Shaped Charge Jet Research Articles

Study on the Interference of Multi-point Shaped Charge Structure on Jet

in order to improve the defense ability of reactive armor against shaped charge jet, a multi-point shaped charge structure is designed in the first layer of traditional explosive reaction armor, and the active passive combination method is used to interfere with the jet. The specific action process is as follows: after obtaining the signal of series warhead charge impacting explosive reactive armor. Take the initiative to detonate the shaped charge. Multiple damage elements are formed to interfere with the shaped charge jet actively. Based on LS-DYNA, the numerical simulation of multi-point shaped charge structure is carried out, and the charge structure and angle are optimized. The results show that the damage elements in different directions can be focused along the axial direction of the incoming jet by adjusting the charge structure. Changing the focal length of the converging jet can cause interference or fracture at different positions of the jet. The research results of this paper can provide reference for the design of active passive reactive armor.

Physical and numerical assessments of the penetration behavior of coplanar linear shape charges

In this study, we aimed to demolish irregular constructions that are usually composed of convex, concave, and straight structures based on the shaped charge jet. Accordingly, the penetration behaviour of convergent, divergent, and straight linear shaped charges (LSCs) have been detected with numerical and physical methods. For comparison purposes, numerical models for all three types of LSCs with identical cross-sections have been established to investigate the impacts of structural features. It is found that the shaped charge structure not only determines the kinematic consumption during the penetration process but also influences the initial value of the jet velocity. Additionally, because of the interactions between the previous and subsequent jets, the jet velocity of the convergent LSC shows an obvious undulation during the penetration process. Furthermore, quantitative analyses of the kinematic consumption and initial velocity differences for three types of LSCs are conducted with physical models. A kinematic consumption difference is revealed, and the mass of the charge that determines the initial jet velocity as a function of the geometric parameters in three types of LSCs is deduced. Finally, we combined the numerical and physical models and conducted integral analyses to assess the penetration behaviours of the three LSC types.

High Strain Rate Effect on Tensile and Compressive Property of Carbon Fiber Reinforced Composites

With high strength and stiffness-to-weight ratios, Carbon-Fiber-Reinforced Polymer (CFRP) composite has been applied to the separation device of the rocket by shaped charge jet. But dynamic tensile and compressive properties of CFRP under high rate strain are still unclear. In the article, tensile testing along transverse direction are conducted. The quasi-static tests (10-3 s-1) use a universal testing machine and high dynamic loadings of 800 s-1 and 1600 s-1 tests adopt a high-speed tensile testing machine. Meanwhile, dynamic compressive tests of unidirectional and cross-ply laminated specimen under the thickness direction loading are implemented by a Split Hopkinson Pressure Bar (SHPB) from dynamic loading 500 s-1 to 2500 s-1. Test results show that compared with static tests data, both transverse tensile modulus and strength of CFRP composites materials at dynamic loadings are sensitive to tensile tests. The compressive peak stress and stiffness of specimens also have an increasing tendency with the increases of the strain rate. Furthermore, for failure mode of tensile specimens, the crack propagation of the specimen fracture is along the interface of the fiber/matrix under all loading conditions. The failure modes of compressive specimens are different as the strain rate changes. The higher the strain rate, the more severe the crushing.

Экспериментальное исследование влияния канала малого диаметра на пробивное действие кумулятивной струи

The paper focuses on experiments carried out to determine the effect of a small-diameter channel, passed by a shaped-charge jet before interacting with an obstacle, on its penetrating action. These experiments were conducted in relation to the study of the features of shaped-charge jet motion through the cavity of an elongated solenoid with electromagnetic stabilization of the jet stretching process. For this purpose, steel sleeves with a channel were installed in front of the shaped charge, which made it possible to simulate the mechanical factors affecting the shaped-charge jet when it moves in the air channel. For the conditions implemented in the experiments, it was found that in the absence of collisions of the shaped-charge jet with the channel walls, the penetration depth decreases insignificantly, i.e. within 5%. In experiments in which there were traces of contact interaction with the shaped-charge jet on the channel surface, a significant decrease in the penetrating action was recorded.

