Projectile-target Interaction Research Articles

A graph network-based learnable simulator for spatial-temporal prediction of rigid projectile penetration

Predicting plate penetration by rigid projectiles (PPRP) is crucial in terminal ballistics, with broad applications in civil and military engineering. Empirical and analytical methods face challenges in predicting field variables like displacement and stress in target plates. Although numerical methods offer high accuracy, they suffer from low computational efficiency. Herein, we introduce an efficient data-driven machine learning (ML) method based on graph neural networks (GNNs), named PGN, specifically tailored to address the PPRP problem. Unlike traditional ML methods that establish direct input-output mappings, PGN predicts comprehensive spatial-temporal information pertaining to the projectile-target interaction process. A thorough analysis of PGN's performance in terms of accuracy, computational efficiency and generalization ability was performed. Compared to validated results of numerical simulations, PGN maintained high precision with RMSE for displacement, stress, and strain predictions below 0.5 %, 9.5 %, and 2.1 %, respectively. It also achieved R2 values exceeding 0.92 for the time history of projectile velocity and acceleration, while requiring only 9.8 % of the computation time compared to LS-DYNA. In generalization tests, PGN exhibited remarkable adaptability in tackling challenging scenarios that extend far beyond the training data distribution, with overall RMSE between 11 % and 13 %. Furthermore, we find that the maximum information propagation capacity of a simulated physical system must meet or exceed the information propagation need of the real-world physical phenomenon it aims to replicate. Consequently, an approach was proposed to determine the critical connectivity radius of the massage passing method directly from the wave speed in the target medium, which greatly improved the accuracy and efficiency of PGN.

Australasian microtektites: early target-projectile interaction in large impacts on Earth

Australasian microtektites: early target-projectile interaction in large impacts on Earth

High-velocity projectile penetration test and theoretical calculation of pseudo fluid penetration of calcareous sand

To explore the penetration resistance of calcareous sand media, penetration tests have been conducted in the velocity range of 200–1000 m/s using conical-nosed projectiles with a diameter of 14.5 mm. Further, a pseudo fluid penetration model applicable to the penetration of rigid projectiles in sand media is established according to the approximate flow of compacted sand in the adjacent zone of penetration. The correlation between the impedance function of projectile-target interaction and the internal friction features of pseudo fluid is clarified, and the effects of sand density, cone angle of nose-shaped projectile, and dynamic hardness on the penetration depth are investigated. The results verify the feasibility, wide applicability, and much lower error (with respect to the experimental data) of the proposed model as compared to the Slepyan hydrodynamic model.

EWS Time Delay in Low Energy e−C60 Elastic Scattering

Access to time delay in a projectile-target scattering is a fundamental tool in understanding their interactions by probing the temporal domain. The present study focuses on computing and analyzing the Eisenbud-Wigner-Smith (EWS) time delay in low energy elastic e−C60 scattering. The investigation is carried out in the framework of a non-relativistic partial wave analysis (PWA) technique. The projectile-target interaction is described in (i) Density Functional Theory (DFT) and (ii) Annular Square Well (ASW) static model, and their final results are compared in details. The impact of polarization on resonant and non-resonant time delay is also investigated.

Nuclear symmetry energy at work in heavy ion reactions: new results from the INDRA-FAZIA apparatus

The recently coupled INDRA-FAZIA apparatus offers unique opportunities to investigate heavy ion collisions at Fermi energies by combining the optimal identification capabilities of FAZIA and the large angular coverage of INDRA. We present a selection of the results of the analysis of the first experimental campaign performed with INDRA-FAZIA, in which the four reactions 58,64Ni+58,64Ni have been studied at two different beam energies (32 and 52 MeV/nucleon) in the intermediate energy regime. The present work is focused on the isospin diffusion effects in semiperipheral and peripheral collisions. A stronger isospin equilibration is found at 32 MeV/nucleon than at 52 MeV/nucleon, as expected due to a shorter projectile-target interaction time in the latter case.

