Single-stage Gas Gun Research Articles

Mechanical characterization and impact damage assessment of Al/SiC functionally graded coating under elevated temperatures

Functionally graded materials are a class of composite materials that finds widespread use in aerospace, defense and automobile applications due to their tailored material properties for the specific need. In the present research, impact dynamics and the damage behavior of functionally graded plasma spray coating (FGPS) on an aluminium 6061-T6 substrate under high velocity impact at various temperatures were studied. The FGPS coating consists of four layers having various proportions of Al and SiC (50/50, 40/60, 30/70 and 20/80 weight percentages) and the coating thickness was measured to be 232.8 μm. Experiments were carried out at 260 J of impact energy on the FGPS samples at various temperatures using a single-stage gas gun along with the thermal setup. A finite element model was developed with the Johnson-Cook damage model and piecewise linear plasticity material model, along with suitable contact algorithms. Impact simulations at various temperatures reveal that the stiffness reduction at higher temperatures results in decreased peak contact force, decreased rebound velocity and increased central deflection. The molten splats observed through the micro-morphological study have spread several micrometers, which indicates excellent bonding between the particles and the porosity content was found to be 1.35%. The research findings on the impact dynamics and damage behavior of FGPS can significantly improve material design for a wide range of applications.

Impact resistance and energy absorption characteristics of nickel-based alloy ring at elevated temperatures

To evaluate the high-temperature containment capability of a turbine casing, the impact resistance of half-ring specimens and full circular casings made of GH4169 nickel-based alloy was investigated. Ballistic impact tests were first conducted on GH4169 half-ring specimens using blade-shaped projectiles of DZ125 material fired from a single-stage gas gun. Meanwhile, explicit finite element simulations of the half-ring impact tests were performed with LS-DYNA. Comparing experimental and simulation results validated the accuracy of the model and revealed the effects of impact angle and ambient temperature. Then the process of a turbine casing containing a blade at 500 °C was simulated using the validated FE model. The results showed that the impact angle and the ambient temperature significantly affect the impact resistance of GH4169 half-ring specimen. Furthermore, the interaction mechanism between the turbine blade and casing differs across the three stages of the containment process.

Constitutive and impact response of AA7475-T7351 under different projectile shapes and velocities: An experimental and numerical investigation

Through experimental and numerical investigation, this article investigates the constitutive and impact response of the 1.6 mm thick AA7474-T7351 plate under the impact of blunt and hemispherical-nosed projectiles at different velocities. The Johnson-Cook plasticity and failure model parameters were calibrated for the target material using experimental data from the tensile experiments, which took into consideration the effects of plastic strain, strain rate, temperature and stress triaxiality. Further, JC plasticity model parameters were also optimised using a parametric optimisation process. The flow stress of AA7475-T7351 shows positive and negative sensitivity toward loading rate and temperature. It is observed that the ductility of AA7475-T7351 decreases with increases in stress triaxiality, whereas the flow stress increases. Perforation experiments on 1.6 mm thick circular AA7475-T7351 plates were carried out using a single-stage gas gun along with the high-speed Digital Image Correlation (3D-DIC) technique. The blunt nose projectile causes shear failure, whereas hemispherical nose projectile causes combined tension-shear failure; a microscopic study is performed to confirm this phenomenon. Experimental results obtained from DIC were validated using the numerical analysis in the Abaqus/Explicit platform in terms of transient out-of-plane deformation of the target plate. The quantitative error between experimental and numerical analysis was evaluated using the Russell error technique. Numerical analysis revealed that constitutive relations could predict the physical fracture mechanisms during perforation qualitatively as well as quantitatively.

