One-stage Light Gas Gun Research Articles

Influence of the Storage Energy Capacitance on Their Electrical Output Characteristics of Piezoelectric Ceramic during the Process of High-Velocity Impact

In order to reveal influence of external capacitance on the voltage input and input energy provided by the PZT-5H piezoelectric ceramic composite structure under high-speed impact loading, experiments have been performed by using one-stage light gas gun loading system combining with a power supplier circuit and power output testing system, which the aspect ratio of 1:1 column projectile impact monolithic and multi-piece piezoelectric ceramic composite structure at the near impact velocity and different storage capacity. The experimental results show that the more larger storage capacitance is, the smaller the piezoelectric ceramic output voltage is. However, the smaller of the capacitor voltage is, the smaller the value of energy storage is; with the energy storage capacitance increasing, the piezoelectric capacitance ratio and the energy conversion rate of piezoelectric ceramics decreases; In addition, the storage energy capacitor increases with the increasing of the piezoelectric ceramic layers; the relationships of storage energy capacitor and piezoelectric ceramic capacitor has a great influence on the input voltage and storage energy for storage energy capacitor.

Research on dynamic response characteristics of CFRP/Al HC SPs subjected to high-velocity impact

Abstract CFRP/Al HC SPs (Carbon Fiber Reinforced Plastic/Aluminum Honeycomb Sandwich Panels)composite structures are widely used in the aerospace and many other fields due to their excellent performances. In order to reveal profoundly the dynamic response characteristics of CFRP/Al HC SPs composite structure under high-velocity impact loading, the experiments about aluminum honeycomb core and CFRP/Al HC SPs composite structure impacted by high-velocity projectiles have been performed by using a one-stage light gas gun loading and a high-speed camera systems, respectively. The whole physical process of collision is analyzed by using TEMA software which is provided by high-speed camera's manufacturer, and the pictures and related physical parameters of the projectile passing through the different layers at the key moments are extracted based on the set frame rate of the video. Meanwhile, the ABAQUS/Explicit module was used to conduct numerical simulation under the same conditions as the experiments, and extracting the pictures and related physical parameters during the projectile penetrating through aluminum honeycomb core and the sandwich panels at the different key moments. The results show that the durations of action for the projectile impacting the Al HC core and the CFRP/Al HC SPs at the velocity about 280 m/s were 86 μs and 240 μs in experiments, respectively, and the durations of action were 90.7 μs and 236.2 μs at the same experimental conditions in numerical simulation, which were basically consistent comparing the experimental to simulated results. Moreover, more than 70% for the kinetic energy of the projectile consumed by the sandwich panels was attributed to the front panel and the aluminum honeycomb core during the entire impact process, and all these have verified the reliability of the numerical simulation.

Effects of the phase interface on initial spallation damage nucleation and evolution in dual phase titanium alloy

The Ti-6Al-4V dual phase alloy samples were dynamic loaded by one-stage light gas gun experiment and samples with initial spallation were softly recovered. During the loading experiment, the velocity of free surface particles was measured by photonic doppler velocimetry (PDV). The effect of α/β phase interface on nucleation, growth, and coalescence of dynamic damage in Ti-6Al-4V were investigated by 2-D or 3-D testing techniques, such as optical microscopy(OM), x-ray computer tomography(XRCT), and electron backscattered diffraction(EBSD). The results showed that the majority of voids were nucleated within α phases, rather than on the α/β phase interface as predicted by quasi-static damage theory. Due to the effects of reflection and transmission of shock wave at the phase interface, a tensile pulse would be formed within α phase when the shock wave transmit from α phase with high impedance to β phase with low impedance. When this tensile pulse was large enough, voids would be formed within α phase. The analyses of OM and XRCT indicated that the voids at the beginning of nucleation were nearly spherical, then grew up along the direction of 45° with the shock loading direction, and finally the rod-shaped voids were formed. Besides, the voids were not randomly nucleated within α phase, and the EBSD analysis showed that the voids were mainly nucleated at grain boundary triple points which composed of grains with large difference of Taylor Factor(TF) value within α phase. This is because the difference of plastic deformation capacity of this grains is larger, and it is easier to produce stress concentration. Thus these sites became the prior nucleation position of voids.

