Kinetic Energy Of Projectile Research Articles

Ballistic limit determination of aluminum honeycombs—Experimental study

Honeycombs are widely used as core structures in sandwich panels as energy absorbers. In this paper the ballistic limit velocity, energy dissipation and damaged zone of metallic honeycombs at normal impact are studied experimentally and compared with analytical formulae. In experiments aluminum 5052-H39 honeycombs are impacted by rigid steel cylindrical projectiles with a blunt nose. The ballistic limit velocities calculated from Alavi Nia's formulae [A. Alavi Nia, Ph.D. Thesis, Tarbiat Modarres University, 2002] show good conformity with experimental values. The differences between predicted ballistic limits and experimental data are found to be less than 10%. Energy studies show that folding of cell walls and shearing of plug have the main role in energy dissipation. The energy needed for folding of cell walls is about 71–85% of the initial kinetic energy of projectile. This quantity for shearing of plug is about 13–28%. The shearing of plug portion in energy dissipation is proportional to the second power of panel thickness, so that 25% growth in panel thickness results in 56.2% increase in the shearing of plug portion. The damaged zone formed by the projectile is almost circular in shape and its diameter is equal to the projectile diameter on the impacted side of the panels, but on the rear side of the panel the damage is elliptical in shape and its diameter is about 1.5–3 times of the projectile diameter.

Effect of frame size, frame type, and clamping pressure on the ballistic performance of soft body armor

We analyze, with the computer code LS-DYNA, three-dimensional (3D) transient deformations of a 10-layer woven Kevlar armor held in a square steel frame and impacted at normal incidence by a 9 mm FMJ (full metal jacket), 124 grain projectile. The composite armor is discretized into weft and warp yarns to simulate its woven structure. The yarn is modeled as a 3D continuum. We consider failure of the yarn, and friction between adjoining layers and between the armor and the frame bars. For the armor perfectly bonded to the rigid frame bars, the computed residual speed and the residual kinetic energy of the projectile are found to increase with a decrease in the frame size implying thereby that the armor fixed in a smaller frame will have lower V 50 than that of the same armor clamped in a larger frame. (The V 50 of an armor equals the speed of a standard projectile that upon normal impact has 50% probability of just perforating the armor). For the armor allowed to slide between the frame bars, we have studied the effect of the pressure applied to the bars of the two- and the four-bar frames on the speed and the kinetic energy of the residual projectile. For both the two- and the four-bar frames, the speed of the residual projectile is found to increase with an increase in the applied pressure. Computed results also show that the armor fixed in the two-bar frame exhibits higher impact resistance than that held in the four-bar frame. The V 50 is found to be ∼270 m/s when the woven armor is held in a four-bar frame with a clamping pressure of 200 MPa. The V 50 decreases with an increase in the pressure applied to either the two-bar or the four-bar frames.

Dynamic Fracture of Ceramics in Armor Applications

Ceramic materials have been extensively used in armor applications for both personnel and vehicle protection. As the types of threats have diversified recently, e.g., improvised explosive devices and explosively formed projectiles, a proper set of ceramic material selection criteria is needed to design and optimize corresponding mitigating structures. However, the dynamic fracture and failure behavior of engineering ceramics is still not well understood. Using examples of thin ceramic plates and confined thick ceramics subjected to kinetic energy projectile impact, this article provides a brief summary on the current understanding of dynamic failure processes of ceramics under dynamic penetration loading conditions. Laboratory examination of dynamic fracture of ceramics is conducted using split Hopkinson bars with various loading rates, stress states, and loading histories.

Formation of negative ions in collisions between fluorine ions and C60 molecule versus the kinetic energy of projectiles

We have measured the rate of negative ion formation in F+-C60 collisions at different projectile velocities (v • 0.1 a.u to 0.4 a.u.). The measured rate has been found to decrease from 9.6% to 7.1% for projectile energy increasing from 7.3 keV to 18.3 keV. The fragmentation patterns of C60r+multicharged ions charged r+ formed in the collisions have been analyzed.

