电磁轨道炮电感梯度影响因素分析

利用Ansoft Maxwell 14.0有限元分析软件,在考虑和不考虑电枢2种情况下对简单电磁轨道炮电感梯度的影响作对比分析,得出计算电感梯度时有必要将电枢的影响考虑进去的结论.为提高增强型轨道炮的电感梯度,分析不同轨道间距、厚度以及不同炮口宽度对2种增强型轨道炮电感梯度的影响,得出电感梯度随轨道参数变化的规律.     

FCG电枢膨胀过程流体计算

建立了爆炸磁压缩装置 (FCG)的 2 D轴对称有限元模型 ,应用显式非线性动力分析程序进行求解 ,得到了爆磁压缩装置电枢膨胀过程的图像。电枢使用Johnson Cook材料模型和根据实验Hugoniot曲线确定的Gr櫣ｎｅｉｓｅｎ状态方程 ,考虑到了材料应变率硬化和塑性功绝热加热过程 ;炸药材料采用JWL状态方程 ,得到了铝金属管电枢的膨胀过程、膨胀张角以及塑性功导致的电枢温度升高     

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 secondary 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.     

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.     

电磁轨道发射装置动态电感梯度分析

推导了导轨间磁场均匀分布和非均匀分布两种情况下电感梯度数学计算模型。引入了速度频率来模拟电枢发射过程速度趋肤效应,对导轨二维模型以及三维电磁场模型进行时谐仿真,并将获得的单位长度电感以及电感梯度,分别用于电气仿真系统中电感和电枢推力的计算。电气仿真和试验结果表明,电流和出口速度误差均在2%以内,证明了动态电感梯度分析及参数提取方法的正确性和准确性。     

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 elec-tromagnetic 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.     

电磁轨道炮轨道温度场与热应力数值仿真

在电磁轨道炮发射过程中,因热量累积而引起的急速温升与热应力对轨道性能和寿命有着重要的影响。为获得发射过程中轨道温度场及热应力分布情况,在分析轨道热载荷的基础上,建立了热载荷计算模型,并在给定的参数下,利用有限元仿真软件ANSYS Workbench对3种典型截面轨道的温度场与热应力进行了数值仿真。仿真结果表明:轨道温度场与热应力轴向上呈梯度分布,纵向上只扩散到内表面很薄的区域,温度与热应力最大值在电枢初始位置处;相较于矩形与凹形截面轨道,凸形截面轨道温升与热应力较低,性能较好。     

电磁轨道发射中内弹道动力响应特性分析

将轨道简化为移动载荷作用下固定在弹性支撑上的Bernoulli-Euler梁，通过静态电磁-结构耦合有限元模型求得外围封装的等效刚度，计算得到发射器的临界速度。另外，利用混合有限元/边界元法建立电磁-结构-运动多物理场耦合的动力学模型，求得枢轨动态接触压力和轨道的应力应变分布特性。通过在轨道背面布置光纤光栅应变传感器，利用测量数据验证了动力响应特性，并分析了弹丸在内弹道的稳定性。针对典型30 mm × 30 mm矩形口径发射器，分析及试验结果表明：C型电枢对轨道的电磁挤压力在平顶沿起始时刻达到最大值，之后随着时间推移逐渐减小；电枢通过引起的应力波在高速段容易与轨道中反射应力波发生共振，并且轨道在电枢运动的中间高速段区域受力最为集中，应力集中水平约是起始低速段区域的2.44倍；电枢运动高速段会出现晃动现象，进而引起上下轨道受力的不对称性。分析及试验结果对研究电磁轨道发射器内弹道动力响应特性和发射器结构设计具有重要指导意义。     