The void nucleation mechanism within lead phase during spallation of leaded brass

The incipient spall behaviours of Cu-34%Zn-3%Pb leaded brass samples with annealed and cryogenic-treated conditions were loaded using one-stage light gas gun experiments. The effect of Pb-phase on dynamic damage nucleation in leaded brass specimens was investigated by means of optical microscopy, scanning electron microscopy and x-ray computer tomography. It was found that the voids of incipient spall were mainly nucleated in the interior of the lead (no tensile stress would be produced within lead according to the impact theory) instead of nucleated at the phase interface as expected by quasi-static damage fracture theory. A nucleation model is proposed in the present work that is the asymmetry high compression zones in the centre of the lead-phase were formed by the rarefaction wave convergence effects of matrix/quasi-spherical lead interface, which caused adiabatic temperature rise that exceeded melting point of lead due to severe plastic deformation, finally led to local melting and void nucleation. In addition, the spall strength and damage rate increased with the increase in the Pb-phase number.

The Propagation of Stress Wave in the PZT-5H Composite Target and the Influence of Load Resistance on the Electrical Output Under the Strong Shock Loading

To introduce the application background the self-powered technology for Fuze bridge fire, high overload microthermal battery activation, rocket ignition, and the aircraft escape actual condition lifesaving system ignition power supply, which intends to use the high-speed impact of piezoelectric ceramic in the process of missile launching high overload pressure or missile and target intersection in the process of high overload stress wave of piezoelectric ceramics and the transformation of power, for closer to confession technology for Fuze bridge ignition, high overload microthermal battery activation, rocket ignition, and aircraft escape system engineering problems. The stress wave propagation in the PZT-5H piezoelectric ceramic composite target and load resistance effect to the electrical output characteristics is investigated under the strong shock loading; the experiments have been performed about cylindrical steel projectiles normal impact on PZT-5H piezoelectric ceramic composite target by using polyvinylidene fluoride stress test system and electrical output test system combining with one-stage light gas gun loading system. The experimental results show that the stress duration and peak stress are about $9~\mu \text{s}$ and 232 MPa, respectively, when the cylindrical projectile impacts on piezoelectric ceramic composite target at the impact velocity of 345 m/s. The outputs of current pulse peak, voltage pulse peak, and energy peak are 20 A, 734 V, and 11 mJ under the stress interactions of 200–300 MPa. At the near-impact stress conditions, the electrical output characteristics of piezoelectric ceramics are greatly affected by the load resistance. The output voltage pulse increases with the increasing of load resistance value, and the values of the load resistance have a significant effect on output energy; output energy conversion rate is up to 82% when the load resistance is $50~\Omega $ .

Effects of the phase interface on spallation damage nucleation and evolution in multiphase alloy

The spall behaviors of Cu-34%Zn-3%Pb leaded brass samples with annealing and cryogenic treating conditions were dynamic loaded using one-stage light gas gun experiments under ∼1.515 GPa shock pressure. The effects of α/β phase interface and Pb/matrix phase interface on dynamic damage nucleation, growth, and coalescence in leaded brass specimens were investigated by multidimensional testing techniques. Experiment results showed that voids of incipient spall were mainly nucleated in the interior of the Pb-phases with signs of melting, and a small number of voids were nucleated in α-phase, and both are not nucleated at the interface which contradicts the damage fracture theory under quasi-static loading. Due to the effect of reflection and transmission of shock wave at the phase interface, when the shock wave propagates from α-phase with higher impedance to Pb-phase or β-phase with lower impedance, a tensile pulse will be formed within α-phase. If the tensile pulse has sufficient amplitude voids would be nucleated in α-phase. On the other hand, it is considered that the asymmetry high compression zones in the center of the lead-phase with low impedance were formed by the shock wave convergence effects of matrix/lead quasi-spherical interface, which caused adiabatic temperature rise exceeded melting point of lead due to severe plastic deformation, and finally led to local melting and void nucleation in the center of the lead-phase rather than the tensile stress.

