Projectile Exit Research Articles

Development of the Johnson-Cook flow stress and damage parameters for the impact response of polycarbonate: Experimental and numerical approach

The Johnson and Cook (JC) flow stress and damage model parameters of a polycarbonate (PC) plate were determined by the mechanical tests and numerical simulations of the tests. The experimental tests included quasi-static and high strain rate tension and compression, quasi-static notched-specimen tension, quasi-static indentation (QSI), low velocity impact (LVI) and projectile impact (PI). Initially, five different quasi-static flow stress-strain equations were extracted from the experimental and numerical tests. The flow stress equation determined from the experimental average true stress-true strain curve well agreed with the effective stress-strain obtained from the quasi-static numerical tension test. The numerical QSI force-displacement curve based on the experimental average true stress-true strain equation was further shown to be very similar to that of the experiment. The LVI and PI test simulations were then continued with the experimental average true stress-true strain equation using five different flow stress-strain rate relations: JC, Huh and Kang (HK), Allen-Rule and Jones (ARJ), Cowper-Symonds (CS) and the nonlinear rate approach (NLA). The rate sensitivity parameters of these relations were extracted from the quasi-static and high strain rate tests. The LVI test simulations using the stress-strain rate relations exhibited force-displacement curves higher than those of the experiments. The detected almost no strain rate sensitivity in the LVI tests was ascribed to low strain rate dependency of the flow stress at these intermediate strain rates and large strains involved. On the other side, all the stress-strain rate relations investigated nearly predicted the experimental damage types: dishing at 100 and 140 m s−1 and petalling at 160 m s−1, except the CS relation which predicted the fracture of the plate at 140 m s−1. The experimental average projectile exit velocity at 160 m s−1 was further well predicted by the used stress-strain rate relations while the experimental average petal thicknesses were under estimated by the models. The absorbed energy at 160 m s−1 PI test was determined 1.6 times that of the QSI test, which proved an increased energy absorption capability of the tested PC at the investigated impact velocities.

Study on Anti-Penetration Performance of Semi-Cylindrical Ceramic Composite Armor against 12.7 mm API Projectile

To explore the anti-penetration performance of the specially shaped ceramic/metal composite armor, such an armor is designed and fabricated using a semi-cylindrical projectile resistant ceramic and metal back plate, and its anti-penetration performance for the 12.7 mm armor-piercing incendiary (API) projectile (also known as the 0.50 caliber API projectile) is investigated experimentally and numerically. The results show that due to the significant attitude deflection during projectile penetration, the penetration into the designed ceramic composite armor is quite different from that into the conventional homogeneous ceramic/metal composite armor, which can be roughly divided into the following four stages: asymmetric erosion of the projectile, ceramic cone squeezing movement, back plate failure and projectile exit. The failure mode of the back plate is mainly dishing deformation and petaling failure. When obvious attitude deflection occurs to the projectile, the breaches in the back plate are elliptical in varying degrees, and the height and size of petals are apparently different. The area of the composite armor is divided into different zones according to its anti-penetration performance. The influence of the ratio of semi-cylindrical ceramic diameter to projectile core diameter ξ on the anti-penetration performance is studied under constant areal density. The results show that the deflection effect of the composite armor is small when the ratio ξ is less than 2, and the anti-penetration performance is the strongest when ξ is close to 2. With the increase in the initial velocity of the projectile, the deflection effect of the composite armor on the projectile gradually weakened, and the erosion effect gradually increased.

Multidisciplinary analysis of a mummy from the War of the Pacific.

The War of the Pacific (1879-1884) was a big scale war between Chile against the alliance of Peru and Bolivia. One of the most important battles, the "Batalla del Campo de la Alianza" was situated in the desert near Tacna, Peru. The conditions of this environment favored the conservation of the dead soldiers after many years. Decades ago, the Natural History Museum of Concepción in Chile, received a naturally mummified individual of a probably Chilean soldier as a donation; its uncertain context was never studied nor confirmed. Considering this, our investigation analyzed this body under exploratory methods, ballistic analysis, archaeological contrast, 14C radiocarbon dating, ancient DNA, and isotopic analysis to reconstruct the biological profile of this mummy. The results indicated that the mummy belongs to an adult man between 33-39 years of age (> 1.50 m) and has a perimortem wound in the left flank of the abdomen. CT scan and X-rays revealed the presence of a bullet (Comblain II or Gras) hosted near the L2 vertebra. It is possible that the individual died of bleeding from a gunshot wound done by a long-distance firearm projectile from an inferior level, whose trajectory was from left to right, with slight inclination towards the top, and without a projectile exit. Other analyses confirmed the historical context and suggests the Chilean origin of the mummy. Despite the passage of time and other factors, it was possible to reconstruct the death of this individual thanks to technology and approaches from different disciplines.