活塞式磁通压缩发电机电枢涡流的有限元分析

为了研究活塞式磁通压缩发电机（P-MFCG）电枢内部涡流及周围的磁场分布，在Maxwell方程组的基础上，对电枢附近区域的磁场模型进行理论推导，得出电枢附近区域涡流场的控制方程。采用Ansoft有限元分析软件对应用于P-MFCG的柱状电枢上感应涡流、磁感应强度以及电枢所受电磁力的分布进行仿真分析，其结果对电枢的优化设计有重要参考意义。     

静止条件下轨道发射器瞬态电磁场分布有限元模拟

在电枢静止条件下建立了简单轨道发射器及块状电枢的三维有限元模型。利用ANSYS模拟得到了轨道及电枢内的瞬态电流密度分布。结果显示,在通电过程中电流趋向轨道内侧表面,并在电枢尾部与轨道接触处集中,电流线聚集是造成轨道和电枢之间放电烧蚀的最主要原因。同时得到的还有轨道发射器周围空间的瞬态磁场分布,其结果表明,感应磁场主要集中分布在靠近电枢尾部一侧的两轨道间,并向后延续到约等于4倍口径的长度,电枢所在的位置正好是磁场激增区域。     

静止条件下多种轨道-电枢形状的轨道炮电流分布仿真

针对等轨道截面、等炮口截面、等长度、等材料和等电流8种典型的轨道-电枢结构,在电枢速度为0 m／s的情况下,采用Ansoftl 2有限元分析软件,仿真分析电流分布特征,得到：矩形截面轨道一长方体结构电枢的轨道炮有最不均匀的电流分布特征,电流主要分布在轨道外表面和电枢后部凹表面,并且分别对应于趋肤效应和电流短路径聚集现象,跑道形截面的轨道一回转体结构电枢的轨道炮有最均匀的电流密度分布．     

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.     

杠杆式抽筒子的动态特性研究及拓扑优化设计

针对杠杆式抽筒子工作时出现的断裂失效问题,以动力学和有限元理论为基础,分别进行抽筒子的动态特性研究和拓扑优化设计。得出其在抽筒过程中的动应力分布和危险区域,定性地确定出介质力学参数和工作参数的影响,获得了抽筒子的最佳材料布局和优化改进结构。优化前后抽筒子结构的对比仿真结果表明,改进结构能够使得应力集中危险区域仅为最大动应力降低10.6%的强撞击位置,其余部分均可转换为安全区域且结构刚度提升49%左右。所用方法有效可靠,为解决杠杆式抽筒子的断裂问题提供理论依据和技术手段。     

电磁发射高速旋转弹丸马格努斯效应

和传统火药发射弹丸相比,电磁发射弹丸具有初速高、射程远等优势,但尾部的电枢臂槽会使弹丸部流场不再轴对称,产生独特的气动力特性。基于三维非定常Navier-Stokers方程,采用滑移网格技术,分析电磁发射弹丸的气动力特性。研究表明,对于高速旋转的电磁发射弹丸,马格努斯效应来源于激波层内流场畸变和电枢臂的迎风面积变化的共同作用;电枢臂迎风面积的周期性变化是导致气动力和力矩周期性变化的原因,马格努斯力矩在滚转角45°和135°时分别达到最小值和最大值;电枢臂槽的存在既加剧了马格努斯效应(135°时增加50%以上),又使得压心周期性前移(绝对前移量达5%),并且随着转速的增加,马格努斯力矩增加和压心前移效果越来越显著,不利于弹丸的动稳定。     

Force chains based mesoscale simulation on the dynamic response of Al-PTFE granular composites

