Projectile Velocity Research Articles

New method for predicting perforation parameters of a concrete slab target to a penetrating projectile

The present paper investigates the perforation of a projectile through a concrete slab and proposes a new approach for assessing the perforation parameters, including the projectile residual velocity, and the slab perforation and ballistic limits. The new approach is rather simple and easy to implement and provides a fast solution. A new parameter denoted the “pseudo-residual velocity (VP)” is defined and is theoretically calculated. For a given slab thickness H0, the magnitude of VP(H0) is always smaller than the corresponding true residual velocity. The developed approach reduces the determination of the perforation parameters to a sequence of pseudo-perforation problems that are quickly solved using the modified (hybrid) DISCS method, which had been developed for penetration analysis into thick targets, using the constitutive equations of the slab concrete material. In contrary to many other simplified models, the proposed approach is based on a theoretical model and engineering insight and does not require any empirical constants, or calibrations prior to the analysis. Numerous examples compare the proposed approach predictions to test results, covering different types of concrete, slab thicknesses and projectile impact velocities. In all comparisons, very good predictions of the proposed approach are demonstrated.

Mechanism-driven analytical modelling of UHMWPE laminates under ballistic impact

Ultra-high molecular weight polyethylene (UHMWPE) fiber reinforced composite laminates have been widely used to defend against projectiles and fragments. Although the ballistic performance of UHMWPE composites has been extensively characterized both experimentally and numerically, analytical modelling remains a challenge. This study develops a mechanism-based analytical model of UHMWPE cross-ply laminates, with the progressive process of projectile penetration divided into two sequential stages of local failure and bulging deformation: the former is characterized with the strain concentration model under local shock compaction, and the latter is described using a modified membrane stretching model. Compared with existing energy-based models, the current model enables revealing physical mechanisms underlying the deformation/failure processes of UHMWPE laminate subjected to projectile impact, with relevant parameters correlated with material properties. Further, without using any fitting parameter, the proposed analytical model can predict both the ballistic limit and residual projectile velocity. For validation, the model predictions are compared with existing test data, with good agreement achieved for varying projectile mass, projectile size, laminate type, and laminate thickness. It is demonstrated that the maximum strain under a penetrating projectile is controlled by the thickness of un-penetrated laminate and the growth of bulge, and that the longitudinal wave speed and maximum tensile strain in the UHMWPE laminate dictate its ballistic limit.

Experimental research on the launching system of auxiliary charge with filter cartridge structure

A launching system with a filter cartridge structure was proposed to improve the muzzle velocity of the projectile. The combustion chamber of the launching system is divided into two fixed chambers, one is located in the breech chamber, and the other is arranged in the barrel. The breech chamber charge was ignited first, and the charges in the auxiliary chambers were ignited by the high-temperature, high-pressure combustible gas trailing the projectile. In this way, the combustible gas in the auxiliary chambers could compensate for the pressure drop caused by the movement of the projectile. The proposed device features the advantage of launching a projectile with high muzzle velocity without exceeding the maximum pressure in the chamber. In order to obtain some internal ballistic characteristics of the launch system, some critical structure, such as the length of the filter cartridge auxiliary charge, the combustion degree of the propellant in the chamber, and the length of the barrel, are discussed. The experimental results show that with the increased auxiliary charge length, a pressure plateau or even a secondary peak pressure can be formed, which is less than the peak pressure. The projectile velocity increased by 23.57%, 14.64%, and 7.65% when the diaphragm thickness was 0 mm, 1 mm, and 2 mm, respectively. The muzzle velocity of the projectile can be increased by 13.42% by increasing the length of the barrel. Under the same charge condition, with the increase of barrel length, the energy utilization rate of propellant increases by 28.64%.

Effect of Change of Reluctance Launcher Parameters on Projectile Velocity

Effect of Change of Reluctance Launcher Parameters on Projectile Velocity

Semi-analytic model for plasma production and Cherenkov radiation emission from hypervelocity impacts on soda–lime glass

A semi-analytic method is proposed to compute the produced plasma and the emitted Cherenkov radiation from hypervelocity impacts on soda–lime glass for various projectiles and impact velocities. First, the Taylor–von Neumann–Sedov blast wave model, coupled with the system of nonlinear Saha equations for multispecies, strongly coupled plasma, is adopted to estimate the hydrodynamic profiles and the ionization state of the target material in the early stage of the impact. Second, the Frank–Tamm formula is considered to investigate the onset of the Cherenkov radiation and to compute the emitted energy. The present approach predicts a linear dependence of the produced total electric charge on the projectile density and a quadratic dependence on the projectile velocity, whereas the emitted Cherenkov radiation scales quadratically with the produced charge if the onset conditions are met.

