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Coupling of current skin effect and the contact resistance's piezoresistive effect. (a) Current path analysis for nonskin current; (b) Double concentration spots of the current density under non-skin current; (c) Current path analysis for skin current; (d) Single concentration spots of the current density under skin current.
Source publication
Electromagnetic propulsion technology has important applications in military equipment such as electromagnetic rail guns. The extremely harsh multiphysics environment during electromagnetic propulsion is the key problem that now restricts its practical application. Most previous modeling studies have neglected or set overidealized approximations fo...
Contexts in source publication
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... schematic diagram of the current path under such an assumption is shown in Fig. 6a. Due to the preclamping process of the armature, the pressure in the middle of the contact interface is much larger than that at the left vertex. Correspondingly, the contact resistance at the left vertex of the contact interface is much larger than that in the middle. For an intuitive comparison, the unevenly distributed contact ...
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... 6a. Due to the preclamping process of the armature, the pressure in the middle of the contact interface is much larger than that at the left vertex. Correspondingly, the contact resistance at the left vertex of the contact interface is much larger than that in the middle. For an intuitive comparison, the unevenly distributed contact resistance in Fig. 6a is equivalent to a uniform resistivity layer with unequal thickness, sandwiched between the rail and the armature. It is obvious that current path 2 (passing through the middle of the contact interface) is likely to have a lower cumulative resistance than current path 1 (passing through the left end of the contact interface), which is ...
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... between the rail and the armature. It is obvious that current path 2 (passing through the middle of the contact interface) is likely to have a lower cumulative resistance than current path 1 (passing through the left end of the contact interface), which is the explanation for the double current concentration areas in the literature [18]. Fig. 6b shows the simulation results under this assumption via the model in the literature [18], which is consistent with the analysis in Fig. ...
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... to have a lower cumulative resistance than current path 1 (passing through the left end of the contact interface), which is the explanation for the double current concentration areas in the literature [18]. Fig. 6b shows the simulation results under this assumption via the model in the literature [18], which is consistent with the analysis in Fig. ...
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... considering the coupling of the current skin effect and the contact resistance's piezoresistive effect in practical systems, the situation becomes completely different. A schematic diagram of the current path under such a more realistic assumption is shown in Fig. 6c. Even with the consideration of the nonuniform thickness layer equivalent to the contact resistance, the cumulative resistance of current path 1 (passing through the left vertex of the contact interface) is still significantly smaller than that of current path 2 (passing through the middle of the contact interface) , revealing the ...
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... through comparative simulation: by compulsively setting the input current as the skin current, the defect of the literature model is equally compensated, although it is still far from the actual situation simulated by the proposed model in this paper. Under such a correction, the current density distribution concentrates in one single area (Fig. 6d), which is consistent with the simulation results of the multiphysics coupling model studied in this paper (Fig. 4c). This result fully demonstrates that the coupling of the current skin effect and the contact resistance's piezoresistive effect is the essential mechanism of the single current concentration area in the ...
Citations
... In 2019, Yin et al. [88] analyzed the distribution characteristics of the ballistic magnetic field in C-type armature railguns based on the diffusion equation of a magnetic field. In that same year, Dai et al. [89] analyzed the local convergence characteristics of current and heat during the electromagnetic propulsion process based on the dynamic multifield coupling model. In addition, Li et al. [90] used finite element software simulation to analyze the current distribution characteristics of a non-flat armature-rail contact surface of the electromagnetic railgun. ...
An electromagnetic railgun is a new type of weapon with ultrahigh speed based on electromagnetic thrust. It is used in important military domains, such as long-range strikes, strategic air defense, and ballistic interception. It is also used in aerospace fields, such as space debris cleanup, microsatellite launch, and space station relay launch, so its future prospects are excellent. We analyzed 1324 publications on electromagnetic railgun using CiteSpace and identified information including authors, institutions, journals, and popular research topics and trends. Our analysis found that the University of Texas is the research institution that has published the most documents on electromagnetic railgun, and French researcher Markus Schneider has published the most documents. The journals of IEEE Transactions on Magnetics and IEEE Transactions on Plasma Science have played an important role in promoting the development of electromagnetic railgun. The research direction of electromagnetic railgun has a distinct multidisciplinary characteristic because it touches on physics, engineering science, mathematics, materials science, energy and fuel, communication technology, instrumentation, and computer science. The development process of electromagnetic railgun can be grouped into three stages: basic theoretical research, engineering research, and system optimization research. The major research topics include electromagnetic force, armature design, rail materials, pulsed power supply, armature–rail contact surface characteristics, and coupling analysis of multiple physical fields. Future electromagnetic railgun will be scalable in terms of armature–rail contact characteristics and life span, energy storage density of power supply, current-carrying capability and thermal management of launcher materials, optimization design of armature structure, and complex data processing of control systems.
