Projectile Diameter Research Articles

Projectile nose-length effect on specific cavitation energy and ballistic limit velocity and thickness

The perforation of armour plates by quasi-rigid projectiles in ductile hole growth has been demonstrated to be influenced by the ratio of plate thickness to projectile diameter, referred to as the hole slenderness ratio, h/D. Here we propose a new non-dimensional geometric ratio, termed as the target containment ratio, that uses the projectile nose-length in place of the diameter, i.e., h/L. We demonstrate that the hole slenderness ratio is a special approximation of the target containment ratio for projectiles with a nose-shape ratio (projectile nose-length normalised by projectile shank radius) on the order of 3. We validate the proposed relationship via a comprehensive numerical study and through comparison with experimental data for the 14.5 mm BS41 armour piercing bullet, for which the nose-shape ratio is about 2. We show that the new target containment ratio dependent formulation of the specific cavitation energy improves the accuracy of the model suggested in Masri and Ryan (2024). This new formulation is also used to update existing formulae for ballistic limit predictions of monolithic and multilayer ductile targets.

Numerical Study on the Effect of Geometrical Changes on the Deformation Behaviour of Recycled Aluminium Alloy AA6061 undergoing High Velocity Impact using Hyperworks-Radioss

Numerical analysis is important to predict material behaviour without require an experimental implementation. This manuscript focuses on a numerical prediction establishment of a direct recycled aluminium alloys AA6061 undergoing Taylor Cylinder Impact test using Johnson-Cook model in HyperWorks Radioss. The numerical setup was first validated against the experimental data at the velocity range of 179 to 212 m/s. Good agreement between simulation and experimental data was obtained within the range that exhibits a mushrooming shape fracture mode. A parametric study was then conducted to study the deformation behaviour of the selected recycled aluminum alloys within the validated range at various geometrical settings. The analysis was made by focusing on the post-impact configuration of the projectile at different impact velocities in terms of residual length, deformed diameter, and the final length-to-diameter ratio. It was found that a broader projectile experienced a less significant reduction in its final length (Lf/Lo goes from 0.87 to 0.9 for projectile diameter 9mm to 34mm) and a smaller increase in the deformed diameter compared to a thinner projectile (Df/Do goes from 1.18 to 1.12 for projectile diameter 9mm to 34mm). It was found that a thinner projectile experienced more diameter expansion than length reduction post impact. In addition, a longer projectile experienced more residual length reduction (Lf/Lo goes from 0.92 to 0.87 for projectile length 2mm to 14mm) and more radial deformation compared to the one with a smaller initial length (Df/Do goes from 1.06 to 1.18 for projectile length 2mm to 14mm). All projectiles showed more significant changes on the deformed diameter compared to the changes in residual length post-impact. The results helped the understanding of a critical aspect of the deformation behaviour of recycled aluminum alloy AA6061 more effectively compared to experimental work implementation.

Experimental and Numerical Simulation of Ejecta Size and Velocity of Hypervelocity Impact Rubble-Pile Asteroid

Rubble-pile asteroids may be the type of near-Earth object most likely to threaten Earth in a future collision event. Small-scale impact experiments and numerical simulations for large-scale impacts were conducted to clarify the size ratio of the boulder/projectile diameter effects on ejecta size–velocity distribution. A series of small-scale impact cratering experiments were performed on porous gypsum–basalt targets at velocities of 2.3 to 5.5 km·s−1. Three successive ejection processes were observed by high-speed and ultra-high-speed cameras. The momentum transfer coefficient and cratering size were measured. A three-dimensional numerical model reflecting the random distribution of the interior boulders of the rubble-pile structure asteroid is established. The size ratio (length to diameter) of the boulder size inside the asteroid to the projectile diameter changed from 0.25 to 1.7. We conducted a smoothed particle hydrodynamics numerical simulation in the AUTODYN software to study the boulder size effect on the ejecta size–velocity distribution. Simulation results suggest that the microscopic porosity on regolith affects the propagation of shock waves and reduces the velocity of ejecta. Experiments and numerical simulation results suggest that both excavation flow and spalling ejection mechanism can eject boulders (0.12–0.72 m) out of the rubble-pile asteroid. These experiments and simulation results help us select the potential impact site in a planetary defense scenario and reduce deflection risk. are comprised primarily of boulders of a range of sizes.

