Failure pattern in ceramic metallic target under ballistic impact

The ballistic resistance and failure pattern of a bi-layer alumina 99.5%-aluminium alloy 1100-H12 target against steel 4340 ogival nosed projectile has been explored in the present experimental cum numerical study.In the experimental investigation,damage induced in the ceramic layer has been quantified in terms of number of cracks developed and failure zone dimensions.The resultant damage in the backing layer has been studied with variation in the bulge and perforation hole in the backing layer with the varying incidence velocity.The discussion of the experimental results has been further followed by three dimensional finite element computations using ABAQUS/Explicit finite code to investigate the behaviour of different types of bi-layer targets under multi-hit projectile impact.The JH-2 constitutive model has been used to reproduce the behaviour of alumina 99.5%and JC constitutive model has been used for steel 4340 and aluminium alloy 1100-H12.The total energy dissipation has been noted to be of lesser magnitude in case of sub-sequential impact in comparison to simultaneous impact of two projectiles.The distance between the impact points of two projectiles also effected the ballistic resistance of bi-layer target.The ballistic resistance of single tile ceramic front layer and four tile ceramic of equivalent area found to be dependent upon the boundary conditions provided to the target.

Infrared modeling and imaging simulation of midcourse ballistic targets based on strap-down platform

An infrared （IR） imaging simulation framework based on the strap-down platform is proposed for midcourse ballistic targets. It overcomes the shortcoming of the existing algorithms, which cannot simulate IR imaging from the entire midcourse process. The proposed framework includes three steps, target characteristic modeling, motion modeling, and imaging modeling. In imaging modeling, the staring focal plane is taken into account due to its wide employment. In order to obtain IR images of high fidelity, especially that the fluctuation of the target signal-to-noise ratio （SNR） is reasonably similar to the actual one, this paper proposes an improved IR imaging simulation method. The proposed method considers two critical factors of the pixel plane, occupy-empty ratio and defect elements, which affect the imaging of targets markedly but are neglected in previous work. Finally, the IR image sequence of high fidelity is obtained. And the correlative parameters of simulation can be set according to the given scene. Thus the generated images can satisfy the needs of algorithms validation for tracking and recognition.

Micro-motion effect in inverse synthetic aperture radar imaging of ballistic mid-course targets

For ballistic mid-course targets,in addition to constant orbital motion,the target or any structure on the target undergoes micro-motion dynamics,such as spin,precession and tumbling.The micro-motion characteristics of the ballistic mid-course targets were discussed.The target motion model and inverse synthetic aperture radar(ISAR) imaging model for this kind of targets were built.Then,the influence of micro-motion on ISAR imaging based on the established imaging model was presented.The computer simulation to get mid-course target echoes from static darkroom electromagnetic scattering data based on the established target motion model was realized.The imaging results of computer simulation show the validity of ISAR imaging analysis for micro-motion targets.

Unscented Particle Filter Algorithm for Ballistic Target Tracking

At present, the ballistic Target tracking has a higher demand in convergence rate and tracking precision of filter algorithm. In the paper, a filter algorithm was improved based on particle filter. The algorithm was carried out from the aspects such as particle degradation and particle diversity lack. A novel ballistic coefficient parameter model was built, and was expanded to the state vector for filtering. Finally, the improved algorithm was simulated by MATLAB software. The simulation results show that the algorithm can obtain better convergence speed and tracking precision.

Dependence of impact regime boundaries on the initial temperatures of projectiles and targets

Towards higher impact velocities,ballistic events are increasingly determined by the material temperatures.Related effects might range from moderate thermal softening to full phase transition.In particular,it is of great interest to quantify the conditions for incipient or full melting of metals during impact interactions,which result in a transition from still strength-affected to hydrodynamic material behavior.In this work,we investigate to which extent the respective melting thresholds are also dependent on the initial,and generally elevated,temperatures of projectiles and targets before impact.This is studied through the application of a model developed recently by the authors to characterize the transition regime between high-velocity and hypervelocity impact,for which the melting thresholds of materials were used as the defining quantities.The obtained results are expected to be of general interest for ballistic application cases where projectiles or targets are preheated.Such conditions might result,for example,from aerodynamic forces acting onto a projectile during atmospheric flight,explosive shapedcharge-jet formation or armor exposure to environmental conditions.The performed analyses also broaden the scientific understanding of the relevance of temperature in penetration events,generally known since the 1960s,but often not considered thoroughly in impact studies.

