Range Of Impact Velocities Research Articles

High-velocity impact experiments and quantitative damage evaluation for finite ultra-high-performance concrete targets

In this work, we aim at improved characterization of target damage occurring as the result of projectile impact against ultra-high-performance concrete (UHPC). For this purpose, we present the results of high-velocity impact experiments with spherical steel projectiles and finite-thickness UHPC targets of approximately 115 MPa compressive cylinder strength in the impact velocity range from approximately 600 m/s to 1500 m/s. The data set obtained from these experiments includes residual projectile velocities as well as qualitative and quantitative information on damage. Quantitative damage information is mainly extracted from digital 3D post mortem targets, which are produced by 3D-scanning. For all damage quantities, a dependence on the impact velocity and the target thickness is discussed and used to provide possible explanations for the origin of the particular type of damage. The large data set presented in this work can constitute the basis for a comprehensive and quantitative verification and validation of analytical, empirical, and numerical models that describe the perforation of UHPC targets in the investigated impact velocity range.

Ballistic performance of spaced multi-ply soft fabrics: Experimental and numerical investigation

It has been reported that the ply gap influences the ballistic resistance of spaced multi-ply fabric systems, but its working mechanism was not well-understood. This paper reports the experimental and numerical approaches and results of an investigation on the mechanisms that enable the improved ballistic performance of spaced multi-ply systems. Penetration tests were performed over a range of impact velocities ranging from 200 m/s to 400 m/s. The results confirmed that the ply gap is beneficial to the energy absorption capability of the systems. This is because the front plies tend to absorb more energy when they are not immediately constrained by the rear plies. During a ballistic event, the gap relieves the reflection of the compressive pulse, prolonging the projectile engagement time with the front plies; on the other hand, the rear plies become increasingly less active in dissipating energy as the gap increases. When the gap is sufficiently widened to avoid any interference between the plies before the failure of the front ply, the responses of the whole system no longer vary. It was also found that the ballistic performance of the spaced systems is influenced by ply thickness, impact velocity, and the stacking order of the ply gap.

Penetration performance and failure of long rods impacting aluminum targets

A numerical study concerning the deep penetration of long steel rods into 6061-T6511 aluminum targets at high impact velocities is presented. The range of impact velocities where these rods lose their penetration capability due to their nose deformation, or impact inclination, is explored. The numerical simulations follow several complex phenomena such as the onset of rod deformation and erosion, encountered in the tests with spherical and ogive nosed rods. It turns out that penetration depth decrease of spherical nosed rods at high impact velocities, is due to their nose deformation, while ogive nosed rods are more sensitive to impact inclination. At very high impact velocities both types of rods experience significant mass erosion, and their penetration process can be described by conventional hydrodynamic penetration model for eroding rods. The numerical simulations in this work are shown to follow test results for spherical and ogive nosed rods, impacting an aluminum alloy target at a large range of impact velocities. We show that these agreements can be achieved with relatively simple constitutive relations for the steel rods and the aluminum target.

Dynamic responses of kerosene-filled riveted tanks subjected to hydrodynamic ram caused by ballistic impacts

The hydrodynamic ram (HRAM) is a hydrodynamic pressure phenomenon that occurs when high-speed projectiles impact a liquid-filled tank. During combat missions, aircraft are prone to HRAMs caused by projectile impacts, which can damage the structural integrity of riveted tanks, posing a threat to flight safety. In this study, kerosene-filled riveted tanks were chosen as the research object. The dynamic response histories of the rear panel were observed using the three-dimensional digital image correlation (3D-DIC) technique. Additionally, numerical simulations of the projectile's impact on the tank were performed using the fluid–structure interaction finite element method. The simulation results had a good fit with the experimental results. The spatial and temporal distribution of the HRAM and the effect of the projectile impact velocity on the deformation of the tank structure were further analyzed. The impulse exerted by the drag wave on the rear panel was greater than that of the pioneer wave. However, the drag wave's region was limited to a radius of 6 cm around the exit point with the impact velocity range of the projectile of 955 m·s−1–1607 m·s−1 in both the experiments and simulations. When the impact velocity of the projectile reached 955 m·s−1, radial plastic hinge lines appeared on the rear panel along the diagonal direction. When the impact velocity increased to 1607 m·s−1, radial plastic hinge lines along the diagonal direction, and traveling plastic hinges at the root of the central cross-shaped cracks appeared on the rear panel, accompanied by a petal-shaped hole. Based on the spatial distribution of the impulse on the rear panel, a dimensional relationship was established between the hole size and the impulse on the rear panel. The petal model for describing petal-shaped cracks was proposed based on the law of conservation of energy, which could predict the hole size in the case of projectile impact at high velocity. The research results are of great significance for the study of the damage of riveted tanks with HRAMs and provide support for the vulnerability analysis of aircraft tanks.

