高压物理学报

Experimental Study on the Membraneless Heavy Gas Cylinder and Gas Curtain Interfaces Impacted by a Weak Shock Wave

ZOU Li-Yong, LIU Jin-Hong, TAN Duo-Wang, HUANG Wen-Bin, BAI Jin-Song, LIU Cang-Li

2010, 24(4): 241-247 . doi: 10.11858/gywlxb.2010.04.001

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Abstract:
A modified shock tube apparatus has been developed in order to experimentally investigate the evolution process of a sulfur hexafluoride gas cylinder and gas curtain surrounded by air when impacted by a shock wave with a Mach number of 1.2. By designing the test section, the fog generator, the gas chamber, the suction system and the end section, and controlling the sulfur hexafluoride peak concentration in the mixing gas and the initial vertical flow velocity, we developed a steady and repeatable technique to generate gas cylinder and gas curtain interfaces. Using high-speed camera, the initial interface images in the horizontal plane are obtained, and the developing photographs of dynamic Richtmyer-Meshkov (RM) instability in the vertical direction are also recorded. The gas cylinder evolution photographs exhibit typical vortex pair structure, and the gas curtain evolution images show multi-mushroom structure in the early stage and interfering with neighboring wavelength in the later stage. The height and width of the gas cylinder and the width of the gas curtain increase monotonically with time. Moreover the width increases faster than the height. The evolution mechanism of vortex is explained preliminarily, using two-dimensional vorticity dynamic equation.

Dynamic Behavior of Void Growth in Aluminum with a Preexisting Flaw under Intense Impact Loading

WANG Yong-Gang, LIU Hong-Wei

2010, 24(4): 248-254 . doi: 10.11858/gywlxb.2010.04.002

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Abstract:
By means of the explicit nonlinear dynamic finite element computer code LS-DYNA, the nucleation and growth of void in aluminum with a preexisting flaw under plate impact loading have been investigated. The results are as follows: firstly, the void nucleation occurs from the boundary of the preexisting flaw and the ductile matrix, and once the voids have been nucleated, they grow linearly through the localized plastic deformation; secondly, the growth rate of void radius increases linearly with the shock loading amplitude; thirdly, the yield strength and the size of the preexisting flaw have an obvious influence on the relative growth rate of void; finally, if the threshold stress of the void growth is set as 3.5 times of the yield strength, the simulation results agree reasonably well with the theoretical results, which is helpful for the further understanding of the void growth dynamic behavior.

Preliminary Studies on Real-Time Acoustic Emission Monitoring in Single Crystal Diamond Growth

LIU Lei, ZHANG Yuan-Pei, LAN Wei-Ke, LI He-Sheng, LI Mu-Sen

2010, 24(4): 255-259 . doi: 10.11858/gywlxb.2010.04.003

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Abstract:
The growth process of synthetic diamond single crystals under high-pressure and high-temperature (HPHT) was tested with acoustic emission (AE) technique. A real-time AE monitoring system was built by using a PCI-8 acoustic emission instrument and a LMD-800 hinge-type cubic-anvil press. The characteristics and their variations of the AE signals in the growth and non-growth processes of the diamonds were compared. Furthermore, the spectrum analysis of the AE signals was performed. The experimental results indicated that the AE signals corresponding to the diamond growth process exhibit a low frequency feature. Accordingly, AE testing can be used to study the in-situ reaction mechanics of synthetic diamond single crystals under HPHT.

First Principles Calculation of SiO2 at High Pressures

HAO Jun-Hua, WU Zhi-Qiang, WANG Zheng, JIN Qing-Hua, LI Bao-Hui, DING Da-Tong

2010, 24(4): 260-266 . doi: 10.11858/gywlxb.2010.04.004

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Abstract:
Total energy of SiO2 as a function of unit cell volume has been calculated for -quartz, rutile and CaCl2 structures using the density function theory (DFT) and Hartree-Fork (HF) method. According to the Murnaghan's equation of state, the bulk modulus B0 and B=dB/dp for these three structures have been obtained. The calculated results are all in good agreement with experimental and other theoretical data available in the literature, which indicate that SiO2 will transform from -quartz structure to CaCl2 structure as pressure increasing, and there is no phase transition between rutile structure and CaCl2 structure, namely they can coexist. By analyzing the changes of the lattice parameters, the electronic density of states, and the band gap under pressure, it is found that in -quartz SiO2 the energy band width and charge transfer increase with increasing pressure. Moreover, the Si─O bond length is shortened and the electric charges are redistributed.

