Numerical simulation of the formation of shaped-charge jets from hemispherical liners of degressive thickness

The formation of shaped-charge jets from hemispherical copper liners of degressive thickness (decreasing from apex to bottom) is analyzed by numerical simulation of a twodimensional axisymmetric problem of continuum mechanics. The comparison was based on the parameters of the jet formed from a modern standard shaped charge with a conical liner which provides penetration of a steel target to a depth equal to 10 charge diameters. The comparative analysis was performed using calculated mass–velocity distributions and the ultimate jet length–velocity distributions obtained on their basis, from which the potential penetrability of jets was evaluated. It is shown that the shaped-charge jets formed by hemispherical shaped-charge liners of degressive thickness are comparable in head velocity and penetrability to the jets from conical liners.     

Determination of the Velocity Difference between Jet Fragments for a Range of Copper Liners with Different Small Grain Sizes

A range of small calibre shaped charge copper liners were manufactured experimentally by the electro‐deposition technique. The average grain size of the produced copper liners was determined using the SEM technique. The specific breakup time, which represents the velocity difference between the particulated jet neighboring fragments (V_PL), was determined for the range of copper liners of different grain sizes using Zerelli‐Armstrong constitutive model. The specific breakup time and the total number of the jet fragments were studied over the range of grain size and the predicted jet temperature.     

Formation and Penetration of Jets by Shaped Charges with Reactive Material Liners

Reactive material lining is an efficient damage enhancement technology that incorporates the defeat mechanisms of kinetic energy and chemical energy. The liners are fabricated by cold isostatically pressing at a pressure of 250 MPa. In this paper, the formation behaviors of jet with the polymer‐based reactive material liner are investigated by numerical simulation and X‐ray photographs. The corresponding simulations of jet formation are presented, and the results agree well with experimental ones. They show that the reactive material liner can shape almost continuous and straight jet. Compared with the conventional copper liner, the reactive material liner can shape jet in a shorter time, but the jet break easily and lose stability due to its poor ductility. Although the penetration depth is sacrificed slightly when penetrating steel target, the reactive material liner produce a significantly enlarged hole‐diameter.     

Effect of porosity on shaped-charge flow

It is shown that for shaped charges with porous liners, shaped-charge flow of two types is possible: dispersed jet flow, which fills the entire shaped-charge cavity, and monolithic jet flow. Conditions for transition from one type of flow to the other are estimated, and it is shown that by changing the initial porosity, it is possible to control the physicomechanical characteristics of the liner material during compression of the liner by the detonation products of the explosive charge. For monolithic jet flow, it is shown experimentally that shaped charges with porous liners can have greater penetrating capability into steel targets than charges with monolithic liners of similar design. Dispersed jet flow is used to apply coatings on substrate targets and to synthesize new compounds. Experiments are described in which shaped-charge liners made of a mechanical mixture of W or Ti powders with carbon are used to produce layers containing the carbides of the indicated metals on steel or titanium substrate. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 2, pp. 122–132, March–April, 2000. This work was supported by the Russian Foundation for Fundamental Research (Grant Nos. 97-01-00826 and 98-03-32328).     

Dynamic Behavior of a Shear-Formed Shaped-Charge Liner

A high-resolution, multi-frame, image-converter camera developed for high speed photography is applied to study the dynamic behavior of shear-formed shaped-charge liners. Grid lines applied to the inner liner surface allow the precise quantification of liner collapse, early jet formation, and jet development for comparison with two-dimensional hydrocode simulations. The technique affords the first direct measurement of the angular velocity of jets formed from shear-formed shaped-charge liners.     

The Behavior of Shaped Charges with open-poled hemispherical liners

This paper discusses the effect of an opening at the pole of a hemispherical shaped-charge liner. An experimental study was performed in which various diameter holes were made in otherwise similar shaped-charge liners. Flash radiographs were taken to observe changes in the liner collapse and the jet characteristics. The collapse process and jet characteristics of a hemispherical liner are significantly altered for a hole diameter which is 10% or more of the outer liner diameter. The jet tip velocity is increased by 26% for a hole diameter-to-liner diameter ratio of 0.25. Explanations are presented for the behavior of the tip region of the shaped-charge jet.     

Characteristics of Shaped Charges with Hemispherical Liners

During the last 10 years shaped charges with spherical liners have arosed great interest in research and development because their application in special munition results in an increase of performance. The present report presents measured characteristics of shaped charges with hemispherical liners. A short explanation of the jet formation process and the typical jet characteristics as a function of charge geometries are given, and the effect of liner materials is described. Additionally, the influence of various explosives and wave shapers have been studied. The important feature of such shaped charges is that the projectiles are associated with a high terminal ballistic effective part of the liner mass, which is of particular interest for application.     