Determination of dynamic shear strength of 2024 aluminum alloy under shock compression

A series of plate impact shock-reshock and shock-release experiments were conducted by using an one-stage light gas gun to determine the critical shear strength of the 2024 aluminum alloy under shock compression levels ranging from 0.66 to 3.05 GPa in the present study. In the experiments, a dual flyer plate assembly, i.e., the 2024 aluminum alloy flyer backed either by a brass plate or a PMMA plate, was utilized to produce reshock or release wave. The stress profiles of uniaxial plane strain wave propagation in the 2024 aluminum alloy sample under different pre-compressed states were measured by the embedded stress gauges. The stress-strain data at corresponding states were then calculated by a Lagrangian analysis method named as path line method. The critical shear strengths at different stress levels were finally obtained by self-consistent method. The results show that, at the low shock compression level (0.66 to 3.05 GPa), the critical shear strength of the 2024 aluminum alloy cannot be ignored and increases with the increasing longitudinal stress, which may be attributed to rate-dependence and/or pressure dependent yield behavior of the 2024 aluminum alloy.

Experimental Study on the Dynamic Mechanical Properties of Reinforced Concrete under Shock Loading

A simple experimental method was introduced to study the mechanical properties of reinforced concrete under shock loading. The one-stage light gas gun was used to test the mechanical properties of reinforced concrete with different reinforcement ratios under various impact velocities. Three Mn-Cu piezoresistive pressure gauges embedded in the target were used to record the voltage-time signals, from which the stress-strain curves of reinforced concrete were obtained using Lagrangian analysis. Experimental results indicated that the load-bearing capacities of reinforced concrete increased greatly with the impact velocity and the reinforcement ratio. The peak stress of the shock wave decreased exponentially with the propagation distance.

Mesomechanism of elastic precursor decay in alumina under plate impact loading

The Hugoniot elastic limit (HEL) of ceramics is explained as the limit of elastic response and the onset of failure under dynamic uniaxial strain loading, which is an important parameter for understanding the dynamic properties of ceramic materials. Previous experimental impact studies showed an interesting phenomenon that the HEL decreases with the increase of sample thickness, which is termed the elastic precursor decay. This phenomenon has not been explained by a suitable mechanism to date. Recently it has become apparent that mechanical response of polycrystalline ceramics is governed by mechanism operating at a grain level. So the objective of the present work is to develop a mechanism that can illustrate this phenomenon on a mesoscale. In this paper, the plate impact experiments of alumina with varying thickness values are conducted by using one-stage light gas gun. The histories of the rear free surface velocity of the samples are recorded by a Velocity Interferometer System for Any Reflector (VISAR). The HELs of alumina samples with different thickness values are obtained from turning point of elastic phase to inelastic phase in the temporal curves of free surface velocity. It is confirmed that the HEL of alumina decreases with increasing the sample thickness obviously, namely elastic precursor decay phenomenon. It is considered that this phenomenon is related to the failure mechanism of shocked alumina at a grain level. Thus, the mesoscopic model of alumina, including alumina grain phase and glass binder phase, is developed according to the microstructure properties of tested sample observed experimentally. Mesoscale simulations are presented to study the mesoscale failure properties of alumina at various impact velocities. The results show that inelastic responses, such as microcracking, grain plasticity, are observed in microstructure of alumina even when the peak-shock stress is less than the magnitude of HEL. As is well known, the evolution process of cracking or plasticity is the energy dissipation process essentially, which will reduce the amplitude of elastic wave. Furthermore, the properties of elastic precursor wave propagation in microstructure of alumina are also captured in the present simulations. Since the acoustic impedance of glass binder phase is much lower than that of alumina grain phase, complex reflection and transmission of elastic wave will occur at grain boundaries. Due to a large number of randomly oriented crystals, the wave front, well defined at the continuum, is dispersed to lateral or reverse directions at these length-scales, which can also decay the elastic precursor amplitude in the initial propagating direction. Therefore, the results suggest that energy dissipation caused by the failure process should occur below HEL and energy dispersion due to reflection and transmission of elastic wave at grain boundaries should play a dominant role in the phenomenon of elastic precursor decay.

Diseño y construcción de un cañón de gas de una etapa para pruebas de impacto de alta velocidad

High impact tests are characterized by a projectile traveling at high speed as well as complex events such as flying fragments due to the velocity at which the impact occurs; however, these tests have become increasingly popular due to need for more stringent protective material requirements nowadays. In this paper, the design and construction of a one-stage light gas gun for ballistic testing is presented. This particular design is characterized by its simplicity, excellent performance at low cost and compact dimensions, when compared to commercial systems, presenting an affordable option for materials characterization for high velocity impact tests. The results are completed with the characterization of an armor grade material, obtaining the ballistic limit of the material, as well as demonstrating the effectiveness and versatility of the equipment.

