Charge Jet Research Articles

The damage and failure mechanism of the concrete subjected to shaped charge loading

Abstract In this paper, the experiments of the large-size shaped charge jet penetration in concrete target were carried out. Then, the concrete target was cut off to obtain the internal structure and measure the shape of the penetration hole. Moreover, the cube concrete samples with the sizes of 100 mm length in different location of the concrete target were incised, and the material compressive strength was test by the material testing machine. The test results show that the material strength of the concrete target is enhanced with the increase of the distance to the penetration hole. Therefore, the damage of concrete target can be rough evaluated according to the compressive strength of the concrete samples. Based on the test results, the damage factor was added in the dynamic constitutive, which can describe mechanical behavior of concrete subjected to intensive impact loading was proposed. In this model, the concrete is assumed to be homogenous and consecutive in macroscopically. The results of the model were compared with the experimental results and the results which not considering the damage factor. The comparing results show that the model can be used to describe the dynamic mechanical behavior of concrete.

Numerical simulations of shaped charge jet penetration into concrete-like targets

Shaped charge jet has been widely applied in the military and energy sources’ extraction fields; while the related investigations on the shaped charge jet penetration into concrete-like target are still limited, a series of numerical simulation works are conducted in this article. Holmquist–Johnson–Cook and Johnson–Cook models are used to describe the concrete-like targets and metal liner/casing of the shaped charge, respectively. The whole process including the formation, elongation in the air, and penetration into concrete-like target of shaped charge jet is reproduced using the multi-material arbitrary Lagrange–Euler algorithm and fluid–structure interaction method implemented in LS-DYNA. Simultaneously, the striking velocities of the jet (both tip and tail) and the damage of target (diameter and depth of penetration borehole) are derived. The above constitutive models, the corresponding material parameters, and the finite element algorithms are validated by comparing with the available tests’ data. The analyses of parametric influences are further performed. It indicates that for the unfragmented shaped charge jet, the penetration depth increases and the average penetration borehole diameter decreases with the standoff distance increasing, respectively; the compressive strength of concrete target has slight influence on the penetration depth of shaped charge jet; the diameter of shaped charge jet penetration borehole with aluminum liner is larger, while that with copper liner has a deeper penetration depth. It can also be found that the influence of explosive type on the penetration performance of shaped charge jet is negligible at small standoff distance, while the explosive LX-14 performs better than explosives Octol, B, and 8701 at larger standoff distance.

A Numerical Method for the Determination of the Virtual Origin Point of Shaped Charge Jets Instead of Using Flash X-ray Radiography

ABSTRACTThe effective jet length between the virtual origin (VO) point and the target surface is very important for the calculation of a shaped charge jet penetration. A numerical approach to determine the exact position of the VO of a small caliber shaped charge jet is presented in this paper. The numerical approach includes shaped charge jet formation algorithm using explicit Autodyn solver and estimates the precise location of the VO point using the hydrocode analysis. This is particularly important when the experimental flash X-ray radiograph is not available. The proposed VO model approach was validated by firing four small caliber shaped charges against concrete targets. The maximum difference between the experimental penetration depth and that calculated using the presented VO approach was less than 4%.

Effect of External Magnetic Field Loaded at the Initial Period of Inertial Stretching Stage on the Stability of Shaped Charge Jet

In this paper, the effect of external magnetic field loaded at the initial period of inertial stretching stage on a jet produced by O56-mm shaped charge is evaluated through the depth-of-penetration (DOP) test method. Experimental results are compared with the results obtained under the field loaded at the later inertial stretching stage. A standoff of 650 mm is used in the experiments, in which the shaped charge jet can undergo formation, elongation, breakup, rotation, and drift. The initial energy is provided by a capacitor bank, which is loaded on the solenoid to generate a magnetic field used for coupling with the jet. The external magnetic field loaded at the initial period of inertial stretching stage can enhance the stability of the jet and increase its DOP. The penetration capability of the jet in the above-mentioned condition is increased by 77.4%.

