Shaped Charge Jet Heating

A one-dimensional theoretical model of shaped charge jet heating is developed. The model includes heating due to the shock wave transferred to the liner by the explosive detonation wave and due to the plastic work performed during liner collapse and jet elongation. Results calculated by a one-dimensional shaped charge computer code using this model fall within the lower bound of the experimental range.     

锥形装药形成射流的数值模拟

利用AN SY S/LS-DYNA 3D有限元分析软件,对两种装药(TATB和TNT)两种不同锥角(53°和43°)药型罩的形成射流分别进行了数值模拟与对比分析。结果表明,53°锥角药型罩产生的射流短而粗,43°锥角产生的射流细而长,高能炸药产生的射流速度高,这与现已成熟的理论相吻合,验证了该数学模型和状态方程所选用参数的正确性,为设计或研发新型锥形装药产品有效降低试验成本并缩短研发时间提供了依据。     

Copper-Tungsten Shaped Charge Liner and its Jet

The use of copper-tungsten alloys for shaped charge liners leads to an improving of the jet penetrability into an homogeneous steel target. In comparison with copper jets, the penetration depth can be increased by a factor 1.3. The improving is due to the increasing of both the density and the break-up time. Copper-tungsten shaped charge jets and their aspect of break-up were investigated by flash radiography. Both the effect of rotation of copper-tungsten jets and their standoff performance were examined.     

Breakup Time of Zirconium Shaped Charge Jet

The Johnson‐Cook parameters for the zirconium material were determined based on the data obtained from the tensile testing of zirconium specimens at different strain‐rates and different temperatures. The velocity difference (V_PL) between the particulated jet fragments was calculated for zirconium liners of different thicknesses using Johnson‐Cook constitutive equation. A breakup time formula for the zirconium shaped charge was proposed, which demonstrated better ductility performance than the copper shaped charge.     

Spaced Armor Effects on Shaped Charge Jet Penetration

Spaced armor has a simple structure and is easily produced with low cost. Previous authors calculated how a jet penetrates spaced armor; but, this study provides both a theoretical calculation method describing the interaction of a jet with spaced armor and experimental data which agree well with the theoretical values. The effects of several factors were explored using LS‐DYNA such as the distance between the first plate and the second plate as well as layer thickness on the interaction between the jet and the target. A method for simulating the protection afforded by spaced armor and supporting the design of spaced armor is presented.     

A Formula for the Shaped Charge Jet Breakup-Time

It was found that the breakup-time of jets formed by shaped charges of cylindrical symmetry is given very accurately by the formula: This formula is obtained from a general principal applied here for the first time which says that the breakup-time of homogeneous ductile metals under very high strain rates is equal to the smallest initial dimension of the elongating metal divided by V_PL . When applied to simple configurations such as a pipe which expands due to internal explosion this principal leads to a correct prediction of the average formed fragment dimensions. This principal provides for the first time an explanation to the experimental fact that metals' ductility can increase by an order of magnitude when the strain rate increases from 10⁻² to 10⁵ pro second.     

The Simplified Model for Predicting Shaped Charge Jet Parameters

The model is based on the more recent work of Hirsch and the original analytical work of Pugh, Eichelberger and Rostoker. Namely, the simplified Gurney formula for imploding cylinders derived by Hirsch is combined with the PER theory forming one-dimensional computer code, and then it is used for predicting the 80-mm diameter shaped charge jet parameters. Good agreement has been found with the experimental results.     

The Tip Origin of a Shaped Charge Jet*

This study demonstrates that the pex portion of a typical 42° conically lined shaped charge is not being efficiently utilized. In fact, approximately 40% of the liner height at the apex end of the cone does not provide an efficient jet as far as penetration depth is concerned. In this paper, we present an experimental and theoretical study of the liner apex. First, a series of experiments were conducted in which liner apices were filled to various heights to inhibit the collapse of the apex portion of the liner. Next, a one-dimensional analytical shaped charge model was used to simulate the filled cone experiments. From these experiments and calculations we have determined that approximately 30–40% of the cone height is used to produce a compact tip particle rather than a stretching jet. This indicates that i t may be possible to redesign the apex portion of the liner to achieve a more efficient use of liner height.     

射流撞击下发射装药的易损性响应特性

用空心装药射流作标准射流源,研究了4种典型发射装药在空心装药射流撞击下的易损性响应特性。分析了约束条件、尺度效应等对响应结果的影响。结果表明,4种典型发射装药均发生了较为强烈的反应,由弱到强的排序为太根药、单基药、硝基胍药和硝胺药,其反应等级依次为爆炸、爆炸、部分爆轰和部分爆轰。     

A Model for Explosive Reactive Armor Interaction with Shaped Charge Jet

Study of interaction of explosive reactive armor (ERA) with shaped charge jet is the basis for evaluation of the effectiveness of ERA. The physically based theoretical model of this interaction is given. It is incorporated in the NERA computer code. The influences of backward moving plate and forward moving plate thickness, explosive layer thickness, jet attack angle, and distance between ERA and main armor are investigated. The comprehensive analysis of a longitudinal point of impact effect on ERA efficiency, based on NERA code calculations, is presented. Computational results of NERA code are compared with experimental data. The computational and experimental results of penetration in the steel armour target are in good agreement. The developed code enables optimization of explosive reactive armor characteristics.     