The South Pole‐Aitken Basin: Constraints on Impact Excavation, Melt, and Ejecta

AbstractThe formation and evolution of the South Pole‐Aitken (SPA) basin is critical to relating large impact basin formation and modification to lunar geophysical evolution. Most prior models of the SPA impact were conducted in 2D, making it difficult to compare model output to the 3D crustal structure and ejecta distribution. In order to better constrain the parameters of the SPA impactor and the expected post impact distribution of crust and ejecta, we conducted numerical simulations of the SPA impact in 3D. We tested a wide range of impact parameters and constrained model results with recent geophysical data. We found the crustal structure of the SPA basin is best fit by an oblique impact (30–45°) of a 350–400 km diameter projectile impacting at 12–16 km/s. The impact excavated material from as deep as 80–120 km, and ejecta was deposited in a butterfly pattern with a forbidden region uprange of the impact.

Modeling of the Impact‐Generated Hydrothermal System at the Haughton Impact Structure

AbstractHypervelocity impacts can generate hydrothermal systems, which have been suggested as candidate environments for prebiotic chemistry on the early Earth. The Haughton impact structure (a 23 km diameter crater located on Devon Island, Nunavut, Arctic Canada) displays evidence of water‐rock alteration indicative of a hydrothermal system generated from a cosmic impact. To model the formation of this crater and subsequent hydrothermal alteration, we have successfully developed a new two‐code methodology that utilizes a shock physics code and a hydrothermal code (HYDROTHERM). We can best reproduce the Haughton crater with a ∼700 m diameter projectile with an impact velocity of 14 km/s. With our approach, we were able to match all the major geological constraints observed at the Haughton impact structure. Our models show that the Haughton crater interior could have sustained temperatures ideal for thermophilic and hyperthermophilic life (50–120°C) for more than 50,000 years, indicating that these systems can sustain prebiotic chemistry and life for longer than previously estimated.

The impact of the coupling relationship between projectile size and yarn dimension on the ballistic performance of plain weave fabric

Aramid fibers, due to their relatively high inter-yarn friction, high strength, high modulus, and other characteristics, have become a typical representative of flexible anti-ballistic materials in modern warfare. Current research on the anti-penetration of aramid fabrics mostly focuses unilaterally on the structure and performance of aramid fabrics or the shape and size of projectiles, with fewer studies on the coupled effect of both on ballistic performance. This study analyzes how the coupling relationship (or size effect) between the projectile and fiber bundle dimensions affects the fabric ballistic performance from a mesoscopic scale perspective. Taking plain weave aramid fabric as the research object, considering different diameter projectiles, through a large number of ballistic impact tests and numerical simulations, parameters such as ballistic limit velocity, average energy absorption of fabric, and specific energy absorption ratio (average energy absorption of fabric divided by projectile cross-sectional area) are obtained for ballistic performance analysis. The influence law of projectile size on the ballistic performance of high-performance fabrics is as follows: The relative range of fitted ballistic limit velocity at different target positions gradually decreases and then stabilizes as the projectile diameter increases, indicating that the fabric structure effect gradually disappears at a projectile diameter of 12 mm; The average ballistic limit velocity at three impact positions, P1, P2, and P3, provides the corresponding ballistic limit velocity for 1000D aramid fabric, which increases with projectile diameter but the rate of increase slows down at an inflection point, which in this study occurs where the fabric structure effect nearly disappears at a projectile diameter of 12 mm; The energy absorption ratio increases and then decreases as the projectile diameter increases from 4 mm to 20 mm, reaching a peak at the diameter of 12 mm due to the gradual disappearance of the fabric structural effect. The projectile diameter of 12 mm corresponds to the coupling size of 11.159, which provides a size design reference for the macroscopic-based continuum models of aramid plain weave fabrics.

