高压物理学报

In-Situ High-Pressure X-Ray Diffraction of Natural Beryl

QIN Shan, LIU Jing, LI Hai-Jian, ZHU Xiang-Ping, LI Xiao-Dong

2008, 22(1): 1-5 . doi: 10.11858/gywlxb.2008.01.001

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Abstract:
At room temperature, in situ high-pressure energy dispersive X-ray diffraction (EDXD) inspections on beryl has been carried out using diamond anvil cell (DAC) device with synchrotron radiation source. The maximal pressure in the experiment is 19.2 GPa. In the range of experimental pressure, no evidence for the phase transition of beryl was observed. However, the axial compressibility along c axis is larger than that along a axis. The volume compressibility could be described with Murnaghan equation of state in the range of room pressure to 9.3 GPa, while in 9.3~19.2 GPa, the volume compressibility shifts and increases with pressure in a nearly linear relationship.

Studies on the Distribution of Breakdown Liquid Particle Size under Explosive Detonation

HU Dong, HAN Zhao-Yuan, ZHANG Shou-Qi, ZHAO Yu-Hua, WANG Bing-Ren, CHEN Jun, SUN Zhu-Mei, CAI Qing-Jun, YAO Jiu-Cheng, DONG Shi

2008, 22(1): 6-10 . doi: 10.11858/gywlxb.2008.01.002

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Abstract:
It is important to study liquid particle size in the dispersion in civil and military affairs range. Up to now it is the first time for the liquid particle size in the dispersion to be measured in our country using laser scattering apparatus, under explosive detonation. Based on the analysis on the interaction law between laser and liquid particles and the technique of measuring liquid particle size used by R. A. Dobbins et al, a set of simple and practical apparatus (i. e. laser scattering apparatus) has successfully developed to determine the liquid particle size in the secondary breakup of the fuel dispersion in this paper. For the interaction of laser with liquid particles, we have derived the light intensity formula of scattering on condition of neglecting the effects of reflection and refraction of light and absorption of light. This light intensity formula of scattering allows us to measure the Sauter mean diameter of liquid particles. In our experiment of measuring the liquid particle size in the process of the fuel dispersion, we substitute the explosively dispersed liquid with water. The experimental results show that during the secondary breakup of the liquid dispersion the Sauter mean diameter of liquid particles measured at the fixed position in the atomization area becomes smaller as time increases, the width of the atomization area becomes larger as the distance from the center of the fuel dispersion increases, and the Sauter mean diameter of particles in the front of atomization area decreases rapidly after increasing gradually as the distance increases. To be compared with other experimental results, the liquid particle size has been measured by the recovery method, and a numerical simulation of the secondary breakup of the liquid dispersion has also been performed. The obtained results are in a good agreement with those measured using laser scattering apparatus.

Synthesis of Monodisperse CdSe Nanocrystals: Nucleation and Growth

DAI Quan-Qin, WANG Ying-Nan, LI Dong-Mei, CHEN Hai-Yong, KAN Shi-Hai, ZOU Bo, SONG Yan-Li, GAO Shi-Yong, NIE Yan-Guang, LU Hong-Liang, et al.

2008, 22(1): 11-14 . doi: 10.11858/gywlxb.2008.01.003

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Abstract:
With trioctylphosphine and oleic acid as the ligands of Se and Cd, high-quality CdSe nanocrystals with controlled particle size were synthesized in a 260～300 ℃ noncoordinating solvent octadecene under argon flow. The as-synthesized nanocrystals are monodisperse without any size-selective treatment, and exhibit the clear quantum confinement effect, which makes the first excitonic absorption peak shift to red with increasing particle size. The shape of the emission peak and the reasonable Stokes shift (13 nm) indicate that these nanocrystals have intense band-gap emission, devoid of significant trap-state emission. In addition, experimental results show that the rate of nucleation and subsequent growth can be easily tuned by altering the concentration of trioctylphosphine, by which monodisperse CdSe nanocrystals can be also obtained.

