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

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Defence Technology（防务技术） 2020年第2期16卷 348-353页

作者： Qing-hua Lin bao-ming Li National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyP.O.Box210094NanjingPR China

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 *** this paper present,we first introduced a multi-physical field model of railgun,followed by several examples to investigate the launching ***,we used the explicit finite element method,in which material nonlinearity and geometric nonlinearity were accounted,to investigate the deform behaviors of solid *** results show that the dynamic mechanical process of armature is dependent on the armature geometry,material and exciting electric *** the numerical simulation,the understanding of the fracture mechanism of solid armature was deepened.

关键词： Electromagnetic railgun Solid armature Fracture Explicit finite element Numerical simulation

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

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Defence Technology（防务技术） 2020年第4期16卷 747-752页

作者： Chun-yan Zhu bao-ming Li National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyChina

The contact resistance between the armature and rails is an important indicator of the contact characteristics in electromagnetic *** 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 *** this paper,the contact characteristics of the augmented railgun are analyzed by the combination of contact resistance and sliding friction ***,the theoretical calculation model of the contact resistance and friction coefficient of the augmented electromagnetic railgun is *** the contact resistance and friction coefficient are calculated by the measured values of the muzzle voltage,rail current and armature ***,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 *** 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.

关键词： Augmented railgun Contact resistance Friction coefficient Contact characteristics

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

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Defence Technology（防务技术） 2022年第2期18卷 271-279页

作者： Bo Tang Qing-hua Lin bao-ming Li National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyNanjing210094JiangsuChina China Academy of Ordnance 100089BeijingChina

In this paper,a passive muzzle arc control device(PMACD)of the augmented railguns is *** discussing its performance at different numbers of extra rails,a parameter optimization model is *** 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 *** PMACD may decrease the simple railgun’s armature peak current and muzzle arc,but affect its muzzle velocity not ***,in the augmented railguns it has different *** the parameters of the PMACD are not selected *** may increase the armature peak current and muzzle arc,but greatly decrease 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 *** 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 *** of an augmented railgun with a stainless steel PMACD are carried out to verify this optimization *** show that the muzzle arc is obviously *** work may provide a reference for the design of the muzzle arc control device.

关键词： Augmented railguns Arc suppression Muzzle device Optimization method Shunts

Discrete element method study of parameter optimization and particle mixing behaviour in a soil mixer

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Particuology 2023年第10期81卷 1-14页

作者： ming bao Jiming Lin Feng Zhang Jianhong Yang College of Mechanical Engineering and Automation Huaqiao UniversityXiamen361021China Postdoctoral Workstation Fujian South Highway Machinery CompanyQuanzhou362021China

Soil mixing is an emerging research in the field of construction resource *** this study,the mixing behaviour of soil particles in a mixer is numerically simulated by the discrete element method(DEM).A four-factor,three-level orthogonal experiment is designed to optimize the mixer design by selecting the fly-cutter speed,spindle speed,number of blades and fly-cutter diameter,using Lacey mixing index and power consumption as evaluation ***,the impact of soil cohesion and type on the mixing behaviour is *** results show that the optimal parameter combination of this experiment is 280 rpm fly-cutter speed,40 rpm spindle speed,4 blades and 250 mm fly-cutter *** optimal combination reaches a comparatively uniform state mix in 5.9 s with an average power consumption of 704.11 *** addition,the wear and tear of the mixer increases as soil cohesion increases,while the mixing quality of materials declines,resulting in a“shaft hugging”*** mixing efficiency varies greatly among different soil types,but the radial and tangential velocities have a similar *** work can provide some guidance for the optimization design of a mixer and study of soil mixing.

关键词： Soil mixing Discrete element method Orthogonal experiment Laceymixing index Soil cohesion

Analysis and discussion on launching mechanism and tactical electromagnetic railgun technology

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Defence Technology（防务技术） 2018年第5期14卷 484-495页

作者： bao-ming Li Qing-hua Lin National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyP.O.Box210094NanjingPR China China Academy of Ordnance P.O.Box100089BeijingPR China

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.

