Projectile Shell Research Articles

Polymer-bonded secondary explosives

In this paper, a review of the available literature on physical and explosive properties of explosive compositions containing a secondary explosive and a polymer binder (PBX) is presented. The review focused on an analysis of the properties of compositions containing mostly synthetic polymers. The review showed that, at the moment, the most commonly used composition is a hexogen-based explosive bonded with a chemically cross-linked hydroxylterminated polybutadiene. The use of energetic polymers in PBX compositions was observed only in the experimental systems tested on a laboratory scale. The most popular methods of forming compositions include pressing a previously phlegmatized explosive or chemical cross-linking of the composition in the projectile shell. Compositions which can be formed and reloaded using injection machines are known, but due to many limitations, the method is not widely used.

FACTORS INITIATING THE ACTIVATION OF FIRING CHAIN IN ARTILLERY FUSES

Basic function of an artillery fuse is to ef-fectively initiate the activation of the main charge, located in the projectile shell, at a place and time decided by a gunner. The fuse also has a key role for ensuring the safe use of ammunition. Efficient initiation of the first part of so called firing train decides on proper functioning of the fuse. This element generates an impulse stimulating the activation of subsequent components of the train (chain). In the article, the authors will focus on factors initiating the correct activation of first components of the fire train in artillery fuses. These factors, with some pros and cons, will be discussed on examples of fuses which are used up to now.

Analysis of Operation of a Driving Band Mounting in a Projectile’s Shell

The paper presents computational modelling using the Finite Element Method (FEM) for technological operation of a driving band mounted in a groove of a projectile shell. Exemplary results of analysis for shrapnel cal. 35 mm are given. The analysis showed significant factors influencing the mounting process and a field of residual stresses in a projectile shell. It allowed for determination of mechanical properties of materials of a driving band and a projectile shell as well as of characteristic dimensions of half-finished product of a driving band and a groove in a projectile shell. The obtained investigation results show substantial advantages of such analyses for a design process of new types of gunnery ammunition. Thus, it is possible to optimise the construction and technology, i.e., to minimise the reduced stresses in a field of residual stresses in a projectile shell what limits the possibility of a driving band break (rupture) or cracking a projectile shell inside a barrel during the shot.

Influence of Rotating Band Construction on Gun Tube Loading—Part I: Numerical Approach

The effects of changes in geometries and material properties of rotating band and long range artillery projectile shell body on gun tube stress are presented. The results are based on numerical calculations (finite element analysis, FEA). Numerical explicit dynamic analyses were performed assuming elastic–plastic material behavior and nonlinear kinematics. Mechanical loading of shell body was controlled by pressure–time relationship based on the simulation of internal ballistic cycle. One degree slice of projectile and forcing cone section of gun tube was modeled as simplified smooth bore 3D analysis model. The results were in agreement with the measured results in firing trials and also with the results presented in open literature. Although simplified computations were used, the influences of the structural modifications of the rotating band and the shell body were shown.

Influence of Rotating Band Construction on Gun Tube Loading—Part II: Measurement and Analysis

The soft deformable metallic rotating band of large caliber projectiles prevents the gas leakage between the gun tube wall and the shell body by the band pressure on contact surfaces during the launch cycle of the gun. High rotating band pressures can lead to problems concerning gun tube wear, fatigue, and strength. The effects of changes in construction of rotating band and long range artillery projectile shell body on gun tube loading are studied experimentally. A practical analysis method for tube inner wall pressure computation from outer wall strain measurements is presented. The method is based on assuming stepped pressure load affecting on tube inner wall surface, when the projectile passes the measurement point. Although the analysis method was simplified, it was found to give useful and reliable results for comparative verification of different shell and band structures and their influences on gun tube loading. The structural design of the shell body and the rotating band were shown to be the most important aspects to cause the extreme loadings on the gun tube.

Target dependence for low-Z ion charge state fractions

Equilibrium charge state fractions have been measured for 3–7 MeV lithium, boron and carbon ions passing through thin foils of copper, silver, and gold. The current results are combined with other low-Z ion data from the literature to give the relative influence of different target materials on charge exchange processes. The mean charge of the projectile, the functional form of the charge state distribution, and the charge state distribution width are parameters used to examine the effects of the electronic structure on charge exchange for various target-projectile combinations. Projectile shell structure is found to have a large influence on the widths of the charge state.

