装药长径比对爆炸成型弹丸形成影响的数值模拟

采用LS-DYNA软件对带有外壳的爆炸成型弹丸(EFP)形成过程进行数值模拟。研究了装药长径比对EFP成形的影响规律,并对比分析了不同模型的计算结果差异,得出形成理想EFP外形和装药长径比之间的关系。研究结果可应用于EFP战斗部结构设计。     

复合战斗部结构参数影响分析

应用AUTODYN仿真软件,对一种复合战斗部方案的EFP成型性能进行了分析,结果表明,相对于传统布局方案,在破片方案更改后改变了药型罩的成型过程,导致EFP形状变差从而降低了毁伤性能。通过对结构参数影响进行分析,提出了优化方案,解决了破片方案调整后EFP的成型问题。     

顺序凝固工艺对大长径比装药缩松的影响研究

针对顺序凝固工艺对大长径比装药易形成缩松的问题,分别以受控生长期、自由凝固期的相界面形貌特征参数为中间量,建立了工艺参数到缩松体积的4层关联路径,选择TNT/RDX(33.8/65)炸药、长径比5∶1的装药模具,进行了正交仿真、极差分析以及Spearman相关系数计算,结果表明,降低水温、入水速度以及提高环境换热系数可提高受控生长期的相界面高度、开口角,从而降低自由凝固期的凝固区间最大厚度,最终减少缩松体积;工艺参数影响强弱为：水温、入水速度、环境换热系数;降低入水速度、提高环境换热系数可减少对低水温的依赖。本研究探明了顺序凝固工艺参数对大长径比装药相界面演化及缩松的影响机理,可为相关工艺设计提供理论支撑。     

条形装药在岩体中爆炸成腔过程的数值分析

利用LS-DYNA非线性有限元程序,对不同药量等级的条形装药,进行了无 限域岩体介质中的爆炸成腔数值模拟计算,得到了爆炸成腔过程的基本图像及爆腔形成的 位移时程曲线,通过对爆腔半径的数据分析对比,得到条形装药的长径比值k与爆腔半径和 装药半径之比值ra/R0呈线性关系、条形装药比集团装药具更强爆扩能力的结论。     

强爆轰驱动超高速碎片发射装置设计因素分析

为了得到发射装置设计因素和超高速碎片性能间的关系,考虑了药型罩的材料、炸药种类、装药长径比、药型罩的锥角、药型罩的厚度、药型罩顶部靠近装药侧的曲率半径等设计因素,采用AUTODYNTM,结合正交试验,对超高速碎片的发射过程进行数值模拟。结果表明,3种发射装置结构分别可以提供质量为1. 533 g的紫铜碎片、速度为11. 649 km/s的铝碎片、动能为85. 6 k J的铝碎片; 2种发射装置结构均可以提供质量大于1 g、速度高于11 km/s的密实结构圆柱状碎片。验证了仿真方法的可信性,对影响碎片性能的设计因素进行了分析、排序,并得到了这些设计因素与碎片质量、速度、动能的关系。     

多爆炸成型弹丸性能参数灰关联分析

为了获得各参数对多爆炸成型弹丸毁伤性能的影响程度,以EFP速度和MEFP发散角为参考序列,以药型罩和装药参数为比较序列,运用灰关联理论对影响MEFP毁伤性能的参数进行了灰关联分析。在此基础上,应用灰关联分析结果完成了MEFP战斗部优化设计。结果表明:在较少样本空间前提下,采用灰关联理论可以分析获得影响多爆炸成型弹丸毁伤性能的各因素主次关系,而且经过优化后的MEFP战斗部,大大地提高了EFP的集聚性和毁伤性能。     

激光平行光幕的爆炸成型弹丸形貌测试技术

针对目前爆炸成型弹丸形貌测试普遍使用的脉冲X光摄影法成本昂贵、结构复杂、测试困难的缺点,提出了激光平行光幕形貌测试系统。该系统中,由启动网靶、停止网靶和计时仪组成的区截测速装置测试EFP的速度,激光平行光幕和示波器测试EFP弹丸通过光幕时直径随时间的变化过程。然后将上述测试结果用Matlab软件进行仿真,得出EFP弹丸的形貌。测试与仿真表明:激光平行光幕形貌测试系统可以测试EFP弹丸的速度与形貌,而且成本低廉、可靠性高,可以在大威力战斗部试验中使用。     

近距爆炸装药形状对板架结构的损伤规律研究

为了研究近距爆炸时柱形装药长径比对板架结构变形损伤的影响规律,以某典型缩比板架结构作为研究对象,采用经实验验证的有限元模型,分析了5种不同长径比装药爆炸对板架变形损伤的影响,并对比分析了药柱与板架夹角为0°和90°两种情形的区别。研究结果表明：随着装药长径比的增大,夹角为90°情况下冲击波反射超压和冲量逐渐减小,夹角0°情况下冲击波反射超压和冲量逐渐增大,高压区逐渐从装药轴线方向到径向方向移动;板架的残余位移与装药质量近似满足线性关系,装药长径比增大时,夹角为90°时靶板的残余位移逐渐减小,夹角为0°时位移逐渐增大;基于板架中心点最大残余位移D,拟合得到了药柱轴线与靶板表面夹角为90°和0°时的轴向等效形状因子β₁和径向等效因子β₂,当比例距离在0.4～0.7 m/kg^1/3范围内时,预测误差小于15%,能较好的预估不同装药长径比下板架的中心点残余位移,获取结构的损伤水平。     

