Shaped Charge Warhead Research Articles

Performance study of explosively formed projectile using CoCrFeNi high-entropy alloy as a liner

Based on mechanical tensile experiments on the CoCrFeNi high-entropy alloy (HEA), this study explores the forming patterns of the eccentrically shaped sub-hemispherical lined explosively formed projectile (EFP) made of the HEA material. The CoCrFeNi HEA material is initially prepared, and mechanical tensile tests are conducted at various temperatures and strain rates. The Johnson–Cook (J–C) constitutive equation for this material is derived by fitting the experimental data. Scanning electron microscopy and the energy dispersive spectrometer characterize the fracture surface of the tensile specimens, providing insights into the mechanical ductility and fracture mechanism of CoCrFeNi HEA. The EFP forming process under various charge configurations is simulated using AUTODYN software, leading to the identification of the optimal charge configuration. In addition, the damage performance is evaluated. This study provides a theoretical basis for applying HEA materials in the field of shaped charges and offers new ideas and methods for designing more efficient shaped charge warheads.

The potential of rubber materials as an inhibitor to suppress jet formation of the shaped charge warhead

The potential of rubber materials as an inhibitor to suppress jet formation of the shaped charge warhead

The experimental and theoretical study on the spatial‐temporal distribution of electromagnetic radiation from JO‐8 explosions.

AbstractThe detonating fuse in the multistage warhead will be subjected to strong electromagnetic interference, derived from electromagnetic radiation generated by explosion of the shaped charge warhead, which may cause premature detonation or misfire. In order to explore the possible electromagnetic environment surrounded the detonating fuse, the spatial‐temporal distribution of electromagnetic radiation after the explosion of JO‐8 explosive was investigated in this paper. The electromagnetic radiation signal was collected and its frequency coverage was analyzed in the far‐field area by the field blast test. Moreover, based on electromagnetic theory, a theoretical model of electromagnetic radiation generated by the explosion of JO‐8 explosive was established, and the spatial‐temporal distribution of the electric field intensity was illustrated in detail for several typical positions after the explosion. The better agreement between experimental and theoretical results indicates that the proposed theoretical model and computational method are reasonable. On this basis, the distributions of electric field intensity for different positions and various explosive weights were predicted respectively by using distance and explosive weight as variables. This study is expected to provide a reference for the research on the electromagnetic radiation for explosive explosion and anti‐explosive electromagnetic interference.

Research on the influences of motion characteristics of jetting projectile charge under water

Shaped charge warhead is important for enhancing the damage performance of underwater weapons. This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters (wall thickness, material), charge aspect ratio, and stand-off distance on the movement characteristics of JPC in water. The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water, the effective length of the JPC in water undergoes two distinct phases: a growth phase and a decrease phase, with the velocity of the JPC decaying exponentially. Increasing the liner thickness, stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC. The optimal ranges for liner thickness and stand-off distance are 0.0363Dk to 0.0545Dk (Dk is the charge diameter), the stand-off distance should be within 1.0Dk. After the charge aspect ratio higher than 1.25, the charge structure exerts minimal influence the movement characteristics of the JPC in water. Material density plays a crucial role in the velocity decay pattern of the JPC during penetration. JPC with higher densities exhibit superior velocity retention capabilities in water, with the velocity decay pattern converging if the densities are similar. Consequently, copper, tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead. Finally, the results will provide an important reference for the design of underwater shaped charge warhead.

Optimization of Al/PTFE applied to detonation network used for micro shaped charge warhead.

In order to improve the detonation performance of the explosive network on the basis of achieving high safety and reliable detonation, 3,4-dinitrofurazanyl oxyfurazan (DNTF) was used as the main explosive, glycidyl azide polymer(GAP) was used as the binder, and other auxiliary agents were added to the basic charge formula. Then, polytetrafluoroethylene (PTFE) and aluminum (Al) were introduced to further enhance the output power of the charge formula. The influence of two introduction methods of PTFE and Al was evaluated: directly mechanically mixing method and activation method by metal ball milling. A variety of tests such as particle size, morphology, detonation performance in groove were carried out to study the difference between mixed Al/PTFE and milling activated Al/PTFE. The experiment showed that particle size becomes smaller and Al/PTFE were well compounded. Moreover, results showed that the charge formula with milling activated Al/PTFE possessed good propagation reliability in micro linear groove and stronger external expansion capability. These properties were vital for the charge formula to be applied to the complex explosive circuits used for micro shaped charge warhead.