Spallation affected fracture pattern of a titanium alloy plate subjected to linear shaped charge jet penetration

In this paper, the commercial finite element code LS-DYNA is employed to simulate the process of a certain kind of a linear shaped charge jet penetrating into a TC4 (Ti–6Al–4V) titanium alloy plate of moderate thickness. The fracture profiles agree well with experimental observations, which confirms the validity of the code and the Johnson–Cook material model applied to describe the TC4 plate. The fracture pattern of the plate is drawn based on this comparison.

Deformed Flying-Plate Influence on the Interaction between Jet and ERA

The basic physical mechanisms associated with a shaped charge jet penetrating ERA were described in many previous works. In the previous disturb model, the fly-plate was thought as rigid body with no deformation. In according to the physical phenomenal of flying-panel moving, the fly-plate in ERA is deformed. Followed the deformation model of flying-plate, dynamic model of jet disturbances caused by deformed plate of ERA has been set up. A comparison between theoretical results with the numerical simulation and experiment ones show good agreement.

Numerical Simulation on the Interaction between Shaped Charge Jets and Confined Explosives

Numerical Simulation on the Interaction between Shaped Charge Jets and Confined Explosives

Development and Evaluation of Small Shaped Charge Jet Threats

Because of their prolific nature on the battlefield, rocket propelled and gun-launched grenades are of particular concern to the soldier, particularly because of the severe reaction that occurs when a munition is hit by the shaped charge jet. As a result of the danger that such a detonation poses, it is necessary to more precisely understand the behaviour of munitions subjected to these types of devices. In response to these threats, standardized 81 mm and 40 mm shaped charge warheads were developed for use during threat assessment testing to act as a consistent, lower-cost representative of shaped charge projectiles commonly encountered on the battlefield, and to help quantify the interaction of these jest with explosive charges. The international standards for shaped charge jet threat testing uses the Held initiation criteria V2D, where V is the jet velocity and D is the diameter. V2D was computationally predicted using the high-rate continuum models CALE and ALE-3D. The surrogate warheads were test fired through aluminium target plates to strip off jet mass to adjust the V2D to the threat munition.

Определение энергии кумулятивной струи различными способами

Определение энергии кумулятивной струи различными способами

Theoretical and experimental study on the effect of the external strong magnetic field on the shaped charge jet

The external strong magnetic field coupling with shaped charge is an effectively method to increase the penetration capability of the shaped charge jet. In this study, a theoretical model was developed to analyze the effect of the external strong magnetic field on breakup time and inhibition of rotation and drift of the shaped charge jet. The discharge current of the circuit system and the magnetic field of the shaped charge jet undergoing were calculated in detail. A series of depth of penetration (DOP) experiments were conducted to analyze the coupling mechanism between the external magnetic field and the shaped charge jet. Theoretical and experimental results indicated that the external strong magnetic field coupling with shaped charge jet can effectively improve the stability of the shaped charge jet, which the magnetic field can delay its breakup time and inhibit its rotation and drift. The ability of penetration of the jet produced by the Ø56 mm shaped charge is increased by 69.13% under the action of the external magnetic field.

Damage response of steel plate to underwater explosion: Effect of shaped charge liner

A shape of charge liners has a great effect on formation of a metal jet and its penetration into a target. In this paper, three different shapes of a charge liner, namely, conical, hemispherical and spherical-segment, are chosen to investigate their effect on damage response of a plate to underwater explosion. A Smooth Particle Hydrodynamic (SPH) method based on mesh-free Lagrange formulation is applied to simulate an entire process of a shaped-charge detonation, formation of a metal jet as well as penetration on a steel plate. Initially, a SPH model of the shaped charge with a spherical-segment liner is developed, and its results are compared with experimental data to verify the effectiveness of this method. Then, numerical simulations of shaped charges with different liners are performed to study the damage characteristics of a steel plate subjected to underwater-explosion shock loading and the metal jet. It was found that for the shock wave the peak value of the radial pressure is larger than that of the axial pressure during the detonation process; the level of pressure in the spherical-segment case was higher than that of the other two cases. After the detonation, the metal jet was gradually produced under the effect of the detonation wave. Three types of the metal jet - a shaped charge jet (SCJ), a jetting projectile charge (JPC) and an explosive formed projectile (EFP) – were formed corresponding to three cases with conical, hemispherical and spherical-segment liners. The obtained results show that the velocity and length of the SCJ in the conical case are greater than that of the other cases, and it therefore may lead to a larger penetration depth. In addition, the EFP has a better motion stability for a velocity difference in the spherical case is lower than that of the other two cases. Subsequently, the shock wave arrives at the plate earlier than the metal jet, which will cause deformation of the plate. Due to higher pressure, the shock wave in the spherical-segment case has a stronger damaging effect on the plate than that in the other two cases. Finally, the metal jet reaches the plate causing a hole. Because of a wider jet head, the EFP results in a more serious damage to the plate. The suggested analysis and its results provide a reference for structural design of shaped charge warheads.