Organic mass spectrometry with low-energy projectiles

Molecular dynamics computer simulations have been employed to elucidate mechanisms responsible for uplifting of a monolayer of benzene and polystyrene molecules adsorbed on Ag{1 1 1} by low-energy atomic and cluster Ar projectiles. The sputtering yield and mass distributions of ejected particles are analyzed depending on the type and the kinetic energy of a projectile. It is shown that the relative contribution of intact molecules can be greatly enhanced if the kinetic energy of atomic projectile is reduced below 60 eV. At these energies, however, the efficiency of desorption is low and the ejection process is limited only to loosely bound molecules. Much better results can be obtained for cluster projectiles containing hundreds of Ar atoms with the incident energy of a few eV per atom. The impact of such particles leads to a gentle and very efficient removal of intact organic molecules originally adsorbed at the surface.

Electron yields from uranium dioxide under impact of slow Xe ions

Measurements of the secondary electron yields from uranium dioxide under impact of Xeq+ (q=10–25, 0.03keV⩽EKin⩽81keV) ions are presented. A strong increase of the secondary electron yield is observed with increasing charge state of the projectile both at normal and oblique incidences. No variation of the electron yield with the projectile kinetic energy is observed at normal incidence. Therefore, the electron emission process in highly charged ion – uranium dioxide (UO2) interactions is dominated by potential electron emission.

Multiprojectile Active Electromagnetic Armor

Active electromagnetic armor accelerates the projectile by electromagnetic force, which could be launched to the aggressor missile on its way to protect the object. A solid metal projectile is usually applied in the active electromagnetic armor based on the elements of reconnection launch gun. A novel active multihollow-projectile electromagnetic armor is proposed in this paper based on the research of the reconnection launch gun. Given the same drive coil and pulsed power, the hollow projectile has higher kinetic energy than the solid one, and it can be filled with the detonator, which will be detonated when the projectile hits the aggressor missile. Each projectile's kinetic energy of the multiprojectile structure may be lower than the single projectile, but the general efficiency could be greatly improved. The thickness of the projectile could be designed by finite-element simulation, with the precondition of mechanical strength of the projectile

Railgun Tribology: Characterization and Control of Multishot Wear Debris

Railgun tribology describes the friction and wear sciences of interacting surfaces in relative motion. The novel tribological feature of railguns is the use of high-speed, high-current sliding electrical contacts for the conversion of the electrical energy in a current pulse into projectile kinetic energy. Several wear processes affect the life of components used to construct the bore of a railgun depending upon the severity of the duty cycle. Following multishot testing without refurbishment in solid-armature railguns, wear products have been observed to accumulate on the contact surfaces of rail conductors. Aluminum-alloy armatures produce wear debris that is chemically complex and structurally inhomogeneous. Because electromagnetic propulsion requires that electrical conduction take place across these debris layers, it is important to understand the factors that influence their structure. A critical question for repeatable and predictable railgun performance and for extended rail life is whether easy conduction occurs through these accumulated wear products. It is possible to control the dimensions and properties of these wear debris accumulations on rail contact surfaces using chemical and mechanical aids. Films of rapidly solidified aluminum with layered structures and high levels of gas porosity are the most common debris on copper rails. It is possible to control the structures of these films and to plow them away when they grow thick. Here, results of characterization and control of wear debris are presented and discussed