Surface nano crystallization and nitriding on microstructure and properties of 304J1 stainless steel

To improve the mechanical and antibacterial properties of 304J1 stainless steel, hybrid surface treatments, which include nitriding combined with shot peening operations, are used. Shot peening with different sizes of steel balls makes the material’s surface nanocrystalline, providing more diffusion channels for subsequent nitrogenating, and the nitriding efficiency is improved. Nitrogen cannot only improve the antibacterial property but also significantly enhance the strength of 304J1. The experimental results show that within a certain depth, the surface of 304J1 can be nanosized by shot peening for 20 min with a projectile diameter of 0.2 mm. The depth of the nitriding layer reaches 0.6 um, the surface hardness increases from 560 HV to 1100 HV, and the antibacterial property against Escherichia coli increases from 10% to 85%.

Optimisation of hybrid composite shields for hypervelocity Micro-Meteoroid and Orbital Debris (MMOD) impact

Advancements in space exploration over the last few decades have led to a sharp increase in Micro-Meteoroid and Orbital Debris (MMOD), with the associated increased risk of hypervelocity impact on satellites and space structures. The Whipple shield can mitigate the effects of such impacts and current research is exploring further developments towards effective lightweight passive shielding technology to counter the damaging effects of MMOD. With the increase in MMOD and the prospect of increased space travel in the coming years and decades, it is vital that more research is conducted and improvements are made in the development and design of efficient, lightweight shielding technology to protect both unmanned and manned spacecraft against hypervelocity impacts (HVI). The optimisation of shield design for HVI is a high dimensionality problem, suited to advanced computational approaches. Key variables in HVI shield design that should inform the focus on optimisation include: impact velocity, rear wall thickness, projectile diameter and bumper thickness. A hybrid shield configuration and numerical model are proposed and validated, with alternating layers of aluminium (AL2024) and carbon fibre composites (CFRP, T300 woven-fabric) to form a 5 mm thick target plate consisting of 5 plies. The adaptive coupled FEM-SPH method is used to model the target plates. The proposed hypervelocity shield design optimisation methodology is based on Direct Simulation-based Genetic Algorithm (DSGA) optimisation and is implemented to optimise a multi-variable shield design space. Objective weightings are used to analyse and discuss results, referring to the ratio of the kinetic energy to the shield areal density objectives. A clear transition in the impact behaviour of the optimised MMOD shields is observed in the transition region from high-velocity to hypervelocity impact, where significant levels of kinetic energy dissipation are observed below the transition region, and lower energy dissipation at hypervelocity. The shield design optimisation results show that with a weighted kinetic energy to mass objective of 90:10, the kinetic energy of the back shield plate decreases significantly (62.7%) and the areal density can be reduced by more than 18%. Alternative configurations displayed sub-optimal results based on a trade-off between objective functions.

Investigation of aluminium Whipple Shield response to hypervelocity impacts close to ballistic limit between 2.5 and 5 km/s

For impact velocities larger than a threshold velocity of 3 km/s, aluminium Whipple Shields present an enhanced protection capability with respect to monolithic protections with the same areal density. In particular, in the range between 3 and 7 km/s the projectile partially fragments and melts after impacting the bumper; modelling this transition might be complex due to the high number of parameters affecting the collision. In particular, limited data is available in literature with a systematic evaluation of such parameters.In this context, a campaign of 22 experiments was performed to assess the response of aluminium Whipple Shields to normal impacts of aluminium projectiles in the transition range up to 5 km/s. In the tests, the projectile diameter was fixed at 2.9 mm and the bumper thickness and impact velocity were systematically varied respectively at 1, 1.5, and 2 mm and between 2.6 and 5 km/s. Collected data included high-velocity videos of the debris cloud generated by the impacts at both low resolution (for all shots) and high resolution (for 19 out of 22 tests); in addition, for 10 experiments high-resolution images of both the bumper and the wall were acquired after the tests.In this paper, the experimental campaign is described and the main collected results are presented; in particular, the influence of the different impact parameters is discussed. Experimental results are finally compared with numerical simulations conducted with a smoothed particle hydrodynamics method available in IMPETUS Solver.