Effect of Controlled Perturbations on Buckling of a Conical Liner During Shaped-Charge Jet Formation

Effect of Controlled Perturbations on Buckling of a Conical Liner During Shaped-Charge Jet Formation

О постановке экспериментов по определению пробивной способности хвостовых участков кумулятивных струй

According to the calculations, the penetration effect of shaped charges can be significantly increased (by 40–50 % in the case of a high-strength steel target) if due increasing the accuracy of their manufacture the lower speed threshold is reduced at which the penetration of the tail sections of the shaped-charge jet into the target is stopped. For experimental confirmation of these data, it is proposed to study in detail the penetrability of the tail sections of shaped-charge jets using cut-off rods made of high-density material located at a short distance from the shaped charge (less than its diameter) and designed to eliminate the faster part of the jet. Based on numerical simulation in the framework of a two-dimensional axisymmetric problem of continuum mechanics, possible parameters of the cut-off rods for generating solitary "tails" of shaped-charge jets with different velocities of the leading element are predicted.

Using shaped charges with a “magnetic cut-off” for testing anti-meteoroid shields

This research is an investigation about the possibility of using shaped charges forming high-velocity metal jets to obtain high-velocity compact elements. The particular objective here is testing rocket and space technology objects for anti-meteoroid resistance. In order to “cut off” the jet head section and obtain a compact element with a velocity of 10 km/s, it is proposed to create an axial magnetic field in the shaped charge liner before its explosion. Strengthening the magnetic field in the jet formation region during the liner collapse leads to destroying the main part of the forming shaped-charge jet. This is associated with radial dispersion of its material due to the accompanying “pumping excitation” field of powerful electromagnetic forces. In this case, it is possible to maintain the jet head section at maximum velocity. The possibility of choosing an initial magnetic field intensity has been analyzed. This is done based on numerical modeling in the framework of the two-dimensional axisymmetric problem of continuum mechanics and electrodynamics, assuming ideal conductivity of the liner material. The way of doing so is that only the head section of the jet is formed normally and its subsequent sections are scattered. As calculations showed, the goal is achieved in the case of using conical shaped charge liners with apex angles of 60° … 80° at induction of the magnetic field created in the liner at level of tenths of a tesla which is technically quite easy to implement.

Simple flash screens for shaped charge jet and flyer velocity measurements

The paper describes a novel technique for measuring the velocity of fast flying objects. The technique utilises a series of simple single-use screens which are placed along the expected flight path. The projectile interaction with the screen generates a flash of light which is captured by an optical fibre connected to the light detecting device. The velocities are calculated from the signal arrival times and screen positions. The flash screens were tested using copper shaped charge jets and flyer discs accelerated by explosive charges made of sensitised nitromethane. In addition to the simple time of arrival measurement with VOD-815, the light signals were recorded using an OPTIMEX-64 light analyser which enabled checking their intensity and reproducibility. Some of the experiments were also carried out using a UHSi 12/24 high-speed camera. The flyer plate velocities measured were compared with empirical calculations from a Gurney model.

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 zirconium 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.

The inhibitor effect on the shaped charge jet penetration

A submunition is one of the small shaped charges and has a severe penetration capability when it is dispensed in large numbers from the sky. Neutralizing it is one of the major interests in military science. An inhibitor which can be formed inside of shaped charge liner when a submunition impacts soft material target plays an important role to the penetration performance. A silicone rubber material that shows suitable inhibitor character of being dug deep by submunition impact in penetration mechanism was selected. The penetration performance of a shaped charge adopted inhibitors was investigated through ballistic experiments and numerical simulations. A remarkable reduction of jet penetration capability was obtained from the experiment. Numerical simulation using LS-DYNA, which is a non-linear finite element analysis code, was also carried out to reconstruct the experimental results. The simulation results showed good agreement with the experimental results, providing insights into the noticeable reduction of jet penetration performance due to a silicone rubber inhibitor.

Kinematics of the shaped charge jet formation process

Based on the review of scientific and technical literature, an analysis is made of the problems of the modern theory of formation, extension and destruction of the shaped jet. The focus of the research is on the kinematics of the formation of a shaped jet based on the approach of operating with the characteristics of a real metal when the velocity vector of the cumulative jet is the result of three vectors: strain, strain and displacement of the shaped jet’s material. The numerical experiment of the functioning of the shaped charge is carried out, and the procedure for evaluating the calculation results is proposed. The obtained data correlate with existing knowledge about the physics of the cumulation process.

