high temperatures, high fluid pressure facilitates the peeling of solid part of the armature, thereby accelerating the expansion of the eroded region. At 2.5 ms, the armature melts a volume of 11.91mm(3), with a maximum melting depth of 0.565 mm occurring in the edge region of the armature. Meanwhile, the maximum velocity of the liquefied layer reaches 450 m/s.

The contamination degree, which is used to evaluate the degradation of insulation performance in solid-armature rail launchers, is proposed based on the study of pollution flashover in power systems. Two methods for describing the contamination degree, namely the leakage current method and the partial surface conductivity method, are introduced based on the contamination characteristics of bore insulators. The correlation between two descriptive parameters, the leakage current I-leak and the partial surface conductivity sigma(p) , and flashover voltage U-f was investigated under various sample sizes and experimental conditions. Results indicate that the partial surface conductivity method, in general, is more suitable for describing the contamination degree of bore insulators. In cases where faults or severe contamination occur on insulators, the flashover voltage U-sigma predicted by sigma(p) is closer to the measured value U-f than the U-I predicted by I-leak , with U-I typically being higher than U-f . For a large sample size of 288 samples, the correlation coefficient between sigma(p) and U-f was found to be -0.89. The relationship between sigma(p) and U-f follows a power function, and the regression fitting yielded the equation y=0.853 x(-0.1) . The establishment of the contamination degree and the application of descriptive methods provide valuable insights into the damage distribution and degradation mechanisms of bore insulators.

This article proposes a method for calculating the distribution of the deposition layer on the rail surface based on the simulation of armature melting. A series of 49 launch experiments were conducted to study the distribution of the deposition. The thickness of the deposition, as obtained from both simulations and experimental measurements, shows strong agreement, confirming the accuracy and reliability of the proposed calculation method. Both the simulation and experimental findings reveal that the deposition is thicker during the initial stages of the launch and gradually becomes thinner as the armature reaches the high-speed stage. The trend aligns with conventional theoretical expectations. Further comparative analysis between the deposition thickness and the current waveform identifies a significant time lag: the maximum deposition layer thickness occurs after the peak of the current waveform. During the high-speed stage, despite the relatively high current amplitude, the deposition thickness decreases rapidly and ultimately disappears. This behavior is attributed to the cessation of armature melting, which halts the further deposition of material onto the rail surface.

A three-dimensional transient electro-magneto-thermo-mechanical coupled model was developed to investigate the thermal response of the rail during launch, incorporating contact pressure, contact resistance, and friction at the armature-rail interface. The results are as follows: (1) In spatial distribution, the rail temperature rises first and then falls along the direction of armature movement, with the peak located in the low-to medium-velocity stage. (2) In spatial heat evo-lution, the temperature transitions from a rapid increase to a plateau stage and then to a gradual decrease. (3) As the launch progresses, Joule heating from contact resistance dominates at the beginning, followed by frictional heating, contributing approximately 62% and 38% of the total heat input, respectively. The peak rail temperature rises from 293 K to 887 K. The model in-corporates material thermal softening. This effect, combined with electromagnetic force attenu-ation, leads to a progressive decrease in contact pressure. The reduced pressure, in turn, results in higher contact resistance and intensifies localized heating, which ultimately accelerates the overall rail temperature rise. These findings clarify the coupling between current and heating sources, providing theoretical insight and numerical support for thermal protection design and service life assessment of electromagnetic launchers.

