Light Gas Gun Research Articles

Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity

Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity

Performance assessment of an innovative light and compact dust shield for DISC onboard Comet Interceptor/ESA space probes

The dust ejected by cometary nuclei encodes valuable information on the formation and evolution of the early Solar System. Multiple short-period comets have been studied in situ, but several perihelion passages considerably modified their pristine condition. Comet Interceptor is the first space mission selected by the European Space Agency to study a pristine dynamically new comet in situ. During a fast flyby through the comet coma, hypervelocity impacts with dust particles will represent not only an important source of information, but also a serious hazard to the spacecraft and its payload. Here we discuss the assessment tests performed on the dust shield of the Dust Impact Sensor and Counter instrument (DISC), part of the Comet Interceptor payload, which will be directly exposed to the cometary dust flux. Using a Light-Gas Gun, we shot mm-sized particles at ∼5 km/s, transferring momenta and kinetic energies representative of those foreseen for the mission. The impact effects on the DISC breadboard were compared to theoretical predictions by a ballistic limit equation for hypervelocity impacts. We find that, with a simple improvement in the dust shield design, DISC is compatible with the expected cometary environment.

Study on the attenuation pattern of stress wave in granite impacted by 30CrMnSiA alloy steel projectiles at 1.5–5.5 km/s

The damage ability of hypervelocity kinetic energy projectile penetrating ground has become a hotspot in modern military research. In this study, a hypervelocity impact test on a granite target subjected to projectiles using a two-stage light gas gun is conducted to study the stress wave evolution in granite under hypervelocity penetrations. The parameters of the *MAT_JOHNSON_HOLMQUIST_CERAMICS(JH-2) constitutive equation are calibrated using the results of the splinter impact test and the static test, and numerical simulations are performed using the smoothed particle hydrodynamics method coupled with finite element method (SPH-FEM coupled method) to extend the resulting data. A formula for calculating the stress wave peak attenuation is established, indicating that the maximum impact pressure produced by the hypervelocity impact decreases exponentially with scaling distance, and the attenuation coefficient is related to the degree of rock damage. Additionally, the attenuation of the speed of sound is used to characterize rock damage, and the damage deterioration law of granite under hypervelocity impact is analyzed based on the damage factor.

Effects of electron beam and atomic oxygen irradiation on hypervelocity - Impact tested / polyimide coated carbon fiber-reinforced plates

In a low-Earth orbit, space debris orbit at approximately the first cosmic velocity. When space debris strike a spacecraft, ejecta (fragments) from the spacecraft are widely scattered. The reduction in the number of ejecta (fragments caused by impact) must also be considered when selecting spacecraft materials. The authors’ group has previously examined the size of ejecta (fragments) and reduction in the number of ejecta. In general, the mechanical properties of polymer materials and CFRP plates may be damaged by space environments, such as radiation (gamma rays and electron beams (EBs)), atomic oxygen (AO), ultraviolet rays, temperature, and thermal cycling. The authors suggested an anti-AO coating/polyimide CFRP as a material resistant to space environments. The effects of EB and AO irradiation on the fracture behavior and ejecta of anti-AO coating/polyimide CFRP were examined for hypervelocity impacts. The results of static three-point flexural tests were compared with the fracture behavior and ejecta. A two-stage light-gas gun was used for the impact tests. Spherical projectiles formed of aluminum alloy 2017-T4 with a diameter of 1.6 mm were used. Photographs of the ejecta scattered in front of each polyimide CFRP plate were captured from the side using a high-speed video camera. The number and weight of the ejecta on the front side and perforation holes were examined.