Ballistic target recognition based on multiple data representations and deep-learning algorithms

Target recognition is a significant part of a Ballistic Missile Defense System(BMDS).However,most existing ballistic target recognition methods overlook the impact of data representation on recognition outcomes.This paper focuses on systematically investigating the influences of three novel data representations in the Range-Doppler(RD)domain.Initially,the Radar Cross Section(RCS)and micro-Doppler(m-D)characteristics of a cone-shaped ballistic target are analyzed.Then,three different data representations are proposed:RD data,RD sequence tensor data,and RD trajectory data.To accommodate various data inputs,deep-learning models are designed,including a two-Dimensional Residual Dense Network(2D RDN),a three-Dimensional Residual Dense Network-Gated Recurrent Unit(3D RDN-GRU),and a Dynamic Trajectory Recognition Network(DTRN).Finally,an Electromagnetic(EM)computation dataset is collected to verify the performances of the networks.A broad range of experimental results demonstrates the effectiveness of the proposed framework.Moreover,several key parameters of the proposed networks and datasets are extensively studied in this research.

Ballistic behavior of boron carbide reinforced AA7075 aluminium alloy using friction stir processing-An experimental study and analytical approach

High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.

Experimental Investigation on the Ballistic Resistace of Metal Plates Subjected to Impact of Rigid Projectiles

The ballistic performance of monolithic and multi-layered steel plates impacted by ogival-nosed projectiles was investigated by using a gas gun experimentally.The total thickness of in-contact multi-layered target was equally to that of monolithic target.The results show that,for the high strength targets,the monolithic targets have greater ballistic limit velocities than multi-layered targets,and also the ballistic limit velocities of targets decrease with the increase of the number of layers.However,for the low strength targets,the monolithic targets have lower ballistic limit velocities than multi-layered targets.The differences in target capacity between various impact conditions can be related to the transitions of perforation mechanisms and failure models.

加强筋位置对半穿甲战斗部侵彻多层钢靶性能影响研究

为了研究加强筋位置对半穿甲战斗部侵彻多层钢靶性能的影响,通过试验及数值仿真,研究了加强筋在弹体轴向不同位置处的2种半穿甲战斗部,以一定速度(710 m/s)、着角(20°)侵彻8层钢靶的弹道偏转、弹孔尺寸、余速的差异。研究结果表明:加强筋位置由弹尖向质心位置逼近时弹道偏转角减小、弹孔长轴减小、穿甲能力提升;弹道偏转角增量与靶间距呈正相关关系;弹道偏转角、侵彻余速、弹头侵蚀量及弹孔仿真结果与试验实测值最大偏差为8.82%,仿真与试验结果符合较好。研究结果可为半穿甲战斗部方案设计提供参考。

高速动能弹撞击装甲结构引起的螺栓连接失效及部件过载损伤研究

目的 验证和揭示高速动能弹对装甲结构的损伤机理。方法 聚焦高速动能弹打击装甲目标时,弹道冲击造成的靶标结构连接失效及部件过载损伤这2种损伤效应,以典型螺栓连接为研究对象,采用高速球形弹丸撞击螺栓连接结构的小尺寸试验对数值模拟方法和材料模型参数进行校验。在此基础上,采用数值模拟和冲击响应谱分析方法对高速动能弹打击全尺寸坦克进行模拟分析,获得撞击过程螺栓连接失效特征、主要影响因素及坦克典型位置部件的冲击加速度曲线和冲击响应谱曲线。结果 在小尺寸试验中,动能输入为0.042MJ时,螺栓连接未发生失效;但25.6MJ动能输入全尺寸坦克时,螺栓发生断裂而使连接失效。数值模拟结果揭示了螺栓发生断裂的主要原因。结论 输入动能大小、连接螺栓直径、模拟设备部件质量和撞击位置为螺栓是否断裂的主要影响因素。坦克某些位置的冲击响应谱曲线高于军用标准给出的临界曲线的下限甚至上限,表明这些位置的部件因高过载损伤导致失效的概率较高。