Variability of input gunshot injuries of clothing fabrics

One of the main components of a gunshot injury is the entrance hole. Its characteristic features: round shape, size, the presence of a central tissue defect, abrasion collar (contamination, metallization), are differential diagnostic signs of an entrance gunshot injury. Under the conditions of the conducted experiments, the peculiarities of the variability of the described signs of the entrance holes on the clothing fabrics were studied, depending on the nature of the objects to be subjected and the contact velocity of the firearm projectile. The identified features must be taken into account when examining gunshot injuries, as well as planning and conducting experimental studies with firearms.

Effects of semicore electrons on stopping power in helium-irradiated aluminum nanosheets.

The stopping power of energetic He ions traversing an Al film is studied by combining the time-dependent density-functional theory method with molecular dynamics simulations. We investigated the dependence of the semicore electron excitation of the Al film on the projectile's trajectory and its charge state. Our results show that for the off-channeling trajectories the semicore electrons contribute significantly to the stopping power of the Al film as the He+ ion velocity exceeds 1.0 a.u, and in contrast, it is negligible for the channeling trajectories. Most importantly, we found two unexpected effects of semicore electrons on the stopping power in helium-irradiated aluminum nanosheets, i.e., (1) the semicore electrons can contribute to the energy loss for both high and low energy projectiles under the off-channeling trajectory; (2) as the projectile velocity increases from 0.4 a.u. to 2.0 a.u. although semicore electron excitation (including transition in the target, ionization away from the target and transfer to the projectile ion) of the target atom is gradually inhibited, the influence of semicore electrons on valence electron excitation is gradually enhanced. Our finding allows us to gain new insights into the stopping of ions in metals.

Functional gradation of aluminum alloy by impact of ballistics as severe plastic deformation process

In the present effort, impact of bullets fired at high speeds on a stationary target was used as a high strain-rate plastic deformation method to generate Functionally Graded Materials (FGMs). The bullet-shaped Aluminum alloy Al5052 specimens impacted the UHMWPE target at different projectile velocities ranging from 100 m/s to 750 m/s, to study the effect of the impact speed. Moreover, few of the projectiles impacted along the longitudinal axis whereas the remaining projectiles impacted with an obliquity to investigate the effect of leading-edge shape. The metallography of the projectile specimens fired at 750 m/s shows grain refinement from 70 ± 3 μm at the rear/ un-deformed point to 10 ± 1 μm at the front/ severely deformed point which is in the impact zone. Similar but of less magnitude variations were observed at other impact speeds also. The hardness variation was 45% (70 ± 3 HV at the rear surface to 102 ± 2 HV at the front face) at 750 m/s. Moreover, least variation in hardness and grain size was observed for projectile impacted at lowest velocity tested (100 m/s). Further, functionality in hardness and grain refinement was seen in graded direction due to shape of the projectile specimens, impact velocity, and target material. Depending upon the impact angles, axisymmetric (impacted normal to the longitudinal axis) or unsymmetrical (impacted at an angle) variation of grain refinement and hardness was observed.

Full state constrained command filtered output feedback control for the electro‐hydraulic ammunition ramming system

AbstractA barrier Lyapunov functions‐based command filtered output feedback control scheme is presented for the electro‐hydraulic ammunition ramming system (EHARS) with position and velocity constraints in this paper. Due to the limitation of compact installation space in ramming mechanism, there remain some immeasurable signals such as the velocity of projectile and pressures in hydro‐cylinder; thus, a state observer is designed to estimate the unmeasured states of EHARS. The barrier Lyapunov functions theory is adopted to guarantee position and velocity constraints of projectile are not violated. In order to suppress the complexity of differential explosion in backstepping iteration, command filtered technology and corresponding compensating technique of filtering errors are applied. By the stability theory of Lyapunov, the stability of the closed‐loop system and the boundedness of the whole state in EHARS are theoretically proved. Simulation results show prescribed position‐tracking accuracy and desired velocity of projectile under different firing angles, which indicates the effectiveness of the proposed method.