Ballistic performance of functionally graded B4C/Al composites without abrupt interfaces: experiments and simulations

Functionally graded materials (FGMs) are promising protective structures for lightweight armor plates because of their features and designability. However, traditional discretely layered FGMs with macroscopic interfaces can generate unfavorable interlaminar stresses under ballistic attacks, eventually leading to delamination or interlayer tearing. Herein, we constructed new B4C/2024Al FGMs without sharp interfaces between layers. The FGM armor systems with varying through-the-thickness distributions were tested against 7.62 mm armor-piercing incendiary projectiles. The effects of compositional gradient exponent on the damage characteristics, stress distribution and energy evolution were numerically and experimentally investigated. The results indicated that the smooth transition within through-the-thickness microstructures effectively avoided the occurrence of interlayer delamination or tearing. The compositional gradient exponent played an essential role in the impact response of the FGM targets. The FGM having a linear composition gradient outperformed other nonlinear types with respect to energy absorption and ballistic properties due to the reduced tensile wave strength and prolonged projectile-target interaction time. Furthermore, the structural optimization problem with the objective of maximizing ballistic efficiency was solved using the conjugate gradient method, and the optimal design of the FGM targets was achieved. The current research provides a promising design guideline for developing and optimizing new advanced lightweight composite armor.

Projectile Coherence Effects in Twisted Electron Ionization of Helium

Over the last decade, it has become clear that for heavy ion projectiles, the projectile’s transverse coherence length must be considered in theoretical models. While traditional scattering theory often assumes that the projectile has an infinite coherence length, many studies have demonstrated that the effect of projectile coherence cannot be ignored, even when the projectile-target interaction is within the perturbative regime. This has led to a surge in studies that examine the effects of the projectile’s coherence length. Heavy-ion collisions are particularly well-suited to this because the projectile’s momentum can be large, leading to a small deBroglie wavelength. In contrast, electron projectiles that have larger deBroglie wavelengths and coherence effects can usually be safely ignored. However, the recent demonstration of sculpted electron wave packets opens the door to studying projectile coherence effects in electron-impact collisions. We report here theoretical triple differential cross-sections (TDCSs) for the electron-impact ionization of helium using Bessel and Laguerre-Gauss projectiles. We show that the projectile’s transverse coherence length affects the shape and magnitude of the TDCSs and that the atomic target’s position within the projectile beam plays a significant role in the probability of ionization. We also demonstrate that projectiles with large coherence lengths result in cross-sections that more closely resemble their fully coherent counterparts.

Improved ballistic performance of a continuous-gradient B4C/Al composite inspired by nacre

Functionally gradient materials (FGMs) primarily composed of a discretely layered structure with relatively sharp macroscopic interfaces are highly susceptible to interlayer failure under impact loading. Nacre is regarded as a model system for lightweight armor with high impact-resistant performance owing to its multiple length-scale and gradient structures. However, the simultaneous translation of both structural features into artificial assemblies remains challenging. Herein, we constructed new B4C/2024Al FGMs with eliminated sharp interfaces, which reproduced the hierarchical and gradient architectures of nacre. A combined experimental and numerical approach was employed to investigate the protective mechanisms of nacre-like FGMs subjected to 7.62 mm armor-piercing incendiary bullet, and two homogeneous composites were also tested under the same conditions for comparison purposes. The FGMs exhibited improved performance to resist ballistic attacks and maintain integrity compared with the uniform structures. As the ceramic contents decreased along the thickness, the energy dissipation mechanisms transitioned from eroding projectile to plastic deformation. The toughness gradient and varying energy dissipation modes prevented the formation of crushed cones at the ceramic-rich layers. The nacre-like structure created several extrinsic toughening mechanisms, which led to the increased energy-absorbing capability of the target. Meanwhile, the eliminated abrupt interfaces avoided the occurrence of interlayer tearing by diminishing the tensile wave strength and the sudden change of wave impedance, which prolonged the projectile-target interaction period and strengthened the eroding effect on the projectile. The present study opens new opportunities to design advanced lightweight FGMs armors with high impact-resistant protective performance.