Development of modelling design tool for harpoon for active space debris removal

The level of debris in Earth orbit presents an increasing risk. Active debris removal, involving capture and deorbit of larger items, has been identified as important in controlling future debris population growth. One concept for capturing debris is a harpoon, with low post-penetration residual velocity being a key design requirement. Aluminium sandwich panels are common structural components on typical spacecraft and consequently a probable target structure. An ideal harpooning event is characterised with complete penetration of the sandwich panel and low harpoon residual (post penetration) velocity. This paper presents development of a numerical modelling tool for a harpoon design for active orbital debris removal. The ability to predict the ballistic limit of an aluminium sandwich panel with a honeycomb core representative of a large satellite structural element being the primary requirement for the modelling tool. The modelling approach was validated against the experimental results from normal and oblique impact tests performed for ogive and flat nose projectiles over a velocity range between 50 m/s to 120 m/s. The modelling was based on explicit finite element method, using the commercial LS-DYNA code. An element failure criterion was used to approximate material damage and failure. Sensitivity studies were performed to investigate the influence of model key features on the projectile exit velocity. The features with the strongest influence were the face sheet material model and the projectile-panel friction model. The projectile exist velocities observed in the experiments were used to select the final parameters used. The use of an element deletion criterion that incorporated the influence of stress triaxiality improved the agreement for the plate deformation behaviour between the numerical and experimental results. For the ogive nose projectile, the exit velocity agreed well with the experiments for the range of impact velocities and angles considered. For the flat nose projectile, the model overestimated the exit velocity. In the case of the normal impact this was due to the model's inability to capture the honeycomb crushing ahead of the projectile.

Ballistic performance of synergistically toughened Kevlar/epoxy composite targets reinforced with multiwalled carbon nanotubes/graphene nanofillers

AbstractThe individual and synergistic effects of multi‐walled carbon nano tubes (MWCNT) and graphene nano‐platelets (GNP) on the ballistic performance (low and high velocity) of functionalized Kevlar reinforced polymer matrix composites have been investigated. Low‐velocity impact tests were carried out on the composite targets (6 layers) using a gas gun setup. Surface hardened conical nose projectiles of 10 mm diameter were used and the inlet velocity was in the range of 122–128 m/s. Similarly, high‐velocity ballistic impact experiments were conducted on the targets (24 layers) using a 9 mm full metal jacketed (FMJ) projectile with an initial velocity of 430 ± 15 m/s. Acid treatment was done to functionalize the Kevlar fiber surface. From the low‐velocity impact experiments, the hybrid targets had better ballistic resistance when compared to the unfilled and individually filled nanocomposites. A reduced projectile exit velocity, improved impact energy absorption (32.5 J), and an improved energy absorption percentage of 27.57 were observed for the hybrid combination. Similar improvements were observed during high‐velocity ballistic experiments which were evident from the fractographic analysis. The macroscopic investigation on the target containing both the nano‐fillers had the least penetration depth of 5.8 mm and a high damage area compared to the other targets. This is due to the addition of f‐MWCNT and f‐GNP which has increased the matrix toughening and functionalization of Kevlar which increased the interfacial bonding. In addition, the crack bridging property of CNTs and encapsulation behavior of graphene due to stacking has synergistically improved the overall toughness of the composites.

Analysis of the effect of bore centerline on projectile exit conditions in small arms

Most finite element models of small arms focus on an idealized barrel, typically one with a perfectly straight bore centerline. Using five different experimentally measured bore centerlines, this investigation analyzes the effect centerline nonlinearity has on projectile exit conditions. This includes the effect of rotating a centerline through several orientations. Modeled using Abaqus/Explicit, this dynamic analysis simulates a single firing cycle for each centerline. Projectile jump is calculated for each model as a measure of the effects of warped centerlines. The warped centerlines have a small effect on barrel dynamics.