Reliability Assessment of Steel-Lined and Prestressed FRC Slabs against Projectile Impact

A simulation-based probabilistic method is proposed for assessing the reliability of steel-lined and prestressed fiber-reinforced concrete (PFRC) slabs against the impact loads. The impact testing of several prestressed and non-prestressed FRC slabs of 800 × 800 × 100 mm in size was carried out. The experimental program involved projectile impact testing of prestressed and non-prestressed FRC slabs using a gas gun. Three parameters were varied for testing of slabs under the projectile impact, viz., a quantity of steel fibers in the concrete, steel lining on the backside of the slab, and the prestressing level. The probability-based reliability analysis of all the tested specimens was then performed to highlight the influence of steel lining, steel fibers, and prestress in enhancing the safety of RC (reinforced concrete) slabs against projectile impacts. Projectile impact velocity exceeding the slab’s ballistic limit was assumed to lead to the failure of the PFRC slab, i.e., the perforation failure of the slab. Study results indicate that when no steel fiber was present, slab reliability was low. Adding fibers to slabs increases slabs’ reliability significantly. Specimens with the highest steel fiber content (1.2%) showed the greatest increase in reliability. The steel lining on the back face makes the slab’s reliability almost doubled in comparison with those without lining. Additionally, steel lining makes the PFRC slabs as reliable as desired. It was further noticed that the prestressing helps in enhancing the slab safety against projectile impacts. Even a minimal amount of prestressing makes a noticeable improvement in the reliability of PFRC slabs.

Temperature influences of the recoil characteristics for aluminum honeycomb buffer in the tether-net launcher

Fluctuations in outer space's temperature would affect the spacecraft's regular operation. This paper aims to study the temperature influences of the aluminum honeycomb buffer in the tether-net launcher. Firstly, a buffer structure was designed to attenuate the pyroshock generated by the pyrotechnic device. Secondly, the mechanical properties of aluminum honeycomb at different temperatures were obtained through quasi-static compression experiments. Then, the internal ballistic responses of the launcher were gained by the closed bomb tests and the equivalent classical interior ballistic model. Finally, the recoil performance of the launcher with aluminum honeycomb buffer at different temperatures was studied. It is revealed that the aluminum honeycomb crushing force gradually decreases with the temperature increases. The peak pressure, burning rate coefficient and velocity increase while the peak time decreases with the temperature increase for the interior ballistics. For the launcher recoil responses, the average launch recoil decreases if the aluminum honeycomb doesn't enter the dense stage. The impact acceleration, projectile velocity and displacement increase as the temperature increase. The paper spotlights the temperature's influence on the recoil characteristics of the aluminum honeycomb buffer, which provides a new idea for buffering technology of pyrotechnic devices in a complex space environment.

Ballistic resistance of high-strength armor steel against ogive-nosed projectile impact

The advanced high-strength armor steel with the superior strength-to-weight ratio can extremely improve the ballistic resistance and mobility of military equipment and structures. Aiming to assess the ballistic resistance including the ballistic limit and failure modes of two types of advanced high-strength armor steels, the projectile perforation test and numerical simulations were conducted. Firstly, ten shots of 15 mm-caliber ogive-nosed projectile perforation test were performed under the initial impact velocities of 164–428 m/s. The failure mode and out-of-plane displacement (OPD) response of target plate were recorded by utilizing the high-speed 3D digital image correlation system. Then, the classical finite element (FE) and mesh-free Smoothed Particle Galerkin (SPG) methods were adopted to conduct the numerical simulations, respectively. The predicted residual velocities of projectile were compared with the test data to verify the accuracy of the calibrated constitutive model parameters and numerical analysis approaches. By further comparing the failure modes and OPD–time histories of target, it was drawn that the FE method is preferable to reproduce the failure mode of target, while the SPG method is recommended to quickly predict the residual velocity of projectile. Finally, by adopting the validated numerical analysis approach, the residual velocities for two types of high-strength armor steels under the initial impact velocity range of 150–600 m/s were obtained. The reliabilities of the existing seven analytical models in predicting the ballistic limit and residual velocity for high-strength armor steels were further evaluated.

Modular electromagnetic railgun accelerator for high velocity impact studies.

A modular electromagnetic railgun accelerator facility named "RAFTAR" (i.e., Railgun Accelerator Facility for Technology and Research) has been commissioned and its performance has been characterized for high velocity impact testing on materials in a single-shot mode. In the first tests, RAFTAR demonstrated an acceleration of more than 1000m/s for an 8g solid aluminum-7075 armature projectile. The current fed was 220kA, having a muzzle time of about 1.75ms. It is a single pulse breech-fed rectangular bore (14 × 13mm2) railgun, and its 1.15m long barrel assembly consists of two parallel copper bars with an inter-gap of 13mm that are encased within 50mm thick high strength reinforced fiberglass sheets (Garolite G10-FR4) and bolted from both the sides. RAFTAR is powered by two capacitor bank modules that have a maximum stored energy of 160 kJ each (containing eight 178 μF/15kV capacitors), two high power ignitron switches, and a pulse shaping inductor. To obtain consistent acceleration of the armature inside the barrel, reversal of driving current is prevented, and its pulse duration is stretched by tactical integration of the crowbar switch and bitter coil inductor in the circuit. Armature projectile velocity measurement in-bore and outside in free space was performed by the time-of-flight technique using indigenously made miniature B-dot sensors and a novel shorting-foil arrangement, respectively. The time resolved measurement of the in-bore armature evidenced a velocity-skin-effect in the high acceleration phase. There is good agreement between the experimentally measured and theoretically predicted efficiency, confirming the optimal choice of operating parameters. The conclusion summarizes important experimental findings and analyzes the underlying causes that limit the performance of railguns.