Synthesis and Properties of TiN/TiB2 Composite Materials

DING Zhan-Hui, YAO Bin, MA Hong-An, ZHENG You-Jin, QIU Li-Xia, JIA Xiao-Peng, WANG De-Yong

2008, 22(1): 15-18 . doi: 10.11858/gywlxb.2008.01.004

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Abstract:
Planetary milling and subsequent high-pressure high temperature treatment fabricated TiN/TiB2 composite materials. The structure developments of the materials were monitored by X-Ray diffraction and Raman spectrum. The mechanisms of ball milling and high-pressure high temperature treatment were researched in detail. It was found that the diffraction peaks of -TiNx appeared after milling 50 h. No self-propagating high temperature synthesis (SHS) reaction was found during the whole milling process. The sample that milled for 70 h was transformed into TiN/TiB2 composite materials after subsequent high-pressure high temperature treatment (5 GPa and 1 300 ℃).

A Numerical Analysis of the Influence of Buffer Material on Tantalum Flier Plate Velocity in the Hypervelocity Launcher

BAI Jing-Song, SHEN Qiang, TANG Mi, HU Jian-Bo, LUO Guo-Qiang, TAN Hua, ZHANG Lian-Meng

2008, 22(1): 19-24 . doi: 10.11858/gywlxb.2008.01.005

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Abstract:
Buffer material plays an important role in the hypervelocity launching experiments. By using numerical calculations, the influence of TPX buffer material's thickness on high impedance tantalum flier plate's velocity is analyzed, and the optimal thickness of buffer material is also evaluated. For thickness of 0.3 mm and 0.5 mm tantalum flier plate, the relative error of tantalum flier plate's center velocity is about 5%~6% at different thicknesses of the TPX buffer materials. In order to compare the influence of different buffer materials on tantalum flier plate's velocity, the two-dimensional results of tantalum flier plate's center velocity and pressure histories are calculated at the same thickness of TPX and Lexan buffer.

Electrical Conductivity Measurement of -Boron under High Temperature and High Pressure

ZHANG Dong-Mei, GAO Chun-Xiao, HUANG Xiao-Wei, LI Ming, HE Chun-Yuan, HAO Ai-Min, YU Cui-Ling, CUI Xiao-Yan, LI Yan-Chun

2008, 22(1): 25-29 . doi: 10.11858/gywlxb.2008.01.006

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Abstract:
Boron possesses very complex structures and various physical characteristics under high pressure, which always attracts much attention in the field of theory and experiment. In situ electrical conductivity measurement under variable pressure and temperature conditions is a very important research into exploring conductive property of substance. Electrical conductivity of -B was measured with metallic microcircuit fabricated on the diamond anvil cell (DAC), and the conductive physical mechanism of -boron at high pressure and high temperature was analyzed. When sample was not heated, electrical conductivity of boron was rising with increasing pressure to 28 GPa; furthermore, we found that it almost recovers original state upon decompression. When temperature is changed from room temperature to 423 K, electrical conductivity begins to rise with increasing temperature, and the change rate becomes gradually high and the change trend of electrical conductivity is similar to that under different pressures in the same temperature range. Subsequently, laser-heating was performed on -B with designed DAC, Al2O3 thin film was deposited on the diamond anvil and used as heat resistant and electrical insulating layer. Electrical conductivity was separately measured at 14.5 GPa and 18.6 GPa. The highest temperature reached is 2 224 K. -boron is confirmed semiconductor property based on electrical conductivity increasing with elevated temperature.

Shock Wave Compression of PZT 95/5 Ferroelectric Ceramic

LIU Gao-Min, DU Jin-Mei, LIU Yu-Sheng, TAN Hua, HE Hong-Liang

2008, 22(1): 30-34 . doi: 10.11858/gywlxb.2008.01.007

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Abstract:
Reverse-impact experiments were conducted on a gas-gun facility to determine the poled and unpoled PZT 95/5 ceramic Hugoniot states. Instrumented VISAR recorded the u-t profile at the interface between the buffer and window. Comparisons between the obtained results and reference data indicated that Hugoniot curves for PZT 95/5 ceramic are quite sensitive to the differences in initial density. Hugoniot curve of higher density PZT 95/5 ceramic shows that the -u curve is in linearity below 3.0 GPa. The Hugoniot curves for the unpoled PZT 95/5 ceramic and poled PZT 95/5 ceramic have also been obtained. In addition, the phase transition of FR/AO has been identified over the stress range of interest.