Protection mechanism of underwater double-hull coated with UHMW-PE subjected to shaped charge

Shaped charge warhead which is widely utilized for underwater weapons has a severe threat to the survivability of naval ships. Therefore, it is of great significance to improve their anti-destructive capability. Three types of loads - shock wave (SW), shaped charge projectile (SCP) and bubble - are generated during the process of shaped charge associated with underwater explosion, which can cause different damage characteristics into double-hull structure. In this paper, these three loads characteristics and their combined damage into double-hull structure are analyzed. Besides, the protection of fiber metal laminates on this structure are discussed. Firstly, Coupled Eulerian-Lagrangian (CEL) is used to simulate the full physical process of double-hull subjected to shaped charge associated with underwater explosion. Secondly, the damage characteristics of double-hull are obtained under the combined damage of the shock wave, shaped charge projectile and bubble. After that, the steel plate/UHMW-PE laminate (Fiber Metal Laminate, FML) is designed according to the equal surface density theory. The blast and penetration resistance of ultra-high molecular weight polyethylene (UHMW-PE) material is analyzed and the optimized FML models are discussed. The results show that a small plastic deformation and hole of the outer and inner plates of the double-hull are generated by the shock wave and the shaped charge projectile, respectively. A large plastic deformation of the outer plate is caused by the subsequent bubble load, which is torn and pulled off. The hole size of plate coated with PE and the residual velocity of projectile reduced by 26.66% and 69.50% compared with those of the steel plate, respectively. Besides, for the coated cases the outer and inner plates is respectively not pulled off and penetrated by projectile. Additionally, it is worth noting that the bubble collapses and cannot cause the secondary damage into double-hull due to the protection of coated PE. It indicates that the PE has a great protection performance of the double-hull subjected to shock wave, bubble and projectile, which can provide a reference for the naval ships protection design.

Formation and Penetration Properties of a Shaped Charge with Zr41.2Ti13.8Cu12.5Ni10Be22.5 Liner.

In the military field, determining how to increase the hole-expanding ability of shaped charge warheads is a key and difficult issue with respect to warhead development. Amorphous alloys have grains or grain boundaries, with unique mechanical properties. Zr41.2Ti13.8Cu12.5Ni10Be22.5 can be used as the liner material of shaped charges, resulting in high-speed particle flows that differ from those of traditionally shaped charges. In this paper, based on the analysis of the mechanical response characteristics of Zr41.2Ti13.8Cu12.5Ni10Be22.5 and its fracture morphology under impact, combined with the formation theory of shaped charge jets, a semi-empirical formula is derived to calculate the velocity of non-cohesive high-speed particle flow considering the elastic strain energy loss. Additionally, the reliability of the proposed theoretical model is verified through experiments. The penetration process of Zr-based amorphous alloy high-speed particle flow into a concrete target is theoretically analyzed, and the penetration stages of the high-speed particle flow into the target are clearly distinguished. Combined with the penetration theory of shaped charge particle jets, a high-speed particle flow penetration model is proposed, and a pore expansion model is established through an energy method. The experimentally obtained data on depth of penetration are in agreement with the theoretical calculation results.

Formation of Shaped Charge Projectile in Air and Water.

With the improvement of the antiknock performance of warships, shaped charge warheads have been focused on and widely used to design underwater weapons. In order to cause efficient damage to warships, it is of great significance to study the formation of shaped charge projectiles in air and water. This paper uses Euler governing equations to establish numerical models of shaped charges subjected to air and underwater explosions. The formation and the movement of Explosively Formed Projectiles (EFPs) in different media for three cases: air explosion and underwater explosions with and without air cavities are discussed. First, the velocity distributions of EFPs in the formation process are discussed. Then, the empirical coefficient of the maximum head velocity of EFPs in air is obtained by simulations of air explosions of shaped charges with different types of explosives. The obtained results agree well with the practical solution, which validates the numerical model. Further, this empirical coefficient in water is deduced. After that, the evolutions of the head velocity of EFPs in different media for the above three cases are further compared and analyzed. The fitting formulas of velocity attenuation of EFPs, which form and move in different media, are gained. The obtained results can provide a theoretical basis and numerical support for the design of underwater weapons.