Reactive‐Injecting Follow‐Through Shaped Charges from Sequent‐Material Conical Liners

Shaped charges using reactive‐metal liners have the potential for beyond‐penetration effects, e.g. thermodynamic events that increase pressure in a volume adjacent to the penetration. Shaped charge liners made from a copper penetrating‐ and an aluminum reactive‐component in a sequent‐material configuration were compared in tests to baseline homogeneous copper liners. Copper lined shaped charges had greater mild steel penetration performance, but lacked beyond‐penetration pressurization effects exhibited by the sequent‐material lined units. Jet capture experiments, beyond‐penetration constant‐volume tests, and thermochemical equilibrium calculations provide evidence supporting the aluminum slug comminution into unoxidized reactive fuel, augmenting beyond‐penetration effects.     

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.     

Demolition Mechanism and Behavior of Shaped Charge with Reactive Liner

The application of reactive materials on shaped charge liners has received much attention. Herein, the demolition mechanism and behavior of reactive materials based shaped charge liner are investigated by experiment, numerical simulation, and theoretical analysis. Three reactive shaped charge liners, composed of a mixture of Al/PTFE (26.5/73.5 wt‐%) powders, are fabricated by pressing and sintering. The damage effects of the multi‐layered target against reactive materials based shaped charge are investigated. The results show that the reactive liners create excellent collateral damage due to the release of chemical energy contained in reactive materials. An Eulerian computational model is developed to investigate penetration behavior of the reactive jet formed by shaped charge liner. In addition, a theoretical model based on cavity expansion is derived to predict the initiated location of reactive materials. Comprehensive analysis indicates that the TNT equivalence factor for these powder mixtures used in this work is 3.41–7.77 and that the self‐delay time is about 0.8 ms. This work will provide guidance and reference for the design of reactive shaped charge liner.     

Characterization and comparison of gray cast iron powder produced by target jet milling and high energy ball milling of machining scraps

Target jet milling and conventional ball milling were used to produce powders from gray cast iron scraps. Powders of similar size distribution produced by the two methods were pressed at different compacting pressures. Green compacts were made at the compacting pressures of 500, 600, 700 and 800 MPa. Jet milled powder showed good compaction behavior while ball milled powder showed very poor compressibility. Also, balanced compacts composed of 50% Hoganas SC100.26 iron powder and each of the cast iron powders produced in this work were made at 500 and 800 MPa and their green properties were determined. Results showed that, green properties of the jet milled powder were acceptable and superior compared to ball milled powder. The jet milling process proved to be a much more efficient process compared to ball milling in terms of time and production capacity.     

In-flight formation and characterization of nickel aluminide powders in a dc thermal plasma jet

The strength of some intermetallics increases with temperature instead of exhibiting a decrease: thus, they are ideally suited for high temperature applications. The formation of intermetallic compound during the spray process leads to metallurgical bonding due to the high exothermicity of the formation reaction. In this paper formation of nickel aluminide in a thermal plasma jet from ball-milled nickel–aluminium powders is reported. Commercially available nickel and aluminium powders were mixed in the appropriate amount and injected in to a thermal plasma jet produced by an atmospheric plasma torch. During in flight the formation of nickel aluminide takes place in plasma jet. Powders were collected at two different collection distances (40 and 80 cm) for three power levels (10, 15 and 20 kW), different plasma gas flow rates (15 and 20 lpm) and different powder feed rate (7 and 14 g/min). The powders are characterized using SEM, optical micrograph, TG/DTA and XRD analysis. The effect of plasma parameters on the formation have been studied and reported. The formation is better at higher power levels, low powder feed rate, low plasma gas flow rate and longer collection distances.     