High-velocity impact study of an advanced ceramic using finite element model coupling with a machine learning approach

A numerical approach combining finite element modeling and machine learning is used to inform the material performance of an alumina ceramic tile undergoing high-velocity impact. In this study, the alumina ceramic tile is simulated by incorporating a user-defined Johnson–Holmquist–Beissel (JHB) material model within the framework of smoothed particle hydrodynamics (SPH) in LS-DYNA finite element software. The implementation of the JHB model is verified by comparing equivalent stress–pressure responses through a single element simulation test. After implementation, the computational framework is simulated across our chosen range of conditions by matching the results from both plate impact experiments and ballistic testing from the literature. The computational model is then used to generate training data sets for an artificial neural network (ANN) to predict the residual velocity and projectile erosion for an alumina ceramic tile undergoing high-velocity impact in the SPH framework. The ANN is then used to perform a sensitivity analysis involving exploring the effect of mechanical properties (e.g., strength and shear modulus) and impact simulation geometries (e.g., thickness of ceramic tile) on material performance (i.e., residual projectile velocity and erosion). Overall, this study shows the capability of the FEM-ANN approach in studying the high-velocity impact on ceramic tiles and is applicable to guide the structural-scale design of ceramic-based protection systems.

Experimental and numerical study on ballistic resistance of aluminum foam sandwich panel considering porosity and dimensional effect

Sandwich panels have been widely used in various industries due to their high strength and energy absorption capacity. In this study, the ballistic behavior of a sandwich panel comprised of two aluminum face-sheets and an aluminum foam as the sandwich core is studied. The panels are constructed and subjected to the blunt-nosed projectile. The experimental test consists of a sandwich panel with three different ranges of foam densities and two thicknesses for the panels beside hardened steel projectiles. Then, numerical simulations of the projectile perforation in the panels are conducted that are in good agreement with the experiments. The failure mechanism of the sandwich panels is investigated and the role of foam core is discussed. Failure mechanism and the amount of plug depends on foam density and projectile velocity, such that different failure mechanisms such as plugging, petaling, and dishing occurred for the face-sheets. After that, the ballistic limit velocity (VBL) of sandwich panels was calculated via experiments and finite element simulations. The experiments and simulations showed that increasing the density and thickness of the foam core generally leads to an increase in VBL. Finally, we study the panels with the constant mass and (or) constant height with different foam densities and the effect of foam density is investigated in these cases.

Mechanism of polyurea in protecting liquid-filled square aluminum tube from the impact of high-velocity projectile

The impact of projectile on liquid-filled containers produce hydrodynamic ram (HRAM), which results in local damage and overall deformation of the container. Aiming at enhancing the protection capability of liquid-filled containers under projectile impact loads, this study proposes a scheme of spraying polyurea on liquid-filled containers. Calibrated numerical modeling with an experiment was conducted to investigate the dynamic response process of the polyurea coated water-filled square aluminum tube (PCST) under the high-velocity impact of projectile. The effects of projectile velocity (700–1100 m/s) and polyurea thickness (0–6 mm) on the damage characteristics of the liquid-filled containers were analyzed and summarized. Results showed that the strength of HRAM increased with the rise initial velocity of the projectile. The polyurea layer reduced the plastic deformation of the square aluminum tube, restricted the crack expansion of the corner, and wrapped the petaling failure of the tube. The restraining action of the polyurea coating on the deformation of the container enhanced the peak pressure in the liquid, whereas the deceleration of the polyurea layer on the projectile weakened the deformation of the tube. A competitive relationship existed between the restraining action of the container and the deceleration effect of the projectile on HRAM. With the increase in polyurea layer thickness, the strength of HRAM trended to initially increase and then decrease. The leading cause of HRAM was gradually changed from container restraint action to projectile deceleration effect.