Numerical Simulation of Steel Target Penetration by Shaped Charge Distended Jet with a High-Polymer Liner

This study investigates the characteristics of shaped charge jet formed with a high-polymer (PTFE) liner, as well as its penetration capabilities, by theoretical, experimental, and numerical methods. This work presents a viscoplastic model and equation of compressible fluid to describe the jet cohesive condition. It also shows that the high-polymer jet is inevitably distended. Two types of liner materials were studied: a high-polymer PTFE liner and a pure copper one. The corresponding numerical simulations of the two jet formations are presented. The pulse X-ray photographic technology was employed to observe the distended jet of the PTFE liner and the particulate jet of the copper one. The simulation and jet radiography results show that the two types of jet behavior with particulate and radial dispersion are ductile and related to the liner material. The distended jet formation result from the liner material was crushed at the high-pressure region because a sudden pressure jump induces the radial velocity rise, which results in lateral expansion. As compared with a typical copper penetration performance, the polymer distended jet had a larger aperture and lower penetration depth. Due to polymer liner lower density, this jet will have limited penetration as compared to that of a copper liner. The simulated results strongly agree with the experimental ones. The polymer material can be modified to obtain much better performance, which will greatly enhance the penetration capacity of polymer jets.

Spallation Affected Fracture Pattern of a Titanium Alloy Plate Subjected to Linear Shaped Charge Jet Penetration

Spallation Affected Fracture Pattern of a Titanium Alloy Plate Subjected to Linear Shaped Charge Jet Penetration

Hydrocode simulations of liquid filled channels for understanding erosion in shaped charge jet penetration

Hypervelocity impacts of copper rods into liquid filled channels circumferentially confined by steel cylinders were investigated using 2D axisymmetric hydrocode simulations. The confined liquid was utilized as a means to investigate the interplay of eroded target material and the remaining projectile in order to elucidate relevant penetration behaviors in solid materials. This led to a better understanding of two significant contributing parameters in the flow characteristics: the density (how difficult the material is to accelerate) and the channel diameter (how far the material has to move). While the liquid eliminates direct strength effects on penetration of the rods, varying the channel width allows a survey of parameter space that is typically a function of both material strength and density. Three successive copper rods with varying velocities and delays were used to model a penetrator representative of select sections of a shaped charge jet. For each target material, the residual penetration in solid rolled homogeneous armor (RHA) was then measured as a function of the liquid channel width. A strong dependence on both the material density and channel width was observed in regards to the efficiency of the material against penetration.

Fragment impact modeling and experimental results for Insensitive Munitions compliance of a 120mm warhead

