Explosively Formed Penetrator Research Articles

Formation of an Explosively Formed Penetrator Warhead Using a Step-Shaped Charge

In this study, the formation mechanism of an explosively formed penetrator (EFP) with tail fins was analyzed. Through static denotation and dynamic flight tests, the feasibility of using a step-shaped liner during the formation of an EFP with tail fins was verified. The influences of the step depth, h, and the step angle, Φ, on the flight stability were then explored. Based on the consistency between the numerical simulation and experimental results, the influences of the step-shaped liner’s spherical arc radius, number of steps, and wall thickness on the formation and flight stability of an EFP with tail fins were further studied. The results showed that a T2 copper step-shaped liner performed better than a H90 brass liner. Compared with a hemispherical liner with an equal wall thickness, the step-shaped liners resulted in EFPs with initial angular velocities and relatively better flight stability. Moreover, a greater initial angular velocity led to a higher EFP landing accuracy.

Research on the Penetrator Characteristics and Flight Stability of Explosively Formed Penetrator

Research on the Penetrator Characteristics and Flight Stability of Explosively Formed Penetrator

Study of Shape and Microstructure Changes of Ta Linear for Building an Explosively Formed Penetrator

Study of Shape and Microstructure Changes of Ta Linear for Building an Explosively Formed Penetrator

EFP Structure Optimal Design for Satellite Attack through Air-space Platform

Air-space combat is the inevitable tendency for future war. Building weapon system on spacecraft is prerequisite for passive defense and active attack. Considering limited space and constrained posture adjust ability, this paper established a weapon system by installing EFP (explosively formed penetrator) warhead and the optimal design of EFP structure. Several critical technologies related to EFP design were studied, an optimal design project of EFP warhead structure war acquired after constructing mathematic models and numerical simulations, which can effectively solve the critical technical difficulties of constructing weapon system on spacecraft.

Effect of the liner material on the shape of dual mode penetrators

The effect of the liner material density and elongation on the shape of dual mode penetrators is studied by using the LS-DYNA software. Characteristics of liners made of five types of materials (aluminum, pure iron, copper, tantalum, and tungsten) under the same conditions of the liner volume or liner mass are compared. It is established that it is better to choose liner materials with good dynamic elongation and moderate density, such as pure iron and copper, to form good dual mode penetrators, namely, the explosively formed penetrator (EFP) and the jetting projectile charge (JPC). Characteristics of penetrators formed from aluminum, steel 20, and copper are considered. The simulation results are in good agreement with x-ray imaging experimental results.

Analysis of forming characteristics of Ta EFP according to material model

This paper presents numerical analysis result of forming characteristics of Ta explosively formed penetrator (EFP) according to various material models and their values. Dynamic material properties of Ta were measured with static tensile testing machine and Hopkinson pressure bar tests. We used AUTODYN hydrodynamic code to simulate these phenomena. We used three material models, such as Von-Mises model, linear hardening model and Johnson-Cook model. We also compared the numerical results with the EFP forming test data. The numerical results show that material model and its parameter are so important to predict the shape of formed penetrator and Von-Mises model predicts the shape of the formed liner most well. We also analysed the influence of liner thickness on EFP formation using the verified numerical model.

Formation of explosively formed penetrator with fins and its flight characteristics

Abstract 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.

Method of converting a multimode penetrator through point initiation

This study presents the problem of achieving multimode penetrator conversion. By using the same shaped charge and by changing the position of point initiation, the trial demonstrates two types of the penetrator, which are the explosively formed penetrator (EFP) and the rod-shaped EFP. Compared with the EFP, the penetration depth of the rod-shaped EFP is 2.17 times higher, and the penetration aperture only decreases by 31.8%.

Research on the optimum length–diameter ratio of the charge of a multimode warhead

This paper outlines our research on a multimode warhead in which we adopted center point and annular initiation modes to form multimode penetrators. Using LS-DYNA software, we studied the effect of the configuration parameters, namely the length/diameter ratio of the shaped charge, on the formation parameters, such as the velocity and length/diameter ratio, of multimode penetrators. We found that when the charge length was in the range of 0.9–1.2 times the charge diameter, the same structure of shaped charge can form suitable multimode penetrators. Either an explosively formed penetrator (EFP) or a long stretchy rod-shaped EFP penetrator can be formed. We establish an optimum charge length for penetrator formation of 1.4 times the charge diameter. Simulation results were validated using X-ray imaging experiments and they were in good agreement. The results found that by increasing the charge length from 0.9 to 1.4 times the charge diameter, the penetration depth of the EFP increased by 74.5%, while increasing the charge length from 1.4 to 1.6 times the charge diameter only increased the penetration depth by 1.9%.