Effects of shock stress and microstructure on shock response of Al-Hf reactive materials

Reactive materials are functional structural materials that balance structural strength and reactivity, and their shock response is greatly influenced by the characteristics of reactive components. This article aims at understanding the shock compression and reaction of Al-Hf reactive materials with two values of the Al-Hf particle size ratio α (1 µm:10 µm and 10 µm:10 µm), which were prepared through hot pressing with a compactness (the ratio of density to theoretical maximum density) greater than 96.46%. The free surface velocity of the materials was measured in the impact velocity range of 279–865 m/s. The Hugoniot elastic limit (HEL), spall strength, and Hugoniot relationships under shock stresses of 1.83–14.46 GPa were analyzed on the basis of the microstructure and phase change. Continuous Al phase was formed in the sample with α = 0.1, while more Hf–Hf contact and crushed Hf appeared in the sample with α = 1. The velocity profiles presented clear signs of the linear growth to the HEL, the slow increase to the peak, and the subsequent pullback, indicating the transition from elastic to plastic and spall behavior. The HEL fluctuated significantly with increasing shock stress, while the spall strength first increased and then decreased. The sample with a continuous Al phase exhibited a lower HEL (0.52–0.97 GPa) and higher spall strength (0.31–0.46 GPa). The microstructure had a significant effect on the shock induced chemical reaction of the materials. Shock velocity was linearly related to particle velocity for the α = 0.1 sample, while a notable quadratic growth was observed for the α = 1 sample owing to self-reactions under the lower shock stress (5.32 GPa). The intermetallic Hf4Al3 observed in the recovered product by X-ray diffraction further verified the phenomenon.

Experimental method of determining bulk cargo losses quantitative characteristics during grappling overload

The proposed experimental method of determining the losses of bulk cargo prone to dust formation allows, based on model researches results, to predict the bulk cargo losses amount when working with a grab in real conditions of cargo operations. The article presents developed by the authors experimental equipment, which makes it possible to obtain physical models of cargo scooping and unloading the grab processes, during which the most intense dust formation and the maximum losses amount of the reloaded cargo occur. In addition, the methods of using the specified experimental equipment are given, which provide for the determination of losses quantitative characteristics when using full-scale bulk cargo in researches, which is permissible under certain model parameters. Also, the methods provide for the possibility of determining the wind action speed influence on the amount of cargo losses from dusting, therefore, the researches were carried out in two stages - both in the absence of wind action during the grab operation, and in its presence. The range of wind impact velocities ranged from 0 to 10 m/s. As a result of processing modeling researches results, mathematical models of losses amount of a number of bulk cargoes during grappling overload considering wind impact were obtained.

A molecular dynamics study of the effects of velocity and diameter on the impact behavior of zinc oxide nanoparticles

Molecular dynamics simulations of particle impact have been conducted for a ceramic with mixed ionic-covalent bonding. For these simulations, individual zinc oxide (ZnO) nanoparticles (NPs) were impacted onto a ZnO substrate to observe the effects of impact velocity (1500–3500 m s−1) and particle diameter (10, 20, and 30 nm) on particle deformation and film formation mechanisms that arise during the micro-cold spray process for producing films. The study shows that a critical impact velocity range exists, generally between 1500 and 3000 m s−1, for sticking of the NP to the substrate. Results suggest that solid-state amorphization-induced viscous flow is the primary deformation mechanism present during impact. Decreasing particle diameter and increasing impact velocity results in an increased degree of amorphization and higher local temperatures within the particle. The impact behavior of mixed ionic-covalent bonded ZnO is compared to the behavior of previously studied ionic and covalent materials.