Study on the Simulation of Electromagnetic Squint

This paper introduces the simulation electromagnetic gun device based on STM32, which mainly uses openmv and laser ranging module as recognition sensor. The system obtains the target position through openmv, uses PID algorithm to control the steering gear with two degrees of freedom to make the gun barrel aim at the target, then obtains the target distance through the laser ranging module, obtains the target and controls the energy storage capacitor voltage of the electromagnetic gun, increases the voltage through the DC power supply, charges and discharges the capacitor through the thyristor controlled by the relay, the capacitor discharge generates the magnetic field through the coil, and generates the magnetic field inside the steel ball Instead, a magnetic field ejects the ball. This design realizes the closed-loop control of the capacitor voltage to ensure the stability of the projectile exit velocity. The system is stable in operation and has high precision.

Crack propagation through sandwich bones due to low-velocity projectile impact.

Projectile impact in sandwich bones typically results in formation of conoidal wounds exhibiting a larger region of damage on the inner cortical plate termed the bevel. To date, a number of hypotheses have been put forward to explain the formation of this wound type. The plug and spall hypothesis suggests that the conoidal morphology is produced by a two-phase mechanism of shear plug formation followed by internal bevel production during projectile exit. In contrast, the cone crack hypothesis suggests that such wounds are produced by cone crack propagation through the three laminae of the sandwich bone, resulting in the formation of bioceramic conoids consisting of all three bone laminae. In order to test these hypotheses, 28 non-human sandwich bones were impacted with 6-mm carbon steel spheres at velocities ranging from 26 to 96metres per second (m/s). Impacts were filmed utilizing high-speed videography and fracture morphology analysed using micro-computerized tomography (μ-CT). Sequential increase in velocity successfully captured the genesis of conoidal wounds. Low-velocity impact produced circular depressed fractures in the outer cortex exhibiting angulated cortical fracture edges. An increase in velocity resulted in translaminar fracture and production of one intact and three fragmentary bioceramic conoids. At the highest velocities, conoids were fragmented and lost in the ejecta plume, with attached fragments undergoing dynamic movement during and after perforation. Significantly, projectile exit was not required for bevel production. The implications of these findings in wound interpretation are discussed.

Dynamic perforation of ultra-hard high-strength armor steel: Impact experiments and modeling

The dynamic perforation of 3 mm thick target plates extracted from ultra-high strength steel (Mars® 300) is investigated experimentally and computationally. Projectiles of 8 mm diameter are also extracted from Mars® 300 plates featuring blunt, conical and hemispherical tips. Using a single stage gas gun, impact experiments are performed with projectile velocities of up to 380 m/s. A minimum impact velocity of about 240 m/s (ballistic limit) was required to perforate the armor steel targets with conical and hemispherical projectiles of a mass of about 14 g. In all successful perforation experiments, the plate targets failed through plugging. At the same time, the conical and blunt projectiles are heavily deformed in a way that their final tip shape resembles that of the hemispherical projectiles. The latter turned out to be slightly more efficient than conical ones in the sense that their exit velocities are approximately 10% higher. Numerical simulations are performed of all impact experiments using the finite element software LS-DYNA. The plasticity model made use of a quadratic yield function with non-associated flow rule, a Swift-Voce strain hardening law and Johnson–Cook type of multipliers accounting for the effects of strain rate and temperature. The stress-triaxiality, Lode angle parameter and strain-rate dependent Hosford-Coulomb fracture initiation model is employed to predict the ductile failure of the Mars 300 steel. Overall, the simulation results are in good agreement with the experimental observations, including the mode of perforation (shear plugging) and the projectile exit velocities. The numerical simulations also show that a ring-like band of localized plastic deformation forms inside the targets with temperatures of up to 700 °C. Fracture initiates from the back face of the plate under biaxial tension, while the cracks propagate through the band of localized plastic deformation towards the impacted front face of the plate, thereby forming a plug as the projectile passes through the target.

Study on measuring method of the angular displacement of muzzle vibration for the small caliber gun

In order to solving the key technique of the angular displacement of muzzle vibration for the small caliber gun, a measuring method of double eddy current displacement sensors for the angular displacement of muzzle vibration is proposed. Two sensors are installed at the measuring points which are distributed near the muzzle. Then, by the triangle transformation method, the vertical and horizontal linear displacement of the muzzle vibration can be transformed to the vertical and horizontal angular displacement. It has been verified by the firing test that the method is non-contact and has the capability of anti-muzzle-flash and anti-shock, and that the test accuracy can meet the requirement of the gun firing environment. By this method, the law of the angular displacement of muzzle vibration under three running firing is obtained during the process that after projectile exit, about three circles of attenuation vibration for the muzzle happen, and then the next projectile begins to leave the muzzle. It shows that the average value of the angular displacement of muzzle vibration is 1.93 minute in azimuth and 1.42 minute in elevation.

