Effect of initiation manners on the scattering characteristics of semi-preformed fragment warhead

The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge of have been drawing great attention from researchers and designer in this filed. In present paper,in order to investigate the influence of charge initiation manners on the scattering characteristics of semi-preformed fragment warhead, the numerical simulations and experimental test are conducted.Firstly, the influence of grid density on numerical results is investigated, and a proper numerical model with relatively high accuracy and effectiveness is determined. Then. numerical simulations of three kinds of different initiation position of a semi-preformed fragment warhead are carried out. An experimental test of the explosion of a semi-preformed fragment warhead is carried out. By comparing and analyzing the numerical results and experimental data, it is found that the initiation manners have great influence on scattering characteristics of semi-preformed fragment warhead. The researcher work of this paper would provide an effective alternative method to optimize the design of warhead.

Warhead fragments motion trajectories tracking and spatio-temporal distribution reconstruction method based on high-speed stereo photography

High speed photography technique is potentially the most effective way to measure the motion parameter of warhead fragment benefiting from its advantages of high accuracy,high resolution and high efficiency.However,it faces challenge in dense objects tracking and 3D trajectories reconstruction due to the characteristics of small size and dense distribution of fragment swarm.To address these challenges,this work presents a warhead fragments motion trajectories tracking and spatio-temporal distribution reconstruction method based on high-speed stereo photography.Firstly,background difference algorithm is utilized to extract the center and area of each fragment in the image sequence.Subsequently,a multi-object tracking(MOT)algorithm using Kalman filtering and Hungarian optimal assignment is developed to realize real-time and robust trajectories tracking of fragment swarm.To reconstruct 3D motion trajectories,a global stereo trajectories matching strategy is presented,which takes advantages of epipolar constraint and continuity constraint to correctly retrieve stereo correspondence followed by 3D trajectories refinement using polynomial fitting.Finally,the simulation and experimental results demonstrate that the proposed method can accurately track the motion trajectories and reconstruct the spatio-temporal distribution of 1.0×10^(3)fragments in a field of view(FOV)of 3.2 m×2.5 m,and the accuracy of the velocity estimation can achieve 98.6%.

Experimental and numerical study of the fragmentation of expanding warhead casings by using different numerical codes and solution techniques

There has been increasing interest in numerical simulations of fragmentation of expanding warheads in 3D.Accordingly there is a pressure on developers of leading commercial codes,such as LS-DYNA.AUTODYN and IMPETUS Afea.to implement the reliable fracture models and the efficient solution techniques.The applicability of the Johnson—Cook strength and fracture model is evaluated by comparing the fracture behaviour of an expanding steel casing of a warhead with experiments.The numerical codes and different numerical solution techniques,such as Eulerian,Lagrangian.Smooth particle hydrodynamics(SPH).and the corpuscular models recently implemented in IMPETUS Afea are compared.For the same solution techniques and material models we find that the codes give similar results.The SPH technique and the corpuscular technique are superior to the Eulerian technique and the Lagrangian technique(with erosion) when it is applied to materials that have fluid like behaviour such as the explosive and the tracer.The Eulerian technique gives much larger calculation time and both the Lagrangian and Eulerian techniques seem to give less agreement with our measurements.To more correctly simulate the fracture behaviours of the expanding steel casing,we applied that ductility decreases with strain rate.The phenomena may be explained by the realization of adiabatic shear bands.An implemented node splitting algorithm in IMPETUS Afea seems very promising.