OPTIMIZATION OF LINER STRUCTURE TO ENHANCE THE PENETRATION PERFORMANCE OF SHAPED CHARGE WARHEAD

In this study, the Gravitational Search Algorithm (GSA) programmed on MATLAB software is applied to solve the optimal problem of determining the liner structure to enhance the penetration performance of the shaped charge warhead. The obtained results show that when using the optimal set of parameters found by the proposed approach (the internal apex angle α0 = 16°, the thickness δ = 4.9 mm), the penetration performance of the shaped charged warhead is significantly improved (the penetration depth b = 553 mm, 38% higher than the original plan).

Study on optimization of jet forming of tandem shaped charge warhead

In order to greatly improve the length of shaped charge jet and optimize the jet forming performance, the forming process of a tandem shaped charge structure with reverse detonation mode was numerically simulated. The effects of the rear and front stage liner thickness on the jet length, jet head velocity, jet kinetic energy and energy conversion rate were analyzed respectively using LS-DYNA finite element analysis software. Then the optimal thickness of the front and rear stage liner of the tandem shaped charge structure was optimized, and the jet length was measured. Under the condition of charge diameter of 200 mm, when the liner thickness was 0.02CD (charge diameter) for K-charge and liner thickness was 0.25CD for the front stage warhead, the jet forming was stable and the length is the longest. After the two-stage warhead was detonated in reverse order (the initiation delay time was 220 μs), a tandem jet can be formed, and the effective jet length (excluding the pestle body) is 65 % higher than that of the later stage charge.

Simulation and Experimental Study on Jet Velocity of Zr-Based Amorphous Alloy Liner

Zr-based amorphous alloy is a new energetic material that has been closely monitored and extensively studied for the design of highly effective shaped charge warheads in recent years. In order to accurately determine the motion parameters of shaped charge jets during the detonation-driven formation process of Zr-based amorphous alloy liners, we prepared conical ZrCuNiAlAg liners by vacuum die casting and supercooled liquid high-rheological-rate formation processes. Based on jet-formation numerical simulation, pulsed X-ray imaging and copper foil target velocity measuring tests were conducted to identify the variation trend of the jet velocity of Zr-based amorphous alloy liners with time. The jet velocities at typical moments in the free flight stage were verified. The research results showed that Zr-based amorphous alloy liners could produce solid jets, whose velocity was in gradient descent from the head to the tail, and that the jet’s head velocity peaked at 12 μs and then slowly decreased with time. The average velocities measured by the X-ray imaging and copper foil target tests were 6913 m/s and 7177 m/s, respectively, and both of them were in good agreement with the simulation results, verifying the accuracy of the numerical simulation model for jet formation. The formation processes of shaped charge liners were found to affect the mechanical properties of the material and thus, the jet’s formation process and motion parameters. The Zr-based amorphous alloy liner formed by the supercooled liquid-phase high-rheological-rate formation process exhibited a jet velocity 6.5% higher than that formed by the vacuum die casting process.

Experimental Study on Damage Characteristics of Copper-Reinforced Polytetrafluoroethylene Shaped-Charge Warhead Liner.

Polymer materials have important applications in the4 terminal effect and damage by shaped-charge warheads. However, the low strength of pure PTFE materials reduces the penetrability of the expansive jet from these warheads, hindering its application. This study improves the strength of pure PTFE material by adding Cu powder to the shaped-charge liner. Three types of PTFE/Cu composites with different densities are prepared. The effect of increasing the density on the performance of an expansive jet is studied by a dynamic mechanical property experiment, microscopic analysis, numerical simulation, and a penetration experiment. The results show that the toughness and impact strength of the PTFE/Cu composites improve when 18–50.5% Cu is added. The strength of the composite increases linearly with the increase in Cu content. Numerical simulations and X-ray pulse experiments reveal that the addition of Cu powder enhances the cohesiveness of the head of the expansive jet. The jet head becomes more cohesive as the Cu content is increased. However, the length and diameter of the jet become smaller. The jet can create a deeper hole in the steel target and increase damage as more Cu is added to the liner.

Efficiency of Different Cage Armour Systems

Cage armour systems have been in use since the 1960s and are still being used extensively on many armoured vehicles up to this day to offer protection against mainly a number of RPG-7 shaped charge warheads. Nevertheless, many misunderstandings still exist up to this day as well as regarding their working principle as regarding their actual efficiency. This article will start by exploring the origins of the current cage armour systems and by explaining the working principle behind them. This will be followed by the development of a methodology to calculate the efficiency of different types of cage armour systems (slat, bar, net and inertial distributed weight systems) as a function of impact conditions for a specific RPG-7 shaped charge warhead. The results of the developed methodology will be compared to experimental results for four different cage armour systems, in order to validate the followed approach. It will then be applied to different cage armour systems in order to calculate their overall ballistic and mass efficiency as a function of the impact angle. The analysis will finally be refined taking into account the likely impact conditions for an RPG-7 shaped charge warhead, based on a simple trajectory model.