Normal high velocity solid dust impacts on tiles of tokamak-relevant temperature

Runaway electron incidence on plasma facing components triggers explosive events that are accompanied by the expulsion of fast solid debris. Subsequent dust-wall high speed impacts constitute a mechanism of wall damage and dust destruction. Empirical damage laws that can be employed for erosion estimates are based on room-temperature impact experiments. We use light-gas gun shooting systems to accelerate solid tungsten dust to near-supersonic speeds towards bulk tungsten targets that are maintained at different temperatures. This concerns targets cooled down to −100°C with liquid nitrogen and targets resistively heated up to 400 °C. Post-mortem surface analysis reveals that the three erosion regimes (plastic deformation, bonding, partial disintegration) weakly depend on the target temperature within the investigated range. It is concluded that empirical damage laws based on room-temperature measurements can be safely employed for predictions.

Ignition mechanism and chemical reaction of the micro-damage polymer-bonded explosives under different inertial loading conditions

Understanding the impact-induced ignition properties and energy release behavior of polymer-bonded explosives (PBXs) is critical for the safety of explosive systems. In this study, a new impact test component was designed using a light gas gun to quantify the ignition mechanism and chemical reaction of micro-damaged PBXs under different inertial loading conditions. A constitutive model was developed to describe the mechanical-thermal-chemical response of the PBXs. This model was employed to further investigate the correlation between microcracks, debonding, hot spots, and chemical reactions. The results show that the stress state of the material is not uniformly distributed due to the micro-inhomogeneities and structural defects of PBXs. The shear friction of the microcracks contributes to localized hot spots, thereby inducing ignition. The critical loading condition for ignition is the length of the steel pillar is 32 mm. The damage and hotspot temperatures of the anterior lateral and posterior lateral regions are greater than those of other locations. The ignition response is accentuated with longer steel pillars, resulting in a more violent release of energy.

Dynamic response of UHMWPE/polyurea composite plates under combined blast and ballistic impact

Combined load caused by blast impulse and fragmentation impact poses a synergetic damage threat to the protective structure. To improve the blast and ballistic impact resistance of Ultra-high molecular weight polyethylene (UHMWPE), polyurea coated Ultra-high molecular weight polyethylene structure was proposed, and the composite structures with different coating thickness and coating position were prepared. Composite projectiles formed by combining foam projectiles and steel projectiles were launched by light gas gun to simulate the combined load of explosion impact and fragmentation. Comparative experimental studies were carried out. The experimental results show that the polyurea layer has good elastic properties, preventing the excessive deformation of the PE layer. The polyurea coating position and the time interval of the combined load show significant influence on the impact resistance of the composite structure. When the load was relatively low, PE plate with polyurea coating on booth face has both the advantages of PE plate with coating on the front and back face, but when the load increased, the impact resistance potential of polyurea layer was not fully developed. With the increase of the combined load, structures with polyurea coating on the back face has a good resistance of combined impact.

Research on ballistic properties of UHMWPE hybrid laminates impregnated with shear thickening fluid

In this paper, a technology of impregnating ultra-high molecular weight polyethylene (UHMWPE) with shear thickening fluid (STF) was proposed to prepare composite laminates, and the ballistic properties of laminates with hybrid configurations were studied. Firstly, two kinds of STFs were prepared using silica particles of 20 nm and 500 nm. Then, STF-impregnated UHMWPE composite laminates were prepared using the hot-press lamination process. Finally, a ballistic experimental study of different combinations of laminates was carried out using a two-stage light gas gun. The results of the study show that the energy absorption rate of the hybridized laminate with the 20 nm + 50 nm configuration scheme is enhanced by more than 9.3 % compared to the laminate impregnated with the single STF. The laminate’s back face deformation depth (BFD depth) after impregnation with shear thickening fluid is only 66.8 % of that of pure UHMWPE laminate. The research work can provide new ideas and references for designing and developing new protective equipment.

Synthesis of Phenanthrene/Pyrene Hybrid Microparticles: Useful Synthetic Mimics for Polycyclic Aromatic Hydrocarbon-Based Cosmic Dust.

