Powder Gun Research Articles

305 火薬銃を用いた自動車用衝撃吸収部材の衝突試験機の開発(材料力学V)

305 火薬銃を用いた自動車用衝撃吸収部材の衝突試験機の開発(材料力学V)

Properties of Zr-based bulk metallic glass under shock compression

Many kinds of bulk metallic glasses have been discovered since the 1990s. However, there have been very few investigations of the dynamic compression properties of bulk metallic glasses with amorphous structured single-phase. In this study, Hugoniot-measurement experiments have been performed on Zr 55Al 10Ni 5Cu 30 (at.%) bulk metallic glass by the inclined-mirror method combined with a powder gun in the pressure range up to 45 GPa in order to investigate the elasto-plastic transition and phase transition of the bulk metallic glass. The Hugoniot-elastic limit stress of Zr 55Al 10Ni 5Cu 30 bulk metallic glass was >5 GPa which is much larger than that of the other metals. A kink was observed on the shock velocity versus particle velocity relationship of bulk metallic glass, which may be caused by phase transition. Ductile dimple fracture with a vein pattern was observed on the fracture surfaces of the recovered bulk metallic glass under low pressures.

Dynamic properties and microstructural behavior of pure iron below and above shock induced α↔ε phase transition

The study of dynamic damage and fracture of iron has been undertaken below and above phase transition by series of time resolved experiments using both light gas launcher and powder gun. Shock wave tests were conducted by symmetrical impacts of high purity iron. To reveal the material behavior we have done shock experiments where the target is covered with a window in order to limit release amplitude and to avoid specimen fragmentation. Metallurgical analysis of soft recovered samples yields information about damage and fracture processes related to thermo-mechanical loading paths. Tests conducted without window allow studying effects of both phase change and release transition. Optical and SEM characterizations lead us to observe several modes of damage: brittle, ductile diffuse with void growth and heavily localized smooth one. These figures are related with rarefaction shock waves occurrence or interfaces between transformed and not transformed iron. Simulations are performed with the ID to compare experimental data with numerical results. We explain post-mortem observations by the complex shock wave structure interactions: P1 and P2 shock fronts associated with some corresponding shock release during unloading stages.

Design Considerations for Electromagnetic Railguns

Electromagnetic (EM) railguns are similar to powder guns in that both provide an accelerative force to the projectile, while accepting the resulting recoil impulse. They are designed to contain lateral and axial pressure. They must be capable of surviving the thermal environment to which they are exposed. Although there are similarities, there are also striking differences. Both are explored in the present paper with emphasis placed on EM railgun design.

Shock compression behaviour of titanium diboride

Titanium diboride (TiB 2) has excellent mechanical properties, and is expected to be used as crashworthy material. In this study, the Hugoniot-measurements were performed on the TiB 2 polycrystal by means of the inclined-mirror method combined with the powder gun and two-stage gas gun to study the elastoplastic transition and to search phase transition. The Hugoniot-elastic limit (HEL) stress was measured to be approximately 12 GPa. The shock velocity ( U S) vs. particle velocity ( U P) relation of the final phase was given by U S = 8.79 + 0.78 U P km / s in the plastic region of 0.6–3.0 km/s in particle velocity. The shock velocities were much large compared with the bulk sound velocity, and those in 0.24–0.6 km/s were further larger than the linear Hugoniot relation. This result showed that this material preserved the large shear strength also in the plastic region. No phase transition was observed up to 120 GPa.

Dynamic behavior of selected ceramic powders

An experimental setup has been developed on the continuous recording of the stress profiles in ceramic powders subject to shock loading with manganin gauges. A series of plate impact experiments on highly porous ceramic powders such as Al 2O 3, SiC and B 4C were conducted at the laboratory's single stage powder gun facility. The relationship between shock wave velocity and particle velocity was measured to obtain the Hugoniot data. Plate impact onto powder sample experiments were conducted at loading stresses ranging from 1.6 to 4.2 GPa. The experimental results show that the shock wave speeds in various ceramic powders vary between 1 and 2 km/s. Linear Hugoniot relations between shock velocity ( D) and particle velocity ( u) are observed. The loading stress–specific volume form of Hugoniot relations ( P– V) was constructed using the data from quasistatic compression test results, Hopkinson bar dynamic compression test results and powder gun plate impact experiment results. The P–V diagram shows that the crush strength of ceramic powders is comparable to the loading stress level. The B 4C and SiC powders with bigger particle size more easily reach the solid state Hugoniot than the powders with smaller particle size at the same loading condition. In the case of Al 2O 3, the material shows less sensitivity to particle size difference at the same level of loading rate as compared to B 4C and SiC.