关键词： Railgun Launching mechanism Dynamic measurement Numerical simulation

Different response of North Pacific storm tracks in the upper and lower troposphere to jet strength

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Atmospheric and Oceanic Science Letters 2023年第1期16卷 1-7页

作者： Chenming Ma ming bao School of Atmospheric Sciences Nanjing UniversityNanjingChina

北太平洋风暴轴的深冬抑制表明风暴轴强度与斜压性之间的线性关系在冬季破裂,本研究基于1979-2019年冷季的再分析数据和拉格朗日跟踪算法,对比分析了高低层扰动的具体生长过程,结果表明太平洋急流的增强有利于高层扰动在急流核东北侧产... 详细信息

北太平洋风暴轴的深冬抑制表明风暴轴强度与斜压性之间的线性关系在冬季破裂,本研究基于1979-2019年冷季的再分析数据和拉格朗日跟踪算法,对比分析了高低层扰动的具体生长过程,结果表明太平洋急流的增强有利于高层扰动在急流核东北侧产生,但却抑制其在西北太平洋的生成,在急流核上游产生的高层扰动在整个冷季都无法充分发展,只有在急流核下游产生的高层扰动才能正常生长且它们是构成高层太平洋风暴轴的主体,相比之下,低层扰动的生成区和生长区都与斜压区重合,并且它们的生成数量和局部增长率随着斜压性的增强而增强.

关键词：深冬抑制风暴轴斜压性生长过程生成

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

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Defence Technology（防务技术） 2020年第4期16卷 893-899页

作者： Dong-mei Yin bao-ming Li Hong-cheng Xiao National Key Laboratory of Transient Physics Nanjing University of Science&TechnologyNanjing210094China

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 *** 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 *** results obtained by the two methods are *** reveals that the distribution trends of residual prestress are *** the difference for residual prestress in the filament wound composite housing of barrel is relatively *** 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 *** results mean that the residual prestress in barrel will increase while the taper coefficient for winding is ***,the sealing performance in bore is improved,but the strength of the filament wound composite housing *** 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.

关键词： Railgun Barrel Composite materials Filament winding Winding tension Residual prestress

Prediction of three-dimensional elastic behavior of filament-wound composites based on the bridging model

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Defence Technology（防务技术） 2021年第2期17卷 609-616页

作者： Dong-mei Yin bao-ming Li Hong-cheng Xiao National Key Laboratory of Transient Physics Nanjing University of Science&TechnologyNanjing210094China

This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization *** the meso-scale,a representative volume element(RVE)is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic *** results obtained through this method for the previous experimental model are compared with the ones gained respectively by experiments and classical laminate theory to verify the reliability of this *** addition,the effects of some winding parameters,such as winding angle,on the equivalent elastic behavior of the filament-wound composites are *** rules gained can provide a theoretical reference for the optimum design of filament-wound composites.

关键词： Lightweight design Filament-wound composites Bridging model Three-dimensional elastic properties

Study on Non-Newtonian Behaviors of Lennard-Jones Fluids via Molecular Dynamics Simulations

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Chinese Journal of Chemical Physics 2016年第6期29卷 754-760,I0002页

作者： Ruo-yu Dong Bing-yang Cao He-ming Yun bao-ming Chen KeyLaboratoryofRenewableEnergyUtilizationTechnologiesinBuildingofMinistryofEducation ShandongJianzhuUniversityJinan250101China KeyLaboratoryforThermalScienceandPowerEngineeringofMinistryofEducation DepartmentofEngineeringMechanicsTsinghuaUniversityBeijing100084China

Using nonequilibrium molecular dynamics simulations, we study the non-Newtonian rhe-ological behaviors of a monoatomic fluid governed by the Lennard-Jones potential. Both steady Couette and oscillatory shear flows are investigated. Shear thinning and normal stress effects are observed in the steady Couette flow simulations. The radial distribution function is calculated at different shear rates to exhibit the change of the microscopic struc- ture of molecules due to shear. We observe that for a larger shear rate the repulsion between molecules is more powerful while the attraction is weaker, and the above phenomena can also be confirmed by the analyses of the potential energy. By applying an oscillatory shear to the system, several findings are worth mentioning here： First, the phase difference between the shear stress and shear rate increases with the frequency. Second, the real part of complex viscosity first increases and then decreases while the imaginary part tends to increase mono- tonically, which results in the increase of the proportion of the imaginary part to the real part with the increasing frequency. Third, the ratio of the elastic modulus to the viscous modulus also increases with the frequency. These phenomena all indicate the appearance of viscoelasticity and the domination of elasticity over viscosity at high oscillation frequency for Lennard-Jones fluids.

关键词： Non-Newtonian Viscoelasticity Lennard-Jones fluids Molecular dynamics