Polycyclic aromatic hydrocarbons (PAHs) are found throughout the interstellar medium and are important markers for the evolution of galaxies and both star and planet formation. They are also widely regarded as a major source of carbon, which has implications in the search for extraterrestrial life. Herein we construct a melting point phase diagram for a series of phenanthrene/pyrene binary mixtures to identify the eutectic composition (75 mol % phenanthrene) and its melting point (83 °C). The molten oil obtained on heating this eutectic composition to 90 °C in aqueous solution is homogenized in the presence of a water-soluble polymeric emulsifier. On cooling to 20 °C, polydisperse spherical phenanthrene/pyrene hybrid microparticles are obtained. Varying the stirring rate and emulsifier type enables the mean microparticle diameter to be adjusted from 11 to 279 μm. Importantly, the phenanthrene content of individual microparticles remains constant during processing, as expected for the eutectic composition. These new hybrid microparticles form impact craters and undergo partial fragmentation when fired into a metal target at 1 km s-1 using a light gas gun. When fired into an aerogel target at the same speed, microparticles are located at the ends of characteristic "carrot tracks". Autofluorescence is observed in both types of experiments, which at first sight suggests minimal degradation. However, Raman microscopy analysis of the aerogel-captured microparticles indicates prominent pyrene signals but no trace of the more volatile phenanthrene component. Such differential ablation during aerogel capture is expected to inform the in situ analysis of PAH-rich cosmic dust in future space missions.

Production of high velocity micron-sized ice particles using the NASA Ames Vertical Gun Range for application to missions to icy moons.

The Ames Vertical Gun Range (AVGR) is a hypervelocity impact facility hosting a variable angle, two-stage, light-gas gun that can accelerate projectiles up to 7 km s−1. We have used the AVGR to produce impacts into supercooled (73–89 K) synthetic seawater ice targets inside a large impact chamber, whose pressure is 0.3 to 0.7 Torr.We report on the effective novel use of stainless steel meshes (49 μm, 100 μm, 149 μm, and 500 μm) to filter the ejecta plume for the ice grains of a desired size and demonstrate that reproducible temperature, speed, and particle size distribution can be achieved.The resulting ejecta plume of micrometer-sized ice particles (micro grains) from these impacts provides a method to simulate spacecraft encounters with ice particles found in the plumes of the outer Solar System, especially Enceladus. Image analysis of ejecta plume impacts onto aluminum (Al) foil enabled us to determine the ice particle diameter range. We find that the particles in the ejecta plume have speeds from 0.2 to 2 km s−1 and temperatures from 102 to 113 K (−171 to −160 °C). Furthermore, 61–97% by numberof the ice grains have equivalent diameter between 2.5 and 20 μm, that is, in the range 1 μm ≤ radii ≤10 μm, the upper size constrained by Cassini, i.e., ∼2 μm to 50 μm. Overall, the AVGR provides a high-fidelity simulation of ice micro grains impacting spacecraft surfaces and sample-collecting systems. This may be useful in the design, testing, and data analysis of future missions to Enceladus, Europa, and other icy moons.

High-impact dynamic loading method for calibration of triaxial acceleration sensors

Abstract In this study, a high-impact dynamic loading device was designed to generate a three-dimensional pulse excitation signal with high intensity shock acceleration and achieve triaxial synchronous calibration of a triaxial acceleration sensor. A light-gas gun interior ballistic model and a sensor mechanical response model were developed, and the relationships between the bullet impact velocity, barrel length, and initial chamber pressure were obtained. Additionally, the transformation relationship of the sensor’s triaxial acceleration in different coordinate systems was derived. Based on the stress wave theory and the finite element method, the influence of the bullet impact velocity on the variation pulse, and different slope and deflection angles on the triaxial acceleration were analyzed. By optimizing the parameter design, machining the prototype, and conducting high-impact dynamic loading tests, the results showed that the deviation between theoretical and measured values of the generated triaxial acceleration signal was small, and the maximum deviation was less than 4%. This indicated that the proposed high-impact dynamic loading device satisfied the calibration requirements for calibrating triaxial acceleration sensors, which can generate a three-dimensional acceleration with a peak value of not less than 700 000 m s−2.