Structural Design and Parameter Optimization of Linear Explosive Forming Projectile

AbstractThe development of new warhead structures is an important means to enhance the destructive ability of projectiles. Compared with the traditional projectiles, the shaped charge warhead has a better destructive effect. Based on the traditional optimization method, a multi‐objective optimization method based on an approximate model is used for the structural design of linear explosive forming projectile (LEFP). In this paper, four different methods are applied to optimize the structure of LEFP. Numerical simulations of penetration into steel target are carried out for the optimization results, and the reliability of the numerical results are verified by experiments. The results indicate that: 1) the optimization method can improve the molding effect and penetration ability of LEFP reliably; 2) the combined optimization method has obvious advantages in promoting the performance of LEFP over the single one.

Effect of fragment impact on shaped charge jet formation and penetration into steel target

Purpose This paper aims to investigate the effects of fragment impacts to shaped charge warheads in terms of shaped charge jet formation geometries and penetration performances. Design/methodology/approach In experimental process, a fragment was accelerated to a shaped charge warhead by means of a powder gun to a velocity more than 1,000 m/s, and this impact led to conical damage in the explosive of the warhead. Deformation on the warhead was visualized using X-ray technique to observe holes generated during fragment impact. Penetration test was performed against AISI 1040 steel plates with the damaged shaped charge warhead. Penetration performance of shaped charge jet, which deviated from the symmetry axis, was simulated by using SPEED software with 3-D Eulerian method to validate the numerical modelling method by comparing penetration test and simulation results of damaged warhead. Findings Simulation and test results showed good correlation for the warhead in terms of penetration depth and hole geometry at the impact surface of steel plates. In addition, the effects of the numbers and the geometries of fragment holes on shaped charge jet penetration performances were investigated with validated numerical methods. Simulation results showed that the increase in the number of fragment holes in the explosive of the warhead led to particulation of shaped charge jet that diminished penetration depth in the target plate. Additionally, simulation results also showed that the fragment hole geometry in the explosive after different fragment impact angles affected the amount of jet deviation from the symmetry axis as well as penetration depth in the target plate. Practical implications The results obtained from the current study revealed that fragment impact angle and different number of fragment impact reduced the penetration performance of shaped charge warhead by influencing the symmetry of shaped charge jet negatively. Originality/value The current study fulfils the need to investigate how fragment impact on the shaped charge warhead affect the formation symmetry of shaped charge jet as well as penetration performance by experimental and numerical methods. Penetration performance result of asymmetric jet is compared by experimental and numerical studies. A detailed methodology on numerically modelling of the effect of fragment impact angle and number of fragment impact on shaped charge jet performance is given in this study.

Comparison of Shaped Charge Jet Performance Generated by Machined and Additively Manufactured CuSn10 Liners.

The Selective Laser Melting (SLM) technique has attracted attention in a wide range of manufacturing research areas, including the defense industry because of its high efficiency and good consistency of manufactured material properties. Shaped charge liner is the crucial unit in the shaped charge warhead. However, jet performance formed by SLM-produced liner remains to be studied systematically. In the present research work, the SLM technique was applied to manufacture CuSn10 shaped charge liners. Casted CuSn10 liners were also fabricated using the classical turning method for comparison. The grain size of the SLM-produced liner was found to be much smaller than the machined liner due to the rapid heating and cooling rate during the SLM manufacturing process. This contributed to improved jet performance. A flash X-ray photography system was applied to capture jet stretching appearances. Necking appears at the jet tip formed by the machined liner, while the jet formed by the SLM-produced liner remains continuous. Penetration test results show that the penetration depth of the jet formed by the SLM-produced liner is around 27% larger than that formed by the machined liner. Segments along the sidewall of the penetration tunnels were selected for in-depth micro analysis. Energy dispersed spectrum (EDS) surface scanning results indicate the composition at the side wall of the penetrated tunnel. Metallurgical microscope was applied to distinguish four different phase zones of the target. The width of these different zones indicates the severity of the lateral interaction between the jet and target, which can be adopted to evaluate jet penetration capability. The present study analyzes the factors that influence jet performances and proves that SLM technology is well-adapted in the manufacturing of shaped charge liners.