Effect of surface strengthening by ultrasonic shot peening on TC17 alloy

This paper investigates the effects of ultrasonic shot peening (USP) on surface morphology, microstructure, and residual stress field distribution of TC17 alloy under different process parameters. The aim is to reveal the surface strengthening mechanism of TC17 alloy caused by USP. The results suggest that the use of the 2.5 mm projectile diameter leads to an increase in surface roughness, plastic deformation, and a deeper grain refinement layer compared to the 1.5 mm projectile diameter. Additionally, it results in a greater depth of the compressive residual stress layer and maximum compressive residual stress. The crack initiation sites under two projectile diameters are located below the compressive residual stress layer. The USP treatment introduces compressive residual stress on the surface, inhibiting the initiation of surface cracks, and the deeper compressive residual stress layer offsets the early fatigue failure caused by higher roughness.

Numerical Study of High-Speed Vertical Water Entry of Hollow Projectiles with Different Aperture Sizes and Velocities

The hollow projectile is a new type of projectile that has complex water entry hydrodynamics characteristics and has attracted significant attention in recent years. As such, it is important to investigate the effects of different entry velocities and aperture diameters on the cavity morphology, cavitation, dynamics, and motion characteristics of hollow projectiles when entering water at high speeds. In this study, four stages of an open cavity, cavity stretching, cavity closure, and cavity contraction in the water entry processes of a hollow projectile at 50–200 m/s and four aperture diameter projectiles at 100 m/s were studied using the volume of fluid (VOF), realizable k-ε turbulence, and Schnerr-Sauer cavitation model. With an increase in the speed, the depth of the cavity closure increases, thereby advancing the closure time. The timing of the surface closure at 50 m/s is clearly different from that at 100–200 m/s. Cavitation is not obvious and is near the cavity wall at 50 m/s, although the entire cavity is almost filled with vapor at 100–200 m/s. The friction resistance has two step points when impacting the water surface and entering the water completely. As the velocity increases or the aperture ratio reduces, the splash is higher, the cavity volume is larger, the cavitation phenomenon is more obvious, the cavity closure time is delayed, and the frictional resistance of the projectile is greater. The results of this study can guide the production and application of hollow projectiles in the future.

Experimental and theoretical study on cavitation of concrete targets penetrated by hypervelocity long rod projectiles

The cavitation phenomenon can seriously decrease the strike performance of military weapons. As military terminal-ballistic activities have turned to hypervelocity attacks, the cavitation effect existing in the hypervelocity penetration deserves more attention. In terms of long-rod hypervelocity penetration into concretes, this study presents an analytical cavity model for the prediction of the cavity diameter based on the two-stage cavitation mechanism and the u-v relationship. The two-stage mechanism involving mushrooming and radial momentum expansion is used to describe the cavitation modes and the penetration parameters for the projectiles used in the analytical model are determined by numerical simulations empirically. Besides, the three modes including rigidity, deformation and erosion are introduced into the cavity model to elucidate the projectile state. Moreover, the hypervelocity impact experiments on the long rods into semi-infinite concrete targets at velocities of 2117 ∼ 3086 m/s are carried out to observe the cavitation effect of concrete targets and for further validating the model through comparing with the experimental cavity profiles, where the cavity profile is quantified with silica gel, and the cavity diameter is found to be more than five times the projectile diameter. The cavitation effect is observed significantly and quantified from the experiment results. The cavity model is compared with the experimental cavity profiles, showing that the model has good applicability.

High-speed projectile perforation of nickel-based Inconel 718 superalloy plates: Experiments and modeling

Understanding ballistic behavior of structural materials is important for their applications in aeronautical and astronautical industries. We investigate perforation of 2-mm thick Inconel 718 superalloy plates by spherical stainless steel 304 projectiles with high-speed photography at impact velocities ranging from 548 ms−1 to 1360 ms−1. Postmortem target samples are characterized with optical metallography, scanning electron microscopy and electron backscatter diffraction as regards bullet hole morphology and deformation. Grain refinement and shear banding are the main microstructural deformation modes near the bullet holes. Shear dominated deformation and tension–shear dominated deformation of target material occur sequentially in bullet hole along the impact direction. The morphologies of bullet holes and postmortem projectiles are obtained from the experiments and simulations. The effect of projectile deformation on ballistic behavior of the target is investigated. On the basis of dimensional analysis, a quadratic relation is derived between the energy absorption ratio of target and the dimensionless postmortem projectile diameter, along with a phenomenological model that can well predict projectile residual velocities.