Heat Generation During the Firing of a Capacitor-Based Railgun System

Railguns use a high-current, high-energy electrical pulse to accelerate projectiles to hypersonic velocities. Pulse-forming networks that employ capacitors as the energy store are typically used to shape the required electrical pulse. A significant fraction of the stored energy (2% to 40% in large caliber railguns) is converted to projectile kinetic energy during launch. After the projectile exits the launcher, the balance of the energy has either been dissipated as heat in the circuit components or is stored in system inductance. If an energy recovery scheme is not employed, the inductor energy will also be dissipated in the resistance of the active circuit components. A circuit analysis has been performed in order to calculate the current profile from the PFN. A higher fidelity solution was achieved by accounting for the temperature dependent resistance of the rails. This information along with individual component resistance and inductance was used to calculate the distribution of energy subsequent to a single pulse. Detailed component heating information is important when considering the overall thermal management of the system. Once this information has been obtained, the components that require external cooling can be identified, and an appropriate thermal management system can in turn be designed

Pulsed-Power Driven Metafex Launchers

A conventional electromagnetic (EM) launcher propels a projectile with electromagnetic forces. By contrast, a Metafex launcher contains a dense, initially-inert material, activated by an electrical pulse, that reacts, creating a gas that propels the projectile. Because the reaction energy is four times as energetic as the electrical pulse, the ratio of projectile kinetic energy to electrical energy is much larger for a Metafex launcher than it is for a conventional EM launcher. Conventional EM launchers generally use long rails or barrels to gradually accelerate projectiles and are suitable replacements for entire guns. Metafex launchers are compact, provide rapid acceleration, and are more suitable for flyer plate applications. We have obtained positive test results for Metafex configurations that operate at practical voltages of approximately 20 kV. We describe the outcome of the testing, the potential uses of the material, and the opportunities for development of related pulsed power components such as capacitors and switches that will follow from Metafex commercialization

Physics of deformation and fracture at impact loading and penetration

The structure, dislocation substructure, and mechanical properties of the targets made of four aluminum alloys after a impact loading by kinetic energy projectile have been investigated. The formula for approximation of the ballistic limit velocity by indentation technique is proposed. It has been shown that the maximum nonequiaxiality of the grain shape, increase of dislocation density, and decrease of dislocation cell size correspond to the 40–70% of plastic deformation at static compression for the investigated aluminum alloys.

Wave vector matching in charge exchange collisions involving positrons

We present a simple model based upon wave vector matching which gives a plausible explanation for the empirical observation that, for positron collisions with a wide variety of targets, cross sections for positronium formation are largest when the projectile kinetic energy is in the vicinity of twice the relevant threshold energy. The model is used to make predictions of cross-section trends for charge exchange processes for collisions involving a number of other positronic species.

Lightweight ceramic composite armour system

The development of lightweight armour systems for ballistic protection is under continuing attention of the manufacturers and users. A new design of the composite armour systems has been developed and ballistically tested. A new armour system consists of a ceramic plate, an intermediate ceramic–polymer layer and a polymer fibre lining as a backing material. The proposed composite armour systems prepared with a use of specially selected compositions of the intermediate layer promoting the absorption of the kinetic energy of projectiles provide adequate ballistic protection to National Institute of Justice (NIJ) level III and level IV, and they successfully withstand multiple hits.

Quantitative analysis of the projectile impact on rock using infrared thermography

The transient process of rock, normally impacted by a gas gun, was monitored with a thermal infrared (TIR) imager. The geometric features and the radiant characteristics of the infrared thermography in target region were extracted and regressively analyzed. Both the projectile's impacting velocity and kinetic energy were back analyzed based on the extracted geometric features and the radiant characteristic parameters of target thermography. It was revealed that: (1) there is a critical velocity at which target thermography is regular and centrally symmetrical; (2) within the critical velocity, the impacting velocity is linearly correlated to the perimeter of target thermography and is quadratically correlated to the TIR temperature increment, while the projectile kinetic energy is linearly correlated to both the area and the increment of the TIR radiant flux of the target thermography; (3) for a quantitative back analysis of the impact-related parameters, both geometric features and radiant characteristics can be applied. It was suggested that the perimeter and the TIR radiant flux increment of the target thermography can applied as the principal indices (with an error of less than 5%), while the area and the TIR temperature increment of target thermography can act as other auxiliary indices (with an error of less than 15%). The possible mechanisms of variations in IR radiation for impact on rock are discussed. The results are of general significance for the impact on other types of rocks or solid materials, and might extend the application of infrared remote sensing from a static geosciences domain to a dynamic mechanical domain.