Shell effect on stabilization processes following multi-electron transfer in slow Ar q+–Ar ( q = 6–9, 11) collisions

We experimentally investigate the shell effect on the stabilization processes following the multi-electron transfer in slow collisions of Ar q +–Ar ( q = 6–9, 11). The relative cross-section ratios of multi-electron transfer and of the subsequent stabilization with respect to single-electron capture are measured meanwhile compared with the theoretical results predicted by the classical over-barrier model. Our result indicates that the multi-electron transfer is dominant when the projectile charge is large and the subsequent stabilization shows a dramatic variation if the projectile L-shell configuration becomes open. It shows that the subsequent stabilization processes of multiply excited scattering ions have a strong dependence on the projectile shell.

Extension of the Brandt–Kitagawa model for Hartree–Fock electronic densities

An extension of the Brandt–Kitagawa model for the effective charge calculation is presented in the case of ions with atomic numbers from Z1=3 to 10. The Hartree–Fock method is used to provide electronic densities for projectiles with various charge states. The projectile screening lengths obtained using the Hartree–Fock method are larger than those calculated using the variational method as proposed in the Brandt–Kitagawa model. Differences between the effective charge calculated by the original method and the one presented here can be as high as 50% especially in the case of low charge states. With this alternative procedure, it is possible to input projectile shell effects in the stopping power such as Z1-oscillations. The differences between the present method and the original one are attributed to a poor description of the heavy ion screening length by the variational method assumed in the Brandt–Kitagawa model.

Stabilization of electrons onArq+ions after slow collisions withC60

We discuss hollow atom formation and stabilization of electrons on ${\mathrm{Ar}}^{q+}$ following ${\mathrm{Ar}}^{q+}+{\mathrm{C}}_{60}\ensuremath{\rightarrow}{\mathrm{Ar}}^{(q\ensuremath{-}s)+}+\ensuremath{\cdot}\ensuremath{\cdot}\ensuremath{\cdot}$ collisions at $3.3q \mathrm{keV}$ $(q=4--18).$ The experimental information consists of the final projectile charge-state distributions ${f}_{q}^{s},$ i.e., the relative distributions of the number of stabilized electrons, s, and the corresponding mean values $〈s〉={\ensuremath{\sum}}_{s=1}^{q}{\mathrm{sf}}_{q}^{s}$ as functions of q. We use the classical over-the-barrier model to deduce sequences of effective principal quantum numbers and find that the hollow atom formation is completed $3--{4a}_{0}$ above the surface of the ${\mathrm{C}}_{60}$ cage for all q. For $q<~8$ (filled L shells), the last electrons are transferred from delocalized outer ${\mathrm{C}}_{60}$ orbitals directly to the projectile M shell (side-feeding), while several intermediate shells are left open for larger q leading to further electron transfer at intermediate distances and simultaneous electron emission from higher projectile shells. At still closer distances, localized carbon K-shell electrons are transferred directly to the argon L $(q=10$ and 11) and M shells $(q>~12).$ The direct transfer to the L shell of ${\mathrm{Ar}}^{10+}$ and ${\mathrm{Ar}}^{11+}$ is manifested as significant enhancements of $〈s〉$ for $q=10$ and $q=11.$

Improved Dynamic Simulation of Highly Charged Ion-Surface Collisions

On the basis of a refined classical overbarrier model, we simulate the evolution of level occupations of slow highly charged ions (HCIs) reflected by metal surfaces. Our calculation includes the full trajectory of the projectile and incorporates atomic structure calculations which provide accurate asymptotic projectile energy levels. We scrutinize effects related to proposed interaction mechanisms, such as peeling off atomic Rydberg levels and small-distance side feeding from the target valence band to inner projectile shells. The simultaneous evaluation of projectile energy gains, final charge state distributions, and the emission of projectile Auger electrons agrees well with experiments.

Energy gain in collisions of highly charged ions withC60

We have extended the recently developed dynamical classical over-barrier model for charge transfer in soft ion-cluster collisions in order to simulate the projectile kinetic energy gain of 3.3$q$-keV Ar${}^{q+}$ ions in large-impact-parameter collisions with neutral C${}_{60}$ targets. Our semiclassical theory allows for the direct calculation of the energy defect $Q$ and of the projectile kinetic-energy gain in two different ways: either as difference of electronic binding energies before and after the collision or by integration of the dynamically varying force between the collision partners along the trajectory. A comparison between the two ways provides an intrinsic test of the model calculations. A comparison with recent experimental data shows good agreement in the main features of the projectile energy gain spectra and facilitates their interpretation in terms of the number of transferred electrons and projectile shells into which electrons are captured.

