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.     

Formation of a high-velocity particle flow from shaped charges with a liner consisting of a hemisphere and a degressive-thickness cylinder

Particle flows formed from shaped charges with a combined steel liner consisting of a hemisphere and a cylinder with a hemispherical part of degressive thickness (decreasing from top to bottom) were investigated by flash radiography. It has been found experimentally that the change from a constant to a degressive thickness of the hemispherical part increases the velocity of the head part of the liner jet formed during its compression, which is subsequently separated upon collapse of the cylindrical part. The maximum particle velocity obtained as a result of separation in the experiments was 8.6 km/s.     

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.     

Disruption of Shaped-Charge Jets by a Current

In our previous experiments on disruption of metal shaped-charge jets by a capacitor-bank current, we attained almost complete disruption of the entire jet. In those experiments, the distance between the shaped charge and the current electrodes was approximately equal to the diameter of the shaped-charge cavity. Physically, jet disruption by a high current consisted of initial development of MHD instability of the jet in the form of growth of necks and subsequent electric explosion of the necks. The present paper describes similar experiments in which the distance between the shaped charge and electrodes was increased. It is shown that this can worsen results of jet disruption because the change in the initial state of the jet changes the physical picture of the process of jet disruption by a current. Key words: shaped-charge effect, shaped-charge jet, capacitor bank, MHD instability, electric explosion of a conductor, electric-current pulse.     

The Penetration Resistance of a Titanium Alloy against Jets From Tantalum Shaped Charge Liners

Titanium alloys, notably Ti—6Al—4V, are known to provide high mass effectiveness against kinetic energy penetrators. However, the penetration effectiveness of titanium against shaped charge jets has not been investigated in detail. An experimental study was conducted with Ti—6Al—4V billets impacted by shaped charge jets formed from 100–mm, 42° conical shaped charge liners fabricated from tantalum. This work represents the first study of hypervelocity, high–density jet penetration into titanium alloys.     

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).     

Magnetic-field amplification in metal shaped-charge jets during their inertial elongation

This paper considers magnetic-field amplification in inertially elongating metal shaped-charge jets formed by explosion of a shaped charge with an axial field previously produced in the charge liner. The amplification is related to the effect of magnetic-field freezing in a conducting material and is due to the deformation of the jet material with particle elongation along the magnetic lines. The model of a uniformly elongating, conducting, incompressible, cylindrical rod was used to determine the nature of the field variation in the jet elements versus the magnetic Reynolds number determined by the electrical resistance of the material, the initial axial-strain rate, and the element radius. In high-gradient copper shaped-charge jets, the magnetic field can be amplified by more than a factor of five during elongation. It is shown that the joint action of the force and thermal factors accompanying field amplification in the jet material can lead to jet breakup with radial scattering of the material particles.Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 1, pp. 120–128, January–February, 2005.     

Formation of a shaped-charge jet upon nonsymmetric compression of a shell

The effect of technological errors on the formation and displacement of components of a shaped-charge jet is studied numerically. The linear character of the dependence of the radial center-of-mass velocity of the transverse cross section of a linear on the magnitude of the variation in the wall thickness of shells and a layer of an explosive substance, and the variation in its charge along the circumferential coordinate is clarified. Computations have shown that, for a shaped-charge jet, the magnitude of the radial velocity can be considerably larger compared to the entire liner. This is due to a conversion of only a part of the linear material to the jet, with large values of the radial velocity. The different values of the radial velocity along the liner length lead to distortion of the jet shape, and, hence, to a decrease in the effectiveness of its action. Estimation of the degree of influence of each technological error on the curving of a shaped-charge jet makes it possible to give concrete recommendations concerning the increase in the precision of treatment and assembling of the corresponding members of an explosive system. Institute of Applied Mathematics and Mechanics at Tomsk State University, Tomsk 634050. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 6, pp. 121–126, November–December, 1997.     

Auslegung von Einstoff-Druckdüsen

Design of single substance pressure jets . The single substance pressure jet most commonly used produces liquid lamellae. These then degenerate to drops in the surrounding gas as a consequence of aerodynamic wave formation. The size of the droplets generated decreases according to Δp^?1/3. Calculation of droplet size can be unified by defining a lamella number. The lamella number expresses the drop in lamella thickness with increasing jet distance relative to the diameter of the jet. The smaller the geometry-dependent lamella number, the smaller the droplets relative to the diameter of the jet. The hollow cone jet produces the smallest lamella number and thus generates the smallest droplets. However, the liquid in the twist chamber of hollow conical jets at higher viscosities are decelerated much slower than in fan-shaped jets. Measuring methods for determining the principal characteristics of jets are demonstrated for hollow conical and fanshaped jets. Turbulence jets, such as solid conical jets, produce droplets some 5 to 10 times larger than those in hollow conical jets at the same jet diameter and pressure. Droplet formation occurs mainly by turbulence in the jet. It is important to minimize the danger of blockage when operating jets. For this reason, preference is often given to that jet which gives the smallest droplet size for a given pressure and a given narrowest orifice diameter. This is particularly significant at droplet sizes d < 20 μm. Comparison and choice of jets is accomplished with the aid of a diagram representing the relative droplet size d₃₂/D in terms of the jet pressure number Δp = ΔpD/σ and the Ohnesorge number. However, a characteristic field representation containing only characteristic quantities formed with the characteristic droplet size, apart from the relative droplet size, is suitable for determining the jet dimensions.     