Fragmentation model for large L/D (Length over Diameter) explosive fragmentation warheads

New advanced numerical computer model enabling accurate simulation of fragmentation parameters of large Length over Diameter(L/D)explosively driven metal shells has been developed and validated.The newly developed large L/D multi-region model links three-dimensional axisymmetric high strain high strain-rate hydrocode analyses with the conventional set of Picatinny Arsenal FRAGmentation(PAFRAG)simulation routines.The standard PAFRAG modeling technique is based on the Mott's theory of break-up of idealized cylindrical"ring-bombs",in which the length of the average fragment is a function of the radius and velocity of the shell at the moment of break-up,and the mechanical properties of the metal.In the newly developed multi-region model,each of the shell region,the break-up is assumed to occur instantaneously,whereas the entire shell is modeled to fragment at multiple times,according to the number of the regions considered.According to PAFRAG methodology,the required input for both the natural and the controlled fragmentation models including the geometry and the velocity of the shell at moment of break-up had been provided from the hydrocode analyses and validated with available experimental data.The newly developed large L/D multi-region PAFRAG model has been shown to accurately reproduce available experimental fragmentation data.

Preparation and Properties of PBXs Based on FOX-7 in Controlled Fragmentation Warhead Application

Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1,1-diamino-2,2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of polyurethane(PU)based on glycidyl azide polymer(GAP) and hydroxyl-terminated polybutadiene(HTPB) as an energetic and inert polymeric binder respectively.Casting technique was used for the preparation of different PBX formulations based on FOX-7/RDX and PU(GAP/HTPB)with 14% binder.The sensitivity to different initial impulses and performance characteristics of the explosive and lethal zone of the tested controlled fragmentation warhead by the fragmentation warhead assessment test(arena test)were studied,in which the arena test was carried out with a controlled fragmentation warhead made from Ck45 steel,with dimensions(100 mm length,30 mm outer diameter and 3 mm thickness).Results show that PBXGF4 has lower sensitivity to impact and heat than those of PBXGR4 by 188.4% and 3.2% respectively.Its friction sensitivity is the same as that of PBXGR4.It has better performance,in which detonation velocity increases by 2.1% and brisance increases by 0.5% when compared with those of PBXGR4.It was concluded that PBXGF4 which based on FOX-7 bonded with PU/GAP matrix has good characteristics as PBX,specially in the sensitivity to impact and can be applied for replacing PBXs based on RDX in the advanced PBXs for low sensitive fragmentation warheads.

Quantification of projection angle in fragment generator warhead

Tactical Ballistic Missile(TBM) class target neutralization by the fragment spray of a Fragment Generator Warhead(FGW) calls for quantification of fragment projection angle scatter to finalize the end game engagement logic.For conventional axi-symmetric warhead,dispersion is assumed to be normal with a standard deviation of 3~O.However,such information is not available in case of FGW.Hence,a set of experiments are conducted to determine the dispersion of fragments.The experiments are conducted with a specific configuration of FGW in an identical arena to quantify the scatter and then verified its applicability to other configurations having a range of L/D and C/M ratios,and contoured fragmenting discs.From the experimental study,it is concluded that the scatter in projection angle follows normal distribution with a standard deviation of 0.75° at Chi-square significance level of 0.01(x_(0.99)~2).

Simulation of natural fragmentation of rings cut from warheads

Natural fragmentation of warheads that detonates causes the casing of the warhead to split into various sized fragments through shear or radial fractures depending on the toughness,density,and grain size of the material.The best known formula for the prediction of the size distribution is the Mott formulae,which is further examined by Grady and Kipp by investigating more carefully the statistical most random way of portioning a given area into a number of entities.We examine the fragmentation behavior of radially expanding steel rings cut from a 25 mm warhead by using an in house smooth particle hydrodynamic(SPH) simulation code called REGULUS.Experimental results were compared with numerical results applying varying particle size and stochastic fracture strain.The numerically obtained number of fragments was consistent with experimental results.Increasing expansion velocity of the rings increases the number of fragments.Statistical variation of the material parameters influences the fragment characteristics,especially for low expansion velocities.A least square regression fit to the cumulative number of fragments by applying a generalized Mott distribution shows that the shape parameter is around 4 for the rings,which is in contrast to the Mott distribution with a shape parameter of 1/2.For initially polar distributed particles,we see signs of a bimodal cumulative fragment distribution.Adding statistical variation in material parameters of the fracture model causes the velocity numerical solutions to become less sensitive to changes in resolution for Cartesian distributed particles.