Synthesis and Characterization of Two-Dimensional Rh-C60 Polymer

WANG Su-Qin, GU Min

2008, 22(1): 35-38 . doi: 10.11858/gywlxb.2008.01.008

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Abstract:
A rhombohedral two-dimensional (2D-Rh) C60 polymer has been successfully synthesized by cubic press methods under the conditions of 6 GPa and 700 ℃. X-ray diffraction (XRD) and nuclear magenatic resonance (NMR) were performed to characterize the samples. XRD spectrum indicates that the C60 polymer is rhombohedral, and sp3 bonds have formed between adjacent fullerene molecules via ［2+2］ cycloaddition reaction. 13C MAS NMR spectrum shows a broadened peak at 145, which has two sidebands, and one small peak at about 72. The broadening of the peak at 145 could be related to the presence of inequivalent sp2 sites and structure disorder. The sidebands of the peak at 145 show the large structure anisotropy of the corresponding carbons. The peak at 72 indicates the presence sp3 bond of adjacent C60 molecules.

Electrical Property and Phase Transition of CdSe under High Pressure

HE Chun-Yuan, GAO Chun-Xiao, LI Ming, HAO Ai-Min, HUANG Xiao-Wei, YU Cui-Ling, ZHANG Dong-Mei, WANG Yue, ZOU Guang-Tian

2008, 22(1): 39-42 . doi: 10.11858/gywlxb.2008.01.009

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Abstract:
The electrical resistivity of powdered CdSe has been measured at 300～450 K and pressure up to 23 GPa using fabricating microcircuit on a diamond anvil. It is found that during loading the pressure dependence of the electrical resistivity shows anomaly at about 2.6 GPa, corresponding to the structure transition of CdSe from wurtzite to rock-salt structure. While the anomalies observed at 6.0 GPa, 9.8 GPa and 17.0 GPa are due to the electronic structure transitions. During unloading two extra anomalies can be detected which happen at 14.0 GPa and 3.0 GPa, respectively. By fitting to the curve of pressure dependence of electrical resistivity the pressure dependence of band gap of CdSe high pressure phase has been obtained. The pressure of metallization of CdSe can be predicted to happen in the pressure range of 70～100 GPa. The elevated experiment results indicate that the electrical resistivity of CdSe increases with increasing temperature in the measured pressure and temperature range.

Electrical Conductivity Evidence for Phase Transitions of FeS under High Temperature and High Pressure

LI Ming, GAO Chun-Xiao, ZHANG Dong-Mei, HAO Ai-Min, HE Chun-Yuan, HUANG Xiao-Wei, YU Cui-Ling, ZOU Guang-Tian

2008, 22(1): 43-47 . doi: 10.11858/gywlxb.2008.01.010

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Abstract:
The electrical properties of stoichiometric iron sulfide (FeS) were investigated under high pressure with a designed diamond anvil cell (DAC). The process of phase transition was reflected on the discontinuity of electrical conductivity changing with high pressure. The conductivity of FeS with NiAs structure was found to be much smaller than other phases. Two new phase transitions without structural change were observed at 34.7 GPa and 61.3 GPa.

Instantaneous Void between Thermo-Baric Charge and Warhead Shell under Launching

ZHANG Qi, CUI Jun-Mei, JI Yan-Hua, WEI Ke-Zhen, DANG Hai-Yan, QIN Bin

2008, 22(1): 48-52 . doi: 10.11858/gywlxb.2008.01.011

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Abstract:
The safety theory on the warhead under launching is a interesting subject in the weapon science. The stress state in the charge medium of a warhead under launching is a key question to be studied. It is very difficult to measure local stress in a warhead under launching. There have not been any better measurement technique and results until now. We investigated the dynamical response of the charge medium in a warhead under launching by numeral simulation and mechanical analysis. This work became a theoretic base for the use of thermo-baric warhead. The obtained results show that the stress states in charge medium in the low and middle parts are pressurized mostly in the launching history. The instantaneous void will appear between the top end of charge and the shell of warhead. This is because the stress wave velocity in the shell is larger than that in the thermo-baric charge medium. This instantaneous void may be a risk for explosion of charged thermo-baric explosive in a warhead under launching.