Influential Factors of a Reactive Materials Projectile’s Damage Evolution Behavior

To determine the mechanism of penetration of multi-layer aluminum targets (MLAT) by a reactive materials projectile (RMP), AUTODYN-3D numerical simulations and experimental tests were carried out. The Powder Burn equation of the state ignition model was introduced for the reactive core activation under different projectile–target interaction conditions, which effectively simulated the deflagration reaction damage effects behavior of the RMP and the damage evolution behavior of the MLAT. The activation rate of the reactive core increased significantly when the thickness of the steel target was 8–15 mm; a significant combined destructive effect of kinetic and chemical energy was produced on the MLAT. The initial velocity was proportional to the penetration and destruction effect of the front-layer aluminum target. For the rear-layer aluminum target, the detonation damage showed a tendency to increase and then decrease. If the head metal block was too thick, the penetration ability would be improved at the same time, and the deflagration reaction damage effects ability of the steel target would be significantly reduced. In order to achieve good battlefield damage efficacy, all of the influencing factors should be comprehensively considered.

First results from the INDRA-FAZIA apparatus on isospin diffusion in Ni58,64+Ni58,64 systems at Fermi energies

An investigation of the isospin equilibration process in the reactions Ni58,64+Ni58,64 at two bombarding energies in the Fermi regime (32 and 52 MeV/nucleon) is presented. Data have been acquired during the first experimental campaign of the coupled INDRA-FAZIA apparatus in GANIL. Selecting from peripheral to semicentral collisions, both the neutron content of the quasiprojectile residue and that of the light ejectiles coming from the quasiprojectile evaporation have been used as probes of the dynamical process of isospin diffusion between projectile and target for the asymmetric systems. The isospin transport ratio technique has been employed. The relaxation of the initial isospin imbalance with increasing centrality has been clearly evidenced. The isospin equilibration appears stronger for the reactions at 32 MeV/nucleon, as expected due to the longer projectile-target interaction time than at 52 MeV/nucleon. Coherent indications of isospin equilibration come from the quasiprojectile residue characteristics and from particles ascribed to the quasiprojectile decay.6 MoreReceived 23 May 2022Accepted 26 July 2022DOI:https://doi.org/10.1103/PhysRevC.106.024603©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEquations of state of nuclear matterLow & intermediate energy heavy-ion reactionsNuclear fragmentationNuclear reactionsTechniquesSpectrometers & spectroscopic techniquesNuclear Physics

Kinematic Analyses of Metallic Plate Perforation by Penetrators with Various Nose Geometries

This study analyses kinematics of a metallic plate perforation by a penetrator with truncated ogive nose geometry to find solutions also to blunt, conical, ogive, and hemi-spherical nosed penetrators. Plugging, ductile hole enlargement, dishing, and petal forming failure modes are used in the analyses. Acceleration throughout perforation is calculated by using the related failure mode, analytical model, and the target-penetrator interaction geometry. Depending on the failure model; back lip and front lip formation during ductile hole enlargement, plug formation during plugging, and deflection of target plate during dishing is also analysed. Analyses are based on projectile’s equation of motion, momentum and energy equations, and projectile-target plate interactions. The analyses results for selected cases, with the impact velocity range 215-863 m/s, are compared with the test data. The residual velocity estimation for a strike velocity is close to the related test data with an error of 0.3-2.2 %, except for conical nosed penetrators at impact velocities approaching the ballistic limit velocity

A Simplified Approach for the Determination of Penetrant Residual Velocity for Penetration Processes

The study’s main aim was to predict the penetrant residual velocity, with it being a vital output parameter in the projectile target interaction. The ballistics have been probed on a wide spectrum of impact velocities for different applications. Determination of the residual velocity by analytical methods entails the use of the impulse momentum principle, and the process is further challenged by the necessary inclusion of various variables that directly affect the calculation of the residual velocity. These problems can be overcome by adopting a non-dimensional approach by determining the combination of variables required for the penetration process by carrying out and validating the non-dimensionalization of the pertinent variables. The process discussed in this study provides a reasonable correlation of the non-dimensional parameters, which was used to estimate and validate penetrant residual velocity. A generalized solution predicting the penetrator residual velocity for a wide range of materials for a variety of impact velocities is proposed. The result of this correlation was validated against the published data, and the method was largely in agreement, showing the robustness of the proposed finding.