Force chains based mesoscale simulation is conducted to investigate the response behavior of aluminum-polytetrafluoroethylene (Al-PTFE) granular composites under a low-velocity impact. A two-dimensional model followed the randomly normal distribution of real Al particles size is developed. The dynamic compressive process of Al-PTFE composites with varied Al mass fraction is simulated and validated against the experiments. The results indicate that, force chains behavior governed by the number and the size of agglomerated Al particles, significantly affects the impact response of the material. The failure mode of the material evolves from shear failure of matrix to debonding failure of particles with increasing density. A high crack area of the material is critical mechanism to arouse the initiation re-action. The damage maintained by force chains during large plastic strain builds up more local stresses concentration to enhance a possible reaction performance. In addition, simulation is performed with identical mass fraction but various Al size distribution to explore the effects of size centralization and dispersion on the mechanical properties of materials. It is found that smaller sized Al particle of com-posites are more preferred than its bulky material in ultimate strength. Increasing dispersed degree is facilitated to create stable force chains in samples with comparable particle number. The simulation studies provide further insights into the plastic deformation, failure mechanism, and possible energy release capacity for Al-PTFE composites, which is helpful for further design and application of reactive materials.     

美国电磁轨道发射技术现状及特点分析

以电磁轨道炮为主,介绍美国陆、海军电磁轨道发射技术的发展历程及阶段性研究成果、发展目标与未来规划、研究机构及相关研究方向、潜在应用领域以及近期电磁轨道炮的主要战术技术指标,并对其关键技术特点进行了分析。     

Kevlar fabric reinforced polybenzoxazine composites filled with silane treated microcrystalline cellulose in the interlayers: The next generation of multi-layered armor panels

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.     

应急机场沥青道面高温稳定性试验研究

利用MTS～810型材料伺服试验机对应急机场道面沥青混凝土进行了高温条件下车辙试验和蠕变试验。试验结果表明：随应力的增大，沥青混凝土的弹性应变增大，塑性应力增大，破坏时间提前，应变的发展速度越来越快；得出了应急机场道面沥青混凝土的粘、弹性参数与应力的关系及本构模型；求出了不同机型的不同胎压作用下应急机场面层沥青混凝土的动稳定度；根据应急机场跑道上的飞机重复作用次数及车辙试验结果，计算了不同胎压作用下应急机场沥青混凝土面层的变形厚度，在允许寿命内面层沥青混凝土的动稳定度满足要求。     

Numerical investigation of the failure mechanism of cubic concrete specimens in SHPB tests

Cylindrical specimens are commonly used in Split Hopkinson pressure bar (SHPB) tests to study the uniaxial dynamic properties of concrete-like materials.In recent years,true tri-axial SHPB equipment has also been developed or is under development to investigate the material dynamic properties under tri-axial impact loads.For such tests,cubic specimens are needed.It is well understood that static material strength obtained from cylinder and cube specimens are different.Conversion factors are obtained and adopted in some guidelines to convert the material strength obtained from the two types of specimens.Previous uniaxial impact tests have also demonstrated that the failure mode and the strain rate effect of cubic specimens are very different from that of cylindrical ones.However,the mechanical background of these findings is unclear.As an extension of the previous laboratory study,this study performs numerical SHPB tests of cubic and cylindrical concrete specimens subjected to uniaxial impact load with the validated numerical model.The stress states of cubic specimens in relation to its failure mode under different strain rates is analyzed and compared with cylindrical specimens.The detailed analyses of the numerical simulation results show that the lateral inertial confinement of the cylindrical specimen is higher than that of the cubic specimen under the same strain rates.For cubic specimen,the corners are more severely damaged because of the lower lateral confinement and the occurrence of the tensile radial stress which is not observed in cylindrical specimens.These results explain why the dynamic material strengths obtained from the two types of specimens are different and are strain rate dependent.Based on the simulation results,an empirical formula of conversion factor as a function of strain rate is proposed,which supplements the traditional conversion factor for quasi-static material strength.It can be used for transforming the dynamic compressive strength from cylinders to cubes obtained from impact tests at different strain rates.     

某型铜材料动态力学性能的数值模拟研究

采用一种高效的应力更新算法,运用Fortran语言编写Johnson—Cook本构模型的Vuamt子程序,模拟材料在高速冲击工况下的动态力学性能,研究塑性大应变、高应变率以及温度软化作用对材料力学性能的影响。