Scaling of the Shaped Charge Jet Break‐Up Time

Since the formula for the shaped charge jet break‐up time was published on 1979 many attempts were made to interpret it and to make its use more efficient. It is shown herein that the V_pl parameter depends on the ratio of the liner thickness to the charge explosive diameter by the formula: 1/V_pl=13.9−101⋅(T_L/CD), where T_L is the liner thickness, CD is the explosive charge diameter and the numbers are for a published set of measurements with an OFE copper liner driven by COMP‐B explosive. To find how the numbers used in this formula change with the liner material and its metallurgical state and with the type of explosive, measurements should be made as prescribed herein. An attempt to begin explaining this formula is made in the discussion.     

起爆方式对线性聚能装药射流形成的影响

以工程中常用的柔性切割器为研究对象,在不考虑端部效应的前提下,对3种起爆方式下线性聚能装药射流的形成过程进行了理论分析和数值模拟。结果表明,不同起爆方式下射流头部速度以端部面起爆最大,线起爆次之,端部点起爆在端面附近处形成的最低,但在距端面一定距离处,射流头部速度又能增大到与端部面起爆的速度相近。在射流内部,端部面起爆形成的射流在内部各点处的速度都是3种起爆方式中最大的,而端部点起爆时,则是随着距起爆点距离的增加由处处小于线起爆的射流速度分布转变到与端部面起爆相同的射流速度分布。在此基础上进一步提出3种起爆方式下线性聚能装药切割目标的数值模拟方法。     

The Natural Spread and Tumbling of the Shaped Charge Jet Segments

The collapse mechanism of the shaped charge jet prevents the formation of a jet, the segments of which move in a straight line with absolute accuracy, even under the assumption that the shaped charge is ideally symmetrical. This is a result of the fact that the jet break-up mechanism already starts at the collapse stage, in which the liner material has a big transversal velocity component. A model for calculating the distribution of the angle by which the jet segments' direction of movement deviates from the shaped charge axis of symmetry (the spread angle) is presented in detail. The tumbling frequency of the segments as a function of their velocity and final length is also predicted by the theory. The predictions made by applying the model to the standard 83.8 mm 42 degrees opening angle B.R.L. precision shaped charge were found to be consistent with the data published in open literature. The comparison of these predictions with the data leads also to the conclusion that the cutoff in the copper jet penetration into steel targets occurs when the jet segments start to hit the walls of the already formed hole instead of reaching its bottom without being disturbed on their way.     

某成型装药射流的数值模拟与射流转化率

应用LS-DYNA及示踪点处理技术,对某一球锥罩成型装药结构的射流形成过程及射流侵彻靶板过程进行了研究,获得了有效射流沿其运动方向的速度分布、头部速度、侵彻孔几何描述等多项评估射流微元性能的重要参数。计算结果表明,对于普通强度钢质目标靶,在射流侵彻靶板过程中,常规小锥角药型罩产生的有效射流为2000m/s以上的射流段,杆式射流的临界侵彻速度值为1400m/s,从而进一步得到其射流转化率为29.65%。     

钨铜粉末药型罩形成聚能射流的数值模拟

利用LS-DYNA3D软件对钨铜粉末药型罩聚能射流的形成过程进行了数值模拟,采用多物质ALE算法,模拟了钨铜聚能射流的形成过程,并与实验结果进行了对比。结果表明,随着药型罩密度的增加,射流直径变细,头部速度降低,数值模拟结果与实验结果较一致。     

装药长径比对半球形聚能装药射流成型的数值模拟

为了得到均匀、不易中断的射流,运用ANSYS/LS-DYNA软件的二维多物质纯ALE算法,建立不同装药长径比有限元模型,数值模拟了6种不同长径比的半球形聚能装药产生射流的过程,对比分析了同一时刻、同一时间段6种装药长径比对射流成型的影响。结果表明,70.5μs时,装药长径比从0.8增至1.8,射流头部速度增大31.9%,射流长度减小23.2%;46.5~70.5μs时段,射流长径比与时间呈类线性增长,射流在装药长径比约为1.2时不易断裂,均匀性最好。     

聚能装药逆向环形起爆射流形成的数值计算

用LS－DYNA程序对小长径比聚能装药逆向环形起爆时形成高速射流以及正向起爆时形成低速射流进行了三维数值模拟,计算结果与实验吻合,计算的逆向起爆形成射流头部速度为8．78km/s,而正向起爆形成的射流头部速度为4．86km/s。数值模拟证明：长径比聚能装药逆向环形起爆时形成高速金属射流是可行的。     

一种截顶线性聚能装药射流特性的数值模拟

为了得到特性更好的线性聚能射流,设计了一种截顶线性药型罩加矩形辅助药型罩的新型装药结构,利用ANSYS/LS-DYNA3D有限元程序对6组新型装药结构及传统装药结构进行了模拟计算,分析了矩形辅助药型罩宽度和截顶间隙长度对线性射流特性的影响。结果表明,该新型结构形成的线性射流的头部最大速度总体较传统线性聚能射流高,形成的线性射流形态更细更长,并且杵体相对较少,药型罩质量利用率较高。在6组方案中,矩形辅助药型罩宽度为1.0cm、截顶间隙为0.4cm时,该结构形成的线性聚能射流头部速度最大,为3.58km/s,连续性较好,有效宽度最大。