Synchrotron Radiation X-Ray Diffraction Study of AlN Nanowires under High Pressures

SHEN Long-Hai, CUI Qi-Liang, LI Xue-Fei

2010, 24(4): 267-270 . doi: 10.11858/gywlxb.2010.04.005

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Abstract:
The high-pressure behavior of wurtzite AlN nanowires is studied up to 51.1 GPa by in situ angle dispersive X-ray diffraction using synchrotron radiation source and a diamond anvil cell. With increasing pressure up to 24.9 GPa, the wurtzite-to-rocksalt phase transition was observed. The rocksalt phase is quenched after a complete pressure release. The axial ratio c/a of the wurtzite AlN nanowires decreases linearly with increasing pressure. The unique wire-like structure in AlN nanowires results in the high pressure behavior being different from that of the bulk and nanocrystal AlN.

Molecular Dynamics Simulation of CO2-Expanded Liquids

WANG Wei-Bin, YIN Jian-Zhong

2010, 24(4): 271-278 . doi: 10.11858/gywlxb.2010.04.006

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Abstract:
Thermodynamic and transport properties of CO2-expanded methanol system and CO2-expanded ethanol system, as well as the diffusivities of p-chloronitrobenzene/CO2-expanded methanol system and benzonitrile/CO2-expanded ethanol system were modeled with molecular dynamics simulation method. The density data obtained in CO2-expanded methanol system are slightly higher than the experimental ones, while that achieved from CO2-expanded ethanol system are very close to the experimental results. Simulation results show that the volume of methanol or ethanol solutions can be expanded significantly by CO2. When the mole fraction of CO2 reaches 50%, the volume swelling of the solution is 100%. In addition, the diffusion coefficients of CO2, methanol, ethanol, p-chloronitrobenzene and benzonitrile were simulated, in which p-chloronitrobenzene and benzonitrile are similar to experimental data. Finally, viscosities of two expanded liquids are correlated by their diffusion coefficients, which is in agreement with the calculated results of modified Wilke-Chang equation.

Understanding and Interpreting of the Measured Wave Signals in Impact Dynamics Studies

WANG Li-Li, ZHU Jue, LAI Hua-Wei

2010, 24(4): 279-285 . doi: 10.11858/gywlxb.2010.04.007

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Abstract:
The significance and difficulty of the multi-position measuring were analyzed when understanding and interpreting the wave signals measured in impact dynamic experiments. By combining the Lagrange inverse analysis with the Hopkinson pressure bar technique, a new method was proposed, which substantially resolves the problem of measuring simultaneously both stress wave and particle velocity at a Lagrange position in impact tests. When the particle velocity wave signals at n (n3) Lagrange positions are measured, by using this new method, the dynamic stress-strain curves at n Lagrange positions of specimen can be determined and interpreted. The feasibility and validity of this new method was consistently confirmed by numerical tests for two viscoelastic materials (PMMA and cement mortar).

Cavitation and Wear in the Micro Jewel Nozzle of Ultra-High Pressure Water Jet

YANG Min-Guan, WANG Yu-Li, KANG Can, YU Feng

2010, 24(4): 286-292 . doi: 10.11858/gywlxb.2010.04.008

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Abstract:
In an ultra-high pressure water jet cutting system, the micro jewel nozzle has important influences on the machining efficiency. Cavitation inside the jewel orifice affects the jet formation directly and is a crucial reason for the nozzle wear. By simulating the cavitation flow in the orifice at pressure within 400 MPa, the jet formation process in the nozzle was expounded. The influence of pressure, the aspect ratio and the inlet shape of orifice on the cavitation and jet were also analyzed. At the same time, an experiment was carried out to study the nozzle wear. The results show that the cavitation region in orifice reduces along the nozzle axis with the increasing of the aspect ratio. Moreover, the cavitation region can reach the nozzle outlet when the aspect ratio is smaller than a certain value. At this condition, the jet initial diameter is smaller than the orifice diameter and increases with the increase of pressure. The orifice inlet with a streamline design can effectively restrict the cavitation development. The wear in the jewel orifice inlet due to the cavitation and water erosion is much more severe than in the outlet and is more serious under higher operating pressure. Accordingly, it is useful to select a appropriate aspect ratio for reducing the erosion in the nozzle.