Evaporative and non-evaporative droplet impact on a heated phase change material pool: A comparison between ethanol, acetone, and distilled water

The interaction between liquid droplet and phase change material (PCM) underlies the direct contact approach, which is an efficient way for precipitating the melting and solidification processes of PCMs. In this experimental research, to comprehend the direct contact method more profoundly, the impingement of a single droplet on the heated paraffin pool, having a temperature of 70–95 °C, is scrutinized systematically for the first time. Droplet impact solidifies a portion of the pool and may lead to droplet evaporation. Acetone, ethanol, and distilled water are exploited as droplet liquids, whose diameter and impact velocity range from 2.32 to 3.36 mm and from 1.70 to 2.28 m/s, respectively. Through impact visualizations, six distinct regimes are observed, whose regime maps are constructed. Moreover, the effects of fluid properties, pool temperature, and the Weber number on the evolution of crater and jet, crater depth, crater shape, and solidified PCM area (A) generated after the impingement are investigated. It is ascertained that the low PCM temperature instigates the coalescence phenomenon regardless of the Weber number. Additionally, the crater depth is a function of the PCM temperature, Weber number, and Ohnesorge number; thus, a dimensionless correlation is proposed for the maximum crater depth. Furthermore, droplet evaporation augments the extracted heat from the paraffin, provoking a more sizeable solidified area. Interestingly, though absorbing the greatest amount of heat from the PCM, ethanol droplet generates a smaller solidified area than acetone since acetone favorably spreads on the pool surface, enhancing the effective heat exchange area.

Suppressing the pancake bouncing induced secondary contact on superhydrophobic surfaces via jet splash

Pancake bouncing of water droplets on superhydrophobic surfaces has been extensively studied, because the reduction in solid–liquid contact time shows great potential for self-cleaning, anti-icing, etc. However, the behavior of a pancake-bouncing droplet in the ambient air and its subsequent interaction with the underlying surface remain unrevealed, which is actually crucial for practical applications. In this Letter, we comprehensively investigate the overall dynamics of droplets on post-array superhydrophobic surfaces by extending the range of impact velocities. An unreported phenomenon was observed, whereby the retracting droplet undergoes vertical elongation and re-contacts the underlying surface following the pancake bouncing event. As the impact velocity increases, the submillimeter-scale posts notably influence the droplet splash, where tiny droplets are ejected from the edges of lateral liquid jets through the posts. Experimental results and scale analysis show that the critical Weber number for this jet splash phenomenon decreases with the post spacing and the post edge length over a certain range. The violent jet splash occurring at higher Weber numbers reduces the mass of the remaining droplet and, consequently, diminishes the diameter prior to retraction, thereby suppressing the secondary contact with the surface. Our findings are believed to provide valuable insight for the understanding and the application of the pancake bouncing effect.

Mechanical properties of refractory HEA WNbTaV and its penetration behavior to aluminum alloy plate

Quasi-static and dynamic compression experiments were conducted on WNbTaV to investigate its mechanical characteristics and its penetration behavior into an aluminum alloy target plate. Additionally, ballistic experiments with WNbTaV projectiles against 2A12 aluminum alloy thin targets were performed. The results indicate that HEA WNbTaV at a strain rate of 10−3 s−1 has a fracture strength of 1340 MPa, a yield strength of around 980 MPa, and a fracture strain of less than 7%. However, its dynamic yield strength is almost twice its quasi-static yield strength, and its dynamic fracture strain is more than twice the quasi-static compression fracture strain.When striking a 2 mm thick 2A12 aluminum alloy target plate with a velocity less than 348.5 m/s, the HEA WNbTaV projectile remains stiff and undeformed. Its maximum velocity before entering the target plate is roughly 273 m/s. Furthermore, within a certain impact velocity range, the residual velocity, initial impact velocity, and ultimate penetration velocity of the HEA WNbTaV projectile penetrating the 2 mm thick 2A12 aluminum alloy target plate meet the following relationships. vr=v02−2.13vb2.