Numerical Evaluation of a Light-Gas Gun Facility for Impact Test

Experimental tests which match the application conditions might be used to properly evaluate materials for specific applications. High velocity impacts can be simulated using light-gas gun facilities, which come in different types and complexities. In this work different setups for a one-stage light-gas gun facility have been numerically analyzed in order to evaluate their suitability for testing materials and composites used as armor protection. A maximal barrel length of 6 m and a maximal reservoir pressure of a standard industrial gas bottle (20 MPa) were chosen as limitations. The numerical predictions show that it is not possible to accelerate the projectile directly to the desired velocity with nitrogen, helium, or hydrogen as propellant gas. When using a sabot corresponding to a higher bore diameter, the necessary velocity is achievable with helium and hydrogen gases.

The Impact Induced Demagnetization Mechanism in NdFeB Permanent Magnets

Compression of unmagnetized Nd2Fe14B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system. The microstructure, crystal structure, and magnetic properties of the magnets are examined with scanning electronic microscopy, x-ray diffraction, hysteresis loop instruments, and a vibrating sample magnetometer, respectively. The NdFeB magnets display a demagnetization phenomenon after shock wave compression. The coercivity dropped from about 21.4 kOe to 3.2 kOe. The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92 GPa. The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900°C and 520°C for 2 h, sequentially. The chaotic orientation of Nd2Fe14B grains in the compressed magnets is the source of demagnetization.

Mechanical Behavior of Steel Fiber Reinforced Concrete Investigated by One-Stage Light Gas Gun Experiment

This paper presents shock Hugoniot compression data for several concrete materials obtained from flat plate impact experiments. The manganin pressure gauge was used to measure the pressure-time curves of the samples. The physical quantities were all obtained by the Lagrange method. Moreover, it is observed from the measured pressure-time curves that the rate sensitivity of the dynamic response to the concrete is not negligible. Based on the polynomial Grüneisen equation, the parameters of the equation of state of concrete were obtained. The steel fiber reinforcement effect was analyzed.

Study on the mechanical behavior of steel reinforced high strength concrete subjected to impact loading

In this paper, the impact experiments of steel fiber reinforced concrete with same impact velocity and different steel fiber contents are processed by one-stage light gas gun. Through the manganin gauges embedded in the target, the voltage-time signals are recorded. Lagrangian method is used to analyze the flow field, then the particle velocity (u), specific energy, specific volume with time are obtained. Moreover, it was observed from the measured pressure-time curves that the decay factor is smaller in the steel reinforced high strength concrete. The dynamic response is analyzed. Key words: Concrete, relationship, steel fiber.

Dynamic Mechanical Properties of Steel Fiber-Reinforced Concrete Subjected to Shock Loading

One-stage light gas gun is used to study the dynamic mechanical properties of reinforced concrete (SFRC) subjected to shock loading. The material of projectile is the same as of the target. The stress-time curves are recorded by three manganin pressure transducers embedded in the targets beforehand. The data of experiment are analyzed by self-designed program using the path line principle of Lagrangian analysis method. With the stress records, complete histories of particle velocity, density (and thus strain) and specific internal energy can be obtained at any point within the gaged region of the material. Moreover, the numerical constitutive relations of RC are obtained and the strain rate ranges from 104 to 105 per second. The result of experiment indicates that the stress-strain curves of SFRC present stagnant-return properties. And some other dynamic properties can be gained, such as rate dependent, waveform dissipation etc.