复合杆式射流成型及威力性能的数值模拟及试验验证

为了阐明复合杆式射流的性能,设计了8种不同材料的复合球缺罩,包括聚乙烯/铜、铝/铜、钛/铜、铁/铜、铜/铜、钼/铜、钽/铜、钨/铜材料,并采用LS-DYNA软件对其杆式射流的成型过程进行三维数值模拟,分析了杆式射流威力性能,通过静破甲试验验证了数值模拟结果。结果表明,在保持内罩材料为紫铜的条件下,随着外罩材料密度的增大,射流整体速度减小,射流动能随外罩材料密度的增大而减小;在外罩为金属材料时,外罩材料冲击阻抗越大,内罩所受爆轰波透射压力越小,射流整体速度、射流动能随外罩冲击阻抗增大而减小;经对比发现,聚乙烯/铜复合杆式射流整体速度最高,动能最大,破甲威力较佳,铝/铜复合杆式射流次之。静破甲试验结果表明,聚乙烯/铜复合杆式射流对钢靶侵彻深度较铝/铜复合杆式射流有一定提高,与数值模拟结果一致。     

Reactive Liners Prepared Using Powders of Aluminum and Aluminum‐Magnesium Alloys

Cylindrical reactive liners filled with powders of aluminum, aluminum‐magnesium alloys, and aluminum‐magnesium powder blends were prepared and initiated by a centrally located explosive charge. The experiments were performed in a cubic chamber. Several transient pressure measurements were taken in addition to the quasistatic pressure caused by the explosion. Results were compared against a reference case with an inert liner filled with aluminum oxide powder. For all reactive liners, an increase in both quasistatic pressure and blast wave strength were observed compared to the case of an inert liner. In experiments with mechanically alloyed Al ⋅ Mg powders, the quasistatic pressure is effectively the same as in experiments with pure aluminum. An improvement in the achieved quasistatic pressure is observed for the liners with a cast alloyed Al ⋅ Mg powder. Most interestingly, a substantial contribution to the air blast indicative of very early reaction occurring in sub‐millisecond time scale is observed for all experiments with reactive liners. The most substantial improvement in the blast characteristics is observed in experiments with mechanically alloyed Al ⋅ Mg powders. While the mechanisms of prompt reactions of metals and alloys remain largely unexplored, the present results highlight the importance of such reactions for reactive liners and other components of energetic systems.     

Development and electrical conductivity behavior of copper‐powder‐filled‐epoxy graded composites

This article reports the development and direct‐current (dc) conductivity behavior of copper‐powder‐filled‐epoxy graded composite. Copper‐powder‐filled‐epoxy composites with 10 wt % copper powder and epoxy resin were developed. dc conductivity measurements were performed on the graded composites with an electrometer in the temperature range of 28–146°C. The dc conductivity decreased with an increase in the distance in the direction of the centrifugal force, and this showed the formation of a graded structure. The dc conductivity increased as the copper powder content increased. Two‐phase conduction occurred in all the copper‐filled‐epoxy graded samples. The activation energy calculated with an Arrhenius equation for one sample was 0.88 eV, and this was mainly due to conduction electronic. Another sample had an activation energy of 1.33 eV. Three samples exhibited ionic conduction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Analysis of Strains,Strain Rates and Temperatures during the early stages of shaped charge liner collapse

In trying to understand the extraordinarily high dynamic ductility of a copper shaped charge jet, prior work by the authors has utilized the Eulerian MESA 2D code with a novel form of the LaGrangean tracer particle technique as well as the experimental “soft recovery” and metallurgical examination of partially collapsed copper liners. This work had indicated that localized material processing occurs during the earliest stages of liner collapse and causes dramatic visible grain size refinement, evident in the photomicrographs. Further computational analysis shows that the localized plastic flow is accompanied by very high localized engineering strains (>200), extremely high (>4 × 10⁷ s⁻¹) localized strain rates, as well as elevated temperatures, all of which favor a dynamic recrystallization process. In this paper, the focus is on a detailed quantitative analysis of strain, strain rate and temperature distribution history within the collapsing liner, in the region of the inner liner apex and the early location of the moving collision zone, where the early material conditioning first occurs. Correlations are sought between the computed, time-dependent values of these three paremeters and the microstructures observed in the interiors of the partially collapsed liners, in those regions where the grain size changes are observed. This data may ultimately permit quantitative comparisons with the predictions of dynamic recrystallization models.     

Limits of Increasing the Penetration of Shaped‐Charge Jets by Pulsed Thermal Action on Shaped‐Charge Liners

The effect of preheating of liners on the penetration capability of shaped charges is considered theoretically. It is shown that for a plastically fractured shapedcharge jet, preheating of the liner generally increases the effective jet length and shapedcharge jet penetration. Restrictions on the parameters of preheating of shapedcharge liners due to the possible thermal initiation of the explosive are established. It is noted that excessive weakening of a shapedcharge jet can lead to transition from plastic to volume fracture with a corresponding decrease in shapedcharge jet penetration. The ultimate possibilities of the thermal method for increasing the penetration capability of shaped charges are estimated. Calculation results are compared with available experimental data.     

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。