Showing papers on "Projectile published in 2020"

Analytical and numerical modelling of high-velocity impact on multilayer alumina/aramid fiber composite ballistic shields: Improvement in modelling approaches

Abstract: In this paper, analytical and numerical models were developed to simulate the perforation of ceramic-composite targets by small-caliber projectiles. The modified Bernoulli equation has been implemented in a new analytical model to simulate the interaction between projectile and ceramic tile and an energy formulation based on the wave propagation theory has been adopted to describe energy absorption of the composite backing. The numerical model, developed with the software LS-DYNA, is based on a full-Lagrangian finite-element analysis. Both models yielded good agreement with the performed impact tests on pure alumina single tile and on multilayer Al2O3-Kevlar 29/epoxy using actual 7.62 mm NATO Ball projectile.

Ballistic response of hemispherical sandwich shell structure against ogive nosed projectile

Abstract: This study presents the experimental and numerical investigation of the response of hemispherical sandwich shell structure having hexagonal honeycomb core against ogive nosed projectile impact. Aluminum AA-1100 was considered for the front and rear face sheet of 200 and 160 mm diameter whereas AA-3003H19 was used for the honeycomb core of 3.2 mm cell size, 0.05 mm cell wall thickness and 20 mm core thickness. The cylindrical ogive nosed projectile having diameter 19 mm, mass 52.5 g and length 50.8 mm was hit at the crown of the hemispherical sandwich shell structure. The experiments were carried out through a pneumatic gun whereas for numerical simulations, 3D finite element code Abaqus explicit solver was used. The ballistic resistance, failure mechanism and the energy absorption of the sandwich shell structure was investigated thoroughly through experimentation and numerical simulations and found close to each other. Moreover, the parametric study was performed through numerical simulations to study the influence of face sheet thickness (0.7, 1, 1.5 and 2 mm), cell wall thickness (0.03, 0.05, 0.07 and 0.09 mm) and cell size (3.2, 5.0, 7.0 and 9.0 mm) of the honeycomb core on the ballistic response and energy absorption. Against ogive nosed projectile, face sheets failed in radial stretching with petal formation and the core failed in crushing. Also, the face sheet thickness had a dominant effect on the ballistic limit and the energy absorption of the hemispherical sandwich shell structure. Moreover by increasing core stiffness (by using thick cell wall and small cell size) enhance energy absorption capacity of the sandwich structure.

An investigation of the ballistic performance of independent ceramic target

Abstract: The ballistic experiments have been carried out on alumina 99.5% bare ceramic plates for studying the initiation and propagation of brittle fracture and the resistance offered by the target. The ceramic tiles of size, 100 mm × 100 mm, and thickness, 5 mm, were impacted by the ogival nosed hardened steel 4340 projectiles of diameter 10.9 mm and mass 30 grams at velocities in the range 52–275 m/s. The ceramic fragments were carefully collected to examine the cracking patterns at the front and the back surfaces. The cracks developed in the target were studied extensively to develop more insight into the fracture mechanism. The energy absorbed by the target has been studied and correlated with respect to the fracture mechanism of the target. Numerical simulations have been performed on a commercial finite element code and the experimental findings have been reproduced in order to further understand the fracture and fragmentation behaviour and its influence thereon the ballistic characteristics of the target. The Johnson-Holmquist-2 (JH-2) constitutive model has been used for simulating the material behaviour of ceramic and the Johnson-Cook (JC) elasto-viscoplastic material model for simulating the behaviour of the steel projectile. The behaviour of ceramic target under oblique impact was explored numerically. The damage in the projectile was found to be higher in case of oblique impact. Both the experimental and numerical findings have described an increase in the crack density with the increase in the incidence velocity of the projectile. The average size of the fragments has also been found to be reduced with the increase in the projectile incidence velocity.