Numerical Simulation on Bifurcate Fracture of Linear Red Copper Penetrator

The Red copper has been widely used in shaped charge liner because of good ductility. Red copper penetrator is a Linear Explosively Formed Penetrator (LEFP) when linear red copper shaped charge liner overturned under the effect of detonation production. Compared with ordinary jet swords, red copper penetrator has a wider range of stand-off, bigger cratering and significant aftereffect, which can meet the requirements in various environments. It was observed that bifurcate fracturing of red copper penetrator occurred in the performance testing of LEFP initiated on edge midpoint as the stand-off increased, which resulted in the separate craters on the target and the cratering effect was weakened. The Propagation of detonation wave and the interaction with red copper shaped charge liner were theoretically and experimentally studied, also numerical simulations were conducted. The results showed that velocities of charge liner elements were directly proportional to those of detonation waves, which caused different velocity directions and values of different elements, and great velocity gradient formed in the penetrator. The penetrator fractured as the elongations both on the vertical and horizontal directions were greater than the dynamic elongation of red copper. It was concluded that the main factor which resulted in the bifurcate fracture phenomenon was velocity gradient in the penetrator.

Formation Mechanism of Linear Explosive Formed Penetrator by Midpoint Initiating Manner

Linear explosively formed penetrator (LEFP) is an optimal combination of linear cutting sword and conical shaped charge but is completely different with those two above. Initiating manner of LEFP is one of the most important factors that can affect its performance obviously. LEFP forming mechanisms of linear shaped charge initiated from the mid-point were studied with combined method of theoretical analysis, experiments and numerical simulation. Liner movement driven by the detonation wave action was analyzed as a three-dimensional issue and a synthetical model of liner movement was established. The model were verified by the penetrating experiments with the LEFP initiated from midpoint under stand-off which is 5 times distance of the LEFP caliber size. Formation processes of LEFP were described through numerical simulation and the simulation results were in concordance with those of experiments.

The Effect of Explosive Material on the Formation of Explosively Formed Penetrator

In order to research the effect of explosive material on the formation of EFP, this paper studies the effect of five different explosive materials, PETN, SEP, TNT, PE4BOOSTER and 8701, on forming EFP, using ANSYS/LS-DYNA simulation software. It obtained the influence of the material character of the explosive on the formation parameters of EFP, such as velocity and length-diameter ratio. It can be found that, when the density of explosive increases from 1.26g/cm3 to 1.7g/cm3, the velocity of EFP increases by 50.8%, and the length-diameter ratio improves by 2.16 times. It is good to choose the explosive with high energy and speed in design charge warhead at the same condition. The simulation results were validated through X-ray imaging experimentation. Both results are in agreement well.

The Bifurcate Fracture Analysis of Linear Red Copper Penetrator

Red copper has been widely used in shaped charge liner because of its good ductility. Red copper penetrator is the Linear Explosively Formed Penetrator (LEFP) with some length and energy which has been produced when linear red copper shaped charge liner is overturned under the effect of detonation production. Compared with some ordinary jets sword, it has some characteristics such as the broad range of stand-off, big cratering and obvious rear effect and may meet with many operating requirements in different environment. It has been discovered that the bifurcate fracture phenomenon of red copper penetrator will occur with the increase of stand-off when it is initiated on edge midpoint in its property test experiment, and results in the separating cratering on the target which influences its effect. The Propagation characteristics of detonation wave in explosive and the effect of detonation wave on red copper shaped charge liner are analyzed, and then the velocity change obtained by each element and the velocity relationship between each element are studied. So it can be drawn a conclusion that the velocity gradient is the main factor which results in the bifurcate fracture phenomenon of red copper penetrator. In addition, the theoretic analysis model of the bifurcate fracture in red copper penetrator is built. On the basis of modeling analysis and calculation, the criterion of the occurring bifurcate fracture and the measures avoiding the bifurcate fracture are put forward. The results agree well with that of experiments.

DESIGN OF AN EXPLOSIVELY FORMED PENETRATOR CAPABLE OF DEFEATING A SPECIFIC METALLIC TARGET

ABSTRACTDesign of a warhead that forms upon detonation an explosively formed penetrator(EFP) capable of penetrating a specific rolled homogeneous armor (RHA) is the maintheme of this paper. Six different preliminary warhead models have been simulatedusing Autodyn-2D code. The main features of each EFP formed from eachpreliminary model are predicted. The obtained results serve in determining thedesign parameters of the required (refind) warhead model. In addition, the simulatedEFP from the refined warhead model and its penetration into a specific RHA havebeen simulated.Samples of the obtained predicted results by the code for EFPs formed from differentpreliminary and refined warhead models, respectively, are presented with relevantanalysis and discussions. For the refined warhead model, the code predicts that theobtained EFP has a high velocity, high aspect ratio and is capable of penetrating theRHA to the specified thickness. Moreover, the influence of explosive type, its aspectratio and liner material of the refined model on the formed EFP have been predicted.