Theoretical investigation on energy absorption of single-layer graphene under ballistic impact

The superb mechanical properties make graphene an ideal candidate material for impact protection. Combining molecular dynamics simulations and theoretical analyses, the deformation and failure modes, energy absorption of single-layer graphene under ballistic impact are investigated. According to numerical and theoretical results, the expression for residual velocity of projectile after impact is given. The dependence of deformation and failure modes, energy absorption mechanisms, specific penetration energy (SPE) on impact velocity is analyzed. The results show that during low-velocity impact, there are conical deformation region (CDR), star-like crack and monoatomic carbon chain in graphene. Energy absorption mechanisms of graphene are mainly local deformation and fracture. With increasing impact velocity, the size of CDR decreases. The star-like crack gradually transforms into circular hole. When impact velocity is high enough, carbon atoms within projectile projection area in graphene will be ejected in the form of debris. The kinetic energy (KE) loss of projectile is converted into KE of debris carbon atoms and fracture energy of carbon bonds. Besides, it is also found that SPE (dominant factors are deformation of conical region and KE increments) exhibits a decreasing–increasing trend with increasing impact velocity. When impact velocity is the same, SPE decreases with increasing projectile diameter.

Numerical study on debris cloud and channeling effect of honeycomb sandwich shields under hypervelocity impact

In this study, the finite element and smoothed-particle hydrodynamics adaptive method was used to reproduce experiments on honeycomb sandwich shields impacted by spherical projectiles at hypervelocities, which can provide phenomena that are difficult to observe experimentally. The simulation results clearly reproduced the formation, development, and stabilization processes of the debris cloud as well as the damage and response processes of the honeycomb sandwich shield. The petal-shaped multicellular internal structure of the debris cloud was proposed by combining the formation and development of the debris cloud with its experimentally observed morphology. The damage and response processes of the honeycomb sandwich shield can be divided into two stages, namely, the crushing and inertial motion stages, to elaborate the varying failure modes of the honeycomb sandwich shield in different stages. The crushing stage represents the response of the material, whose failure modes include penetration, bending, buckling, tensile fracture, and compression failure. The inertial motion stage represents the structural response (bending and buckling of foils), which, at different positions, leads to folding and compaction of the honeycomb core layer by layer along the radial direction. The factors influencing the channeling effect were investigated, and the influences of the projectile diameter and impact position on the channeling effect and protection performance of the honeycomb sandwich shield were analyzed. The envelope analysis method for damage areas, which can predict the damage to the honeycomb core and rear plate at any impact position using an envelope diagram, was proposed. It was shown that the foil at different positions works by blocking or partitioning, which seriously affects the channeling effect. This study provides new ideas for optimizing the design of Whipple shields.

Ballistic performance and damage behavior of three-dimensional angle-interlock woven composites under high velocity impact: Experimental and numerical studies

Three-dimensional angle-interlock woven composites (3DAWCs) are usually employed as exposed components in aerospace and other high-tech areas due to their superior impact resistance. In this work, the experimental characterization and numerical modeling are combined together to study the ballistic performance and damage behavior of 3DAWCs under high velocity impact (HVI). The initial-residual velocity relation is examined by ballistic impact test and the penetration process is recorded by high-speed camera. A nonlinear finite element (FE) model based on a multi-scale modeling framework is established to simulate the ballistic impact response and damage behavior of 3DAWCs. The proposed FE model is verified by comparing the predicted initial-residual velocity curve and penetration propagation with the experimental data. Parameter analysis is conducted to address the influences of projectile diameter and impact angle on the impact performance of 3DAWCs and the corresponding damage mechanisms are revealed in detail. The present work provides a transferable approach for studying the HVI problems of other textile composite structures.