Dynamic response and fracture characteristics of thermally-treated granite under dynamic loading

In the process of deep underground resource development and utilisation, the response of the surrounding rock mass is affected by high temperatures and the dynamic loadings that can trigger strain bursts. Therefore, strain burst failure is highly related to the rock mass's dynamic fracture toughness and energy absorption capacities. Understanding the dynamic fracturing behaviour of rock mass is crucial for designing stable underground structures and controlling the hazard associated with strain bursts. In this paper, dynamic Mode I fracture toughness tests using a split Hopkinson pressure bar (SHPB) were conducted on Cracked Chevron Notched Semicircular Bend (CCNSCB) granite specimens to investigate the relationship between the strain burst mechanism and its dynamic fracture propagation. The tests were performed on thermally treated granite specimens (from 25 to 250 °C) under a wide range of impact velocities. The dynamic fracturing characteristics and crack propagation speeds were measured by a high-speed camera (HSC). The dynamic fracturing process and the effects of thermal damage on the dynamic fracture modes were identified by detailed image analysis. Energy partition characteristics in dynamic fracture of granite samples were quantified. The results revealed that dynamic fracture initiation toughness and energy partitions highly depend on loading rate and temperature. As the loading rate increased, the failure modes changed from axial splitting to pulverisation. Under the same dynamic loading, an increase in the temperature can exacerbate the fragmentation degree of granite. Under the same dynamic loading, the dissipated and released energies increased with increasing temperature. When the loading rate was high, the loading rate strengthening effect became remarkable, and the dynamic fracture toughness of granite increased under all temperatures. Finally, the dynamic energy mechanism of strain burst with the increased loading rate and heat-treatment temperature was further discussed.

Impact of nanodroplets on cone-textured surfaces.

Molecular dynamics simulations have been performed to study the dynamics of nanodroplets impacting on a flat superhydrophobic surface and surfaces covered with nanocone structures. We present a panorama of nanodroplet behaviors for a wide range of impact velocities and different cone geometrics, and develop a model to predict whether a nanodroplet impacting onto cone-textured surfaces will touch the underlying substrate during impact. The advantages and disadvantages of applying nanocone structures to the solid surface are revealed by the investigations into restitution coefficient and contact time. The effects of nanocone structures on droplet bouncing dynamics are probed using momentum analysis rather than conventional energy analysis. We further demonstrate that a single Weber number is inadequate for unifying the dynamics of macroscale and nanoscale droplets on cone-textured surfaces, and propose a combined dimensionless number to address it. The extensive findings of this study carry noteworthy implications for engineering applications, such as nanoprinting and nanomedicine on functional patterned surfaces, providing fundamental support for these technologies.

Experimental investigation of hail impacts over a wide range of high velocities

In the presented work, high velocity hail impact tests have been conducted on an instrumented rigid target. The synthetic hails, consisting of ice spheres with a nominal diameter of 48 mm and a mass between 50 and 55 g conditioned to temperatures in the range of -3, -20 and -50 °C were accelerated using a gas gun. The range of impact velocities was 46–314 m/s leading to maximal impact energies between 2000 and 3000 J which had not been investigated so far in the literature. Peak force and time to reach the peak force where extracted from the experimental tests. The obtained results were compared with results from the literature using empirical equations established in another publication from the literature. The obtained results confirm the trend reported in the literature in terms of dimensionless peak force versus dimensionless impact velocity. However, the dimensionless time to reach the peak force during the impact could not be compared successfully with previous results. The role of the target characteristics is estimated to be the reason for this difference.