During the electromagnetic launching process, the actual current input into the launcher is obtained by controlling the discharge of the pulsed power supply. Generally, the waveform of the pulse current is determined by the discharge characteristics and discharge time of the pulse power supply. Due to the limitation of control accuracy, the driving current is not an ideal trapezoidal wave, but there is a certain fluctuation (current ripple) in the flat top portion of the trapezoidal wave. The fluctuation of the current will affect the thickness of the liquefied layer at the armature–rail interface as well as the magnitude of the contact pressure, thereby inducing instability at the armature–rail interface and generating micro-arcs, which result in a reduction in the service life of the rails within the launcher. Consequently, it is imperative to conduct an in-depth analysis of the influence of current ripple on the liquefied layer during electromagnetic launching. In this paper, a thermoelastic magnetohydrodynamic model is constructed by coupling temperature, stress, and electromagnetic fields, which are predicated on the Reynolds equation of the metal liquefied layer at the armature–rail contact interface. The effects of current fluctuations on the melting rate of the surface of the armature, the thickness of the liquefied layer, and the hydraulic pressure of the liquefied layer under four different current ripple coefficients (RCs) were analyzed. The results show the following: (1) The thickness and the pressure of the liquefied layer at the armature–rail interface fluctuate with the fluctuation of the current, and, the larger the ripple coefficient, the greater the fluctuations in the thickness and pressure of the liquefied layer. (2) The falling edge of the current fluctuation leads to a decrease in the hydraulic pressure of the liquefied layer, which results in the instability of the liquefied layer between the armature and rails. (3) As the ripple coefficient increases, the time taken for the liquefied layer to reach a stable state increases. In addition, a launching experiment was also conducted in this paper, and the results showed that, at the falling edge of the current fluctuation, the liquefied layer is unstable, and a phenomenon such as the ejection of molten armature and transition may occur. The results of the experiment and simulations mutually confirm that the impact of current fluctuations on the armature–rail interface increases with increases in the ripple coefficient.

This article establishes a simulation model and a measurement experimental platform for static armature–rail interface contact resistance. By comparing simulation and experimental measurement results of different magnitudes of interference, the applicability of the Cooper–Mikic–Yovanovich (CMY) contact resistance calculation method in the assembly phase of railguns is validated. Subsequently, the relationship between the magnitude of interference and contact resistance is investigated. The results suggest that a moderate increase in the magnitude of interference leads to a decrease in contact resistance and an increase in robustness to assembly variations. The analysis of the components of contact resistance is conducted, which reveals that contact spots and uneven contact pressures jointly contribute to the increase/decrease of contact resistance. The current concentrating at the edges of the spots at the microscopic level leads to contact resistance. Additionally, at the macroscopic level, the current concentrating in regions with higher contact pressure results in contact resistance. According to the research, the increase in magnitude of interference can reduce the amount of both sources of contact resistance.

During the launching process of electromagnetic energy equipment, the contact resistance between the armature and the rails are an important index to measure the contact state of the rails and can reflect the contact state of the rails during the turning of the bore. Since it is difficult to directly measure the armature-rail contact resistance during the launch process, this paper proposes a method for calculating the armature-rail contact resistance of electromagnetic energy equipment based on discrete wavelet transformation, which is based on the measurement of the muzzle voltage and current, the use of discrete wavelet transformation to de-noise the measurement data, and then combining with the recursive solving equations of the muzzle circuit model, the size of the armature-rail contact resistance is calculated and analyzed in comparison to that of the Fourier transform results. Compare and analyze with the results solved by Fourier transform. It is found that the contact resistance of the armature-rail is large at the beginning, then decreases rapidly and has a tendency to rise, and finally increases rapidly at the moment of the muzzle discharge. The numerical calculation method proposed in this paper has important reference value for solving the armature-rail contact resistance of electromagnetic energy equipment.

The armature-rail contact resistance is generally considered to reflect the contact state of the armature and the rail during the launch process of the electromagnetic railgun. However, due to the extremely short time of the armature acceleration process, it is difficult to directly measure the armature-rail contact resistance. In this paper, based on the simplified muzzle voltage model of the electromagnetic railgun, a numerical calculation method of contact resistance is proposed, which considers the armature body resistance and current skin effect, based on the experimental current, muzzle voltage waveform and combined with finite element simulation and MATLAB Program to perform calculations. Comparing the calculated results with the ratio of muzzle voltage to current (muzzle resistance), it is found that the value of the muzzle resistance is 2 to 3 times that of the calculated contact resistance.