EFP速度测量的高速摄影试验研究

EFP的速度和形状是其侵彻和稳定飞行的重要参量,为了高效准确地测量EFP的速度并观测其形状,设计了高速摄像机与网靶相结合的观测方案,运用PCC软件进行后处理,可快速测量出EFP的速度。用高速摄像机中的两点法测速得到的结果与天幕靶测速结果吻合较好,证明此种方法操作简单,测试精度高,且能准确观测到EFP的形貌。     

加质源项技术在装药燃烧中的仿真研究北大核心

在弹射器燃烧室装药燃烧升压非稳态过程中,燃气发生器燃烧室内流场的压强数据在很大程度上影响着导弹弹射过程的安全与稳定。针对管状装药燃气发生器的特殊装药结构形式,运用Fluent软件建立了二维轴对称非定常计算模型,采用加质源项技术,通过UDF编译来实现燃气的质量、动量、能量向燃烧室的注入。通过设置不同的观测点,对燃烧室装药不同部位的压力和温度变化情况进行监测,计算得到了在装药加质燃烧升压过程中装药表面各点的压强和温度分布,随后分析了燃烧室喷管口打开后燃气流场的流动情况,得到了燃烧室内弹道压力变化曲线。所得结论可为燃气发生器的抗热冲击设计和喷管的结构设计提供参考。     

复合战斗部爆炸成型弹丸结构参数影响分析

应用AUTODYN仿真软件,对一种复合战斗部方案的爆炸成型弹丸成型性能进行了分析,结果表明,相对于传统布局方案,破片方案更改后改变了药型罩的成型过程,导致爆炸成型弹丸形状变差从而降低了毁伤性能。通过对结构参数影响进行分析,提出了优化方案,解决了破片方案调整后爆炸成型弹丸的成型问题。     

A study on the surface overpressure distribution and formation of a double curvature liner under a two-point initiation

The formation mechanism of an EFP(explosively formed projectile) using a double curvature liner under the overpressure effect generated by a regular oblique reflection was investigated in this paper.Based on the detonation wave propagation theory,the change of the incident angle of the detonation wave collision at different positions and the distribution area of the overpressure on the surface of the liner were calculated.Three-dimensional numerical simulations of the formation process of the EFP with tail as well as the ability to penetrate 45# steel were performed using LS-DYNA software,and the EFP ve-locity,the penetration ability,and the forming were assessed via experiments and x-ray photographs.The experimental results coincides with those of the simulations.Results indicate that the collision of the detonation wave was controlled to be a regular oblique reflection acting on the liner by setting the di-mensions of the unit charge and maintaining the pressure at the collision point region at more than 2.4 times the CJ detonation when the incident angle approached the critical angle.The distance from the liner midline to the boundary of the area within which the pressure ratio of the regular oblique reflection pressure to the CJ detonation pressure was greater than 2.5,2,and 1.5was approximately 0.66 mm,1.32 mm,and 3.3 mm,respectively.It is noted that pressure gradient caused the liner to turn inside out in the middle to form the head of the EFP and close the two tails of the EFP at approximately 120μs.The penetration depth of the EFP into a 45# steel target exceeded 30 mm,and there was radial expansion between the head and tail of the EFE increasing the penetration resistance of the EFP.Therefore,the structural size of the unit charge and the liner can be further optimized to reduce resistance to increase the penetration ability of the EFP.     

爆炸成型弹丸侵彻靶板的数值仿真

基于LS-DYNA的动力学分析通用有限元程序,对爆炸成型弹丸形成和侵彻靶板过程进行了数值仿真。建立了数值仿真模型,利用数值模拟技术实现了弹丸的形成以及不同药型罩结构对爆炸成型弹丸形成的影响,实现了侵彻过程中弹丸的变形与靶板的破坏状况可视化,同时对仿真结果进行了分析。通过对爆炸成型弹丸侵彻靶板的数值仿真,为开展爆炸成型弹丸毁伤机理研究奠定了良好的基础。     