Ballistic penetration of high-entropy CrMnFeCoNi alloy: Experiments and modelling

Ballistic impact experiments are conducted on a CrMnFeCoNi high-entropy alloy (HEA) using spherical steel projectiles, to investigate the penetration behavior in a wide range of impact velocities (∼800 to 2300 m s−1). Penetration processes are captured by high-speed camera. Postmortem samples are characterized via three-dimensional laser scanning, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and microhardness tests. Both depth and diameter of impact crater show a nearly linear increase with increasing impact velocity. Penetration induces increased hardness; hardness is the same near the crater bottom and the sidewall, and the peak hardness (∼400 Hv1.0) is independent of impact velocity. The penetration-induced hardening is caused by multiple deformation defects including dislocations, twins and kink bands (KBs). Quantitative analysis further reveals that KB boundaries have a 5–50° misorientation angle, and their density decreases with increasing misorientation angle. KB boundary density is higher near the crater bottom than near the crater sidewall, while this trend is inverse for twinning boundary density. A finite element method model based on measured static and dynamic mechanical properties reproduces experimental observations and is used for interpreting deformation mechanisms.

Evaluation of Absorbed Energy in High-Velocity Particle Impact for Aero-Engine Materials

A single particle impact testing system was developed to estimate an absorbed energy in particle perforation process of aero-engine materials. Thin target plates of 0.1-1 mm thickness were impacted by a 3 mm diameter spherical particle. A wide range of impact velocities from 50-375 m/s was covered using a compressed gas gun. First, particle impact tests were conducted on aluminum and copper plates to evaluate the validity of the experimental system. The experimental results show that there is no significant difference in the effect of the particle impact velocity on the absorbed energy of aluminum and copper, and the ballistic limit can be reasonably estimated based on a simple energy balance equation. Second, impact tests were conducted on TiAl alloys and Ni-based alloys. There was no clear ballistic limit for the TiAl alloys, and the absorbed energy tended to increase as the particle impact velocity increased. The absorbed energy of the TiAl alloy was half that of the Ni-based alloy for specimens of the same thickness. Radial and petal-shaped cracks were observed in the Ni-based alloys after impact tests, while brittle cracks, fractures, and scattering of debris were observed at the periphery of the penetration hole in the TiAl alloys.

On the impact damage characteristics of spread-tow woven composites: From high velocity to hyper velocity

Spread-tow woven composites are known to be economically efficient with great potential for use in aerospace applications where components will inevitably suffer various impact threats during their service. In this work, the impact damage behavior of woven composite panels under a wide range of velocities (from about 0.2 km/s to 1.5 km/s) are experimentally and numerically investigated. The damage distribution, ballistic failure mode, and delamination areas are examined in detail. A systematic series of verification studies at a variety of projectile velocity scales—ranging from damage distributions to simulations of the evolution of delamination—were performed to fully evaluate the capabilities of the impact model. The model predictions show good agreement with the experimental results: the delamination zone as determined by ultrasonic C-scan images and the damage behavior of the spread tow woven composite under a wide range of impact velocities were accurately predicted. At high and hyper velocities, the asymmetrical patterns of damage in the panels are similar. The predictions of damage evolution indicate that the larger delamination area results from the large deformation of the rear side of the panel, reducing the bending stiffness of the woven composite and allowing extensive local delamination that is not visible. These results can provide a useful reference for obtaining the dynamic response of a carbon fiber–reinforced polymer woven composite and can aid in the design of composite panels with appropriate impact resistance properties.

Plasticity, ductile fracture and ballistic impact behavior of Ti-6Al-4V Alloy

The strength and fracture behavior of a metal are crucial to its response in impact events. In the present paper, a hybrid experimental-numerical study was conducted to characterize the plasticity and ductile fracture behavior of Ti-6Al-4V alloy. To this end, ten types of specimens were utilized to cover a range of stress states from uniaxial tension to high stress triaxiality, shear, plane strain as well as elevated temperatures and strain rates. Especially, a slightly modified in-plane shear specimen suggested by Roth and Mohr was proposed and adopted to prevent premature fracture initiation from the free boundaries at a tension stress state. Aside from a Split Hopkinson Pressure Bar (SHPB) system, a high-speed servo-hydraulic testing machine was applied to conduct high-rate tests. A Modified Johnson-Cook (MJC) plasticity model and an extended Xue–Wierzbicki (XW) fracture criterion with strain rate and temperature effects were used and calibrated using a combined experimental-numerical approach. It was found that the fracture strain of the metal is sensitive to both the stress triaxiality and the deviatoric state parameter, and reduced ductility is reached at increasing stress triaxialities and a plane strain as well as shear stress states. The yield strength increases with increasing strain rate and decreasing temperature. An enhanced ductility is achieved at elevated temperatures and lower strain rates, except for at the highest strain rate of 750 /s, at which a higher ductility is observed compared with that at slightly lower strain rates. Ballistic impact tests on 4 mm thick Ti-6Al-4V alloy targets were conducted using 5.95 mm diameter blunt rigid projectiles in an impact velocity range of 167.9 – 321.6 m/s. Parallel finite element simulations were performed for the ballistic tests and the validity of the calibrated material models was confirmed by comparing the predicted ballistic resistance and failure pattern of the target with the experimental ones. In addition, it was found that a finite element prediction on the ballistic resistance of the Ti-6Al-4V alloy targets struck by blunt projectiles is highly mesh size sensitive and a converged solution was obtained by using a mesh size of 20 μm.