Quantitative Characterization of the Perforation Behaviour of Direct Recycled Aluminum Alloy 6061 Plates Subjected to High-Velocity Impact

This study aims to establish the perforation behaviour of direct recycled AA6061 to help establish the properties of the current most optimized direct recycled AA6061 through the hot press forging technique. This was achieved by subjecting direct recycled AA6061 plates of varying thickness to high-velocity impacts using a single-stage gas gun setup. The impactor is a hemispherical steel projectile of 13mm in length and 8.5mm in diameter. Plates of 3,4,5 and 10mm thickness were tested at velocities ranging from 120 m/s to 402 m/s. The deformation profiles of the impacted plates were captured and analyzed to quantitatively establish the perforation behaviour of recycled AA6061 plates. The plates showed irregular and non-axis symmetric patterns of deformation hinting the material exhibits anisotropic properties. The changes in the deformation profile were investigated in relation to changes in impact velocities and plate thickness were made to understand how they impact the profile. The deformation area was observed to be decreasing when the bullet impact velocity was increased. Higher velocity impact events lead to more material ejection from the plate in the form of fragmentation. Additionally, the deformation zone was observed to be getting smaller with an increase in the thickness of the plate. Thicker plates were found to have more fragmentation compared to thinner plates. Ductile failure characteristics such as petal formation and plugging were observed along with brittle characteristics such as fragmentation and conal fractures. Lower-velocity impacts lead to more energy absorbed by the target plates. Thicker plates observed more of the bullet’s energy. Through experimentation, the deformation behaviour of the directly recycled AA6061 material was established. This data can be used as a base for further research into the material’s behaviour characterisation.

High-Velocity Impact Penetration Behavior of Recycled Aluminum Alloy 6061: A Brief Look

Aluminum demand is projected to increase in the future. To help meet the demand, recycling aluminum has been employed for quite some time. Conventional recycling of aluminum leads to CO2 and greenhouse gas emissions. Therefore, direct recycling techniques such as hot press forging are being used and researched to provide an alternate recycling route that leads to even lower emissions, material losses, and energy consumption. The recycled aluminum 6061 alloy obtained from hot press forging is relatively new. Hence, not much is known about its capabilities and properties, including its impact penetration behavior. In this study, recycled 6061 aluminum alloy plates of 5 mm obtained through hot press forging are used in high-velocity impact tests using a single-stage gas gun to test the material’s penetration behavior. Two tests are carried out at velocities ranging from 141 to 308 m/s, all resulting in full penetration. The material was observed to have decent energy absorption capabilities, ranging from 70% to 81%. The penetration behavior, however erratic, shows signs of both ductile and brittle failure modes.

A New Approach for Protection against Ejection Trajectory of Scabbed Materials of Ultrahigh-Performance Concrete under Projectile Impact

Scabbing on the rear face of concrete under impact produces fragments that act as additional projectiles causing fatality or severe damage to the occupants or systems. Ultrahigh-performance concrete (UHPC) has outstanding properties and has proven efficacy in the impact-resistant design of structures. However, the potential damage due to the impact of fragments of scabbed pieces still prevails. This study developed a new approach for preventing ejection of scabbed materials of UHPC under single and repeated bullet impact (using a single-stage gas gun facility). The ejection of scabbed materials was controlled using woven carbon–epoxy and glass–epoxy laminated composite sheets attached to the rear face of UHPC samples. The ejection of scabbed pieces was controlled in UHPC targets with composite backing in the case of both single and repeated impact under similar conditions. Furthermore, a numerical simulation based on nonlinear finite-element code was performed for repeated impact on a UHPC target with a carbon–epoxy laminated composite. The results of the numerical simulation had a good agreement with the experimental data. Thus, the synergistic effects of steel fiber–reinforced UHPC with composite backing can be used to enhance the impact performance of UHPC.

Normal and oblique ballistic impact damage behaviour of functionally graded plates: Experimental and numerical