This paper considers the resistance to the heat flow between two thick solids with a high contact ratio in a vacuum. Based on the least-action principle, we derive closed-form mathematical expressions for the temperature distribution and non-dimensional thermal contact resistance, both expressed as functions of the radii ratio. Furthermore, the thermal contact resistance is investigated as a function of contact pressure and microhardness. A comparison of the conventional and proposed methods reveals that the proposed method is more accurate for calculating the thermal contact resistance with a high contact ratio. In equipment with high contact pressure, such as electromagnetic launch, we compare armature melting models using different calculation methods for contact resistance. Small and all contact models were established based on the traditional and proposed methods, respectively. The melting morphology of the armature obtained from the all contact model is highly consistent with the experimental results. During the experiment, in areas where the armature did not melt, the small contact model incorrectly calculated the melting of the armature. The all contact model can describe the strong cooling effect of the rail on the armature, preventing the armature from melting. The all contact model obtained higher heat sources, contact thermal conductivity, and contact pressure in the melting region. Under the combined effect of the three factors, a deeper and more concentrated melting morphology was obtained. This morphology is more consistent with the experimental results.

A model of electromagnetic launcher under non-ideal conditions is established based on the theory of impact dynamics and practical engineering considerations. Numerical simulation is conducted using specialized software to investigate the mechanical properties and gouging characteristics of rail-armature contact during electromagnetic launch under non-ideal conditions. Through numerical computations, distributions of current density, Lorentz force, and stress on the rail/armature interface are obtained. The study explores the gouging characteristics under different conditions, revealing that the non-steady motion of the armature results in high-speed collisions, which are the primary cause of rail gouging. By analyzing the gouging characteristics of electromagnetic launcher under non-ideal conditions, this study provides a basis for further efforts to suppress rail gouging phenomena.

In the practical application of EMR, the support mode of overhanging beam is mostly used to meet the tactical requirement of azimuth pitch. However, under the condition of the self-weight of the launcher, there must be self-weight curved, as well as the straightness deviation generated in the processing, assembly, manufacturing and molding of tube, forming a non-ideal spatial-curved armature-rail contact interface. In this paper, based on the previous analysis of the armature-rail contact characteristics of horizontal curved and vertical cured, the space cured characteristic model of electromagnetic emission was constructed, and the characteristics of the comprehensive influencing parameters of armature-rail contact were studied by analyzing the input parameters including the space cured, and the output parameters including the mass and velocity of the armature. The research can be used to guide the axial stiffness design of the launcher in the practical application of electromagnetic launch, and to perfect the theoretical research of the non-ideal armature-rail contact interface.

During the discharge of the electromagnetic rail launcher (EMRL), the electromagnetic repulsive force and the armature-rail contact force act on the rail, resulting in complex dynamic response of the rail. In-depth study and analysis of the dynamic response of the launcher can provide theoretical basis for its engineering application. In this paper, a three-dimensional model of EMRL is established, in which the insulating supports are not simplified as previously reported, they are treated as real three-dimensional objects. The results show that the inward deformation of the rail is reduced due to the existence of insulating supports. The smaller the elastic modulus of the insulating supports, the greater the maximum deformation of the rail in the direction of load.

The key assumption of this article is that the liquid metal generated by armature melting will rapidly deposit on the rail surface [1]. Combining the calculation method for armature melting morphology [2], this paper introduces a calculation method for determining the distribution of the deposition layer on the rail surface. The evolution law of the deposition layer distribution on the rail surface was obtained by 49 launch experiments. Additionally, the distribution of the deposition layer was calculated based on the launch conditions. Compared with experiments results about the deposition layer from perspectives of distribution trend and thickness, the calculation results was verified. Analysis of deposition layers in the launch direction and vertical direction relative to the insulator during multiple launches reveals that areas with thicker deposition layers carry more current, leading the armature to melt more easily under the influence of Joule heating. Consequently, during multiple launches, the concentration of the deposition layer tends to increase, leading to a thicker layer overall. This ultimately results in significant alterations to the shape of the inner chamber.