Perforating characters of Zr-based bulk metallic glass fragment against thin steel target

To investigate the perforating characteristics of Zr-based bulk metallic glass fragments against thin steel target, ballistic experiments were carried out to measure ballistic the limit velocities of fragments perforating against different thicknesses of targets. The fragments were driven by a 57 mm one-stage light gas gun to impact the thin steel target. The numerical model of Zr-based bulk metallic glass fragments perforating against thin steel target was established using Autodyn2D commercial software, and the perforating process and perforating mechanism were analyzed by numerical simulation. The semi-empirical model to predict the ballistic limit velocity was fitted. An energy model for calculating the residual velocity of a fragment was derived based on the conservation of energy. The theoretical results of the semi-empirical model and the energy model are in good agreement with experiment results and simulation results. And the energy model has good applicability without fitting the parameters for different target thicknesses.

Damage effects of aluminum alloy honeycomb sandwich panel double-layer structure induced by reactive projectile hypervelocity impact

In this paper, the experiments of Al2024 and reactive projectiles with hypervelocity impact on aluminum alloy honeycomb sandwich panel double-layer structure respectively were carried out by using two-stage light-gas gun, and the impact processes were recorded through high speed camera. According to the analysis of the experimental results, the debris clouds motion process and the damage effects on double-layer structure were compared. The damage enhancement mechanism of reactive projectile was revealed through numerical simulation and theoretical methods. The impact-induced detonation reaction of the reactive projectile can significantly reduce the "channel effect" of the honeycomb sandwich panel by destroying the honeycomb core cell wall, increase the perforation on the back facesheet of the honeycomb sandwich panel, and generate the debris cloud with higher temperature and faster expansion velocity. The debris cloud induced by the reactive projectile has a larger load distribution area on the rear plate, avoiding the concentration of loads in the center of the rear plate, and cause large area impact and thermal combined damage effects on the rear plate and internal space of the double-layer structure, while ensuring that the target structure cannot be penetrated. The reactive projectile efficiently applies the kinetic energy and chemical energy released by the impact-induced reaction to the interior of the target structure, the waste of kinetic energy caused by whole structure penetration can be avoided, resulting in significantly higher damage effects than the inert Al2024 projectile.

Dynamic mechanical properties and energy release characteristics of Mg-Na-Al alloy under impact load

To investigate the ignition behavior of Mg-Na-Al alloy under impact load and its mechanical properties under different strain rates, the universal testing machine and Separated Hopkinson Pressure Bar (SHPB) experimental system were used to conduct static and dynamic mechanical performance tests of Mg-Na-Al alloy, and the mechanical properties of Mg-Na-Al alloy under different strain rates were discussed. The light gas gun experimental setup was used to launch Mg-Na-Al alloy projectiles and impact rigid target plates to study the energy release behavior of Mg-Na-Al alloy under impact loads. Finally, based on the 12.7 mm ballistic gun experimental platform, the penetration of 12.7 mm armor-piercing projectiles equipped with Mg-Na-Al alloy wind caps into the homogeneous armor steel plates with a thickness of 15 mm, and the ignition test of the oil box behind the steel plates were conducted. The results indicate that the yield strength of Mg-Na-Al alloy under static compression is 265 MPa, while under high strain rates (from 2490 s−1 to 5640 s−1), the yield strength of Mg-Na-Al alloy is 406–423 MPa, which is 53∼60% higher than that under quasi-static compression. When reaching a certain impact velocity, the Mg-Na-Al alloy projectile breaks and induces ignition behavior, releasing energy. The 12.7 mm armor-piercing projectile equipped with an Mg-Na-Al alloy wind cap penetrated the homogeneous armor steel plate with a thickness of 15 mm and ignited. The released energy and the kinetic energy of the fragments ignited the oil box behind the steel plate.