Melting Property of Mo at High Pressure from Molecular Dynamics Simulation

ZHANG Gong-Mu, LIU Hai-Feng, DUAN Su-Qing

2008, 22(1): 53-56 . doi: 10.11858/gywlxb.2008.01.012

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Abstract:
Ab initio calculations are performed on Mo to investigate the structure at zero Kelvin, indicating that Mo is stable in a bcc phase up to the pressure of at least 500 GPa. Ab initio molecular dynamics simulations are also performed on Mo to reveal the melting property under high pressure. An NVT (N, number of particles; T, temperature) ensemble at five volumes (V=0.015 48, 0.012 19, 0.010 98, 0.009 84, and 0.009 10 nm3/atom) and N=128 atoms arranged initially in an ideal bcc lattice are used in the simulations. The obtained melting curve is located above the one determined in diamond anvil cell experiments. Change of the initial arrangement to fcc phase leads to the decreasing of melting temperature and approaching of melting curve to that from laser-heating diamond anvil cell experiments. It is possibly revealed that the Mo melt under high pressure is similar to fcc rather than bcc structure at ambient conditions.

The Microstructure and Thermal Performance of Phenolic Resin (PF)/Rectorite (REC) Nanocomposites Produced by High Pressure Method

LI Ming-Fa, FAN Duan, SUN Zhen-Ya, TIAN Xu, CHEN Li-Ying, YE Xian-Xian

2008, 22(1): 57-61 . doi: 10.11858/gywlxb.2008.01.013

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Abstract:
High pressure method was used to produce phenolic resin (PF)/rectorite (REC) nanocomposites. The microstructure and thermal performance of the nanocomposites was studied by X-ray diffraction (XRD), transmission electron microscope (TEM), and thermal analysis. The experimental results show that exfoiated resin/clay nanocomposites can be formed under high pressure conditions by the intercalation of polymeric molecules without interlayer polymerization. Morphological studies using TEM and XRD indicated that the clay particles within the phenolic resin was exfoliated and dispersed homogenously in the phenolic resin, and the thermal performance of the nanocomposites changed obviously.

Experimental Studies on Shock Properties of H2O-C6H6-C35H64O11 (OP-10)

SUN Yue, SUN Dong, SHUAI Jun-Qing, WU Guo-Dong, SHI Shang-Chun

2008, 22(1): 62-66 . doi: 10.11858/gywlxb.2008.01.014

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Abstract:
A series of dynamic loading experiments have been successfully conducted for liquid H2O-C6H6-C35H64O11 (OP-10) mixture of which the voluminal proportion is 10∶10∶1 on a two-stage light gas gun, and 10 Hugoniot data in pressure range from 3.75~57.87 GPa are obtained. The linear regression for these experimental data indicates that D-u relation of the mixture can be approximately expressed as D=1.407+1.503up, and the standard deviation is 0.102. The shock compressibility of the liquid system are basically consistent with the estimates from volume adding theory. The knees occurring at 6 GPa, 10 GPa and 30 GPa, possibly suggest the successive structural phase transitions. Furthermore, the effect on repulsive part of the interaction potential, e.g. Exp-6 type potential, is analyzed by modifying three coefficients in the Lawrence-Berthlot's mixing rule.