... With advancements in science and technology, simulating VSE through FEA has demonstrated more powerful and efficient capabilities. Dai et al. [55] revealed that through analyzing a multi-field coupling dynamic model, the dominant role of the VSE significantly diminishes the piezoresistive effect of the ECIs on current distribution during the EMR propulsion process. This leads to the formation of a single concentrated area of current density at the ECIs, instead of multiple concentrated areas. ...
This work provides a comprehensive review of the utilization of the Finite Element Analysis (FEA) in optimizing current density distribution within the Electrical Contact Interfaces (ECIs) of Electromagnetic Railguns (EMRs). Mastery over the current density distribution at ECIs is crucial for boosting the operational efficiency and longevity of EMRs. FEA is instrumental in identifying and rectifying issues stemming from non-uniform current density distributions, which can result in severe problems like local overheating, material degradation, increased friction wear, and a decline in launch capabilities. This review delineates the pivotal factors affecting current density at ECIs, including the Velocity Skin Effect (VSE), Current Skin Effect (CSE), Proximity Effect (PE), input current, contact pressure, and contact resistance. It then explores recent advancements on the FEA-driven optimizations of material and structures, which have markedly enhanced performance of EMRs. Challenges in applying FEA—such as the complexity of modeling multi-field interactions, computational demands, and ensuring simulation reliability—are also addressed, with recent innovations offering promising solutions. This work concludes by underlining the indispensable contribution of FEA to the progressive development of EMRs, spotlighting its vital role in spearheading future innovations through the fusion of cutting-edge methodologies and interdisciplinary collaborations.
... An electrical contact refers to the contact between different conductors to achieve the current flow [1], which can be divided into fixed contact, separable contact and sliding contact [2], [3]. Among them, the sliding contact is widely used in industry, rail transit, electromagnetic propulsion, such as the commutator in the motor, the arch arc structure in the rail transit [4], the boot rail structure in the subway [5], and the brush-rail device in the electromagnetic propulsion [6], [7]. At present, the electrical devices mainly use AC, and the excellent electrical contact state is a necessary condition to ensure the safe and stable operation of the system. ...
An excellent electrical contact state is necessary to ensure safe and stable operation of the system. Therein, contact resistance and arc ablation are essential indexes for estimating the contact state. In view of the characteristics of brush-rail device with transient large current for AC electromagnetic propulsion, a contact resistance model and the concept of arc ablative trigger boundary are proposed in this paper. Firstly, an equivalent circuit model is developed based on structural properties of brush-rail device. Then, the corresponding contact resistance model is established considering the contact pressure, amplitude and frequency of current, sliding velocity and consecutive run times. In addition, the main affecting factors of arc ablation are analyzed and the p-v parameters of arc ablation boundary are determined. Finally, the contact resistance and arc ablative trigger boundary of the brush-rail device are tested on a rotating transient large current experimental platform, which proves the correctness of the proposed method.
... To achieve an accurate strike, intelligent designs are being developed for the launch load of electromagnetic railguns [4]. However, high current exists in the rail and armature during launch, which produces an in-bore pulsed high magnetic field [5], [6]. To optimize the intelligent launch load, it is necessary to understand the pulsed high magnetic field. ...
Compared with a conventional propulsion system, an electromagnetic railgun is characterized by an in-bore pulsed high magnetic field. However, the dynamic distribution of the magnetic field in the projectile has rarely been experimentally studied. To this end, this paper discusses the possibility of utilizing magnetic field environment information. An equivalent model of an electromagnetic railgun is established by using the finite element method. Based on the magnetic diffusion equation and the Biot-Savart law, the in-bore magnetic induction is determined. The velocity skin effect and projectile shielding are considered in the model. Furthermore, the magnetic measurement method is presented to validate a simulation result. The results obtained from the simulation and experiment show that package shielding affects the pulse width and amplitude of the internal value. The peak magnetic induction of low carbon steel and copper is reduced by 33.6 %, and the pulse width lags by 2.7 ms. Moreover, projectile shielding has a substantial influence on the timing accuracy during launch, and the time error reaches approximately 18 %. Therefore, the in-bore magnetic field is a practical signal for the control module since it considers the influence of different projectile shields.
