Characteristics and measurement of supersonic projectile shock waves by a 32-microphone ring array

This paper discusses about the characteristics of supersonic projectile shock wave in muzzle region during firing of high explosive anti-tank (HEAT) and high explosive (HE) projectiles. HEAT projectiles are fired horizontally at a muzzle velocity of Mach 3.5 from a medium caliber tank gun equipped with a newly designed multi-perforated muzzle brake, whereas HE projectiles are fired at elevation angles at a muzzle velocity of Mach 2 from a large caliber howitzer equipped with a newly designed double-baffle muzzle brake. In the near field, pressure signatures of the N-wave generated from projectiles are measured by 32-microphone ring array wrapped by cotton sheath. Records measured by the microphone array are used to demonstrate several key characteristics of the shock wave of supersonic projectile. All measurements made in this study can be a significant reference for developing guns, tanks, or the chassis of fighting vehicles.     

双管火炮异步发射时膛口流场分析

采用计算流体力学方法结合动网格技术建立了双管火炮异步发射时膛口流场的二维数值模拟模型,正确描述了双管不同步发射时炮口流场的激波系结构的形成﹑发展与相互干扰的过程。模拟结果得出双管不同步发射时对弹丸飞出膛口后的飞行姿态影响较大,从而弹丸偏移速度会影响双管火炮的射击精度。     

恒定动能打击变初速发射原理

为实现新型防暴枪的恒定动能打击,提出了在身管内增加刚性凸起增大弹丸挤进阻力的变初速原理.建立了刚性凸起的变初速计算模型,利用LS-DYNA软件探索了凸出量变化对弹丸初速的影响规律,并通过调节刚性凸起的凸出量,拟定了在12 J/cm2,16 J/cm2,22 J/cm2的三种恒定打击动能条件下初速调节设计方案.     

喷管高效膛口制退器对机枪射击性能的影响

在半开腔膛口制退器基础上进行改进,提出喷管高效膛口制退器的概念,在半开腔膛口制退器两侧引出可水平向后的拉瓦尔喷管,利用火药燃气通过喷管气流的反推作用达到减后坐效果,通过编程进行内弹道计算。运用刚柔耦合动力学理论,对安装喷管高效膛口制退器车载转管机枪系统建立动力学模型,进行动力学仿真计算。计算结果表明,安装喷管高效膛口制退器后,机枪后坐力、后坐位移、膛口角位移和弹丸出膛口时角位移均得到减小,提高了机枪的射击性能。     

Investigations on the exterior flow field and the efficiency of the muzzle brake

Numerical investigations of the projectile launch process with different muzzle brakes have been performed in a nearly realistic situation. Both two- and three-dimensional unsteady Euler equations are used as the governing equations. The hybrid Roe type scheme is employed to solve the flow fields with strong blast waves, and structured dynamic mesh technique is used for describing projectile motion. Based on the numerical solutions, the flow structures of a bare muzzle, the three-way and multi-hole muzzle brakes have been described, respectively, which agree well with our previous experimental shadowgraphs. Moreover, the efficiency of the three-way muzzle brake is calculated, which is also comparable to the corresponding experimental value. Our results showed that the numerical simulation can be a useful and efficient way for the design of new muzzle brakes.     

Friction and wear at high sliding speeds

The wear of rotating band materials and projectile steel at very high sliding speeds is of great importance in the development of improved cannon. This is especially true for large caliber, high muzzle velocity weapons where excess wear on the bore near the muzzle can limit their useful lives. An extensive experimental study was supported by the U. S. Army from about 1946 to 1956 and a great deal of data was collected at sliding speeds up to 1800 ft s^?1 using a sophisticated high speed pin-on-disk test device. These data indicate that the mechanism of wear at high sliding speeds is surface melting followed by subsequent removal of a portion of the melted surface layer. This means that a rotating band material must be high melting if it is to have good wear resistance at high sliding speeds. It does not mean, however, that compatibility, crystal structure, hardness etc. have no effect because, for a short distance down the bore, the surface of the rotating bands is not completely melted.     

转管机枪外弹道特性分析与射表计算软件研究

对某转管武器外弹道特性以及身管旋转对弹道的影响进行了理论分析,并对影响因素加以修正.以弹丸外弹道微分方程为基础建立了转管武器修正的数学模型,对弹丸出膛时的运动速度进行了分析,考虑枪管坐标和地面坐标间的变换,提出了不同转速下身管旋转修正量计算的方法,为转管武器射表编制提供了技术依据.利用MATLAB软件对弹道修正的数学模型进行计算,并编译成为可执行文件,能够直接输出编制射袁所需数据.     