Effect of Magnetic Field of Elongated Solenoid on Deformation of Metal Shaped-Charge Jets

Inertial stretching of a metal shaped-charge jet in the presence of magnetic field of elongated solenoid is analyzed. Effect of the magnetic field on the shaped-charge jet is aimed at inhibition of the development of plastic instability of the jet with an increase in its ultimate elongation and penetration capability. Several simplifying assumptions are used to obtain analytical description of electromagnetic processes in a fragment of the jet that moves inside and outside the solenoid. Induction heating of a fragment of the jet and the stress state therein are calculated with allowance for electromagnetic forces under the experimental conditions of the earlier experiments on the effect of the magnetic field of solenoid on shaped-charge jets. The results are used to substantiate the hypothesis on the possible reason for a relatively large difference between the experimental data of different authors on an increase in the penetration capability of shaped charges.

Investigate the effects of magnetic fields on the penetration ability of a shaped charge jet at different standoffs

The influence of a magnetic field on the stability of a shaped charge jet is experimentally investigated at standoffs of 490, 650 and 800 mm. The experimental results without and with the magnetic field are compared in terms of the shaped charge jet form, stability and penetration ability. A theoretical model based on one-dimension fluid dynamics is then developed to assess the depth of penetration of the shaped charge at those three standoffs and magnetic conditions. The results show that the penetration capability can be enhanced in more than 70% by the magnetic field. The theoretical calculations are compared with the experimental results with reasonably good correlation. In addition, the parameters introduced in the theory are discussed together with the experiments at three standoffs studied.

Computational and Experimental Study of Operation of Shaped Charges with Hemispherical Liners of Degressive Thickness

Operation of shaped charges with copper hemispherical liners of degressive (decreasing from top to bottom) thickness is experimentally studied. The velocity of the head of generated shaped-charge jets is determined along with how deep they penetrate a type-setting target made of steel disks and the sizes of holes made in the disks. The experimental data on an increase in the velocity and a decrease in the mass of the heads of shaped-charge jets, which occur with an increase in the difference in the thicknesses of the hemispherical liner at the apex and at the base are in good agreement with the results of numerical simulation carried out within the framework of a two-dimensional axisymmetric problem of continuous mechanics. According to the experimental results, the effect of technological manufacturing errors on the operation of these charges becomes stronger, which eliminates or significantly limits the increase in the penetrating action. In one of the versions of liners of degressive thickness, the depth of penetration of a target, which is average in two tests, increases by 7.5% as compared to the liner of constant thickness.

A semi-empirical study of penetration of shaped charge jet into high and ultra-high strength reactive powder concrete targets

In this study, a semi-empirical model was proposed to calculate the penetration depth and cavity diameters generated by shaped charge jet into high and ultra-high strength concrete (H&UHSC) targets. A recently proposed axial penetration equation and the two-step mechanism of cavity growth were employed to determine the analysis. The predictions were validated with reference to the experiments conducted using a kind of H&UHSC named reactive powder concrete (RPC). Furthermore, the influences of the RPC compressive strength and the jet velocity on the penetration were analyzed. The results showed that the RPC targets had good protection efficiency for both penetration depth and cavity diameters as the compressive strength approaches approximately 250∼280MPa. Moreover, the radial cavity growth efficiency increased linearly with the increase of the jet velocity, while the axial penetration efficiency increased rapidly when the jet velocity was 1.0∼4.0km/s and reached the maximum at 4.0∼7.0km/s and tended to be stable as the jet velocity increased to greater than about 7.0km/s.

Study on Plastic Deformation Behavior of Mo-10Ta under Ultra-High Strain Rate

This study investigated the deformation behavior of the Mo-10Ta alloy with a strain rate range of 102–105 s−1. The Split Hopkinson pressure bar (SHPB) experiments were conducted to investigate the influence of deformation conditions on the stress-strain relationship and strain rate sensitivity of the material within a strain rate range of 0.001–4500 s−1. The Shaped Charge Jet (SCJ) forming experiments under detonation loading was conducted to clarify the dynamic response and microstructure evolution of the material within an ultra-high strain rates range of 104–105 s−1. Based on the stress-strain relationship of Mo-10Ta alloy at high temperature (286–873 K) and high strain rate (460–4500 s−1), the influence of temperature and strain rate on the activation energy Q was analyzed. The results indicate that the material strain rate sensitivity increased with the increase in strain rate and strain. Meanwhile, the activation energy Q decreased as the temperature and strain rate increased. The plasticity of the Mo-10Ta alloy under the condition of SCJ forming was substantially enhanced compared with that under quasi-static deformation. The material grain was also refined under ultra-high strain rate, as reflected by the reduction in grain size from 232 μm to less than 10 μm.