... The use of launching technologies for space exploration has been reviewed and indicates a strong correlation with defense applications and rocket launcher systems [7], [8]. By employing the principles of railgun and coilgun, higher muzzle velocity can be achieved [9]. ...
... k = π τ W ave constant, per meter (8) λ n = nπ 2d , n = 1, 3, 5... ...
p>This paper presents the design aspects and thermal characteristics of single-sided linear induction motor (SLIM) for Electromagnetic launchers. It is designed to accelerate a 50 kg mass through a distance of 3 meters within a minuscule time to an exit velocity of 50 m/s. A study of the motor’s parametric variation based on the launching requirement has been performed. Its performance characteristics are obtained using 3D FEM and verified analytically using Parseval’s method. The FEM, analytical and experimental verification of the thrust characteristics of different secondary conductive sheet materials namely, aluminum, beryllium copper and German silver shows that, the latter exhibits superior characteristics than the former two, because its thrust-velocity curve is close to inverse linear relationship (stable region of operation of LIM) , which significantly reduces the accelerating time during the launch. The designed SLIM is assessed for its thermal performance with materials having temperature-dependent electrical properties by carrying out a coupled-field FEM simulation. The conclusions demonstrate that the electromagnetic and thermal assessments are in tandem with each other as required for launching.</p
... The use of launching technologies for space exploration has been reviewed and indicates a strong correlation with defense applications and rocket launcher systems [7], [8]. By employing the principles of railgun and coilgun, higher muzzle velocity can be achieved [9]. ...
... k = π τ W ave constant, per meter (8) λ n = nπ 2d , n = 1, 3, 5... ...
p>This paper presents the design aspects and thermal characteristics of single-sided linear induction motor (SLIM) for Electromagnetic launchers. It is designed to accelerate a 50 kg mass through a distance of 3 meters within a minuscule time to an exit velocity of 50 m/s. A study of the motor’s parametric variation based on the launching requirement has been performed. Its performance characteristics are obtained using 3D FEM and verified analytically using Parseval’s method. The FEM, analytical and experimental verification of the thrust characteristics of different secondary conductive sheet materials namely, aluminum, beryllium copper and German silver shows that, the latter exhibits superior characteristics than the former two, because its thrust-velocity curve is close to inverse linear relationship (stable region of operation of LIM) , which significantly reduces the accelerating time during the launch. The designed SLIM is assessed for its thermal performance with materials having temperature-dependent electrical properties by carrying out a coupled-field FEM simulation. The conclusions demonstrate that the electromagnetic and thermal assessments are in tandem with each other as required for launching.</p
... However, the effects of the frictional heat and Ohmic heat caused by contact resistance were not considered in this study. Ref. [7] analyzed the influence of contact force on current distribution based on the twodimensional electromagnetic field model, whereby the frictional heat and Ohmic heat were introduced into the heat source at the armature-rail interface, but the heat absorption process of armature melting was not considered in ref. [7]. Therefore, we aimed to establish a more comprehensive energy equation at the armaturerail interface. ...
... However, the effects of the frictional heat and Ohmic heat caused by contact resistance were not considered in this study. Ref. [7] analyzed the influence of contact force on current distribution based on the twodimensional electromagnetic field model, whereby the frictional heat and Ohmic heat were introduced into the heat source at the armature-rail interface, but the heat absorption process of armature melting was not considered in ref. [7]. Therefore, we aimed to establish a more comprehensive energy equation at the armaturerail interface. ...
Under the extreme working conditions of high‐speed and high‐current sliding electrical contact, if an electromagnetic launcher's rails and armature are not in good contact, transition ablation may occur, which will reduce the life of the rails. Though the transition state can be evaluated based on the muzzle voltage waveform, the conventional lumped circuit model does not take into account the strong coupling relationship of the multi‐physical fields in the launching process—in particular, there is a lack of analysis of the melt wear of the armature. To overcome this challenge, a novel approach based on the field‐circuit coupled method is proposed in this study to analyze the performance of armature‐rail contact. First, the basic principle of the co‐simulation model was introduced. The circuit model, the electromagnetic field model, the temperature field model, and the armature‐rail contact force model were then built. Compared with the conventional circuit model, the field‐circuit coupled model presented in this paper can better analyze the transient changes of the contact performance and obtain more details of multi‐physical fields. Besides, the contact performance under different interference were compared through our proposed method. The method proposed in this study comprehensively considers the influence of the velocity skin effect, armature‐rail interference assembly, and the melt wear of the armature on the performance of armature‐rail contacts. The study can provide effective theoretical guidance for conducting performance analysis and designing the armature for an electromagnetic rail launcher. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
... Yin et al. [11] proposed a two-dimensional multi-physics field coupling method based on magnetic diffusion method. In [12], it has been proved that the two-dimensional model can basically restore the current density and flux density distribution between the rails and armature during electromagnetic propulsion, and effectively reproduce the influence of velocity skin effect (VSE) on magnetic diffusion. However, it is impossible to quantitatively obtain the distribution of physical parameters during launch, as the height of rails and armature was ignored. ...