Study on Raman Spectrum of Synthesized cBN Crystal Block

CHEN Li-Xue, ZHU Pin-Wen, MA Hong-An, GUO Wei-Li, CHEN Hong-Liang, SONG Yan-Li, JIA Xiao-Peng, ZOU Guang-Tian

2008, 22(1): 67-71 . doi: 10.11858/gywlxb.2008.01.015

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Abstract:
cBN crystals, hBN and catalyst were used as raw material, to synthesize cBN crystal block, and the synthesized cBN crystal block was characterized using confocal Raman spectroscopy. Raman spectra show that Raman peak positions, 1.088 cm-1 and 1.368 cm-1, might be induced by a new phase of BN which is an intermediate phase between hBN and cBN. This phase may be an incomplete production of the phase transition from hBN to cBN under high pressure and high temperature (HPHT). These results may be helpful to understand the mechanism of cBN formation under HPHT.

An Eulerian Adaptive Mesh Refinement Method for Three Dimensional Elastic-Plastic Hydrodynamic Simulations

LIU Jun, HE Chang-Jiang, LIANG Xian-Hong

2008, 22(1): 72-78 . doi: 10.11858/gywlxb.2008.01.016

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Abstract:
Based on three dimensional elastic-plastic program MEPH3D, we design a three dimensional multi-component block-structured AMR program and solve many important problems which are encountered in combining blockstructured AMR with the uniform-grid program MEPH3D, such as the rule of refinement and derefinement, how to fill in the new blocks or ghost cells, the storage of the ghost cell, how to choose the interpolation functions and how to construct a timestep routine. Here we present two methods to store the ghost cell, and three kinds of interpolation function. We define a variable to control the selection of the boundary condition, and we give three kinds of boundary condition to choose. The numerical results indicate that the program has the ability to computing high-speed impact and explosion problems, and spends less time when getting the same precision.

Measurements in Planar Shock Wave Experiments for OFHC Using Manganin Gauges

FAN Chun-Lei, HU Jin-Wei, CHEN Da-Nian, WANG Huan-Ran, XIE Shu-Gang

2008, 22(1): 79-84 . doi: 10.11858/gywlxb.2008.01.017

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Abstract:
The typical spall signals are obtained in planar shock wave experiments of oxygen-free high-conductivity copper (OFHC) using manganin gauges. The yield stresses of OFHC under planar shock loading are also obtained from longitudinal and transverse stresses recorded by manganin gauges. The experimental data are compared with numerical simulations. The influence of strength models for OFHC at high strain rate and high pressure on the simulated results are revealed. The determination of transverse stresses by using manganin gauges are also discussed.

Possible Existence of Ultra Fast Polarity Diffusion Process of ZnO under High Pressure

ZHAN Xiao-Hong, CAO Da-Hu, LU Zhong, DING Hui-Hui

2008, 22(1): 85-88 . doi: 10.11858/gywlxb.2008.01.018

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Abstract:
The effects of heating temperature and duration time on the process of ZnO crystallization under the pressure of 5 GPa are studied systemically by the methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results show that the diffusion rate of ZnO increases greatly under high-pressure and the sample density higher than 99% of the theoretical value can be achieved after heated at 400 ℃ and 5 GPa for 0.5 h. With the increasing of the heating temperature, micro-cracks develop along crystal boundary in all samples, and eventually ZnO powder mixed with single crystals and poly-crystals forms above 500 ℃. The pale yellow crystallites with an average size of 100 m and the largest size more than 350 m was obtained at 850 ℃ after heating of 5 min. The sample morphology analysis shows that the reason for the ultra fast crystallization of ZnO under highpressure is possibly caused by a very quick diffusion rate of ZnO along certain direction. The crystal boundary along such direction moves very quickly under high-pressure until the neighboring micro-crystals merge into a single crystal in a short time, while the micro-crystals shrink in the other direction and cause micro-cracks along other crystal boundaries.

Shock Induced Phase Transition of Pure Iron and Fe-Based Alloy Cuneal Samples

YU Jin-Quan, TANG Xiao-Jun, YUAN Shuai, HU Hai-Bo

2008, 22(1): 89-94 . doi: 10.11858/gywlxb.2008.01.019

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Abstract:
Planar detonation wave was generated to load the DT2 iron and HR2 steel cuneal sample by detonating TNT. Macroscopical crack perpendicular or 45 angle to the load interface was found in recovered HR2 steel sample and irregular fracture at back surface was found in recovered DT2 iron sample. Metallographic structure observation, microhardness measurement of recovered sample and numerical simulation indicate that there was no shock-induced phase transition in HR2 steel but local incomplete phase transition in DT2 iron. The failure difference between the two materials may be caused by local incomplete phase transition.