Simulation of CFRP/aluminum foam sandwich structure under high velocity impact

Abstract: To profoundly reveal the protective performance of CFRP/aluminum foam sandwich structure, the high-speed impact simulation models of CFRP, aluminum foam and their sandwich structures are built by ABAQUS/Explicit module. The VUMAT user material subroutine is written for CFRP panel, and Hashin damage criterion is introduced. The elastic constitutive model and macro modeling method for the aluminum foam are chosen. The impact process under different working conditions is numerically simulated and the reliability of the model is verified by one-stage light gas gun loading experiment at the corresponding simulation conditions. At the same time, the protective performance of CFRP/ aluminum foam sandwich structure under different steel projectile shapes, impact velocities and impact angles (the angle between the ballistic and the target normal line) are simulated. The results show that the Mises stress nephogram of CFRP panel is peanut-like with obvious directivity. The stress wave propagates fastest in the direction perpendicular to the fiber. In the impact velocity range of 172−450 m/s, with the increase of impact velocities, the loss of kinetic energy will increase, but the increase of kinetic energy loss will decrease with the increase of impact velocities, and the contact force between the projectile and the sandwich structure will also increase. Thus the sandwich structure will have more serious delamination and fiber breakage, which will consume more kinetic energy. When the velocity of the projectile is greater than 300 m/s, the impact capability of the sandwich structure tends to the upper limit of impact capacity. In the impact velocity range of 170∼300m/s, the sandwich structure has stronger protective performance than ball-nosed projectile when the flat-nosed projectile impact, and the difference of the residual velocity between the two kinds of projectiles is larger. The shape of the projectile has a great influence on the protective performance of the CFRP/ aluminum foam sandwich structure. When the impact velocity is greater than 300m/s, the residual velocities of the two kinds of projectiles are almost the same, and the shapes of the projectile have a gradual effect on the performances of the CFRP/ aluminum foam sandwich structure. The anti-shock performance of sandwich structure under oblique impact is stronger than that of vertical impact. With the increase of impact angles, the transverse deformation of sandwich structure increases, and the anti-shock performance of sandwich structure also increases.

Research on Target Deviation Measurement of Projectile Based on Shadow Imaging Method in Laser Screen Velocity Measuring System.

Abstract: In the laser screen velocity measuring (LSVM) system, there is a deviation in the consistency of the optoelectronic response between the start light screen and the stop light screen. When the projectile passes through the light screen, the projectile’s over-target position, at which the timing pulse of the LSVM system is triggered, deviates from the actual position of the light screen (i.e., the target deviation). Therefore, it brings errors to the measurement of the projectile’s velocity, which has become a bottleneck, affecting the construction of a higher precision optoelectronic velocity measuring system. To solve this problem, this paper proposes a method based on high-speed shadow imaging to measure the projectile’s target deviation, ΔS, when the LSVM system triggers the timing pulse. The infrared pulse laser is collimated by the combination of the aspherical lens to form a parallel laser source that is used as the light source of the system. When the projectile passes through the light screen, the projectile’s over-target signal is processed by the specially designed trigger circuit. It uses the rising and falling edges of this signal to trigger the camera and pulsed laser source, respectively, to ensure that the projectile’s over-target image is adequately exposed. By capturing the images of the light screen of the LSVM system and the over-target projectile separately, this method of image edge detection was used to calculate the target deviation, and this value was used to correct the target distance of the LSVM to improve the accuracy of the measurement of the projectile’s velocity.

Influence of target dynamics and number of impacts on ballistic performance of 6061-T6 and 7075-T6 aluminum alloy targets

Abstract: The effect of target condition (static and dynamic) and number of projectile impacts (single and multiple) on the ballistic performance of 6061-T6 Aluminum alloy, 7075-T6 Aluminum alloy and 6061- a...