基于运动模式集精细差异特征估计的真假弹道目标联合跟踪与辨识方法

针对对抗条件下弹道目标和有源多假目标跟踪及辨识难的问题,基于稳健交互多模型(Robust Interacting Multiple Model,RIMM)策略,提出真假弹道目标的联合跟踪与辨识方法。该方法基于推导的真假目标运动模式集以及模式间的精细差异特征设计交互多模型(Interacting Multiple Model,IMM)策略,以扩展卡尔曼滤波(Extended Kalman Filter,EKF)为子滤波器,并引入概率调整因子与时变因子,实时更新概率转移矩阵,有效放大运动模式集的精细差异特征,不仅能实现对真假目标的稳定跟踪,提高跟踪精度,同时也能实时在线辨识真假目标,实现跟踪辨识一体化。仿真结果表明,该方法的跟踪效果比传统单模型EKF算法和经典的IMM+EKF算法更好,能实时跟踪并辨识出真假目标,有利于提高雷达资源调度的效率。

结构间隙对复合靶板抗弹性能的影响

为研究结构间隙对复合靶板抗弹性能的影响,探究弹体与靶板的响应规律,利用有限元软件对4种不同间隙结构的复合靶板在不同弹速冲击下的毁伤变形状态进行仿真分析,得到弹体的剩余速度和靶板各组成部分吸能占比的变化规律。结果表明:结构间隙会影响复合靶板的抗弹性能,在弹体速度相同的情况下,有结构间隙靶板的弹体剩余速度更小;在不同速度段,结构间隙布置在不同位置时发挥的作用是不同的;抗弹芯层在弹体侵彻过程中是吸收弹体动能的主要部分,吸能占比约为58%;靶板间结构间隙能提升靶板的抗弹性能。

基于残差网络ResNet18-SVM的弹道中段目标识别

针对单纯基于深度学习的弹道目标识别算法在小样本下鲁棒性差、识别率低的问题,提出一种残差网络ResNet18与支持向量机(SVM)级联的分类模型,对弹头、重诱饵、轻诱饵和碎片四类典型弹道目标进行识别。该识别以雷达回波信号的时频图像作为输入,利用残差单元自动抽象出目标特征,再输入SVM识别分类,该模型结合了ResNet深层感受野大、SVM对高维特征样本拥有较好的分类能力的优势。文中实验采用的雷达回波数据集通过弹道仿真和目标电磁仿真获得,通过仿真实验表明级联模型ResNet18-SVM比单纯的ResNet18识别率平均提升1.9%;文中模型具有良好的鲁棒性,在不同信噪比下相比于SqueezeNet、ZFNet、AlexNet网络平均精准率分别高出14.3%、16.3%、4.46%。

地球同步轨道卫星对低轨卫星的目标引导方法

在实际作战中,地球同步轨道卫星通常是最先发现弹道导弹发射的预警装备,然而,其提供的缺维探测信息,使得传统的引导交接方法难以直接应用于其对低轨卫星的目标引导上。针对此问题,对地球同步轨道卫星对低轨卫星的目标引导方法进行研究。首先,根据弹道导弹在发射及主动段飞行过程中产生红外辐射特性时的飞行高度约束,计算在单颗地球同步轨道卫星引导下,低轨卫星红外传感器的方位和俯仰探测范围。其次,对低轨卫星红外传感器的探测距离进行建模和计算,实现低轨卫星对目标的成功探测。最后,通过模拟仿真实验,验证了该方法的有效性和准确性。

基于动力学守恒定律的弹道目标关联方法

中段伴飞突防造成的各种有源或无源的弹道群目标会给雷达跟踪系统带来极大的挑战,导致其跟踪非本体实体目标或电假目标,从而出现关联错误的情况。中段实体弹道目标满足动力学守恒定律,可以充分利用该特性来改善跟踪系统的数据关联机制,因此提出一种基于动力学守恒定律的弹道目标概率数据关联(probability data association,PDA)方法,即在传统关联门筛选出有效量测的基础上,对动量矩和机械能进行联合统计检验,进一步剔除电假目标点迹或其他错误量测,并使用动量矩和机械能对加权关联概率进行修正。蒙特卡罗仿真验证了该方法的有效性。仿真结果表明,与传统PDA方法相比,所提方法能够有效抑制有源距离欺骗干扰和杂波的影响,提高跟踪精度。