The High Pressure Synthesis and Situ High Pressure Structural Stability of Ba2CuO2Cl2

LIU Qing-Qing, WANG Fu-Ren, LI Feng-Ying, CHEN Liang-Chen, YU Ri-Cheng, JIN Chang-Qing, LI Yan-Chun, LIU Jing

2008, 22(1): 95-98 . doi: 10.11858/gywlxb.2008.01.020

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Abstract:
Ba2CuO2Cl2 was synthesized under high pressure. The crystal structure stability of Ba2CuO2Cl2 was investigated under high pressure. It shows that Ba2CuO2Cl2 is stable in the studied pressure range but with a relative large anisotropic compressibility.

A High Frequency Hydrostatic Pressure Dielectricity Measuring System Based on Cubic Anvil Apparatus

LU Zhong, ZHAN Xiao-Hong, CAO Da-Hu, ZHANG Liang-Ying, YAO Xi

2008, 22(1): 99-102 . doi: 10.11858/gywlxb.2008.01.021

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Abstract:
By a self-made system based on a cubic anvil high-pressure apparatus and an Agilent 4294A accurate impedance analyzer, real time high frequency dielectricity measurement under hydrostatic pressure is realized by the standard four-wire method widely used in ambient pressure dielectric research. The sealing of liquid cell in solid pressure-transmission medium and multi signal lines out through gaskets including four micro-coaxial cables is achieved by the pre-formation of pyrophyllite cube together with gaskets. The testing fixture, 10 mm10 mm sample, pressure-temperature sensors and as many as 16 signal wires including 4 micro-coaxial cables with an outer diameters of 1.6 mm respectively can be contained simultaneously in a liquid testing cell with a volume of (1315) mm3. Four-wire impedance spectroscopy can be obtained by this system in a measurement range of room temperature to 300 ℃, ambient pressure to about 3 GPa hydrostatic pressure and testing frequency from 40 Hz to 5 MHz with an experiment error below 3%. The pressure induced ferroelectric-paraelectric phase transition of a BaTiO3 single crystal is observed using this setting up.

Experimental Research on the Characters of Laser-Driven Macro-Flyers

GU Zhuo-Wei, ZHANG Xing-Wei, SUN Cheng-Wei

2008, 22(1): 103-107 . doi: 10.11858/gywlxb.2008.01.022

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Abstract:
One-dimensional shock loading on the material can be realized using the technique of laser-driven macro-flyer plate and is of applications to the research of high pressure equation of state (EOS) and dynamics under high strain rate. A table-sized pulse Nd:YAG laser was used to drive macro-flyer in this work. The influence of flyer configuration on its flying parameters was experimentally researched. The experiments show that the energy coupling efficiency of flyer plates in complex configuration is improved, relative to the single foil configuration which the average velocity of flyer plates is enhanced by 15%~30%, furthermore, the integrity and planarity of flyer plates in complex configurations are better than those from single foil configurations. The startup relaxation time of flyer is measured to be within 5~10 ns. The planarity of flyer was measured and the results show that time difference of flyer in the range of 1.0 mm is within 20~30 ns. The flyer velocity history was measured and the results show that the flyer has been accelerated to 90% of its terminal velocity in 20 ns.

The Preliminary Study of Improving DAVIS Gun Launching Capability

DUAN Ji-Yuan, WANG Yan-Ping, LIU Cang-Li, YU Chuan

2008, 22(1): 108-112 . doi: 10.11858/gywlxb.2008.01.023

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Abstract:
Aimed at idiographic conditions of launching target in excess of launching capability in DAVIS gun experiments, two ways of improving DAVIS gun launching capability for enhancing efficiency and exerting function of DAVIS gun, and the interior ballistic performance was assessed. The ballistic analysis can be regarded as the foundation and reference of improving DAVIS and other guns' launching capability.

2008 Vol. 22, No. 1

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