Simplified Approach to Velocities of Axial Forward Projection Fragments from the End of a Warhead

A warhead with axial forward projection fragments is one of the most important forms of aimable warheads. For such warheads the axial forward projection fragments are placed at the end of the explosive charge and form a fragment beam with high fragment density and high speed by the blast, which will obviously increase the damage to the targets. Experimental data showed that the velocities of the forward projection fragments on the convex end of a warhead which was initiated at the opposite end do not match that predicted by the Gurney equation for cylindrical warheads. A new approach for addressing the velocities of fragments of this kind of warhead is proposed. Two limiting conditions are defined, i.e. for fragment on the circumference of a cylindrical charge and fragments on the end of cylindrical charge, respectively.

Split warhead simultaneous impact

A projectile system is proposed to improve efficiency and effectiveness of damage done by anti-tank weapon system on its target by designing a ballistic projectile that can split into multiple warheads and engage a target at the same time. This idea has been developed in interest of saving time consumed from the process of reloading and additional number of rounds wasted on target during an attack. The proposed system is achieved in three steps: Firstly, a mathematical model is prepared using the basic equations of motion. Second, An Ejection Mechanism of proposed warhead is explained with the help of schematics. Third, a part of numerical simulation which is done using the MATLAB software. The final result shows various ranges and times when split can be effectively achieved. With the new system,impact points are increased and hence it has a better probability of hitting a target.

Simulation design of fuze warhead system of air defense missile at very low altitude

A novel simulation method for fuze warhead system (FWS) at very low altitude flight is proposed to solve adaptability issues of the traditional one in the naval battle. Firstly, a simulation system framework is presented. Then the detailed implementation of a novel general fuze model, a novel sea echo model and a novel warhead dynamic effectiveness power field algorithm including the simulation system are presented. Finally, simulation results show good performance of the proposed method. The proposed method can simulate the echo signal when the complex fuze antennas detect target and the sea at the same time, and can truly reflect the target positions hit by the warhead fragments. The proposed method can solve the existing problems in the FWS simulation system.

应用差分进化-神经网络模型的杀爆弹瞄准点分配方法

为在不增加计算时耗的前提下提升多枚杀爆弹对面目标打击毁伤效能,建立融入动爆威力计算的多瞄准点规划方法.对面目标采用结构化网格划分方法实现多枚杀爆弹对目标毁伤区域的精确计算,并进行计算结果验证,基于多次计算结果采用神经网络方法建立单枚弹药对面目标毁伤区域的计算代理模型,在同样计算条件下,比非代理模型计算时间缩短1000倍;据此,通过差分进化算法实现多枚杀爆弹对面目标打击瞄准点及末端弹道参数的规划.通过实例对比分析表明:该瞄准点规划方法形成的打击方案比传统以毁伤半径为输入的方法毁伤效果大幅提升,最低提升25.5%,且单次规划时间不超过3 s,解决了瞄准点规划中毁伤效能模型复杂度与计算耗时之间的矛盾.

战斗部破片光电测速系统设计

战斗部破片的飞行速度是体现其性能指标的重要参数;针对目前在战斗部破片速度参数测试中存在对测试环境要求高,测试面积小,设备结构易被破片误击而损坏,成本昂贵等问题,设计了非接触式战斗部破片光电测速系统,包含原向反射膜、反射式光电探测装置、光电转换电路、信号处理电路及测速装置;阐述了系统结构组成和测速原理,通过反射式光电探测装置与光电转换电路,将得到的光信号转换为电信号,利用集成信号处理电路对电信号滤波放大,比较整形处理,由FPGA,STM32及其他外设组成的测速装置自动处理数据输出并显示战斗部破片的飞行速度结果;实验结果表明:该系统能够可靠,稳定地完成战斗部破片速度的测量任务;与传统测速系统相比,具有不受限于环境,测试区域大,易维护,低成本,操作简单等优势。