Application of the incubation time criterion for dynamic brittle fracture

The complex issue of penetration and perforation of brittle plates subjected to normal impact is addressed. Fracture and fragmentation are simulated numerically by using simultaneously two failure criteria: ductile and brittle failure. A new brittle failure criterion, which is based on incubation time, is proposed. The criterion, inspired from the Tuler–Butcher criterion, is implemented in a commercial finite element code by means of a user subroutine. It is validated by comparing numerical predictions to experimental ballistic results of normal impact on polymethylmethacrylate plates. It is shown that the projectile's exit velocity and the timing of the penetration are faithfully reproduced. It is also verified visually that the experimental damage/fracture pattern, namely radial cracking and dishing, are both well captured by the proposed criterion.

Design of a Compulsator to Drive a Railgun

Compulsators are ac generators which are used for electromagnetic launch applications over the past few decades. This paper presents the work carried out by the authors to design a compulsator for a railgun which has been built and tested with a capacitor bank of 20 kJ as the pulsed-power source in the author’s laboratory. The generator topology selected for the compulsator is a single phase, two-pole machine with iron core and passive compensation. The design is based on the criterion of achieving maximum projectile exit velocity with the additional condition that natural current zero is synchronized with the instant of the projectile’s exit. The effect of varying the different parameters of the compulsator on the performance of the system has also been studied and discussed in this paper. By means of performance analysis, the necessary background for the design of the actual compulsator has also been achieved.

A new analytical model for the low-velocity perforation of thin steel plates by hemispherical-nosed projectiles

Abstract Ballistic experiments were conducted on thin steel plates that are normally impacted by hemispherical-nosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities. The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.

Prediction of the ballistic limit of an aluminium sandwich panel

This paper presents research on modelling the impact of a 150g projectile on a 35mm thick aluminium sandwich panel. The objective of the work is a predictive modelling capability for the ballistic limit of the panel. A predictive modelling capability supports the design of capture and deorbit missions for large items of space debris such as satellites and rocket upper stages. A detailed explicit finite element model was built using the LSDYNA software and results were compared with experimental data for the projectile exit velocity to establish key parameters. The primary parameters influencing the model behaviour were the strength and failure of the aluminium face sheets and the friction between projectile and panel. The model results showed good agreement with experimental results for ogive nose projectiles, but overestimated the exit velocity for flat nose projectiles.

Study of the relevant geometric parameters of the channel leak method for blast overpressure attenuation for a large caliber cannon

This study examines the effect of relevant geometric parameters on blast overpressure attenuation and projectile exit velocity loss due to the channel leak method on a muzzle-loaded large caliber cannon. There are four basic geometric parameters which can be varied independently. These include the number of channels, channel length, channel height and channel width. From these basic parameters, three relevant parameters are selected which are expected to be most influential. These three relevant parameters include total leak volume, channel length, and total aspect ratio. Reduction in blast overpressure, and thus peak overpressure, is most affected by the leak volume, however, leak volume needs to be selected carefully to limit the loss in the projectile exit velocity. On the other hand, use of shorter channels is found to be detrimental for peak overpressure attenuation while a lower total aspect ratio has a positive effect. The best configuration, CLM-A1, shows over 50% reduction in peak overpressure at all monitored locations with about 4.8% loss in the projectile exit velocity which translates to the largest average Figure of Merit of 0.534. Shock structure and strength are also examined for the three best leak configurations, CLM-A1, CLM-E1 and CLM-E2, as well as the baseline configuration.

Numerical Investigation of Channel Leak Geometry for Blast Overpressure Attenuation in a Muzzle Loaded Large Caliber Cannon

This study examines the effect of channel leak geometry on blast overpressure attenuation in the rear of a muzzle-loaded large caliber cannon. Effects of three primary geometric parameters including leak volume as well as number and length of channels are studied. Reduction in blast overpressure, and thus peak overpressure, is most influenced by the leak volume; however, leak volume needs to be selected carefully to limit the loss in the projectile exit velocity. Modification of the channel height in the current range has a minimal effect on peak overpressure, but the number of channels can have a significant effect due to the constriction experienced by the leaking flow, thereby limiting the attenuation. Two channel lengths are considered where the longer channel length, is found to be more effective. The best configuration showed over 50% reduction in peak overpressure at all monitored locations with about 4.8% loss in the projectile exit velocity.