The present study discusses experimental and numerical investigations on the dynamic response of functionally graded plates subjected to normal and oblique ballistic impact. Functionally graded plates were produced in a step-wise manner with powder metallurgy method using powder stacking-hot pressing technique. An experimental configuration was developed where projectiles impact functionally graded plates with three different compositions at impact angles of 0°, 15°, 30°, 45°, and 60°. Ballistic tests of functionally graded plates were carried out with a single-stage gas gun system using fragment simulating projectile (FSP) at velocities of approximately 610 m/s. The effect of the material composition and obliquity on damage and deformation of functionally graded plates was studied by varying the Al 6061 and SiC volumetric ratios to metal-rich (n = 0.1), linear (n = 1.0), and ceramic-rich (n = 10.0). Finite element analyses of functionally graded plates were performed with ANSYS Ls-Dyna explicit solver by employing the Mori Tanaka method to determine local material properties in the graded region and the TTO model to define elasto-plastic material behavior. The normal and oblique ballistic tests of functionally graded plates were compared with the values predicted from the finite element model in terms of damage, deformation, and fracture mechanisms. According to both numerical and experimental studies, the impact angle and material composition were found to be significant influences on damage and deformation of functionally graded plates. Given the complexity of the modeling of the ballistic impact events, the numerical models developed to predict the penetration depth and failure mechanism of plates in the ballistic impact tests showed a good agreement for n = 0.1 and n = 1.0 material compositions due to their metal-rich compositions.

Ballistic Performance of Thermally Exposed CFRP Composites

In this investigation, high velocity impact test was carried out to study the after effect of thermal loading on ballistic limits of composite laminates. Plain woven carbon/epoxy laminates with nominal thickness of 2.3 mm were fabricated by compression moulding technique. To study the effect of thermal loading, laminates were exposed to different temperatures of 60°C, 80°C, 100°C, 120°C, 140°C and 160°C for 24 h in hot air oven and brought back to room temperature. Impact test was carried out using single stage gas gun for velocity up to 115 m/s. The bullet used was Æ 9.6 mm and mass 14.20 gm. The results show that ballistic limit reduces from 83 m/s to 62 m/s with increase in loading temperature from 30°C to 160°C. For impact velocity above ballistic limit, energy absorbed by the laminates reduces with increase in loading temperature. Shear plug formation was observed during experiment as reported in literatures [4, 5 and 6]. An energy base mathematical model is employed to predict the ballistic limit. The model considered the energy loss due to various failure mechanisms that occurred during impact test. The predicted ballistic velocity and energy absorbed by laminates show good agreement with the experimental results.

Trajectory deflection of noncircular cross-section projectile penetrating into metal targets

To analyze the trajectory deflection of a noncircular cross-section projectile penetrating into multiple metal targets, numerical simulations with different impact velocities, projectile tip height and charge geometry are conducted. The simulation model is established using the finite element software LS-DYNA and verified based on the experiment carried out by a single-stage light gas gun. The results show that the impact velocity significantly affects the trajectory deflection of noncircular cross-section projectile. Although the deflections may be different in direction, the magnitudes exhibit decreasing trends with the increasing impact velocity. Besides, the trajectory varies from downward deflection to upward deflection with the increase of projectile tip height, and changes significantly with the tip height ranging from 0.8mm to 1.1mm. Further, as the geometry profile of projectile remains unchanged, the ones with noncircular charge exhibit better ballistic stability as compared with the circular charge projectile. This is mainly related to the variation in projectile mass instead of the variation in moment of inertia.

Ballistic impact of hollow-point ammunition on porcine bone.

Identifying failure mechanisms in skeletal tissue allows a deeper understanding of the effects of specific projectile impacts on bone. While ballistic trauma in flat bones is largely researched, knowledge of how long bones react to gunshot impacts is limited in the literature. The impacts of deforming ammunition appear to produce higher levels of fragmentation; however, these have not been studied in depth. This study compares the damage to femora bone by HP 0.357 and 9 mm projectiles constructed with both full and semi-metal jackets. Impact experiments were undertaken on a single-stage light gas gun involving the use of a high-speed video camera and full reconstruction of the bones to ascertain fracture patterns occurring in the femora. Higher degrees of fragmentation are likened to the presence of semi-jacketed HP projectiles than jacketed HP projectiles. The observations of external facing beveled edges are believed to be associated with the increased separation of the jacket and lead core of projectiles. Additionally, experimentation has shown that the amount of kinetic energy lost postimpact is likely related to the presence or the absence of a metal jacket on an HP projectile. The observed data, therefore, suggest that the composition, rather than the configuration, of a projectile affects the type and extent of the damage.