Calculation of electron transfer cross-sections in Siq+ + H (q = 4-14) collisions at energies of 0.5-14 keV/u

Cross-sections for electron transfer into individual (n,ℓ) projectile states in Siq+ + H collisions (q = 4, 6, 7-14) are calculated at impact energies of 0.5-14 keV/u. The calculations are performed within the semiclassical close-coupling formalism with one-electron atomic orbital basis sets. Calculated electron transfer crosssections for the dominantly populated projectile shell nmax ≃ q¾ plus one to three additional shells are presented in tabular form and are discussed with regard to their dependence on the energy and charge states. The prominent role of the electronic core for the ℓ-distributions of cross-sections is pointed out.

Charge exchange at relativistic velocities

The present understanding of charge exchange at relativistic velocities is briefly reviewed. Special attention is given to the recently developed relativistic eikonal theory which has been applied to transitions from K, L, and M shells of the target to nearly all projectile shells. Calculated results are compared to recently measured data. As a qualitatively new effect, magnetic capture is investigated for 1s-1s transitions. The structure of a relativistic first-order capture amplitude satisfying Coulomb boundary conditions is given.

Atomic collisions with relativistic heavy ions. III. Electron capture.

Cross sections for the electron capture by 82- , 140- , and 200-MeV/amu ${\mathrm{Xe}}^{54+}$, ${\mathrm{Xe}}^{53+}$, and ${\mathrm{Xe}}^{52+}$ ions incident on thin solid targets from Be to Au were measured. The measurements are compared with calculations of radiative and nonradiative capture. The nonradiative capture calculations are based on the relativistic eikonal approximation which includes transitions from K, L, and M shells of the target to nearly all projectile shells. In high-Z targets, nonradiative capture into excited states of the projectile is dominant, as predicted by the eikonal calculations and confirmed by comparing measured cross sections for bare ${\mathrm{Xe}}^{54+}$ and ${\mathrm{Xe}}^{52+}$ (1${s}^{2}$) projectiles. A simple formula for estimating nonradiative-electron-capture cross sections for relativistic-ion accelerator design and other applications is derived. Double and triple electron capture are also observed in the low-velocity, high-Z collisions.

Determination of high-npartial transfer cross sections in bare-nucleus—hydrogen-atom collisions

A method is proposed to determine partial cross sections for transfer into high-$n$ projectile shells in collisions between highly charged ions and atoms at energies around the energy of maximum transfer. Starting from the semiclassical close-coupling method with atomic-orbital basis sets, each group of orbitals belonging to a particular high-$n$ shell is coupled separately to those orbitals which dominate the capture process. Partial transfer cross sections ${\ensuremath{\sigma}}_{\mathrm{nl}}$ are calculated for ${\mathrm{C}}^{6+}$+H, ${\mathrm{N}}^{7+}$+H, and ${\mathrm{O}}^{8+}$+H collisions at 4-25 keV/amu with quantum numbers $n$ labeling shells up to those from which visible transitions take place.

Charge distribution width of heavy ions after passage through carbon foils

Equilibrium charge state distributions have been measured for 45–166 MeV Br ions after passage through carbon foils. Including the Br ion data, systematic investigation has been carried out for the charge distribution width ( d) of various heavy ions (Z 1) over a wide range of projectile velocity ( v). It is found that the variation of d as a function of v is closely related to the variation of projectile shell structure. Based on this concept, trials have been performed to present the expression of d values using new co-ordinates.

TotalK-vacancy production in Ne (10 MeV) traversing Al

Deexcitation of projectile inner shell vacancies created while traversing a solid foil may take place via competing processes: a) vacancy sharing with foil atoms in close impacts, b) radiative and non-radiative electron capture, and c) such X-ray and Auger electron transitions as are possible in the heavy ion projectile. The change inK-vacancy creation with foil thickness can be investigated by measuring either projectile or target X-rays where the vacancies are created by Coulomb excitation and processa. In the system Ne (10 MeV) on Al, detecting AlK X-rays, the NeK-vacancy production probability has been determined.