Some considerations for 3D EFP computations

This article identifies some issues, options and results associated with 3D Explosively Formed Penetrator (EFP) computations. The three broad categories of interest (for Lagrangian computations) are the sliding/contact interfaces, the type and arrangement of elements, and the generation of the grid. The sliding/contact algorithm uses a virtual particle approach that is very robust, and it is described in detail. Tetrahedral elements are considered for both symmetric and non-symmetric arrangement, each with some advantages and disadvantages. A mixed element algorithm is also considered for the non-symmetric arrangement, in an effort to eliminate some of the locking that occurs for the non-symmetric arrangement. Hexahedral (brick) elements are not considered herein, but some of the effects (for tetrahedral elements) also apply to hexahedral elements. For axisymmetric EFPs there are also some trade-offs (symmetric grid vs. equally sized elements) associated with the generation of the grid. Computational results are provided to illustrate each of the issues and effects. The virtual particle algorithm is also well suited for high-velocity impact computations, and an example is included to demonstrate this capability for a complex problem.

Kalman filtering: a new approach for building global approximations. Application to the inverse optimization of an explosively formed penetrator (EFP)

As the use of approximations is often the only way to deal with the optimization of complex structures, this paper discusses the use of Kalman filtering as a new approach for building global approximations. Basic ideas and procedures of Kalman filters are first recalled. Next, key elements of how to implement the method for design problems are described. Finally, in order to evaluate the performance of the approach, an inverse problem which consists in optimizing a warhead with respect to constraints on the resulting projectile is studied. It is shown that global approximations are convenient for the solution of complex optimization problems and that Kalman filtering techniques appear to be an interesting strategy for the construction of global approximations in structural optimization.

Deformation twins in a shock-loaded Ta-2.5 w/ o W precursor plate and a recovered, Ta-2.5 w/ o W explosively formed penetrator

The effect of shock-loading on microstructural evolution and mechanical response of various metals and alloys has been studied for almost five decades. However, BCC metals and alloys, with the exception of iron and ferritic steels, have received much less attention than have FCC materials. Recently, high density BCC materials like tantalum and tantalum-tungsten alloys have generated a lot of interest due to their armor-defeating capability in such applications as shaped charges and explosively formed penetrators (EFPs). High-explosive generated shock waves interact with the metallic liners and form these penetrators in flight. Consequently, the shock-wave parameters and initial liner microstructures can play an important role in both macro- and microstructural development of these ballistic devices. In this study, the authors observed deformation twins in an annealed, shock-loaded Ta-2.5wt%W precursor plate and, for the first time,m in the tail section of a soft-recovered, six-finned Ta-2.5wt%W EFP.

Empirical Determination of the Manufacturing Processes Which Affect EFP Liner Performance

Abstract This paper addresses a recent test series in which an L-8 Taguchi array was used to investigate the effect of various manufacturing factors on the formation of a high-performance aerostable flared explosively formed penetrator (EFP) and its subsequent effect on target. The purpose of the experiment was to develop a method of manufacturing liner blanks that would reduce variances in EFP performance. The factors investigated were: 1. Initial anneal of the material 2. Amount of work in the material prior to the initial anneal 3. Amount of material removed from the diameter of the material prior to forging 4. Forging temperature 5. Forging rate 6. Liner annealing temperature 7. Material lot number The analysis was done using 14 quality characteristics. These were: 1. EFP rod length 2. EFP necking ratio 3. Orthogonality of the flare to the rod 4. Circularity of the EFP flare 5. Sweep angle of the flare with respect to the rod 6. Flight angle 7. Entry hole diameter 8. Throat hole diameter 9. Exit hole diameter 10. Spall diameter 11. Spall volume 12. Impact accuracy 13. Overall shape (beauty) of the EFP 14. Variability between duplicates The analysis was done as a blind experiment in that the persons who were ranking the individual trials were not told what the factor levels were for the individual trial. The results of the rankings were combined and a process was chosen. This process was then used to form the verification units that confirmed the experimental results.

LEDS in ultra-high strain-rate deformation

Regimes involving very high strains (e 900%) and high strain rates (e 10 4 to 10 7 s −1 ) provide intriguing and often systematic examples of low-energy dislocation structures (IEDS). In this broad study, microstructure evolution in plane-wave shock-loaded Ni and Cu is compared with microstructures observed in starting Cu and To shaped charge liner cones, and recovered jet fragments and slugs. These microstructures, in turn, are compared with corresponding end-point microstructures in a Ta explosively formed penetrator (EFP) utilizing TEM techniques. In addition, microstructures associated with a hypervelocity impact crater in Cu are compared with the Cu shaped charge microstructures. Dynamically induced grain refinement (subgrain formation) and recovery play varying and important roles in the evolution and features of observed LEDS, and are a manifestation of adiabatic heating due to high strain and strain-rate effects ( (e) (e)). LEDS, which are characteristic of high strain and ultra-high strain-rate deformation, cause an inversion in hardness and flow stress profiles since as these microstructures decrease in size, hardness will decrease. By contrast when low-temperature LEDS decrease in size hardness increases