The dynamic response of composite auxetic re-entrant honeycomb structure subjected to underwater impulsive loading

The researches on dynamic responses of underwater impulsive loading have been conducted. However, the previous study mainly concentrated on metal sandwich structure and fixed supported boundary. The relative research on composite auxetic re-entrant honeycomb structure and simply supported boundary are rarely. In this paper, the effect of the gradient form and relative density on impact resistance performance of composite auxetic re-entrant honeycomb structure was experimentally and numerically investigated. The one-stage light gas gun was applied to provide initial kinetic energy of the fly plate, and the diffuser-type shock tube was utilized to generate and propagate exponential decaying shock wave. The pressure–time curve was respectively amplified and recorded by the charge amplifier and oscilloscope. The response speed, final deflection of rear panel and failure mode of cores and panels were used to evaluate impact resistance of composite auxetic re-entrant honeycomb structures. Moreover, acoustic-structure interaction algorithm was applied to simulate impact course of specimens in Abaqus/Explicit. The results between experiment and numerical simulation exhibited good consistency. The results indicated that the positive gradient form could excessively slow down response speed of rear panel by dissipating energy of shock wave, and the average gradient demonstrated smaller final displacement of rear panel and less failure compared with graded structures.

Study on transverse high-velocity impact resistance of carbon nanotube films and their based composites

This paper investigates the resistance of Carbon nanotube (CNT) films and their based composites to transverse high-speed impact and explores the effect of resin content on the impact properties. The study utilizes light gas gun experiments and employs numerical simulation to determine the critical penetration velocities for pure CNT films and those films impregnated with 20 %, 50 %, and 80 % epoxy resin solutions. The results demonstrate that including epoxy resin can enhance CNT films' impact-resisting ability, with a noticeable improvement as the resin content increases The observed strengthening mechanism in CNT resin composite films subjected to high-speed impacts primarily is energy absorption. Based on the above results, CNT films were added to the interlayer of composite laminates. It was found that CNTs could help materials resist impact and ensure the integrity of the laminate structure.

Mechanical properties and impact behavior of frozen clay: Insights from static mechanical tests, fly-plate tests, and split-Hopkinson pressure bar analysis

The presence of frozen clay as a natural protective material makes it a crucial layer of defense against potential impacts in various engineering projects. Studying the strength and deformation characteristics of frozen clay is, therefore, particularly important. In this study, static mechanical tests, the Hopkinson impact test, and fly-plate tests were conducted on frozen clay to identify its mechanical properties under an impact load. The uniaxial compression strength, flexural strength, and elastic modulus displayed a linear increase with the change in temperature. The fractal dimension was used to describe the failure characteristics of frozen clay, yielding values ranging from 1.5691 to 1.8785. At the same temperature, the fractal dimension exhibited a strain rate effect as the strain rate increased. A light gas gun system was then used to conduct fly-plate tests on frozen clay at varying temperatures (−3, −20 °C, and ordinary temperature). The impact process was meticulously analyzed, considering factors such as shock wave velocity, particle velocity behind the shock wave, impact pressure, and volume strain. Moreover, our investigation plotted the D–u (volume strain–particle velocity) and P–μ shock (impact pressure–shock wave velocity) adiabatic curves. Notably, we observed that samples with a higher initial strength exhibited an increased resistance to compression under an identical initial density and moisture content, resulting in a discernible leftward shift of the P–μ curve. The results provide a theoretical basis and technical support for similar projects in the future.

Anti-penetration response and response mechanism of laminated structures made of different composite materials under impact load