Failure and impact behavior of facade panels made of glass fiber reinforced cement(GRC)

GRC is a cementitious composite material made up of a cement mortar matrix and chopped glass fibers. Due to its outstanding mechanical properties, GRC has been widely used to produce cladding panels and some civil engineering elements. Impact failure of cladding panels made of GRC may occur during production if some tool falls onto the panel, due to stone or other objects impacting at low velocities or caused by debris projected after a blast. Impact failure of a front panel of a building may have not only an important economic value but also human lives may be at risk if broken pieces of the panel fall from the building to the pavement. Therefore, knowing GRC impact strength is necessary to prevent economic costs and putting human lives at risk. One-stage light gas gun is an impact test machine capable of testing different materials subjected to impact loads. An experimental program was carried out, testing GRC samples of five different formulations, commonly used in building industry. Steel spheres were shot at different velocities on square GRC samples. The residual velocity of the projectiles was obtained both using a high speed camera with multiframe exposure and measuring the projectile’s penetration depth in molding clay blocks. Tests were performed on young and artificially aged GRC samples to compare GRC’s behavior when subjected to high strain rates. Numerical simulations using a hydrocode were made to analyze which parameters are most important during an impact event. GRC impact strength was obtained from test results. Also, GRC’s embrittlement, caused by GRC aging, has no influence on GRC impact behavior due to the small size of the projectile. Also, glass fibers used in GRC production only maintain GRC panels’ integrity but have no influence on GRC’s impact strength. Numerical models have reproduced accurately impact tests.

Dynamic Mechanical Behavior of Reinforced Concrete

The dynamic compression experiments of reinforced concrete are carried out by one-stage light gas gun apparatus which subjects the reinforced concrete to deformation at strain rates of the order of 104/s with confining pressures of 1~1.5GPa. The stress-strain curves of reinforced concrete with different impact velocities are obtained using Lagrangian analysis method. Experimental results indicate that reinforced concrete is non-linear, rate-sensitive and pressure-dependent.

Mechanical behavior of reinforced concrete subjected to impact loading

Understanding the behavior of concrete and reinforced concrete at high strain rates is of critical importance in a range of application. The behavior of concrete and reinforced concrete at strain rates of the order of 10 4/s and pressure up to 1.5 GPa are studied experimentally. The concrete analyzed has the same composition and processing conditions as the matrix phase in the reinforced concrete. The dynamic compression experiments of reinforced concrete are carried out by one-stage light gas gun apparatus which subjects the reinforced concrete to deformation at strain rates of the order of 10 4/s with confining pressures of 1–1.5 GPa. The voltage–time signals are recorded by the manganin pressure gauges embedded in the target. The stress–strain curves of reinforced concrete with different impact velocities are obtained using Lagrangian analysis, from which the distribution regulations of other mechanical parameters such as specific internal energy and specific volume in the flow field are acquired. Experimental results indicate that the load-carrying capacities of concrete and reinforced concrete increase significantly with strain rate. The concrete and reinforced concrete are non-linear, rate-sensitive and pressure-dependent.

Mechanical behaviors and damage constitutive model of ceramics under shock compression

One-stage light gas gun was utilized to study the dynamic mechanical properties of AD90 alumina subjected to the shock loading. Manganin gauges were adopted to obtain the stress-time histories. The velocity interferometer system for any reflector (VISAR) was used to obtain the free surface velocity profile and determine the Hugoniot elastic limit. The Hugoniot curves were fitted with the experimental data. From Hugoniot curves the compressive behaviors of AD90 alumina were found to change typically from elastic to “plastic”. The dynamic mechanical behaviors for alumina under impact loadings were analyzed by using the path line principle of Lagrange analysis, including the nonlinear characteristics, the strain rate dependence, the dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading has been developed. The model was based on the damage micromechanics and wing crack nucleation and growth. The effects of parameters of both the micro-cracks nucleation and the initial crack size on the dynamic fracture strength were discussed. The results of the dynamic damage evolution model were compared with the experimental results and a good agreement was found.

Compressive Properties for Alumina Subjected to Shock Loading

Alumina have been investigated for its distinguished characteristics to be widely used in armor application. One-stage light gas gun were utilized to study the dynamic mechanical properties of alumina subjected to shock loading. Manganin gauges were employed to obtain the stress-time histories at the different Lagrange locations in alumina target. The Hugoniot curves of stress and pressure versus specific volume were fitted based on the experimental data. The compressive behaviors for AD90 alumina are shown to be from elastic to “plastic” below 12GPa and under more higher pressure it will be transferred to similar-fluid state. Adopting LS-DYNA finite element code the dynamic failure of alumina ceramic armor are simulated. It is concluded that nucleation and growth of great number of radial and axial cracks and lateral cracks play dominant role in fractured ceramic target under impact loading.