Impact of conical tungsten projectiles on flat silicon carbide targets: Transition from interface defeat to penetration

Normal impact of conical tungsten projectiles on flat silicon carbide targets was studied experimentally and numerically for half apex angles 5° and 5–15°, respectively, and comparisons were made with cylindrical projectiles. A 30 mm powder gun and two 150 kV and four 450 kV X-ray flashes were used in the impact tests. The numerical simulations were run with the Autodyn code in two steps. In the first, the surface loads were determined for different impact velocities under assumed condition of interface defeat. In the second, these surface loads were applied to the targets in order to obtain critical states of damage and failure related to the transition between interface defeat and penetration, and the corresponding critical velocities. In the impact tests, interface defeat occurred below a transition velocity, which was significantly lower for the conical than for the cylindrical projectiles. Above the transition velocity, the initial penetration of conical projectiles differed markedly from that usually observed for cylindrical projectiles. It occurred along a cone-shaped surface crack, qualitatively corresponding to surface failure observed in the simulations. The transition velocity for the conical projectile was found to be close to the critical velocity associated with this surface failure.

The effect of concrete target diameter on projectile deceleration and penetration depth

We conducted sets of experiments with three diameters of concrete targets that had an average compressive strength of 23 MPa (3.3 ksi) and 76.2-mm-diameter, 3.0 caliber-radius-head, 13-kg projectiles. The three target diameters were D = 1.83 , 1.37, and 0.91, so the ratios of the target diameters to the projectile diameter were D / d = 24 , 18, and 12. The ogive-nose projectiles were machined from 4340 R c45 steel and designed to contain a single-channel acceleration data recorder. Thus, we recorded acceleration during launch and deceleration during penetration. An 83-mm-diameter powder gun launched the 13-kg projectiles to striking velocities between 160 and 340 m/s. Measured penetration depths and deceleration-time data were analyzed with a previously published model. We measured negligible changes in penetration depth and only small decreases in deceleration magnitude as the targets’ diameters were reduced.

Measurement of the electrostatic powder coating properties for corona and triboelectric coating guns

Measurements have been made of the deposited powder layer for conventional electrostatic corona powder guns and triboelectric guns. By selectively removing the powder layer under computer control conditions, measurements of the powder thickness, and the adhesive properties of the powder layer have been obtained for variation in the coating process and detailed comparisons have been obtained for both coating systems.

Alternative calibration techniques for high-speed pyrometers in shock experiments

Optical pyrometry is widely used in industry and research laboratories to perform surface temperature measurements of sample materials. These shock physics experiments are normally conducted at powder or gas gun facilities or at facilities where high explosives can be used as a shock wave source, and using high-speed pyrometers that are usually calibrated by using a blackbody source. But, electrical power, time, and space can be limiting factors in such facilities, and blackbody calibration can be difficult. Crucial parts of the experimental setup (fibers, lenses, and/or mirrors) are destroyed in such experiments, and the pyrometry system must be recalibrated before each experiment. We have developed a calibration technique using integrating-sphere sources that allows us to calibrate pyrometers more rapidly and easily than with blackbodies. Two different integrating-sphere systems are described to cover the wavelength range generally used in pyrometry studies. The characterization of these systems is fully detailed including measurements of their spectral radiances. A discussion of the advantages and drawbacks of both calibration sources is given.

Giant Fullerene-Like Hollow Spheres Generated from Shock-Compressed C<SUB>60</SUB> Fullerene by an Impact of Metal Flyer

C 6 0 fullerene powder set into a stainless capsule was shock-compressed by using a powder gun. The capsule was compressed to 57 GPa by a W flyer with a velocity of 1.72 km/s. The recovered sample was investigated by scanning electron microscopy and Raman spectroscopy. We found the generation of fullerene-like carbon hollow spheres up to several μm in diameter on an internal hollow surface of the recovered sample. The spheres are significantly larger than fullerenes reported so far and are revealed to be in a highly graphitized state by Raman spectroscopy. Also we found exfoliation of the internal hollow surface at intervals. The formation mechanism of the carbon hollow spheres through a liquid phase is proposed.