Composite laminated structures are often subjected to high-speed impact from external objects in high impact environments, resulting in unpredictable forms of damage and even uncontrollable damage modes. To ensure the safety and reliability of these structures, research was conducted on the anti-penetration response and response mechanism of laminated structures made of different composite materials. Using carbon fiber reinforced plastic (CFRP) laminated structures and glass fiber/epoxy resin composite aluminum alloy (GLARE) laminated structures as research objects, a high-impact experimental setup was constructed based on a first-stage light gas gun to explore the relationship between the energy absorption characteristics and impact energy of composite laminates. Combined with the ballistic limit equations, the ballistic limit values of the composite laminated structures were determined, and the ballistic limits of the 2 mm thick CFRP laminated structure and the 2 mm thick GLARE laminated structure were 138.3 m/s and 215.6 m/s, respectively. The damage modes of CFRP laminated structure are mainly fiber fracture on the impact surface and fiber delamination, fiber tensile fracture and fiber bundle splitting on the back surface, while the damage modes of GLARE laminated structure are mainly plastic deformation, internal fiber fracture and crack extension at the penetration. At the same time, the cohesion unit is introduced to carry out numerical simulation research, which shows that the damage pore morphology of the cohesion unit between layers of composite laminated structures are closely related to their fiber layups, and the damage mode of cohesion unit between layers of composite laminated structures have been investigated, which reveals the damage mechanism in high-impact environments. The research results provide theoretical basis and common technical support for reverse design of composite laminated structures suitable for high impact environments.

Shakedown of metallic sandwich beams when subjected to repeated impact loadings

When a monolithic metallic beam/plate subjected to repeated dynamic loadings with fixed impact level experiences elastoplastic deformation, its measurable deformations may cease to develop for further repetitions of the same dynamic load: this phenomenon was referred to as “pseudo-shakedown” in previous studies (Jones, 2014; Shen and Jones, 1992). Would pseudo-shakedown occur in a metallic sandwich structure under repeated shock loadings remains elusive. A combined experimental and numerical study was carried out to explore whether dynamic shakedown could occur in all-metallic ultralightweight corrugated core sandwich beams. For repeated impact tests, the sandwich beams were fabricated via the sequential process of cutting-stamping-vacuum brazing. When subjected to repeated impact loads (achieved via aluminum foam projectiles launched from a light gas gun), the dynamic responses of each sandwich specimen - including structural evolutions, beam deflections, and deformation/failure modes - were measured. Experimental results revealed that, depending upon the level of impact momentum applied to the sandwich beam, either dynamic shakedown or progressive failure could occur. The method of finite elements (FE) was subsequently employed to simulate the repeated shock tests, which was validated against experimental measurements, with good agreement achieved. To explore the physical mechanisms underlying the observed dynamic shakedown, the FE results of final plastic energy and effective plastic strain distribution in the sandwich beam were extracted and analyzed. When shakedown occurred, the measurable permanent deformation of the sandwich beam kept a relatively stable state, but its plastic energy remained positive, which is different from its monolithic beam/plate counterpart (i.e., plastic energy dropping to zero during dynamic shakedown). Such difference is mainly attributed to stress concentration occurring at the connecting joint points between the corrugated core and face sheets of sandwich and clamped endings, which produces plastic deformations that are difficult to reflect in overall large deformations of the beam. Consequently, the dynamic shakedown of metallic corrugated core sandwich beam captured in this study appears to be inexhaustive and hence may be termed as the “apparent pseudo-shakedown” (with danger lurking in the welding joints as well as clamped endings). Finally, based on a simplified bi-linear hardening constitutive law, the mechanisms underlying the dynamic shakedown of sandwich beam were further discussed from a purely base material point of view.

Comprehensive effect of simulated centrifugal force on characteristics of different extent notch-type foreign object damages

To systematically reveal effects of the centrifugal force on macro and micro characteristics and residual stress distributions of notch-type foreign object damages (FODs) on the leading edge of rotating titanium alloy fan/compressor blades, four series of notch-type damages with different depths were obtained under the same impact condition but four kinds of preloading conditions by using a light gas gun equipped with a 4-axial adjustable fixture. Macro and micro characteristics, stress concentrations and predicted numerical residual stress distributions of the notch-type damage impacted under the different preloading conditions were observed, calculated and compared. Finally, a qualitative analysis of fatigue crack initiation locations of FOD specimens was conducted by the comprehensive comparison of locations of stress concentrations, maximum residual stresses, micro damages such as micro cracks.