High speed rotation of the projectile is one of the most effective ways to improve the firing accuracy of electromagnetic launching process. Asymmetrical structures are adopted to generate the asymmetric magnetic field in this paper. The rotation can be obtained by the electromagnetic torques which are generated by asymmetric magnetic force on the armature. The magnitude of torque can be controlled by the current passing through the additional rails. The finite element dynamics simulation model is built with COMSOL. The motion characteristics of the rotational armature are studied with different vertical distances and cross-sectional shapes of additional rails. The vertical distances of the additional rail are considered as the independent variable, with a variable range from 38 to 50 mm. The maximum rotational speed of the armature is about 169,439 rad/s when the vertical distance is set at 38 mm. The effect of launch velocity and rotational speed of the armature is also discussed with different cross-sectional shapes of additional rails. The cross-sectional area of additional rails is kept constant. The velocity of the armature is unchanged, but the rotational speed of the armature is observed a certain decrease with convex and concave additional rails.

In previous studies, the armature–rail sliding contact interface is usually considered to be an ideal slide in which both rails are parallel and symmetric. However, due to the influence of structural deformation of the barrel affected by boundary constraints and the manufacturing errors of rails and armature, it often leads to a variety of nonideal the armature–rail matching such as space curved or twisted rails, offset or deflected armature, and so on. This article focuses on the common vertical curved rail in electromagnetic railgun. By introducing centrifugal force effects and coupling electromagnetic force, the armature–rail contact pressure is analyzed theoretically. According to the 3-D finite-element simulation results, the effect of centrifugal force on sliding contact pressure should not be ignored. The effects of different curved radii, velocities, and densities of armature on the contact pressure are compared and analyzed. The influence law on the contact pressure is obtained, which provides a theoretical basis for the design of the railgun.

The ablation, grooving and transition of rails seriously affect the launch efficiency and life of the railgun. The heat accumulation and uneven contact pressure caused by non-uniform current distribution, and the arc caused by contact instability are the main factors causing the above problems. This paper compares the definition of the cross section shape of traditional artillery and proposes the definition of cross section shape of the railgun, summarizes effects of cross section shape parameters on launching efficiency and service life of railgun in various countries in recent 15 years, and introduces the research progress of inductance gradient, current distribution and contact pressure distribution in detail. According to the summary of the influence of the cross section shape of railgun on inductance gradient, current distribution and contact pressure distribution, the potential research direction of railgun cross section shape optimization is prospected, and suggestions are provided for the development of the railgun.

The startup of the armature has a significant influence on the whole launching process. During the launching, the rail-armature interface suffers high current density, high temperature, high contact pressure and high velocity. The condition of the rail-armature interface increases the complexity of the launching and enable the appearance of the deposition layer. The sliding electrical contact on the rail-armature interface is affected by the deposition layer. The deposition layer also changes the characteristics of contact interface, such as roughness, hardness, and thickness. In this paper, the deposition layer on rails after three launching experiments was investigated. The thickness of the deposition layer was measured by three-dimensional (3D) laser profilometer. The mass of rail blocks of the armature startup stage was measured. Moreover, the dynamic multi-physics field simulation model of startup stage was established. The temperature and current density in startup stage of the interface between the armature and rails were calculated. Three conclusions are obtained. 1) In three experiments, the deposition layer of cross section of rail blocks occurs peaks and fluctuations. The peak value of anode is larger than that of cathode, and the fluctuation of anode is more than that of cathode. 2) The mass of rail blocks increases with the number of experiments. The mass difference of the anode rail block is smaller than that of cathode. 3) The current density and temperature are concentrated at the edge and the rear of the armature.