Simulation and developments for large pellet formation and acceleration for shattered pellet injection of the ITER DMS

Amongst the technological developments needed for ITER, the disruption mitigation system (DMS) is one of the most challenging since it has to mitigate the consequences of high-energy plasma disruptions to ensure the lifetime of ITER's structure and in-vessel components. ITER DMS is using Shattered Pellet Injection, whose technology needs to be developed for ITER specific requirements.In the framework of the “Technology Fundamental Studies for DMS” contract with ITER Organization, as part of the ITER DMS Task Force activities, and CEA, the DSBT (Low Temperature Systems Department) designed and operates a pellet injection test bench to produce and accelerate large cryogenic pellets with diameters from 10 to 28.5 mm and length/diameter ratios up to two. The objective of this activity is to study and to optimise the pellet formation and acceleration process using pure Protium, Deuterium, Neon and mixtures of these gases.Analytic and numerical studies were used to define the geometrical and cryogenic parameters for the pellet desublimation in the in-situ condensation cell of the cryostat. An analytical model has also been developed for the pellet acceleration in the single stage gas gun to validate the propellant valve design aiming at achieving velocities of up to 500 m/s for 28.5 mm protium pellets and 200 m/s for neon pellets.The complete test bench is composed of the gas propulsion system, the cryostat with its key component the pellet formation cell, the flight tube and the target chamber with viewing ports. The mechanical assembly is completed with specific instrumentation and fast data acquisition systems for the observation of the pellet formation and acceleration. The pellet integrity and trajectory are characterised by shadowgraphy with high resolution, high-speed cameras located at 1 m and 3 m after the barrel exit and with an accelerometer and a target foil in the target chamber.This document details the simulation studies, the selected test bench design and first obtained results.

Impact damage assessment of sandwich structures with CFRP face sheets reinforced by CNTs in thermal environment

The damage behaviour of honeycomb sandwich structures with carbon nanotube (CNT) reinforced composite face sheets under high velocity impact at elevated temperatures is investigated in the present study. In order to endure the out-of-plane loading events such as bird hit, runway debris and hail stone impact, CNTs are introduced into the matrix system with the intention of improving the damage resistance. CNT reinforced carbon-epoxy composites with various weight percentages such as 0.2, 0.4, 0.6 and 0.8 were manufactured as quasi-isotropic laminates. Sandwich structures were prepared and tested under high velocity impact at room temperature and elevated temperature (393 K) using a single stage gas gun. Macro structural observations were performed on the perforated specimens and the damage area, depth, central deflection and bulging height were measured. At room temperature, the impact damage pattern was characterized by matrix cracking, fiber breakage, fiber debris, fiber push away, fiber peel up and push delamination. Plastic deformations of the matrix and kink band formation are the significant damage modes in the thermal environment. Adding a higher proportion of nanoscale reinforcement is not always judicious to get improved impact resistance; rather, the temperature dependency must be considered when designing the CFRP composite for structural applications.

Velocity distributions in a gas-gun microparticle accelerator.

Here, we build and characterize a single-stage gas-gun microparticle accelerator, where a pressurized gas expands and launches particles on a target. The microparticles in the range of 60-250 μm are accelerated by the expansion of pressurized nitrogen. By using a high-speed camera, we study how the velocity distribution of accelerated particles is modified by particle size, pressure in the gas reservoir, valve's opening time, and diaphragm's thickness and composition. We employ this microparticle accelerator to study the impact of glass particles with diameters of (69 ± 6) μm accelerated at moderate velocities ∼ (10-25) m/s, using films of poly-dimethylsiloxane as targets.