Penetration of limestone targets by ogive-nosed VAR 4340 steel projectiles at oblique angles: experiments and simulations

In this paper, we document the results of a combined experimental, analytical, and computational research program that investigates the penetration of steel projectiles into limestone targets at oblique angles. We first conducted a series of depth-of-penetration experiments using 20.0 g, 7.11-mm-diameter, 71.12-mm-long, vacuum-arc-remelted (VAR) 4340 ogive-nose steel projectiles. These projectiles were launched with striking velocities between 0.4 and 1.3 km/s using a 20-mm powder gun into 0.5 m square limestone target faces with angles of obliquity of 15° and 30°. Next, we employed the initial conditions obtained from the experiments with a technique that we have developed to calculate permanent projectile deformation without erosion. With this technique we use an explicit, transient dynamic, finite element code to model the projectile and an analytical forcing function based on the dynamic expansion of a spherical cavity to represent the target. Due to angle of obliquity we developed a new free surface effect model based on the solution of a dynamically expanding spherical cavity in a finite sphere of incompressible Mohr–Coulomb target material to account for the difference in target resistance acting on the top and bottom sides of the projectile. Results from the simulations show the final projectile positions are in good agreement with the positions obtained from post-test castings of the projectile trajectories.

Characteristics of impact driven supersonic liquid jets

In this paper, a technique for the generation of supersonic liquid (water and diesel fuel) jets is presented. The supersonic liquid jet is generated by the use of a purpose-developed vertical, single-stage powder gun. The characteristics and behavior of supersonic liquid jets were obtained by visualization using the shadowgraph technique. The visual evidence related to supersonic liquid jets (velocity around 2000 m/s) generated from a variety of nozzle types is presented and the effects of nozzle parameters on the jet behavior are described. The characteristics of the leading edge shock wave and jet shape were found to be significantly related to the nozzle geometry. A one-dimensional analysis of the multiple, reflected shock waves inside the liquid sac and nozzle during the process of supersonic jet generation is presented. The method allows impact pressure, particle velocity and effect of shock wave reflections inside the nozzle cavity on the liquid jet velocity to be obtained. Jet shock waves obtained from the shadowgraph image and CFD simulation are also compared. The jet outflow characteristics and its leading edge shock wave in air were assessed for their potential for auto-ignition using fuel with cetane numbers from 50–100. The contribution of the strong leading edge shock wave to the auto-ignition is discussed.

衝撃圧縮法により作製されたＣｒＷ合金の粒径依存性

Phase-separation process is essential phenomenon owing to influence on quality of alloy. Miscibility gap was found on phase diagram of Cr-W alloy, however other things of Cr-W alloy haven't been studied after that. Therefore the aim of this study is to prepare nonequilibrated alloy under the miscibility gap by shock compression method, and to study grain size dependence on it. W powder of average grain size between 1μm to 8μm mixed Cr powder of 10μm grain size is put pressure on 42GPa using a one-stage powder gun. As a result, the smaller W grain size is, the more Cr-W alloy. And in the case that W powder is small to 0.6μm and enough specific surface area in mixed powder, nearly homogeneous Cr-W alloy prepared. Fluid Cr alloy with W melted as high temperature concentrate on surface of grains.

Penetration of concrete targets with deceleration-time measurements

We conducted two sets of penetration experiments with concrete targets that had average compressive strengths of 23 and 39 MPa (3.3 and 5.7 ksi). The 76.2-mm-diameter, 530-mm-long, ogive-nose projectiles were machined from 4340 R C45 steel and designed to contain a single-channel acceleration data recorder. Thus, we recorded acceleration during launch and deceleration during penetration. An 83-mm-diameter powder gun launched the 13 kg projectiles to striking velocities between 140 and 460 m/s. Measured penetration depths and deceleration-time data were analyzed with a previously published model. In addition, we compared the results of this study with results obtained from smaller diameter projectiles and this comparison suggested a projectile diameter scale effect.