Pre-equilibrium stopping and charge capture in proton-irradiated aluminum sheets

Abstract: We present a first-principles study of pre-equilibrium stopping power and projectile charge capture in thin aluminum sheets irradiated by 6--60 keV protons Our time-dependent density functional theory calculations reveal enhanced stopping power compared to bulk aluminum, particularly near the entrance layers We propose the additional excitation channel of surface plasma oscillations as the most plausible explanation for this behavior We also introduce a technique to compute the orbital-resolved charge state of a proton projectile after transmission through the sheet Our results provide insight into the dynamics of orbital occupations after the projectile exits the aluminum sheet and have important implications for advancing radiation hardness and focused-ion beam techniques, especially for few-layer materials

Assessment of the Impact Resistance of a Composite Material with EN AW-7075 Matrix Reinforced with α-Al2O3 Particles Using a 7.62 × 39 mm Projectile.

Abstract: The paper presents the results of studies on the effects of shooting composite materials produced by pressure infiltration with the EN AW-7075 alloy as a matrix and reinforcement in the form of preforms made of α-Al2O3 particles. Composite materials were made with two reinforcement contents (i.e., 30% and 40% vol. of α-Al2O3 particles). The composites produced in the form of 12 mm thick plates were subjected to impact loads from a 7.62 × 39 FMJ M43 projectile fired from a Kalashnikov. The samples of composites with different contents of strengthening particles were subjected to detailed microscopic examination to determine the mechanism of destruction. The effect of a projectile impact on the microstructure of the material within the perforation holes was identified. There were radial cracks found around the puncture holes and brittle fragmentation of the front surfaces of the specimens. The change in the volume of the reinforcement significantly affected the inlet, puncture and outlet diameters. The observations confirmed that brittle cracking dominated the destruction mechanism and the crack propagation front ran mainly in the matrix material and along the boundaries of the α-Al2O3 particles. In turn, numerical tests were conducted to describe the physical phenomena occurring due to the erosion of a projectile hitting a composite casing. They were performed with the use of the ABAQUS program. Based on constitutive models, the material constants developed from the identification of material properties were modelled and the finite element was generated from homogenization in the form of a representative volume element (RVE). The results of microscopic investigations of the destruction mechanism and numerical investigations were combined. The conducted tests and analyses shed light on the application possibilities of aluminium composites reinforced with Al2O3 particles in the construction of add-on-armour protective structures.

Numerical Investigation on the Regime of Cavitation Shedding and Collapse During the Water-Exit of Submerged Projectile

Abstract: Cavitation may develop on upward-launched submerged objects approaching sea surface with high speed. In this work, the cavitation shedding and collapse during the water-exit of an axisymmetric projectile is investigated using large eddy simulation (LES). High resolution is guaranteed by carefully fulfilling the requisites of y+<1, Δx+<100, and Δz+<40 to resolve at least 80% of the turbulent kinetic energy. The result indicates that the cavity in growth is always undeveloped as the ambient hydrostatic pressure keeps decreasing. The cavity is pushed by the water surface to shed downward and keep shrinking until its final collapse. The vapor inside cavity during the water-exit process is separated by a layer of water so as not to mix with the air. The front of the re-entrant jet barely catches up with the moving wall, and the cavity is pinched off by the joint effect of the jet front and water surface. It is also found that the angle of attack (AOA) generates inversely inclined liquid-vapor contact lines of the cavity leading edge and cavity closure. The advancing contact lines finally intersect on the pressure side to make the cavity break off, which can cause noticeable pressure impulse on the break-off spot. The pressure feature of the water-exit cavitation evolution is studied with intensively arranged monitor points on the wall, which can sense pressure peaks when the liquid-vapor contact lines sweep over them. The instantaneous high pressure induced by cavitation collapse is resolved.