Determination of Delay in Detonation of a Sandwiched Explosive Impacted by a Shaped Charge Jet

A simple analytical model has been developed to determine delay in detonation of an explosive sandwiched between two metal plates and impacted by a shaped charge jet. The analytical model consists of a relation between detonation delay and depth of jet penetration in a target kept in contact across the explosive sandwich. This relation is derived by expressing depth of jet penetration P as a function of detonation delay Tdx and duration Tw of free passage of the jet through the hole in the top plate of the sandwich. One more relation between Tdx and Tw has been obtained from the theory of expansion of hole produced in a metal plate by jet impact. These two relations have been solved simultaneously to get values of both these parameters as a function of jet penetration. It is proposed that this analytical model can be used in two ways. First, this model can be used to calculate detonation delay by experimental measurement of jet penetration in a target. The detonation delay thus determined can be used to calculate insensitivity constant Aj of an explosive. Second, this model can be used to theoretically calculate jet penetrations obtained by different shaped charge warheads when using a sandwich of explosive with a given insensitivity. Both uses of this analytical model are illustrated using numerical examples.

Initiation of shaped charge into booster devices

ABSTRACT In this paper, the initiation capacity of shaped charges against booster devices is carefully examined using both experimental and simulation method. A booster device, which consists of insensitive charges, is investigated by shaped charge jet impact test. The results show that the response degree of the booster device with insensitive charge is detonation reaction. The numerical simulation results of jet initiation into booster devices are also compared with the witness board deformation performance. Furthermore, based on the validated numerical models and the corresponding parameters, a series of numerical simulations are performed to investigate the influence of the explosive types of booster devices, the locations of booster devices and the shell materials of booster devices. By assessing the peak pressure, maximum reaction degree and jet velocity, the influences of the key parameters on the booster device initiation are numerically discussed. The results indicate that, compared with traditional charge, the insensitive charge booster device has low jet initiation insensitivity. As the location of booster device changes, the anti-initiation performance of booster device changes. At the angle of 45°, the minimal initiation performance of the booster device is obtained. It is found that the density and strength of shell material have a slight effect on the jet initiation performance under the given thickness booster device. However, variations in the shell material property are found to impart significant effect on the jet penetration velocity, while variations in the strength impart a significant influence on the low-speed jet.

Reaction characteristics of polymer expansive jet impact on explosive reactive armour

Abstract In this study, a new damage mode for the explosive reactive armour (ERA) of a shaped charge jet was proposed. The response characteristics of polytetrafluoroethylene (PTFE) and polyamide (PA) polymer jet impact on the ERA were analysed. The expansion degree and the diameter of the PTFE jet are larger than those of the PA jet, but the compactness of the PTFE jet head is lower than that of the PA jet, resulting in different impact pressures of the different polymer expansive jets on the target. The PTFE jet achieved the penetration without initiation of the ERA at different standoffs, while the PA jet directly detonated the sandwich charge when impacting the ERA vertically and failed to penetrate the front plate when impacting the ERA at 68°. With the increase of standoff, the reaction degree of the PTFE jet to the ERA decreased gradually, and the aperture of the front plate did not change.

Finite element modeling of the shaped charge jet and design of the reusable perforating gun

Finite element method is used to study the formations of the penetration jet, the bulge, and the burr in the designed reusable perforating gun. The attached layer of the soft metal on the perforator is studied for the controlling of the bulge height on the casing of the reusable perforating gun. Results indicate that the shaped charge jet is initially formed in the center of the shaped charge liner and then the material of the liner is driven to the centerline of the liner by the detonation wave. The attachment of the soft metal layer to the cartridge of the perforator can be beneficial to control the bulge height. The design on the blind holes on the casing can affect the burr height formed by the collision between the jet and the casing. With the increase in the liner angle, the penetration width on the cement wall of the wellbore is increased.