Phase transition of KCl under shock compression

It had been reported that for potassium chloride (KCl) the B1–B2 phasetransition (PT) occurs under shock and static compressions, but the measuredtransition points showed large scatter. In this study, Hugoniot measurementexperiments were performed on KCl single crystals by the inclined-mirror methodcombined with use of a powder gun. The anisotropic Hugoniot elastic limits andPT points were observed. The PT points along the ⟨100⟩, ⟨110⟩ and ⟨111⟩axis directions were determined as 2.5, 2.2 and 2.1 GPa, respectively.The anisotropic transition was reasonably explained in terms ofthe displacement mechanism along the ⟨111⟩ axisdirection.

Supersonic liquid jets: Their generation and shock wave characteristics

The generation of high-speed liquid (water and diesel fuel) jets in the supersonic range using a vertical single-stage powder gun is described. The effect of projectile velocity and mass on the jet velocity is investigated experimentally. Jet exit velocities for a set of nozzle inner profiles (e.g. straight cone with different cone angles, exponential, hyperbolic etc.) are compared. The optimum condition to achieve the maximum jet velocity and hence better atomization and mixing is then determined. The visual images of supersonic diesel fuel jets (velocity about 2000 m/s) were obtained by the shadowgraph method. This provides better understanding of each stage of the generation of the jets and makes the study of their characteristics and the potential for auto-ignition possible. In the experiments, a pressure relief section has been used to minimize the compressed air wave ahead of the projectile. To clarify the processes inside the section, additional experiments have been performed with the use of the shadowgraph method, showing the projectile travelling inside and leaving the pressure relief section at a velocity of about 1100 m/s.

Numerical calculation of electrostatic powder painting using the Euler/Lagrange approach

Numerical calculations of gas-particle flows involving an electrical field, as they are found in the powder painting process, are presented based on the Euler/Lagrange approach. The gas flow is calculated by solving the Reynolds-averaged Navier–Stokes equations including the k– ε turbulence model. In order to solve the Laplace equation for the electrostatic field, a finite-volume approach is applied. The particle phase is simulated by using a Lagrangian treatment where a large number of particles are tracked through the flow and the electrostatic field. In addition to the drag and gravity, also, the electric field force is considered in the equation of motion. Average properties of the particle phase are obtained by ensemble averaging. The method is applied to the powder painting process. Two types of powder guns were considered, a slit nozzle and a round nozzle with a dispersion cone. The calculated general flow structure in the vicinity of the painting gun and the large-scale flow within the painting booth agreed reasonably well with the experimental observations. Additionally, the coating layer thickness was used for comparison, which is also relevant to judge the quality of the coating process. The results showed a reasonable good agreement between calculations and measurements for the slit nozzle. However, the extent of the paint layer was remarkably under-predicted for the round nozzle, which is mainly caused by the complex flow in this case. Nevertheless, the results demonstrate that numerical calculations are useful and effective for supporting the design and optimization of powder painting booths.

Penetration of 6061-T6511 aluminum targets by ogive-nosed VAR 4340 steel projectiles at oblique angles: experiments and simulations

In this paper we present the results from a combined experimental, analytical, and computational penetration program. First, we conducted a series of depth-of-penetration experiments using 0.021 kg, 7.11 mm diameter, 71.12 mm long, vacuum-arc-remelted 4340 ogive-nose steel projectiles. These projectiles were launched with striking velocities between 0.5 and 1.3 km/s using a 20 mm powder gun into 254 mm diameter, 6061-T6511 aluminum targets with angles of obliquity of 15°, 30°, and 45°. Next, we employed the initial conditions obtained from the experiments with a new technique that we have developed to calculate permanent projectile deformation without erosion. With this technique we use an explicit, transient dynamic, finite element code to model the projectile and an analytical forcing function derived from the dynamic expansion of a spherical cavity (which accounts for compressibility, strain hardening, strain-rate sensitivity, and a finite boundary) to represent the target. Results from the simulations show the final projectile positions are in good agreement with the positions obtained from post-test radiographs.

Measurements of thickness and adhesive properties of electrostatic powder coatings for standard and modified powder coating guns

Measurements have been performed with different electrostatic powder coating systems to measure the electrostatic charging processes. The measurements consist of spraying a fixed mass of powder through a powder gun and then analysing the powder coating to determine the optimum parameters. The techniques, which are presented, include (i) the absolute determination of the charge/mass ratio for a tribo gun, (ii) the analysis of a powder deposition on a metalised glass substrate to determine the powder thickness and the adhesion of the powder to the substrate for standard and modified powder coating guns.