Formation of Jets by Shaped Charges with Metal Powder Liners

The characteristics of shaped charges with metal powder liners for perforating borehole pipes are described. The liners were manufactured using powder metallurgy technology. Two types of powder liners were made: a homogeneous one made of copper powder and a heavy one made of copper and tungsten powder blend. Laminar liners consisting of two layers made from powders of different densities were also examined. X‐ray pulse technique was applied to research the process of jet stream formation. Radiograms revealed the discontinuous (discrete) structure of jets formed from powder liners. The corresponding computer simulations of jet formation are presented.     

Motion of a shaped-charge jet in a porous medium

The problem of the motion of a shaped-charge jet in a porous medium is equivalent to the problem of a blunt cylinder in a hypersonic flow whose velocity at infinity is equal to the jet velocity in the porous medium. The flow pattern of the medium is the same as in the case of propagation of a blast wave generated by a point explosion of a cylindrical charge. The approximate theory of a strong explosion is used to obtain the basic relations for the shock wave and the expanding cavity in the hypersonic flow of a porous medium around the blunt cylinder. A comparison with experiments on the motion of a copper shaped-charge jet in porous aluminum is performed. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 6, pp. 119–124, November–December 1999.     

Effect of the strain rate on the tensile strength of a copper shaped-charge jet

The data on the penetration depth of a rotating shaped-charge jet were used to estimate the strength of the material of a copper jet formed from a “low” conical linear with an apex angle of120° under the action of centrifugal forces. The estimates0.07–0.15 GPa obtained are close to the static yield point of deformed copper. The jet strength, which is estimated using the length of the fragments formed upon breakup of a rotation-free jet owing to the axial velocity gradient, attains1–1.5 GPa at a strain rate of ≌2·10⁴ sec⁻¹. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 111–118, January–February, 1997.     

Numerical simulation of the influence of an axially asymmetric charge on the impact initiation capability of a rod-like jet

With the aim to improve the impact initiation capability of a rod-like jet, this paper presents the influence of an axially asymmetric shaped charge on the jet studied by means of numerical simulations. According to Held’s initiation criterion, the impact initiation capability of the jet is affected by the jet tip velocity and diameter. The detonation radius over the longitudinal axis, restricted by the charge radius over the same axis, affects the detonation wave in the charge, the force acting on the liner, and, therefore, the jet velocity and shape. Based on these laws, the structure of the axially asymmetric charge is optimized. Compared with axisymmetric jets, axially asymmetric rod-like jets possess a higher impact initiation capability.     

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.     

Mechanical effect of shaped charges with porous liners

This paper presents experimental data on the penetration of shaped charges with porous liners into metal targets located at distances smaller than or comparable to the diameter of the charge and some experimental data on the velocity of the jets from the investigated charges with liners of metal powders.     

Interaction of a shaped-charge jet with moving reactive armor plates

The mechanisms of the stationary and nonstationary interaction between a metal shaped charge jet and the front reactive armor plate (moving toward the jet) and rear (moving behind the jet) reactive armor plate. The range of interaction parameters in which these mechanisms take place was determined. The interaction of the shaped-charge jet with the front plate is mainly stationary and leads to the wearing of the jet in the transverse direction (reduction in the diameter of the jet) and its deflection by a small angle. The interaction of the shaped-charge jet with the rear plate is mainly of a nonstationary discrete nature and forms unilateral transverse perturbations in the jet, which, developing, lead to its bending and subsequent destruction.     

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.     

Resistance of the medium during high-velocity penetration of long rods and shaped-charge jets

We consider the high-velocity penetration of long rods and shaped-charge jets into semi-infinite targets with initial impact velocities of 2–4 km/sec. At these velocities, the mechanical characteristics of the target materials makes a great contribution to the final parameters of the process: penetration depth and critical velocity of the impactor (jet). The dynamic compressive stability threshold of the material, obtained in experiments with uniaxial dynamic loading of flat targets, is proposed as a parameter that determines the properties of the target in the penetration process.     

Generation of Hypervelocity Particle Flows by Explosive Compression of Ceramic Tubes

The compression of ceramic (corundum) tubes by the detonation products of explosives have been studied experimentally and numerically. The formation of the shaped-charge jet of ceramic particles and its effect on steel witnesses targets has been investigated. The tubes were produced by detonation spraying. Ceramic particles were deposited on copper tubes, which were then dissolved in a solution of ferric chloride. In the experiments, a considerable penetration of the flow of ceramic particles was observed. During the interaction of the flow with the target, the target material was partially evaporated, as shown by metallographic analysis. Numerical analysis of the formation of the discrete shaped-charge jet showed that the maximum velocity of the jet head was about 23 km/s, and the velocity of the main part of the jet was about 14 km/s.