Study on Penetration Performance of Rear Shaped Charge Warhead.

In guided munitions, the shaped charge jet (SCJ) warhead is located behind the simulation compartment (including the control cabin, the steering gear cabin, and the guidance cabin). Therefore, the order of penetration of the SCJ is the simulation cabin and the target. To study the penetration performance of the SCJ to the target plate, the numerical simulation method is used to study the penetration performance of the designed warhead for the steel target at different standoffs, and the depth of penetration (DOP) at the best standoff is obtained, that is, the DOP of the steel target is about 128 mm. Additionally, the penetration performance of the SCJ warhead to target is studied by numerical simulation and experimental verification. Numerical simulation and experimental results show that the DOP of the SCJ warhead to the steel target is 50 mm without the simulation cabin, and about 30 mm with the simulation cabin. The results show that the penetration performance of SCJ is greatly weakened under the condition of non-optimal standoff, but the rear shaped charge warhead still has a strong penetration performance after completing the penetration of the simulated cabin.

Shock Wave Behaviour of Polymeric Materials for Detonation Waveshapers

This paper discusses the experimental determination of explosive shock attenuation parameters of four different polymers viz., Teflon, Phenol formaldehyde, Polyethylene foam and Polypropylene foam. These polymers are candidate materials for waveshapers in shaped charge warheads. Cylindrical specimens of the polymer materials were subjected to explosive shock loading by the detonation of RDX:Wax (95:5). Shock arrival time was measured using piezo-wafers positioned at known spatial intervals in the specimens. Initial shock velocity, stabilised shock velocity and attenuation constant were determined. These parameters are essential for the design of waveshapers. Foams have better shock attenuating properties compared to solids due to their cellular structure. Polypropylene foam has the highest shock attenuating characteristic among the four materials studied.

Influence of shaped charge structure parameters on the formation of linear explosively formed projectiles

The research of LEFP (linear explosive forming projectile) is of great value to the development of new warhead due to its excellent performance. To further improve the damage ability of the shaped charge warhead, a special shell overhanging structure was designed to increase the charge based on the traditional spherical charge, in which case the crushing energy of LEFP could be guaranteed. LS-DYNA was used to simulate different charge structures obtained by changing the number of detonation points, the length of shell platform, the radius of curvature and the thickness of liner. The RSM (response surface model) between the molding parameters of LEFP and the structural parameters of charge was established. Based on RSM model, the structure of shaped charge was optimized by using multi-objective genetic algorithm. Meanwhile, the formation process of jet was analyzed by pulsed X-ray photography. The results show that the velocity, length-diameter ratio and specific kinetic energy of the LEFP were closely related to the structural parameters of the shaped charge. After the optimization of charge structure, the forming effect and penetration ability of LEPP had been significantly improved. The experimental data of jet velocity and length were consistent with the numerical results, which verifies the reliability of the numerical results.

Reaction characteristic of PTFE/Al/Cu/Pb composites and application in shaped charge liner

In this paper, the reaction characteristic and its application in shaped charge warhead of a novel reactive material, which introduced copper (Cu) and plumbum (Pb) into traditional polytetrafluoroethylene/aluminum (PTFE/Al), are studied. The thermal analysis and chemical reaction behavior of the PTFE/Al/Cu/Pb mixture are investigated by Differential Scanning Calorimetry (DSC),Thermo-gravimetry (TG), and X-ray Diffraction (XRD) techniques. Then, the shaped charge liners with PTFE/Al/Cu/Pb reactive materials are fabricated, and the X-ray experiments show that they could form reactive jets with excellent performance under the detonation effects of the shaped charge. Based on that, the penetration experiments of shaped charge with PTFE/Al/Cu/Pb reactive liner against steel plates are carried out, and the results demonstrate that the PTFE/Al/Cu/Pb reactive jets could produce a deeper penetration depth compared to the traditional PTFE/Al reactive jets. Meanwhile, the PTFE/Al/Cu/Pb reactive jets also show significant inner-blast effects, leading to dramatically cracking or fragmentation behavior of the penetrated steel plates. This new PTFE/Al/Cu/Pb reactive liner shaped charge presents enhanced penetration behavior for steel targets that incorporates the penetration capability of a high-density and ductility jet, and the chemical energy release of PTFE-matrix reactive materials.