基于DTCWT-VAE的弹道中段目标RCS识别

针对弹道目标雷达信号易受环境影响、目标识别准确率低的问题,提出了一种基于双树复小波变换(dual-tree complex wavelet transform,DTCWT)和变分自编码器(variational autoencoder,VAE)的弹道目标雷达散射截面(radar cross section,RCS)识别法。首先,采用DTCWT对弹道目标RCS动态数据进行预处理,再利用VAE提取目标的隐变量特征,最后用支持向量机(support vector machine,SVM)分类器进行识别。实验结果表明,与已有方法相比,该方法具有更高的识别概率,且鲁棒性较好。

基于合同网协议的分布式反导资源分配算法

资源分配算法是实现一体化防空反导的关键技术。针对弹道导弹防御过程中“传感器-武器-目标”动态分配问题,提出一种基于合同网协议的分布式分配方法。首先,对“传感器-武器-目标”动态分配问题进行形式化建模,模型考虑传感器和武器空间能力、传感器制导通道和武器拦截弹数量等实际约束,并设计目标函数以实现弹道导弹防御中尽早拦截和尽可能提高拦截成功概率这两个主要原则。然后,在合同网协议框架的基础上,构建反导资源协同动态分配流程,并针对传感器和武器的任务特点分别设计反导资源投标与中标策略。其中,武器资源投标策略设计中考虑对已分配目标的置换,并在估计被置换对象重招标所带来效能损失的基础上提出基于校正效能的置换对象选择方法。计算机仿真实验结果表明,所提算法能够实现分配方案的动态调整,且与传统反导体系下的分配算法相比,对导弹的拦截时间更早,成功概率更高,平均反导效能提高43.7%。

基于两阶段注意力层Transformer的弹道目标多站融合识别

多站弹道目标融合识别旨在利用多个雷达站点信息的互补性提升弹道目标识别性能,而传统多站下弹道目标识别方法未直接考虑多站数据间的关联特性,难以取得准确、稳健的识别性能。针对多站下基于雷达散射截面积(RCS)高速飞行目标的识别问题,提出了一种基于两阶段注意力的弹道目标多站融合识别方法。首先,在现有的Transformer模型上添加维度分段模块将多站雷达数据嵌入于二维向量中,保留站内数据时序及站间关联信息;然后,添加了两阶段注意力层,有效地捕获站内时序信息及跨站维度的依赖关系;最后,基于仿真动态RCS数据模拟多站场景开展了融合识别实验。实验结果表明该方法能够有效提升多站条件下的弹道目标识别性能。

基于ISVM-DS的红外多传感器融合识别方法

弹道中段目标为一个目标群,包括弹头、诱饵、碎片等,并且由于距离传感器较远,红外成像为点目标,可用信息较少,因此单一的红外传感器往往难以满足识别要求,需要融合多个传感器进行识别。针对红外多传感器的融合识别问题,本文提出了基于增量支持向量机和D-S(increment support vector machine-Dempster-Shafer,ISVM-DS)证据理论的融合识别方法。首先,训练多个波段传感器红外特征的支持向量数据描述(support vector data description,SVDD)模型,生成壳向量并训练其ISVM模型;接着,采用ISVM模型的后验概率生成基本概率赋值(basic probability assignment,BPA);最后,利用D-S证据理论对多个证据的BPA进行融合,输出分类结果。实验结果表明,该方法能有效提高目标识别的准确性。

高性能纤维种类及织物结构对防弹性能的影响

为研发不同防弹织物,选取7种高性能纤维织物为研究对象,并制作相同尺寸的软质靶片进行弹道冲击测试,从纤维种类和织物结构两方面分析其影响因素。研究结果表明:纤维成分相同、叠层织物面密度接近时,无纬布的防弹性能较梭织布更好;在质量相近的叠层织物中,多层细薄织物的防弹性能比少层厚重织物更好;织物密度和织物比吸能值SEA呈显著负相关关系,随着织物密度的减小,织物的比吸能值越高,其防弹性能越好,反之则防弹性能越差;选择细薄织物、适当增加叠层织物层数、适当减小织物密度,有利于提高织物的防弹性能。