Nucleon-induced inelastic scattering with statistical strength functions and the ECIS direct reaction code

Modern theoretical descriptions of inelastic scattering make use of multi-step direct reaction approaches together with transition potentials obtained from sophisticated nuclear structure models. Here we demonstrate how the complexity of such calculations can be reduced to permit simpler ones, also using the ECIS code, but providing an almost equally precise alternative to a much more detailed calculation. We have studied the transition form factors within the random phase approximation (RPA), where these are obtained as linear combinations of particle–hole states. At moderate to high excitation energies, where interference effects tend to disappear, we have proposed an independent particle–hole formalism in which particle–hole states are spread in energy with an appropriate strength function obtained from the RPA. The effects of more complex modes, such as 2p–2h ones, are simulated with widths calculated in a semi-classical context. Here, we verify the validity of our approximations for pre-equilibrium proton-induced reactions on $$^{90}$$ Zr target. Our calculations provide a good description of the reaction data and point toward a simplification of the description of nucleon-induced reactions based on averages of microscopic details of the projectile–target interaction.

Study of cluster structures in nuclei through the ratio method

For one-neutron halo nuclei, the cross sections for elastic scattering and breakup at intermediate energy exhibit similar angular dependences. The Recoil Excitation and Breakup (REB) model of reactions elegantly explains this feature. It also leads to the idea of a new reaction observable to study the structure of loosely-bound nuclear systems: the Ratio. This observable consists of the ratio of angular distributions for different reaction channels, viz. elastic scattering and breakup, which cancels most of the dependence on the reaction mechanism; in particular it is insensitive to the choice of optical potentials that simulate the projectile-target interaction. This new observable is very sensitive to the structure of the projectile. In this article, we review a series of previous papers, which have introduced the Ratio Method and its extension to low beam energies and proton-halo nuclei.

Influence of fast emissions and statistical de-excitation on the isospin transport ratio

Isospin transport ratio is a powerful method to estimate the neutron-proton (n-p) equilibration in heavy-ion collisions, and extensively used to obtain information on the asy-stiffness of the nuclear Equation of State. In fact such a ratio is expected to bypass any perturbations introducing a linear transformation of the chosen observable. In particular, it is supposed to overcome contributions due to emission, either of dynamical or statistical nature, from the primary fragments formed during the collisions. In this paper we explore the validity of this assumption, looking at the quasi-projectile n-p ratio ($N/Z$) in peripheral and semi-peripheral events for Ca+Ca reactions at 35\amev{}, simulated via the Antisymmetrized Molecular Dynamics transport model, coupled to different statistical decay codes. The statistical de-excitation of the primary fragments introduces a linear transformation at relatively high excitation energies (above 2\amev{}) when the residue approaches the Evaporation Attractor Line, while some effect is produced at lower excitation energies due to the occurrence of some non-linearities. As for fast emissions after the end of the projectile-target interaction it is shown that they introduce a non-linear transformation too.

Differential Study of Projectile Coherence Effects on Double Capture Processes in p + Ar Collisions

We have measured differential yields for double capture and double capture accompanied by ionization in 75 keV p + Ar collisions. Data were taken for two different transverse projectile coherence lengths. A small effect of the projectile coherence properties on the yields were found for double capture, but not for double capture plus ionization. The results suggest that multiple projectile–target interactions can lead to a significant weakening of projectile coherence effects.