Structural response of sandwich structures with CFRP face sheets under quasi-static indentation and high velocity impact: An experimental and numerical study

Honeycomb sandwich structures (HSSs) with carbon fibre reinforced polymer (CFRP) composite face sheets are extensively used as light-weight structures in aerospace engineering due to their high strength-to-weight ratio and energy absorption properties. However, the composite face sheets are highly vulnerable to impact loads and cause damage to the structure based on the impact energy. This study investigates the structural response of HSS with CFRP face sheets under quasi-static indentation and a wide range of impact energy: low to high velocity impact. A finite-element model was developed and numerical simulations were carried out at various impact energies, thereby providing deeper insights into the impact dynamics and understanding various damage states such as dent, front face sheet perforation, core damage and rear face sheet penetration. The numerical simulation result was compared with the experimentally tested HSS using a single-stage gas gun under 53.6 J to validate the finite-element model in terms of deformation and damage status. A quasi-static indentation test was conducted and numerically predicted force data under impact test for the complete perforation case was compared to address the dependency of rate of loading. The carbon nanotube (CNT) with various weight percentages (wt%), such as 0.2, 0.4 and 0.6, was added to the matrix system through a vacuum assisted resin transfer technique and experiments were conducted at 79, 107 and 135 J. The impact resistance increases with CNT addition and hence no perforation was recorded for all the test cases of 0.6 wt% CNT addition. The influence of CNT addition on the damage area is more on the bottom face sheet and a 57% reduction in damage area was recorded for the case of 0.6 wt% CNT addition at 135 J impact energy when compared to the neat carbon/epoxy composite.

High velocity impact behavior of Hybrid composite under hydrostatic preload

The Hybridization concept creates a niche within the composite segment to customize materials for specific applications with reduced cost without sacrificing strength and durability. The composite structures develop strain during continuous operation, and any sudden impact on these preloaded parts might result in catastrophic accidents. Studying impact response during such conditions is essential in designing and developing structures. This study experimentally investigates the high velocity impact response of Hybrid (Carbon-Glass) composite under normal and hydrostatic preload conditions. Mechanical tests involving Tensile, Izod, and Charpy are conducted. High velocity impact testing is carried out with a vertical single-stage gas gun with additional provision for hydrostatic preloading. An oscilloscope with a laser source measures the initial velocity, and Photogrammetry using a high-speed camera measure the residual velocity of a projectile. The mechanical test results suggest that Hybridization resulted in a significant property enhancement. The high velocity impact resistance and energy absorption are higher for Hybrid under both normal and preloaded impact.

Establishing the lower thresholds for water sterilisation with shock waves and hot gas bubbles from the detonation of explosives in water

Water sterilisation requires the inactivation of waterborne pathogens, like E.coli, to such low levels that its use will not cause illness. Here, we examine a potential methodology for disinfecting water through the combined effect of hot expanding gases and shock waves from underwater explosions. Water pathogens located within the proximity of the explosive charge will be exposed to two different sterilisation conditions: firstly, the high-pressure shock wave moving within the fluid, and secondly, the expanding hot N2, O2, and CO2 bubbles that are products of the explosion. To simulate the first case, we used a flyer-plate technique to understand the lower threshold for inactivation. We did this with a novel capsule design in a single-stage light gas-gun and observed 0.813 Logs of E.coli inactivation after subjecting an entire bacterial broth to a minimum pressure of 3.53 GPa thereby indicating a lower threshold for shock pressure-induced inactivation. For the second case, we show that hot gas bubbles from different explosive gaseous products at 150°C in a bubble column established the minimum gas temperature thresholds required to successfully inactivate E.coli. This work shows that any benefit of using explosives to sterilise water will principally come from the release of hot gaseous bubbles rather than the effect of the shock. This new approach could be used in conflict areas or remote locations with no access to standard sterilisation technologies or power.

Assessment of high-velocity impact effects on carbon fiber reinforced polymer sandwich panel with M-shaped core reinforced by nano-SiO2: Experimental and numerical study