MESOSCALE MODEL FOR SPALL IN ADDITIVELY MANUFACTURED 304L STAINLESS STEEL

The effect of microstructure on the high-rate tensile failure of additively manufactured (AM) 304L stainless steel is analyzed. The method uses state-based peridynamics with a new model for the time dependence of failure within grains. The model incorporates anisotropy in the elastic and plastic response of the grains. The grain shapes and lattice orientations are initialized directly from electron backscatter diffraction (EBSD) images. The model results are compared to test data from plate impact experiments over a range of impact velocities. A set of parameters for a homogenized material derived from the mesoscale model is demonstrated in the CTH hydrocode.

Deformation, damage, and reaction characteristics during the collision between Ni and Al nanoparticles.

The exothermic reaction during the collision between nanoparticles is of importance for the engineering applications of energetic powder materials. This work investigates collision-induced nanoparticle deformation, damage and reaction characteristics in a reactive Ni/Al system via molecular dynamics simulations. The morphological changes and reaction process are explored thoroughly for a wide range of impact velocities v and initial particle radius R. For lower impact velocities (1 km s-1 ≤ v ≤ 1.5 km s-1), the fully melted Al gradually clad the plastic deformed Ni nanoparticles to form an Al-shell/Ni-core structure, and the morphology ultimately develop into a nearly spherical shape possessing minimal surface energy. During this period, the self-sustaining reaction driven by the diffusion of Ni atoms into molten Al leads to slow melting of Ni nanoparticles, and the reaction and melting rates increase with the decrease of the particle radius. There exists one critical radius (R = 10 nm) beyond which the reaction is severely blocked due to the occurrence of fracture behavior at v = 1.5 km s-1. For intermediate velocities (2 km s-1 ≤ v < 3 km s-1), collision-induced debris clouds are observed, which satisfies the power-law distribution in the size of debris and results in an obvious reduction of the final reaction degree. Interestingly, we found that the reactive component in generated debris is lower for the larger-radius nanoparticle, which is also responsible for the lower final reaction degree and thermal kinetic energy. For higher velocities (v ≥ 3 km s-1), the occurrence of spallation damage reduces the contact area due to the formed micro-voids within Al and Ni nanoparticles and consequently the final reaction degree further.

On the relationship between shock and particle velocities in single and bicrystal systems of Aluminum: A molecular dynamics study

Molecular dynamics (MD) simulations are used to study shock wave propagation in various symmetric tilt and symmetric twist grain boundaries (STGB & STwGB) in Al for a range of impact velocities (1 to 3.5 km/s) using the open source LAMMPS package. The calculated shock velocity (US) to particle velocity (UP) relationship for Al single crystal (SC) matches well with the results of ab-initio and experiments. However for the shock simulations in bi-crystals (biC), the calculated shock velocity range fall in the same order of magnitude but does not show a linear, monotonic, US vs UP relationship. The interaction of the shock with the bi-crystal boundary, and shock propagation along different crystal directions on either side of the bi-crystal boundary are possible reasons for such behaviour. Common Neighbour Analysis (CNA) shows that there are more structural changes occurring in the bicrystal than in the single crystal. This is because the impact is along a different plane than the 〈0 1 0〉 direction as is the case of a single direction. We report effect of grain boundary on the calculated shock velocity.