... The velocity and displacement obtained after integration are shown in Fig. 6(b), For the whole propulsion process, the armature is accelerated to nearly 1700 m/s in just 12 ms, with the propulsion distance of only 11 m. Based on Eq. (9)(10)(11)(12)(13)(14), the magnetic field distribution of central axis position is solved, which provides a reference for the design and protection of precision circuit components. As shown in Fig. 7, the simulation results show that the magnetic induction decreases exponentially with the increase of the distance from the armature. ...
Electromagnetic propulsion technology is a new propulsion technology which uses electromagnetic force to push objects into high or ultra-high speed. However, during propulsion, the armature and launch load are affected by harsh multi-physics environment. The coupled effect was often ignored or over idealized in previous numerical simulations, which leads to large errors between simulation and experiment. In this paper, a three-dimensional multi-physics coupling environment simulation model is established. The distribution of electromagnetic field, structure field and temperature field in armature from static to high speed are effectively calculated. Moreover, the coupled effect between physical fields and the influence of key parameters on the simulation results are revealed. In conclusion, this model can reproduce the physical field distribution of armature and rail during electromagnetic propulsion. The time-varying resistance and inductance and the velocity skin effect (VSE) are the key parameters affecting armature movement. This method reveals a feasible path for the simplification of multi-physical model and the mitigation of extreme environment.
... Thus, it has attracted much attention in recent years and many important results haven been obtained. These researches are mainly focus on the theoretical analysis, mathematical and simulation model establishment, parameters optimization of launcher and armature, the designing of the launcher structure, and etc [13]- [16]. As one of the most important electromagnetic launching technologies, the reluctance electromagnetic technology is widely used in small bore launcher. ...
As to the countermeasures of low, small and slow “black flying” UAV, the flying net launching technology scheme for anti-UAV based on reluctance electromagnetic launcher was proposed, and the working principle of the system was analyzed. For the nonlinear large deformation problem of flying net, the default beam element model and mechanical model of flying net were constructed, and the simulation analysis was carried out. Based on the orthogonal experimental method, the optimization analysis of flying net parameters was carried out, and based on the range analysis results, the sensitivity of armature initial velocity, armature mass and initial angle to the effective distance of flying net was obtained, as well as the optimization parameter combination. The flying net launching experimental system was established and validation experiments were carried out. The results show that the reluctance electromagnetic launching technology can be used to launch the flying net, and the flying net can effectively intercept the UAV. Furthermore, the initial angle of the armature has the greatest influence on the effective distance of the flying net, while the velocity of the armature has the least influence.
... The use of launching technologies for space exploration has been reviewed and indicates a strong correlation with defense applications and rocket launcher systems [7], [8]. By employing the principles of railgun and coilgun, higher muzzle velocity can be achieved [9]. ...
... k = π τ Wave constant, per meter (8) λ n = nπ 2d , n = 1, 3, 5 . . . ...
This paper presents the design aspects and thermal characteristics of single-sided linear induction motor (SLIM) for Electromagnetic launchers. It is designed to accelerate a 50 kg mass through a distance of 3 meters within a minuscule time to an exit velocity of 50 m/s. A study of the motor’s parametric variation based on the launching requirement has been performed. Its performance characteristics are obtained using 3D FEM and verified analytically using Parseval’s method. The FEM, analytical and experimental verification of the thrust characteristics of different secondary conductive sheet materials namely, aluminum, Beryllium copper and German silver shows that, the latter exhibits superior characteristics than the former two, because its thrust-velocity curve is close to inverse linear relationship (stable region of operation of LIM), which significantly reduces the accelerating time during the launch. The designed SLIM is assessed for its thermal performance with materials having temperature-dependent electrical properties by carrying out a coupled-field FEM simulation. The conclusions demonstrate that the electromagnetic and thermal assessments are in tandem with each other as required for launching.