This paper describes the high-velocity impact behavior of composite sandwich panels with different amounts of nano-SiO2. The sandwich panels were manufactured by carbon/fiber epoxy composite face sheets and an M-shaped core using the vacuum-assisted resin transfer molding method. To enhance the mechanical strength of the matrix, especially impact resistance, the nanoparticles were added to the resin epoxy matrix as filler with the ratios of 1%, 2%, and 3% of the composite's total weight. A scanning electron microscope was utilized to observe the microscopic structure of the composites, and it revealed an exceptional homogeneous mixture of nano-SiO2 particles in the resin epoxy matrix. Afterward, high-velocity impact tests were carried out using a single-stage gas gun test machine. A spherical steel projectile with a diameter of 8.7 mm was used for the test with a speed of 235 m/s. The experimental results indicated that adding 1–3 wt% of nano-SiO2 into the matrix remarkably increased the impact resistance of the composite. Moreover, the results showed that when the projectile collides with the core of the sandwich panel, it remains in the sandwich panel and its output velocity becomes zero, while when the projectile does not collide with the core, its output velocity is not zero. In order to validate the results, the experimental data were compared to the finite element models, and good agreement was observed.

High-velocity impact resistance of doubly curved sandwich panels with re-entrant honeycomb and foam core

This work describes the high-velocity impact behavior of doubly curved sandwich panels. The sandwich panels are manufactured using carbon/fiber epoxy composite face sheets, polyurethane foam core and 3D-printed PLA plastic cellular auxetic (re-entrant) honeycombs. High-velocity impact tests are carried out by using a single-stage air gas gun test machine. A spherical steel projectile with the radius of 5 mm is impacted to the center of the specimens with the speed of 100 m/s. The experimental data are used to validate explicit finite element models of the doubly curved structures. An analytical model is also developed for the ballistic limit of the flat and doubly curved sandwich panels, and the analytical results are compared to those obtained from the numerical ones. Parametric numerical analyses of the high-speed impact of the curved sandwich panels are then carried out considering various radii of curvature of the panels. The results show that the energy absorption is increased as the curvature is decreased for the panels with both foam and re-entrant core. In addition, the core configuration provides a key role in the impact resistance of the sandwich panels. Re-entrant models show an increase in specific energy absorption (SEA) compared to the foam core types.

Safety assessment of large-scale all steel LNG storage tanks under wind-borne missile impact

Regarding the disastrous consequences, the large-scale all steel liquefied natural gas (LAS-LNG) storage tank is regulated to be designed to resist the potential impact of wind-borne missiles. This paper aims to study the dynamic response and damage of LAS-LNG storage tanks subjected to the accidental typical wind-borne missile impact. Firstly, six Schedule 40 pipe and flange assembly missiles weigh 36.5 kg were designed according to the specifications of BS 7777 and RG 1.76. Based on the 300 mm-caliber single-stage gas gun, the impact test was conducted with a missile striking velocity of 50 m/s. The local deformation and global response of media-filled steel tanks were assessed experimentally. Then, the commercial finite element (FE) program LS-DYNA was utilized to perform the numerical simulations considering the fluid–structure interactions. The adopted numerical algorithm, constitutive models and the corresponding parameters were validated by comparing with the test data. Finally, based on the validated finite element analyses approach, regarding the design-basis wind-borne missiles specified by the regulatory guide of U.S. Nuclear Regulatory Commission and American Nuclear Society, i.e., RG 1.76, RG 1.221 and ANSI/ANS-2.3-2011, the damage levels of the prototype Chinese Yuhuan LAS-LNG storage tank under wind-borne missile impact were assessed numerically. It indicates that the filled media in the tank would provide additional resistance to the missile impact, the present three design-basis wind-borne missiles could bring certain damage to the outer tank of the Yuhuan LNG storage, but the safety of the inner tank can be guaranteed.

Dynamic Behavior of Clay with different Density under Planar Impact

The dynamic behaviour of clay with different initial density was researched by a single-stage light gas gun. Soil samples with four initial density (1.7, 1.8, 1.9 and 2.0 g/cm3) were investigated in this study, the water content, graininess and raw material of which were the same. Four electromagnetic particle velocity gauges were embedded directly into each sample, which was compressed by clay powder. And the motions of shock wave were detected by these gauges. Typical waveforms of the particle velocity and the Hugoniot data of the experiments were presented. The dynamic stress-strain relation could be determined by the Lagrangian analysis method which was utilized to the four particle velocity waveforms. The results show that, the initial density was possibly the most important factor to affect the dynamic behaviour of soft clay soil under intense dynamic load compared with the water content.