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The behind-armor debris (BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components. Aiming at investigating the BAD caused by EFP, flash X-ray radiography combined with an experimental witness plate test method was used, and the FEM-SPH adaptive conversion algorithm in LS-DYNA so...
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... proceeds, the failed Lagrange elements will be replaced by particles for subsequent calculation. Under the impact of EFP, 45# steel target first expanded to form a bulge, and then the radial and axial cracks emerged, which caused the forming of small fragments or debris. Eroded parts from EFP were also involved in the entire debris cloud. In Fig. 12 the velocity distribution image is shown Lagrange elements and SPH particles at 30 ms, ...
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... generally exhibits a normal distribution characteristic, that is, the number of debris first increasing and then decreasing when a change from 0 to 100 . When a is small, due to the large residual EFP, the fragments number is relatively small. The velocity of the debris gradually decreases with the increase of the emission angle a, as shown in Fig. 20. For most target thickness, the velocity decrease in a linear manner. Combined with the kinetic energy distribution characteristics of Fig. 21, it can be found that the kinetic energy of the debris decrease exponentially with the increase of a. The kinetic energy of the fragment is larger under the small emission angle, when a ...
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... 0 to 100 . When a is small, due to the large residual EFP, the fragments number is relatively small. The velocity of the debris gradually decreases with the increase of the emission angle a, as shown in Fig. 20. For most target thickness, the velocity decrease in a linear manner. Combined with the kinetic energy distribution characteristics of Fig. 21, it can be found that the kinetic energy of the debris decrease exponentially with the increase of a. The kinetic energy of the fragment is larger under the small emission angle, when a increases, the fragments terminal effect potential decreases. When h/D 0 ¼ 1.95, the average kinetic energy of the fragment within small emission angle ...
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... order to investigate the effect of variable impact velocity of the EFP on the BAD distribution, simulation of perpendicular impact of EFPs on the target with velocities between 1200 m/s and 2500 m/s is considered. Fig. 22 is the relationship between nomalized impact and residual velocity of EFP. It is observed that the residual velocity has a linear relationship with the impact velocity with range from 1200 m/s to 2500 m/s. When velocity varies, there are differences in the failure mechanisms of the target. At lower velocity, the EFP energy is ...
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... can be seen from Fig. 23 that the number of fragment increases almost linearly with increasing impact velocity for the same target thickness, but the fragments number may not increase at higher ...
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... number of fragments of the EFP that penetrated the steel target thickness of 10 mm, 20 mm, and 30 mm at velocity of v 0 ¼ 1800 m/s, 2100 m/s, 2300 m/s were counted. Fig. 24 shows the change curve of the ratio of the cumulative fragment number to the total number with the scattering angle b f . The growth rate of the fragments increases first and then decreases, which correlates with the Weibull distribution. Most fragments are concentrated in the 15 e30 scattering angle. Considering ratio of the ...
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... the actual application, EFPs do not alway penetrate the target perpendicularly. The more common situation is to interact with the target at certain angle. It is more meaningful to study the conditions of angled impingement. So the debris clouds formed at obliquity angles q ¼ 0 , 15 , 30 , 45 , 60 were simulated. Fig. 27 is the typical time image of BAD fromed by EFP with impact velocity of 2100 m/s penetrate through 10 mm thickness target at different ...
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... black curve in the Fig. 28 represents the relationship of the EFP residual mass with the impact angle. It shows that the residual mass of EFP decreases exponentially with the increase of impact obliquity, and the variation trends of different thicknesses and ...
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... counting the number of debris (Fig. 29), it can be seen that when the impact obliquity increases, the total number of debris decreases first and then ...
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... is found that the number, velocity and kinetic energy of debris are asymmetrically distributed due to the impact obliquity. The emission angle is divided into positive and negative directions to obtain the change trends shown in Fig. 30-Fig. 32. The number of fragments located in b f(þ) increases as the obliquity varies, accounting for 50%, 56%, 67%, 75% and 83%, respectively. The distribution law of fragments in the b f(þ) and b f(À) conforms to the normal condition respectively. The total emission angle of the fragment is basically unchanged, namely about 100 . The change ...
Citations
... In addition, the spatial distribution of BAD is closely related to the damaging effect of the internal components of the armored vehicle [17,18]. Many studies evaluated the relationship between BAD mass and velocity and the scattering angle for long-rod projectiles [19][20][21]. ...
... Dawe et al. [28] obtained the relationship between the cumulative lethality of the BAD and the scattering angle. Wang et al. [17] found ...