The US Army ARDEC at Picatinny Arsenal, NJ is currently developing a 120mm munition to achieve greater Insensitive Munitions (IM) compliance. Several international standardization agreements (STANAGs) outline various IM threats that are designed to simulate the hazards munitions are commonly exposed to on the modern battlefield. These threats include sympathetic reaction (SR), shaped charge jet impact (SCJ), cook-off (CO), and bullet and fragment impact (BI/FI). FI is the focus of this effort. As per NATO STANAG 4496 Ed. 1, FI testing is conducted at 2530±90 m/s with a 14.3mm diameter, L/D~1, 160˚ conical nosed mild steel fragment. Reaction violence resulting from FI can be mitigated by the use of an internal or external liner, commonly referred to as a particle impact mitigation sleeve (PIMS), applied to the warhead body. High rate continuum models were used to interrogate the shock and penetration responses of several PIMS-enhanced 120mm warheads loaded with PAX-3 explosive. The concepts were subsequently tested at the GD-OTS test facility. Test outcomes are reported and are compared with modeling predictions. The models indicate a significant reduction in the induced shock pressures due to application of the PIMS, and provide a good distinction between the initiating and non-initiating impacts which were experimentally observed. However, more work is needed to reduce the violence of the resulting subdetonative responses.

A Modified Penetration Model for Copper-Tungsten Shaped Charge Jet with Non-Uniform Density Distribution

A Modified Penetration Model for Copper-Tungsten Shaped Charge Jet with Non-Uniform Density Distribution

Possibility of the Use of Different Types of Materials in Passive Ventilation Systems of Munitions

The paper presents different types of insensitive munition used in military equipment, especially in western countries. Tests of this munition, their parameters, e.g. fast and slow heating, bullet, fragment and shaped charge jet impact and sympathetic reaction are described. The characteristics of shape-memory materials like alloys and polymers are presented. Behaviour of shape-memory alloy is explained by example of TiNi al-loys during mechanical or thermal loading, and martensitic transformation into austen-ite during unloading. Material parameters of the TiNi alloys, their testing and mathematical equations are shown. Venting systems used in the explosive reactive armour cassettes are presented. Different examples of materials, including shape-memory materials in munition, are demonstrated.

Comparison of penetration performance and penetration mechanism of w-cu shaped charge liner against three kinds of target: Pure copper, carbon steel and Ti-6Al-4V alloy

In order to investigate the interaction between shaped charge jet and target, three different targets, including pure copper target, carbon steel target and Ti-6Al-4V alloy target, were penetrated by W-Cu shaped charge jet. Penetration performance and corresponding penetration mechanisms were studied. Calculated theoretical penetration depth ratio of Ti-6Al-4V alloy target, pure Cu target and carbon steel target is 10:2.8:5.7, while the practical penetration depth ratio is 10:28:21, indicating that the interaction between jet and target has a significant effect on the penetration depth. Microstructural analysis shows that the interaction between jet and Cu target is the lightest among the three kinds of targets, leading to an increased penetration depth of Cu target. The interaction between jet and Ti-6Al-4V alloy target is the severest, resulting in an increased transverse energy dissipation of jet and decreased penetration depth of Ti-6Al-4V alloy target. Given the significant interaction between jet and target, we propose a modified equation of penetration depth by adding an empirical parameter, which provides a platform to predict more accurate penetration depth.

Constraining a shaped charge jet cavity in a barrier with boundary shields

We suggest and validate empirically an acoustic method for decelerating and halting the movement of a shaped charge jet in a barrier by means of implementing an acoustic slit in the body of the barrier, the slit being located on the opposite side of the barrier relatively to the mounted linear charge with a profiled liner. We determine the pressure range created by a linear shaped charge with a profiled liner, and provide an estimation of the hydrodynamic wave length for the penetration process.

From Synthesis to Formulation and Final Application

AbstractMeeting the requirements for insensitive munitions remains a complex route, where all the steps of the production process have to be addressed. NTO is a choice component, especially for large munitions. Various compositions have been optimized, which are now available, in pressed or cast PBX as well as melt cast formulations. Standard products such as RDX have been improved by the synthesis or crystallization methods, giving reduced sensitivity formulations. Some cast PBX can sustain severe shaped charge jet impacts, thanks to their large critical diameter, and are candidates as main filling of large munitions such as IM Mk82. The formulation step is addressing not only new binder principles, allowing an increase in the filler and thus energy contents, but also a bi‐component innovative method to get a semi continuous filling process where the pot life is no longer an issue. Finally a partial toolset for designing IM features is proposed with a recent example of successful application.