Caracterización de las lesiones vasculares por tomografía computada (TC) en heridas de arma de fuego: Experiencia de tres años en Hospital Público del sector suroriente de Santiago de Chile

Abstract: Objectives. To determine the epidemiological and CT characteristics of vascular lesions in patients who have suffered gunshot wounds, in the emergency department of a public hospital in Santiago, Chile, over a period of three years. Material and Methods. Retrospective review of 211 CT performed on patients admitted to the emergency department with gunshot wounds, between 31/05/2009 and 31/05/2012. Patients with a CT within the first 48 hours after the event occurred were included, excluding patients who for their clinical condition, underwent surgery prior to the CT, obtaining a final number of 178. Distribution was analyzed by sex, age, type of vascular injury, topographic segment affected, projectile type and outcome of patients. Results. 96.8% (n° = 31) of those affected were men, 71.8% under 36 years. The most affected segment were to the lower extremi -ties, with 55.8%. The most frequent type of injury was pseudoaneurysm and active hemorrhage, with 20.5% in each case. The type of projectile most frequently found were bullets (65%) and the majority, without projectile exit. In our group there was 1 death.

The high-rate brittle microplane concrete model: Part II: application to projectile perforation of concrete slabs

In this paper, we examine the behavior of the High-Rate Brittle Microplane (HRBM) concrete model based on a series of penetration experiments. These experiments were conducted with three different slab thicknesses (127, 216 and 254 mm) that provided a significant challenge for the numerical simulations. The 127 mm slab provided little resistance, the 216 mm slab provided nominal resistance and the 254 mm slab approached the perforation limit thickness of the projectile. These experiments provide a good baseline for evaluating material models since they have been shown to be extremely challenging; in fact, we have not encountered many material models that can provide quantitatively predictive results in terms of both projectile exit velocity and material damage. In a companion paper, we described the HRBM material model and its fit to various quasi-static material property data for WES-5000 concrete. In this paper, we show that, when adequately fit to these quasi-static data, the HRBM model does not have significant predictive capabilities, even though the quasi-static material fit may be exceptional. This was attributed to the rate-dependent response of the material. After various rate effects were introduced into the HRBM model, the quantitative predictive nature of the calculations dramatically increased. Unfortunately, not much rate-dependent material property data are in the literature; hence, accurate incorporation of rate effects into material models is difficult. Nonetheless, it seems that rate effects may be critical in obtaining an accurate response for concrete during projectile perforation events.

Behavior of Expelled Glass Fragments During Projectile Penetration and Perforation of Glass

Bullets striking common forms of flat glass with an orthogonal intercept angle result in a cloud of ejected glass fragments that are in concert with the exiting bullet's flight path. This is not the case with strikes at angles other than orthogonal. In these situations, the expelled glass fragments follow a very different course from that of the exiting projectile. This is both counterintuitive and a potential source of serious error in the evaluation and reconstruction of a shooting victim's position and orientation at the moment the victim was struck by a bullet that has passed through a nearby source of glass such as a vehicle side window or a window in a building. The flight path of the ejected glass fragments is, however, predictable and is dictated by the orientation of the plane of the glass opposite the projectile's impact site.In all cases, these expelled glass particles have considerable velocity and can produce pseudostippling of the skin in individuals located downrange of bullet-struck glass and near the projectile's exit site. The distribution and location of such pseudostippling and its relationship to the associated bullet hole in glass have important reconstructive value. A proper and reliable reconstruction of the victim's position in such cases will require the integration of scene information with the autopsy findings.

Ballistic impact performance of metallic targets

Performance of metallic targets under ballistic impact loading is presented. The entire ballistic impact event considering target performance can be divided into dynamic plastic penetration, spherical bulge formation, bulge advancement, plug formation and exit and projectile exit. Velocity, displacement, force, deceleration of the projectile and energy absorbed by the target as a function of time are evaluated. Typical experiment studies were carried out on a ballistic impact test apparatus up to incident kinetic energy of 85J. A very good correlation was observed between the analytical predictions and the experimental observations in terms of ballistic limit velocity and energy absorbing mechanisms. The significant observation is that the targets with two different thicknesses can give the same ballistic limit velocity with all the other conditions remaining the same. This behavior is explained based on different prominent energy absorbing mechanisms with different target thicknesses.