Formation and impact-induced separation of tandem EFPs

The formation and separation behaviors of tandem EFPs are studied by the combination of experiments and simulations. The results show that different formation and separation processes can be obtained by adjusting the double-layer liners, and simulations agree with experiments well. Then, the interaction process between the two liners is discussed in details, and the formation and separation mechanism are revealed. It can be found that there are four phases in the formation and separation processes, including impact phase, propulsion phase, slide phase and free flight phase. During the impact phase, the velocities of two liners rise in turns with kinetic energy exchange. In the propulsion phase, the axial impact becomes insignificant, but the radial interaction between two liners influences the appearance of tandem EFPs. Meanwhile, it should be mentioned that the inner surface of foregoing EFP remains to be in contact with the outer surface of following EFP in the propulsion phase, and the following one would continue to push the foregoing one for about 10μ to 20 μs, causing the velocities of following and foregoing EFPs gradually decreasing and increasing respectively. In the slide phase, an obvious relative movement occurs between the two EFPs, and there would be barely kinetic energy exchange. Then, the two EFPs separate gradually and get into the phase of free flight. Generally, if the outer and inner liners have the same thickness, the outer copper-inner copper liners form two long EFPs, the outer copper-inner steel liners become a foregoing short steel EFP and a following long copper EFP, and the outer steel-inner copper liners produce a foregoing long copper EFP and a following conical steel EFP. In addition, thickness match also has an important impact on formation appearance and separation process for both outer copper-inner copper liners and outer steel-inner copper liners. With the thickness ratio of outer liner to inner liner decreasing, the length and length-diameter ratio of both foregoing and following EFPs increase gradually.     

Investigation on the spatial distribution characteristics of behind-armor debris formed by the perforation of EFP through steel target

The behind-armor debris (BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components. Aiming at investigating the BAD caused by EFP, flash X-ray radiography combined with an experimental witness plate test method was used, and the FEM-SPH adaptive conversion algorithm in LS-DYNA software was employed to model the perforation process. The simulation results of the debris cloud shape and number of debris were in good agreement with the flash X-ray radiographs and perforated holes on the witness plate, respectively. Three-dimensional numerical simulations of EFP's penetration under various impact conditions were conducted. The results show that, an ellipsoidal debris cloud, with the major-to-minor axis radio (a/b) smaller than that caused by shaped charge jets, was formed behind the target. With the increase of target thickness (h) and decrease of impact velocity (v₀) and obliquity (θ), the value of a/b decreases. The number of debris ejected from target is significantly higher than that from EFP. Based on the statistical analysis of the spatial distribution of the BAD, An engineering calculation model was established considering the influence of h, v₀ and θ. The model can with reasonable accuracy predict the quantity and velocity distribution characteristics of BAD formed by EFP.     

Experimental and numerical investigation of zirconium jet performance with different liner shapes design

This paper studies the shaped charge jet performance in terms of different liner shapes including conical,bell,hemispherical and bi-conical liners.The critical angles and the relevant flow velocities for the zir-conium liner material were calculated analytically and numerically using Autodyn hydro-code.The relationship between the critical collapse angle and the flow velocity was determined for the conditions of jet formation and coherency.Penetration tests according to the standard testing procedures of API-RP34 (Section-Ⅱ) were performed to validate the numerical predictions of the jet performance of the studied liners.It was found that the four shaped charge liners all produced coherent jets with different performances.The penetration depth of the shaped charges with the bell and the bi-conical liner shapes increased by 10.3％ and 22％,respectively,while the crater diameter of shaped charge with hemispherical liner increased by 85％ representing the formation of an explosively-formed-projectile (EFP),when they are compared with the corresponding jet characteristics of a conical liner shaped charge.     

Formation of explosively formed penetrator with fins and its flight characteristics

The ultimate goal of weapon system employing an explosively formed penetrator (EFP) is to defeat a target at the longest standoff. In order to do this, an EFP must be aerodynamically stable so as to strike the target at a small angle of obliquity, and the decay velocity per meter of EFP must be smaller at extended standoff. As the angle of attack increases, the penetration ability of EFP greatly reduces. The fins improve the EFP aeroballistic characteristics and decrease the flight drag of EFP as well. EFP with fins formed by three-point initiation is presented. The formation of EFP with fins is studied by LS-DYNA, and the aeroballistics is studied through experiment. The experimental results show that the decay velocity per meter of EFP with fins is much smaller than that of normal EFP, and the attitude angle steadily decreases.     

Effects of module number and firing condition on charge thermal safety in gun chamber

Thermal safety of modular charge which is fed into and retained in the chamber after gun fires consecutively is first investigated with cook-off method.A two-dimensional cook-off model of modular charge in gun chamber is established and the cook-off process of modular charge in gun chamber is numerically simulated.Then the effects of module number and firing condition on charge thermal safety are evaluated by researching the cook-off response characteristics of modules.The results show that,under conditions of different module numbers the cook-off responses all occur on the module closest to the boundary of missile,and the single-base propellants located at the inner surface of cartridge ignite first.When the number of loaded module changes from 1 to 6,the cook-off response temperatures vary little,only in a small range of 478.1 K-482.4 K.The cook-off response times decrease logarithmically in the range of 211.2 s-166.7 s with the increasing length of residual air gap in gun chamber.The simulation results are well matched with the experimental data.Furthermore,different firing conditions have great influence on the cook-off response time,minor influence on the initial response position and little in-fluence on the response temperature.Under the three conditions of consecutive 32 launches with 5 rounds/min,43 launches with 1 round/min,and 41 launches with different firing frequencies,the cook-off response temperatures are 479.2 K,481.1 K and 479.9 K respectively and the response times are 709.2 s,211.2 s and 214.4 s respectively.The response position is near the middle area of the inner cartridge surface in the former condition and near the right area in the latter two conditions.