Angular distributions in multifragmentation

Angular distributions are reported for $^{37}\mathrm{Ar}$ and $^{127}\mathrm{Xe}$ from 381-GeV $^{28}\mathrm{Si}+\text{Au}$ interactions and for products between $^{24}\mathrm{Na}$ and $^{149}\mathrm{Gd}$ from 28-GeV $^{1}\mathrm{H}+\text{Au}$. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.

X-ray spectra induced in highly charged 40Ar q+ interacting with Au surface

By use of optical spectrum technology, the spectra of X-ray induced by highly charged 40 Ar q + ions interacting with Au surface have been studied. The results show that the argon Ka X-ray were emitted from the hollow atoms formed below the surface. There is a process of multi-electron exciting in neutralization of the Ar 16+ ion, with electronic configuration 1s 2 in its ground state below the solid surface. The yield of the projectile Kα X-ray is related to its initial electronic configuration, and the yield of the target X-ray is related to the projectile kinetic energy.

THRESHOLD KINETIC ENERGY FOR GOLD X-RAY EMISSION INDUCED BY HIGHLY CHARGED IONS

The X-rays induced in the interaction of highly charged Argon ions with gold surface were investigated. We had altered the projectile kinetic energy from 150keV to about 400keV. The results show that, there is a threshold projectile kinetic energy for this excitation. Combining the colliding theory of classic electrodynamics with the concept of quantized orbits, we crudely give this threshold kinetic energy.

Estimation of Postlaunch Angular Motion for Kinetic Energy Projectiles

Aerodynamic jump is a contributor to projectile launch dispersion errors. To reduce aerodynamic jump with an active control device, a method of estimating the aerodynamic jump is needed to identify the active control that is required. A method is developed for estimating the angular motion of a kinetic energy projectile immediately following launch. The sensors required are two body-fixed accelerometers nominally mounted on the projectile longitudinal axis, the nominal sensing axes of which are orthogonal to the longitudinal axis and orthogonal to each other. This estimation method permits the use of a body-fixed control device to reduce aerodynamic jump.

Improvement of a “mini” two-stage light-gas gun for hypervelocity impact experiments: Technical devices to accelerate and detect a “minute” projectile efficiently

A gas-gun system was improved and optimized in order to obtain higher projectile velocity. The gas gun used in this study was a “mini” two-stage light-gas gun suitable for the acceleration of a “minute” projectile. As a major improvement in the mini gun, the high-pressure coupler was divided into two parts. One part was a generation section of the hot and high-pressure working gas by compression with a piston, and the other was a flow rate control section of the working gas. The mini gun, after installing the improved high-pressure coupler, showed an increase not only in the projectile velocity but also in the energy efficiency converting the combustion energy to the projectile kinetic energy, compared with the conventional mini gun. In the firing test using hydrogen as a working gas, a projectile velocity of 5.91km∕s was achieved by the use of the improved mini gun, as compared with a velocity of 4.70km∕s before the improvements were made. The modifications to the mini-gun system and their effects on the performance of the mini gun are discussed.

X-Ray Emission from Zr, Mo, In and Pb Targets Bombarded bySlow Highly Charged Arq+(q = 13,14,15,16) Ions

We study the L x-ray emission from Zr, Mo and In targets and M x-rayemission from Pb target under bombardment of low energy Arq+(q = 13,14,15,16) ions. The relative x-ray yields were measuredin the projectile kinetic energy range 210–360 keV. It is found thatthe relative x-ray yields from Zr, Mo and Pb targets increase with theincreasing projectile kinetic energy for Ar14+ and Ar16+projectiles and depend on the potential energy of the projectileremarkably.