易熔合金引信弹道安全的气动热力学建模仿真

为使易熔合金引信可靠延期解除保险以保证弹道安全,需要根据弹丸速度确定在安全时间和距离内引信易熔合金的熔点。以瑞士厄利空2ZLa/353式35 mm 双管自行高射炮爆破燃烧榴弹 KZVD 引信为例,从工程的角度出发,简化了外弹道,在初始弹速为1175 m/s 和误差范围为±15 m/s 的条件下,采用气动加热理论对榴弹外弹道起始阶段弹头驻点的温度进行了理论建模计算和仿真验证,通过分析相应弹速下的弹头驻点温度确定出满足安全距离要求的易熔合金熔点温度。仿真结果表明,理论计算与仿真试验确定出1160-1190 m/s 初始弹速范围内的易熔合金熔点温度的结果一致,因此可以利用该热力学模型并根据弹道安全要求来设计相应熔点的易熔合金引信,所用方法可以为高速飞行弹体的热力学研究提供参考。     

75 m/s simulation and experiment of two-stage reluctance coilgun

Magnetic launchers are divided into three main techniques, with one of them being the reluctance coilgun. The projectile in this method is rather simple and the obtained velocity is relatively low, which is its main disadvantage. Also, theoretical simulations for high velocity usually predict much higher velocities than that of the experiments. The aim of this work is to demonstrate an accurate simulation of a two-stage coilgun and show experimental validation of high launching velocity. A two-stage coilgun was designed and optimized by numerical simulations. Accordingly, it was implemented and tested experimentally. As an outcome, the highest reported velocity of 75 m/s was obtained both in the simulation and experiment. This outcome contributes to the understanding that adding stages can increase the launching velocity by carefull implementation of the initial position of the projectile, together with proper timing of the second stage. It is concluded that with this approach a multi-stage coilgun can reach even higher velocity.

     

射弹打击下油箱燃油泄露研究

为了确定射弹击穿飞机油箱后附近干舱的引燃和燃烧,需要对燃油通过穿孔泄露过程中燃油的泄露质量及雾化液滴的数目和尺寸进行定量计算分析。该文建立了用于模拟高速射弹击穿油箱后燃油泄露过程的解析模型,给出了燃油初始泄露速度的定量计算方法,利用最大熵原理和质量守恒定律,推出了弹丸撞击条件下泄露燃油液滴尺寸数目分布函数和索特尔平均直径SMD的计算公式,并采用Harmon液滴索特尔平均直径经验计算公式定量计算泄露燃油的平均直径。研究结果表明燃油的初始泄露速度随射弹速度的增加而呈线性增加,液滴索特尔平均直径随穿孔直径的增加而增加,随射弹速度的增加而呈线性减小。研究结果为下一步进行油箱附近干舱引燃和燃烧提供理论基础。     

Finite element modeling of transverse impact on a ballistic fabric

A 3D finite element analysis model is created using LS-DYNA to simulate the transverse impact of a rigid right circular cylinder onto a square patch of plain-woven Kevlar fabric. The fabric is modeled to yarn level resolution and relative motion between yarns is allowed. A frictional contact is defined between yarns and between the fabric and the projectile. Three different boundary conditions are applied on the fabric: four edges left free; two opposite edges clamped; four edges clamped. Results from the modeling effort show that during initial stage of the impact, the projectile velocity drops very quickly. There exists an abrupt momentum transfer from the projectile to the local fabric at the impact zone. When the impact velocity is low, the fabric boundary condition plays an important role at later stages of the impact. It significantly affects the fabric deformation, stress distribution, energy absorption and failure modes. When the impact velocity is high enough to cause the yarns to break instantaneously, the fabric fails along the periphery of the impact zone and the fabric boundary condition does not take any effects.     

平头弹撞击角度对2A12-T4铝合金板失效特性影响的数值模拟

利用有限元软件ABAQUS建立模拟模型,开展38CrSi钢弹体撞击2A12-T4铝合金板数值模拟研究,分析撞击过程中弹体撞击角度对弹道姿态及靶体失效特性的影响。基于数值仿真和实验结果,分析靶体的失效特性,确立不同撞击条件下靶体主要失效模式的转变规律,以及由此对靶体抗撞击性能的影响。研究结果表明：弹体的弹道极限速度随其撞击角度的增大先减小后增大,弹道极限速度在撞击角度约为15°时达到最小值;弹体撞击角度对靶体失效模式存在很大影响,随着弹体撞击角度的增大,靶体主要失效模式由剪切破坏逐渐过渡到撕裂破坏,靶体的撕裂程度不断加剧;弹体初始撞击角度和速度对其在撞击过程中的弹道姿态存在影响,在弹道极限速度附近表现尤为显著。     