Preparation of Medium-Chain Fatty Acids (MCFA) Nano-Liposome by Means of High Pressure Microfluidization (HPM)

LIU Wei, LIU Wei-Lin, LIU Cheng-Mei, YANG Shui-Bing, ZHENG Hui-Juan, LIU Jian-Hua, WANG Jian-Hong

2010, 24(4): 293-299 . doi: 10.11858/gywlxb.2010.04.009

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Abstract:
Medium-chain fatty acids (MCFA) nano-liposome was prepared and characterized by means of high pressure microfluidization (HPM), sonication and microfiltration, respectively. The average diameter, encapsulated efficiency and stability were investigated after treatment with different pressures and passes number. The results indicated that MCFA liposome prepared by HPM exhibited the smallest average diameter, the largest encapsulated efficiency and the best stability. The smallest average diameter of MCFA liposome could be achieved after a treatment of 6 passes at 120 MPa, with a value of (73.910.2) nm, while the encapsulated efficiency was (52.209.57)%. The largest encapsulated efficiency of (70.6411.25)% and loaded efficiency of (9.420.83)% were obtained when treated 4 passes at 120 MPa, with an average diameter value of (78.921.5) nm. After being treated 4 passes, MCFA liposome exhibited the best stability, with a coefficient value of 0.999 03.695 1.

Effects of High Pressure Heat Treatment on the Thermal Physical Properties of Aluminum Bronze

WANG Hai-Yan, LU Wei, LIU Jian-Hua

2010, 24(4): 300-304 . doi: 10.11858/gywlxb.2010.04.010

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Abstract:
Aluminum bronze was treated at 5 GPa and 750 ℃ for 15 min, after that its electric conductivity, thermal diffusion coefficient, heat capacity, and thermal conductivity between 25 and 600 ℃ were measured. Combining these data with the microstructure images, the effects of high pressure heat treatment on the thermal physical properties of aluminum bronze were investigated. The results showed that high pressure heat treatment can increase the thermal diffusion coefficient and decrease the heat capacity of aluminum bronze. Furthermore, the thermal conductivity of aluminum bronze after high pressure heat treatment increases with increasing temperature until 400 ℃, and then starts to decrease. Analysis shows that this is because the high pressure heat treatment makes the microstructures of aluminum bronze alloy change.

Experimental Study on the Generating Condition of Over-Detonation during the Gaseous DDT

DUAN Ji-Yuan, WANG Jian, HE Zhi

2010, 24(4): 305-310 . doi: 10.11858/gywlxb.2010.04.011

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Abstract:
To verify the three current international views on the generating condition of over-detonation during gaseous deflagration-to-detonation transition (DDT), the DDT process of gaseous hydrogen-oxygen mixture was experimentally studied by using pressure sensors. The whole pressure histories of gaseous DDT from detonation to DDT and then to stable detonation were obtained. The experimental results showed that the generation of DDT requires certain physico-chemical conditions, and for certain initial pressure conditions, the transformation time (or distance) decreases firstly and then increases with increasing concentration of hydrogen. The peak pressure in over-detonation is about 1.5~2 times as much as that in the stable detonation.

A Reaction Rate Model of PBX-9502 Detonation

CHEN Jun, ZENG Dai-Peng, ZHANG Zhen-Yu

2010, 24(4): 311-315 . doi: 10.11858/gywlxb.2010.04.012

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Abstract:
Using Lagrange analysis method for high explosives, a simple detonation reaction rate model of explosive PBX-9502 was proposed. With this model, the longitudinal structure of detonation reaction zone of explosive PBX-9502 was obtained. By Comparing with experimental results and calculated results of ignition and growth model, it shows that current model has good feasibility and validity for the longitudinal structure of detonation reaction zone of PBX-9502.

Experimental Study on Underwater Explosion Performance of Aluminized Explosive

ZHANG Yuan-Ping, CHI Jia-Chun, GONG Yan-Qing, WANG Guang-Jun

2010, 24(4): 316-320 . doi: 10.11858/gywlxb.2010.04.013

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Abstract:
The blast shock wave pressure and the bubble pulse period of RS211, HL-1, HL-2 and TNT explosives were measured, and then the peak pressure, shock wave impulse, shock wave energy and bubble energy were obtained. The experimental results showed that in the studied range, the shock wave energies and the bubble energies of the three aluminized explosives were about 1.20~1.35 and 1.50~2.30 times more than TNT explosive, respectively. The analysis results indicated that the aluminum powder added to explosives can enhance underwater explosion power of the explosives.

2010 Vol. 24, No. 4

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