To understand the influence of the length–diameter ratio (L/D) of explosively formed projectiles (EFPs) on the energy spatial distribution of behind-armor debris (BAD), three EFPs with different L/Ds were designed in this study. The scattering characteristics of the BAD formed by the EFP penetrating a steel target were investigated. High-speed photography was used to observe the shape of the BAD cloud. Fiber and foam plates were sequentially stacked to recover the fragments. The three-dimensional damaged area by the BAD was obtained based on the spatial position information of a large amount of BAD. Finally, the energy spatial distribution characteristics of the EFP and target material fragments were analyzed. The results showed that a large EFP L/D increased the total energy of the BAD, and the proportion of the energy of projectile fragments increased. The difference in the energy spatial distribution between EFPs with varying L/Ds was mainly in the scattering angle range of 3–17°. The total energy of fragments within 17° of scattering angle accounted for 85% of the total energy of all fragments. The BAD energy of the EFP with a large L/D (L/D = 3.86) was concentrated in a small scattering angle range in which the residual projectile was located. The average projectile fragment energy of the EFP with a moderate L/D (L/D = 2.4) was evenly distributed in the scattering angle range of 5–20°. As a result, the energy distribution of the BAD from EFP (L/D = 2.4) shifted towards the large scattering angle, thus leading to a uniform radial distribution of the striking area within the range of 500–1100 mm behind the target. However, with the increase in the distance behind the target, the radial direction of the striking area of the other two EFPs was gradually reduced. The reason was explained according to the force analysis of the fragments resulting from the bulge fracture of target. The spatial energy distribution of BAD is closely related to the damage ability of EFP in relation to the armored target. Thus, it is necessary to design EFPs with appropriate L/Ds in order to maximize the damaging effect behind the armor.
... According to the forming mechanism, the projectile formed by SC is mainly divided into explosive formed projectile (EFP) [4] and shaped charge jet (SCJ) [5]. The velocity of SCJ can reach 2000 m/s to 10000 m/s much higher than that of EFP, and is often used to penetrate high strength target such as RHA and ultra-high strength concrete [6][7][8]. ...
The use of a shaped liner driven by electromagnetic force is a new means of forming jets. To study the mechanism of jet formation driven by electromagnetic force, we considered the current skin effect and the characteristics of electromagnetic loading and established a coupling model of “Electric–Magnetic–Force” and the theoretical model of jet formation under electromagnetic force. The jet formation and penetration of conical and trumpet liners have been calculated. Then, a numerical simulation of liner collapse under electromagnetic force, jet generation, and the stretching motion were performed using an ANSYS multiphysics processor. The calculated jet velocity, jet shape, and depth of penetration were consistent with the experimental results, with a relative error of less than 10%. In addition, we calculated the jet formation of different curvature trumpet liners driven by the same loading condition and obtained the influence rule of the curvature of the liner on jet formation. Results show that the theoretical model and the ANSYS multiphysics numerical method can effectively calculate the jet formation of liners driven by electromagnetic force, and in a certain range, the greater the curvature of the liner is, the greater the jet velocity is.
In this study, a polygonal shell is used to produce an explosively formed projectiles (EFP) with fins for good flight stability. The forming characteristics of an EFP with fins produced by a polygonal shell are studied numerically using the LS-DYNA 3D finite element code. Orthogonal design method combined with range analysis is applied to optimize the EFP with fins. The orthogonal test schemes are established with 5 levels under plane initiation of 0.2 times the charge diameter and point initiation, respectively. The influence rankings of the EFP length-to-head diameter ratio, compactness, velocity, kinetic energy and length of fin-to-tail radius ratio are determined. Furthermore, the EFPs of the optimized design are tested for forming and recycling. Subsequently, the EFPs recovered from the tests are reconstructed. Finally, an EFP penetration performance test is conducted. When ignoring the influence of EFP initial state on target penetration, Steinberg and Johnson-Cook (J-C) constitutive models are used for the formation and penetration processes, respectively. The results show that the forming effects of EFPs with fins are coupled by the structure of liner, charge arrangement and shell structure. The ranges of the various structural parameters of the EFPs are obtained. The numerical simulation results of EFP with fins designed by orthogonal optimization method are in good agreement with the experimental results. The effectiveness of Steinberg algorithm and J-C algorithm in EFP forming and penetration process is verified.
To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building, the combined damage characteristics of the reinforced concrete wall caused by EFP penetration and explosion shock wave were studied. Based on LS-DYNA finite element software and RHT model with modified parameters, a 3D large-scale numerical model was established for simulation analysis, and the rationality of the material model parameters and numerical simulation algorithm were verified. On this basis, the combined damage effect of EFP penetration and explosion shock wave on reinforced concrete wall was studied, the effect of steel bars on the penetration of EFP was highlighted, and the effect of impact positions on the damage of the reinforced concrete wall was also examined. The results reveal that the designed shaped charge can form a crater with a large diameter and high depth on the reinforced concrete wall. The average crater diameter is greater than 67 cm (5.58 times of charge diameter), and crater depth is greater than 22 cm (1.83 times of charge diameter). The failure of the reinforced concrete wall is mainly caused by EFP penetration. When only EFP penetration is considered, the average diameter and depth of the crater are 54.0 cm (4.50 times of charge diameter) and 23.7 cm (1.98 times of charge diameter), respectively. The effect of explosion shock wave on crater depth is not significant, resulting in a slight increase in crater depth. The average crater depth is 24.5 cm (2.04 times of charge diameter) when the explosion shock wave is considered. The effect of explosion shock wave on the crater diameter is obvious, which can aggravate the damage range of the crater, and the effect gradually decreases with the increase of standoff distance. Compared with the results for a plain concrete wall, the crater diameter and crater depth of the reinforced concrete wall are reduced by 5.94% and 9.96%, respectively. Compared to the case in which the steel bar is not hit, when the EFP hit one steel bar and the intersection of two steel bars, the crater diameter decreases by 1.36% and 5.45% respectively, the crater depth decreases by 4.92% and 14.02% respectively. The EFP will be split by steel bar during the penetration process, resulting in an irregular trajectory.