Effects of volume of carbon nanotubes on the angled ballistic impact for carbon kevlar hybrid fabrics

Abstract: Investigations of the angled ballistic impact behavior on Carbon Kevlar® Hybrid fabrics with assorted volumes of carbon nanotubes (CNTs) into epoxy are presented. The ballistic impact behavior of the epoxy composites with/without CNTs is compared. Individual impact studies are conducted on the composite plate made-up of Carbon Kevlar Hybrid fabrics with diverse volumes of CNTs. The plate was fabricated with eight layers of equal thickness arranged in different percentages of CNTs. A conical steel projectile is considered for a high velocity impact. The projectile is placed very close to the plate, at the centre and impacted with sundry speeds. The variation of the kinetic energy, the increase in the internal energy of the laminate and the decrease in the velocity of the projectile with disparate angles are also studied. Based on the results, the percentage of CNTs for the ballistic impact of each angle is suggested. The solution is based on the target material properties at high ballistic impact resistance, the inclined impact and the CNT volumes. Using the ballistic limit velocity, contact duration at ballistic limit, surface thickness of target and the size of the damaged zone are predicted for fabric composites.

Failure characteristics of UHPFRC panels subjected to projectile impact

Abstract: This study investigates the failure characteristics of ultra-high performance fiber-reinforced concrete (UHPFRC) panels subjected to a steel projectile impact. Impact tests for 60–120-mm-thick UHPFRC panels were conducted to examine the failure state and impact resistant performance of the panels by using an 8.3-kg-mass projectile with a diameter of 90 mm at a velocity approximately corresponding to 42 m/s. Experimental parameters included the arrangement of pre-stressing steel wires and enforcement of pre-stress. Although the effect of arranging the pre-stressing steel wires on the damage restraint of UHPFRC panels was observed, the enforcement of pre-stress was not significantly effective in mitigating the damage. The impact response characteristics of UHPFRC panels were investigated by comparison between the impact force, reaction force, and strain response.

Numerical Investigations of Cavitation Nose Structure of a High-Speed Projectile Impact on Water-Entry Characteristics

Abstract: In this study, a detailed analysis of the influences of cavitation nose structure of a high-speed projectile on the trajectory stability during the water-entry process was investigated numerically. The Zwart-Gerber-Belamri (Z-G-B) cavitation model and the Shear Stress Ttransport (SST)k-ω turbulence model based on the Reynolds Averaged Navier–Stokes (RANS) method were employed. The numerical methodology was validated by comparing the numerical simulation results with the experimental photograph of cavitation shape and the experimental underwater velocity. Based on the numerical methodology, the disk and the conical cavitation noses were selected to investigate the water-entry characteristics. The influences of cavitation nose angle and cavitation nose diameter of the projectile on the trajectory stability and flow characteristics were carried out in detail. The variation features of projectile trajectory, velocity attenuation and drag were conducted, respectively. In addition, the cavitation characteristics of water-entry is presented and analyzed. Results show that the trajectory stability can be improved by increasing the cavitation nose angle, but the drag reduction performance will be reduced simultaneously. Additionally, due to the weakening of drag reduction performance, the lower velocity of the projectile will cause the damage of the cavitation shape and the trajectory instability. Furthermore, the conical cavitation nose has preferable trajectory stability and drag reduction performance than the disk cavitation nose.

Performance of Ceramic-Composite Armors under Ballistic Impact Loading

Abstract: Analysis of typical ceramic-composite armors is presented for their ballistic impact performance. Specifically, armor configurations are given for enhancing ballistic limit velocity with minimum armor areal density. The studies are performed using the analytical model presented earlier (Naik et al. in Int J Damage Mech 22(2):145–187, 2013). Wave theory and energy balance between the kinetic energy of the moving projectile and the energy absorbed by different mechanisms by both the armor and the projectile are considered. Analytical predictions and typical experimental results available in the literature are compared. A good match is observed. It is observed that in certain range of armor areal density, ballistic limit velocity remains the same. The explanation for such a behavior is provided considering different major energy absorbing mechanisms at different areal densities of the armor. Further, effects of armor configuration, incident impact velocity and ceramic plate material on ballistic impact performance are presented. Among the ceramic plate materials considered, alumina 99.9% gives higher ballistic limit velocity.