线列式破片战斗部对导弹目标毁伤效能分析

为探究线列式破片战斗部对导弹目标的毁伤效能,通过数值计算方法,研究了线列式战斗部破片排布方式及炸药材料类型对破片威力场分布特性的影响规律,分析了不同着靶姿态对破片侵彻导弹舱段等效靶板的影响,得到破片侵彻不同厚度靶板的极限速度;对导弹目标整体及各舱段毁伤程度进行定义,并对不同弹目交会条件下线列式战斗部对导弹目标的毁伤效能进行了研究。结果表明:弹目交会时,战斗部俯仰角的变化主要影响破片场命中导弹时的轴向位置;战斗部偏航角的变化会影响破片聚焦带的方向;弹目距离主要影响导弹目标附近的破片密度。

锥形头战斗部动态爆炸破片载荷特性分析

为探究锥形头战斗部在不同运动速度下破片的载荷特性,采用SPH仿真方法模拟锥形头战斗部壳体膨胀形成破片的过程和破片载荷特性,并与静爆试验结果对比,验证数值仿真模拟的准确性,研究锥形头战斗部不同运动速度对破片载荷特性的影响。结果表明,战斗部首端部由于截锥面的存在,提高了端部的破片分布区域,增加了战斗部破片的打击范围;战斗部壳体形成的破片初速度沿战斗部轴向呈现明显的阶梯形分布,基于此破片速度可分为四个区域:截锥壳体部、圆柱壳体中前部、圆柱壳体中部和圆柱壳体中后部;动爆条件下,随着战斗部运动速度的增加,尾端部壳体形成的破片初速度呈现出先减小后增大的不规则“V”形,破片飞散角受战斗部运动速度的影响较小,破片飞散方位角沿着战斗部运动方向移动。

基于Unity3D的杀爆战斗部对相控阵雷达毁伤评估可视化设计与实现

为提高战斗部的设计迭代与毁伤评估效率,引入典型相控阵雷达的目标易损性模型,构建了杀爆战斗部威力场计算模型、弹目交会模型以及典型相控阵雷达的毁伤概率计算模型,并基于Unity3D引擎搭建了杀爆战斗部对相控阵雷达的毁伤评估系统。系统能够实现杀爆战斗部的参数化设计、威力场计算以及杀爆战斗部对典型相控阵雷达毁伤概率的计算及毁伤效果的可视化。针对某杀爆战斗部进行试算,系统直观显示了战斗部威力以及对典型相控阵雷达的毁伤效果,设置战斗部落速为100 m/s, CEP为1 m,计算得到了落高为4~7 m,落角在30°~90°的弹目交会条件下战斗部对典型相控阵雷达的毁伤概率。所设计的系统功能完备,可以为杀爆战斗部方案设计及对相控阵雷达的毁伤评估提供支撑,系统开发的思路可以为战斗部威力计算及毁伤评估软件的设计提供参考。

轴向预制破片战斗部飞散特性数值模拟

为分析轴向预制破片战斗部的飞散特性,利用LS-DYNA软件模拟轴向预制破片战斗部中心单点起爆方式和多点起爆方式下破片速度及飞散角特征参数并进行试验验证,得到了中心单点起爆和多点起爆方式对破片速度及飞散角特征参数的影响规律。研究表明:相较于中心单点起爆方式,多点起爆方式可以提升轴向预制破片速度,且随着起爆点数增加,破片速度先增加后趋于稳定,起爆点数从2点增加到6点,破片初速提升了21.1%,当起爆点数继续增加,则破片速度不再增益,而起爆点数对飞散角影响较小。