Bioinspired nacre-like steel-polyurea composite plate subjected to projectile impact

Natural marine biological structures have evolved over a long period of time, and their comprehensive performance has huge advantages over artificial materials. In order to improve the overall strength of the artificial structure, inspired by the layered structure of nacre, a nacre-like steel-polyurea composite plate was designed as a new impact-resistant structure. On this basis, the damage deformation of three different layered steel-polyurea composite plates with nacre-like structure under different projectile velocities was simulated. The damage failure morphology of nacre-like composite plates with different layered numbers was analyzed, and consequently, five failure toughening mechanisms of nacre-like composite plates were summarized. Then, the fitted ballistic performance curves were used to compare the ballistic performance of nacre-like composite plates with different delamination, and it was found that the composite plates could reduce the residual ballistic velocity by 24.58% and increase the ballistic limit by 27.86%, and the energy dissipation mechanism of the composite plates was explained by the energy release of steel and polyurea layers. Finally, the theoretical analysis reveals that the increase in the delamination number can effectively increase the equivalent modulus of the nacre-like composite plate, thus enhancing the penetration resistance of the composite plate.

Analysis on Deflection of Projectile Penetrating into Composite Concrete Targets.

From an offensive point of view, increasing the impact velocity of the projectile is an effective way to enlarge its penetration depth. However, as the projectile penetrates the target, there often exists an angle of attack, the resultant force on the projectile is in a different direction from that of projectile velocity, which causes the deflection of the projectile, and thus the strike effect is greatly weakened. From the other perspective, the deflection of the projectile can contribute to proactive protection of key targets from damage caused by a deeper penetration which has been an important consideration for actual protective structure. Presently, investigations on the deflection mechanism of the impact projectile are relatively few, and there is especially a lack of more comprehensive theoretical and experimental studies. In this paper, the mechanism of projectile deflection when penetrating a composite concrete target is thoroughly analyzed. The composite concrete target composed of a concrete fixed target and multiple diamond-shaped moving targets, similar to the structural system for multi-layer overlay extension, showed better anti-penetration performance in practical protective structures. The analytical model of projectile deflection during penetrating the target is established through simultaneously resolving the dynamic equations for the projectile and moving target. Penetration tests of the composite concrete target plate impacted by a 76 mm projectile were conducted to examine the effectiveness of the analytical model, where impact velocity and point and the size of the moving target were considered. On this basis, the influences of impact velocity and point on the deflection of the projectile are disclosed, and the effects of parameters of moving target are discussed. These findings can provide significant references for optimization of advanced protective structures and improvement of their anti-penetration performance.

Numerical simulation analysis of the flow field in the bore of a two-stage light gas gun

In order to study the effect of different launch tube diameters of gas-driven two-stage light gas guns on the flow field during the launch process, a model of the piston movement in the pump tube to the projectile launch was established using Fluent. Using the dynamic mesh technology and 6DOF model, a numerical simulation of the projectile launch process of the two-stage light gas gun was carried out, and the effects of different launch tubes on the projectile velocity and the flow field in the bore were obtained. The results show that when the mass difference between the piston and the projectile is large, appropriately increasing the diameter of the launch tube is conducive to the flow of gas in the high-pressure cone and increases the projectile launching speed. The numerical simulation analysis of the flow field in the bore provides a basis for the design and optimization of the two-stage light gas gun.

Ballistic Performance Evaluation of High-Performance Fabric Due to Interyarn Friction

This paper discusses the novel multimaterial arbitrary-Lagrange-Euler (MM-ALE) based approach for modeling shear-thickening fluid (STF)–treated fabric under ballistic impact. The friction-based model of fabric implements the effect of interyarn friction on the ballistic performance of the neat and STF-treated fabric. Furthermore, this paper presents the limitations of friction-based modeling of STF-treated fabric under a wide range of projectile velocities. Such a limitation is the exact prediction of interyarn coefficients of friction for STF-treated fabric for the complex phenomenon of ballistic impact. The results obtained from the friction-based model for the ranges of interyarn coefficients and fabric sett showed that there is an enhancement in the ballistic performance due to an increase in the coefficient of friction up to a critical value of friction coefficients. It was observed that beyond the critical level, there was no improvement in the ballistic performance of the fabric. However, there was a decrease in the ballistic performance beyond the critical friction level. Moreover, the numerical model of neat fabric using friction-based models as validated and implemented in the development of MM-ALE-based modeling of STF-treated fabric. The novel MM-ALE-based modeling approach will enrich the understanding of the STF mechanism under ballistic impact for STF-treated fabric systems. The limitations of friction-based models shall be handled using the MM-ALE based technique.