基于小波分析的单个线圈靶速度测量

小波变换具有空间局部化性质，因此可利用小波变换的模极大值点检测动态测量信号的突变点。提出了用单个线圈靶测量水下弹丸初速的原理及方法，由实弹射击实验获得的线圈靶信号，利用小波变换分析了弹丸穿越线圈靶时产生的电动势，建立了弹丸穿越线圈靶时的时间间隔t及运动弹丸速度的计算方法，并与双线圈靶弹丸初速测试结果进行了比对，证明了该方法的可行性。     

Numerical analysis of interior ballistics through eulerian-lagrangian approach

A numerical code for interior ballistics using the Eulerian-Lagrangian approach was developed to analyze polydisperse systems. The internal flows in a gun barrel and the compressibility effects were calculated using the semi-implicit method for pressure-linked equations algorithm. Ghost cell extrapolation was used for the moving boundary with projectile movement. The numerical scheme and moving boundary method were verified through the free piston motion problem. The developed code, including the combustion of the propellant, was compared with simulations of 40 mm gun firings. The results of numerical analysis agree with the simulation results, confirming the reliability of the developed code. Comparative studies were conducted with the results of the interior Ballistics of high-velocity guns code (version 2) according to porosity and propellant size. The numerical analysis of the combustion and movement of individual propellants provides deeper insight into the mechanism of gun firing and the significant factors that influence muzzle velocity.     

电磁发射中初速测量的初步分析

从电磁发射的基本特点出发,对各种典型的区截测速方法进行了分析和对比,并结合实际应用中的三区截靶测速法,给出了基于匀变速假设的炮口初速外推公式和精度分析;结合现代科学技术和先进测试技术的发展,给出了对应于当前超高速发射中的电磁轨道炮炮口初速测量的一些讨论和建议。     

A theoretical study for the design of a new ballistic range

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.     

小型化弹丸速度测试系统

提出了一种基于光幕测速和单片机数据处理的小型化的弹丸速度测试系统。采用半导体激光器、光电探测器、原向反射屏形成大面积光幕测试区,当弹丸穿越光幕时,光通量的变化被光电探测器转变为电信号,经过比较电路后送入单片机进行数据处理,并由LED进行速度显示。文中对测试原理和测试系统的光学设计单元、信号处理单元及数据采集、显示单元进行了介绍,并对该系统进行了壬7．62mm弹丸速度测试,给出了测试数据。试验表明,该测速系统具有灵敏度高、体积小、成本低、使用方便、灵活、工作可靠等优点。     

弹丸炮口初速的智能测量

本文介绍一种弹丸炮口初速的智能测量方法,给出了测量原理、硬件构成、软件设计和误差分析。     

大靶面激光光幕靶研究

针对大靶面、高精度弹丸速度测量的要求,提出一种新型激光光幕靶弹丸速度测量系统。该系统采用大功率90°扇形线状激光器做为光源,两列高灵敏度光电二极管阵列作为接收装置,当弹丸穿越激光光幕面时,遮挡了部分投射在光电二极管上的光线,光电二极管产生微弱电信号,经放大、整形后输出一个脉冲信号,触发计时仪开始或停止计时。两台同样的装置配合测时仪,便可组成激光光幕靶测速系统。经实弹实验证明,该系统具有高灵敏度和高精度的特点。     

抛物线弹道弹丸飞行参数测量模型与 精度分析

现有匀速直线弹道六光幕阵列测量模型无法满足终点抛物线弹道弹丸着靶坐标与飞行速度的测量需求。针对终点弹道测试试验中抛物线弹道的实际,提出一种变速抛物线弹道弹丸飞行参数的测量方法,建立六光幕阵列通用测量模型。综合考虑重力和空气阻力对弹丸运动轨迹的影响,建立弹丸的空间运动方程,结合光幕阵列平面方程和测量得到的弹丸穿过光幕阵列时刻序列,计算出弹丸在预定位置的着靶坐标和飞行速度矢量。对研究的抛物线弹道测量模型与现有的匀速直线弹道模型进行了比较分析,仿真计算了在不同靶距与不同飞行速度情况下2种模型测量数据的差值。对研究的测量算法进行了精度分析。采用六光幕阵列天幕靶和木板靶进行7.62 mm步枪弹的着靶坐标比对试验,结果表明在探测靶面内,着靶坐标测量误差不大于3.5 mm。建立的测量模型拓宽了六光幕阵列在终点弹道的测试领域的应用。