线性聚焦式杀伤战斗部破片飞散特性及规律

线性聚焦式杀伤战斗部通过装药母线设计和破片排布设计,使破片等速线性飞散聚焦,可对目标造成结构性切割毁伤。为研究线性聚焦式杀伤战斗部结构参数对破片飞散聚焦行为的影响规律,采用流固耦合算法开展线性聚焦战斗部破片聚焦过程数值模拟。数值模拟结果揭示线性聚焦式杀伤战斗部破片线性聚焦机理,典型线性聚焦过程包括破片驱动阶段、破片聚焦阶段、聚焦完成阶段和破片发散阶段。通过数值模拟获得战斗部尺寸、破片排布、破片质量以及交汇速度对破片飞散特性和穿孔分布的影响规律。研究结果表明:随装药长度从0.3 m增加至0.5 m,破片速度标准差从125 m/s增加至147 m/s,聚焦完成时间分别为490μs、585μs和590μs,穿孔分布宽度从135 mm增加至234 mm;随破片排布从15列增加至18列,破片速度标准差从117 m/s增加至125 m/s,聚焦完成时间分别为470μs和490μs,穿孔分布宽度分别为235 mm和135 mm;随破片质量从4.08 g增加至9.21 g,破片速度标准差从137 m/s降低至125 m/s,聚焦完成时间分别为380μs和490μs,穿孔分布宽度分别为156 mm和135 mm;随交汇速度从0 m/s增加至1 000 m/s,聚焦完成时间分别为490μs、480μs和469μs,穿孔分布宽度从135 mm增加至138 mm,破片密度从640枚/m^(2)降低至630枚/m^(2),降幅约2%。研究结果能为聚焦战斗部设计提供支撑。

起爆方式对椭圆截面战斗部破片速度分布的影响

为研究椭圆截面战斗部在不同起爆方式下破片速度的分布特性,建立了5种具有不同短长轴比的椭圆截面战斗部数值模拟模型。开展了端面中心单点、短(长)轴中点双点、短长轴中点4点以及端面面起爆5种起爆方式数值模拟研究,分析了不同起爆方式下椭圆截面战斗部破片的速度分布及能量输出特性。研究结果表明:在径向方向,战斗部在不同起爆方式下破片最大径向速度变化规律基本一致,均呈现由长轴至短轴方向对数增长,且随着短长轴比的增大,短长轴方向破片速度差值逐渐减小。然而,不同起爆方式下椭圆截面战斗部最大速度截面上破片速度平均值存在明显差异,具体表现为端面起爆时的破片径向平均速度最高,单点起爆最低,且随着起爆点数量的增加,最大速度截面上的破片的整体平均速度逐渐增大。在轴向方向,受端面稀疏波的影响,不同方位角最大破片速度均出现在靠近非起爆端1/4处,且起爆点在短轴轴线上相较于在长轴轴线上会提高靠近起爆端长轴方向的破片速度,但短轴方向沿轴向的破片速度分布无明显差异。此外,不同起爆方式对椭圆截面装药爆炸能量输出特性无明显影响,其中27%的装药能量转化为壳体动能,有50%的能量被壳体断裂变形以及空气冲击波消耗。

破片战斗部打击轻型装甲车辆易损性快速计算

为了能够对战斗部打击下的目标易损性进行快速计算与分析,基于C++语言和Qt编程框架编制了目标易损性快速计算软件。针对破片战斗部打击轻型装甲车辆目标建立了相应的计算模型,计算得到了破片战斗部单次打击下的轻型装甲车辆目标毁伤情况,进行了爆点模式下的易损性分析。结果表明:所开发的快速计算软件计算物理毁伤的可靠性较高,可大大节约计算资源,缩短计算耗时;给定工况下打击目标车辆左右两侧时相对更易造成车辆更高等级毁伤程度。

基于激光近炸引信最佳起爆延时的目标毁伤建模

针对传统的目标毁伤计算时未详细考虑激光近炸引信的起爆延时,从而导致对目标毁伤效能的计算与实际存在一定差距的问题,提出激光近炸引信弹目交会条件下基于最佳起爆延时的目标毁伤建模方法。推导了使引信处于最佳近炸位置的弹目交会近炸最佳起爆延时函数;在确定最佳起爆延时的基础上,结合对破片群飞散特性的分析,建立了激光近炸引信对目标的毁伤概率计算模型。仿真分析了不同因素对近炸引信最佳起爆延时的影响。通过模拟近炸引信对目标的毁伤实验结果可以看出激光近炸引信的起爆延时影响着最终的目标毁伤概率,这将为提高激光近炸引信的毁伤效能提供参考。