Neutron measurements from the interaction of a thick Ta target with protons at different energies

Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator environment considering its enormous use in a proton accelerator. The Ta target has a unique advantage considering the generation of short half lived radionuclides upon interaction with protons. This advantage extends its use as the beam stopping material at various locations of an accelerator. However, this target has a varied range of reactions to produce neutrons and prompt gammas depending on proton energies. So in the present work, the neutron spectra were generated at various incident proton energies and neutron ambient dose equivalents were estimated close to the target projectile interaction at 90°with respect to the incident beam direction. A comparison of the spectral nature and doses were also done with measurements made by our earlier studies carried out at 0°. The comparison clearly showed that, apart from an increase in the low energy neutron yields at 90°, the overall yield distribution remains similar at both 0°and 90°angles with respect to the incoming beam direction. The ratio of the ambient neutron dose equivalent is found to reduce by a factor of 3–4 at 90°compared to 0°over the entire incident proton energy range. So, the dose equivalent ratio at two angles can be considered as independent of the incident projectile energy.

Identification of characteristic features in scattering cross sections for the electrons colliding with silver, platinum, and gold atoms

A semi-relativistic approach is employed to calculate elastic differential, integral, and momentum transfer cross sections as well as total (elastic plus inelastic) cross sections for the scattering of electrons from silver, platinum, and gold atoms in the energy range 0.1–100 eV. The projectile-target interaction is composed of real (i.e. the sum of static, exchange, and polarization) and imaginary (i.e. absorption) potential. The total optical potential is then used in the solution of the Dirac equation for the scattered electrons. The characteristic features [Ramsauer-Townsend (RT) minimum and shape resonance] which are required for the fundamental understanding of the dynamic processes at the atomic level, are identified in the low energy region. The value of the RT minimum has been correlated with the scattering length to the dipole polarizability of the target atom. The calculated cross sections are compared with available theoretical calculations and experimental measurements in this energy region.

Setup for multicoincidence experiments of photons in the extreme ultraviolet to visible spectral range and charged particles-The solid angle maximization approach.

The coincident detection of particles is a powerful method in experimental physics, enabling the investigation of a variety of projectile-target interactions. The vast majority of coincidence experiments is performed with charged particles, as they can be guided by electric or magnetic fields to yield large detection probabilities. When a neutral species or a photon is one of the particles recorded in coincidence, its detection probability typically suffers from small solid angles. Here, we present two optical assemblies considerably enhancing the solid angle for photon detection in the extreme ultraviolet to visible spectral range. The efficiency and versatility of these assemblies are demonstrated for electron-photon coincidence detection, where electrons and photons emerge from fundamental processes after photoexcitation of gaseous samples by synchrotron radiation.

A comparison of the ballistic behaviour of conventionally sintered and additively manufactured alumina

Production of ceramic armour solutions on-demand/in-theatre would have significant logistical and military advantages. However, even assuming that such technologies could be successfully deployed in the field, such near net-shape manufacturing technology is relatively immature compared to conventional sintering of ceramics. In this study, the ballistic performance of a series of additively manufactured (AM)/rapidly-prototyped (RP) alumina tiles of 97.2% of the density of Sintox FA™ were investigated using both forward- and reverse-ballistic experiments. These experiments, undertaken with compressed gas-guns, employed the depth-of-penetration technique and flash X-ray as primary diagnostics to interrogate both efficiency of penetration and projectile-target interaction, respectively. The RP alumina was found to exhibit useful ballistic properties, successfully defeating steel-cored (AP) 7.62 × 39 mm BXN rounds at velocities of up-to c.a. 850 m/s, while exhibiting comparable failure modes to conventionally sintered armour-grade Sintox FA™. However, where a <1% by vol. Cu dopant was introduced into the RP material failure modes changed dramatically with performance dropping below that of conventionally sintered alumina. Overall, the results from both sets of experiments were complimentary and clearly indicated the potential of such RP materials to play an active role in provision of real-world body armour solutions provided quality control of the RP material can be maintained.