Numerical simulation and analysis of the 3D transient muzzle flow field of underwater artillery

The in-depth study of the muzzle flow field contributes to the improvement of the gun and the design of the projectile. This study establishes an unsteady muzzle multiphase flow model of the underwater sealed launch with a three-dimensional scale. Among that, the VOF model is employed to trace the two-phase interface and the gas-liquid turbulent mixing is described by the standard k-ε turbulence model. Also, the established numerical model was validated by comparing underwater sealed launching experimental results. On this basis, numerical analysis on the muzzle flow field of the 30 mm artillery under different launching conditions were carried out by coupling with revised interior ballistic equations. The results show that the “necking” phenomenon occurs during gas-expansion process due to the interaction between water and projectile. Then, a “bowl-shaped” shock area is obviously formed at the muzzle. In addition, the Mach disk diameter and the corresponding growth rate are closely related to the projectile head cavitation diameter. The growth rate of Mach disk diameter increases with an increase of the cavitation diameter. When the muzzle velocities are different, the positions of the Mach disk formed are also different, presenting that the Mach disk is farther away from the muzzle with the increase of muzzle velocity.

A model to predict the rear face damage caused by non‐deforming projectile impact on plain and steel fiber reinforced concrete barriers

AbstractThis paper presents a model for evaluation of the rear face damage in concrete barriers subjected to impact of non‐deforming projectiles. This is an improved and extended version of a previously published model, which now covers both plain and steel fiber reinforced concrete (SFRC) barriers. The rear face damaged area commonly measured in tests is characterized by an equivalent diameter, evaluated by the model. Calibration and then validation are based on published experimental data. Different sets of experiments, of plain concrete and SFRC, reported by different researchers, were used for the model's calibration and for its validation. The calibrated model's predictions show reasonable agreement with the reported experimental results, especially in view of their considerable scatter. The main findings from a parametric study of the model's predictions refer to the influence on the rear face damage (at barrier thickness lower than the scabbing limit thickness) of including steel fibers in the concrete mix, the barrier thickness, impact level, and the projectile diameter. The model's predictions demonstrate the lower extent of damage in SFRC barriers, compared to plain concrete. The use of the model enables quantitative assessment of this damage and of its reduction in SFRC barriers.

Perforation of carbon fiber reinforced plastic laminates struck transversely by hemispherical-nosed projectiles

This study focuses on perforation of carbon fiber reinforced plastic (CFRP) laminates struck transversely by hemispherical-nosed projectiles. Global deformation with local rupture failures for thin laminates and localized response failures for thick laminates are two common categories of the ballistic perforation of CFRP laminates. An analytical model is proposed considering these two failure modes and their transition conditions. The ballistic limit predicted for laminates in global deformation with a local rupture failure mode is given based on the energy dissipation method, and an ultimate perforation failure criterion is derived based on the bottom surface tensile fracture of the laminate. A critical transition condition of the two failure modes is obtained by combing the localized response failure model and Von Karman’s critical impact velocity concept. Model predictions agree with the experimental and numerical results regarding ballistic limits in a wide ratio range of laminate thickness H and hemispherical-nosed projectile diameter d.

Evaluation of hypervelocity impact of micrometeoroids and orbital debris on next-generation space solar cells

This paper discusses the hypervelocity impacts of micrometeoroids and orbital debris (MMODs) on inverted metamorphic triple-junction (IMM3J) and perovskite solar cells, which are much thinner than conventional triple-junction (3J) solar cells. We experimentally found that IMM3J solar cells can suffer from short-circuit faults due to the hypervelocity impacts of MMODs, unlike conventional 3J cells, and determined the projectile diameters and velocities that could cause them using a model proposed by Burt. No short-circuit mode was identified in perovskite solar cells, but they had open-circuit faults several days after the hypervelocity impact experiment, which are possibly attributed to the decomposition of the perovskite crystal by moisture in the air due to the broken seal.