高压物理学报

Discussion on the Spallation Behavior Resolved by Free-Surface Velocity Profile

HE Hong-Liang

2009, 23(1): 1-8 . doi: 10.11858/gywlxb.2009.01.001

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Abstract:
A few questions on the spallation behavior resolved by the measurement of free-surface velocity profile have been discussed. Firstly, the way from the measured free-surface velocity profile to infer the dynamic damage behavior of the target is an Inverse Problem and the theoretical model and simulation parameters determined by such a solution maybe not represent the real physical nature of spall fracture inside the target. Secondly, how to calculate the spall strength? Due to the attenuation effect of micro-voids or damage on the wave propagation, the spall strength computed from the free-surface velocity profile is apparently lower than the tensile strength suffered by the shocked material. Thirdly, limitation of the traditional single-point measurement on the free-surface velocity profile is briefly reviewed. Given that the shocked target is inhomogeneous, the amplitude of the measured velocity profile is varied from point to point. According to these discussions, future research suggestions have been proposed in order to clearly understand the spallation behavior.

p-T Phase Diagram of Coesite Synthesized from Nanometer SiO2 Powder

ZHANG Guang-Qiang, XU Yue, SUN Jing-Shu, XU Da-Peng, WANG De-Yong, ZHANG Lin, XUE Yan-Feng, SONG Geng-Xin, LIU Xiao-Mei, SU Wen-Hui

2009, 23(1): 9-16 . doi: 10.11858/gywlxb.2009.01.002

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Abstract:
With nanometer SiO2 powder as initial material, the p-T phase diagram (2.0～4.2 GPa, 150～1200 ℃) of -quartz and coesite was obtained by a series of experiments under high pressure and high temperature, and the slope of the boundary in the phase diagram is negative below 650 ℃ and is basically horizontal above 650 ℃. By means of transmission electron microscopy (TEM), X-ray diffractometer (XRD), Raman spectrometry (Raman), fourier transform infrared spectrometry (FT-IR), thermogravimetry and differential thermal analysis measurements (TG-DTA), the phenomenon that the water in the nanometer SiO2 can decrease the synthesis temperature of coesite and quicken reaction velocity was found, and the nanometer SiO2 can be crystallized into coesite under 4.2 GPa and 190 ℃, which is much lower than the synthesis temperatures of coesite that have been reported. Under ambient pressure, the coesite synthesized from nanometer SiO2 can stably exist at 800 ℃ and is transformed into cristobalite above 1 000 ℃.

Stress Wave Analysis of Abnormal Spall in Metal Target Relating to Phase Transition

XU Wei-Wei, TANG Zhi-Ping, ZHANG Xing-Hua

2009, 23(1): 17-23 . doi: 10.11858/gywlxb.2009.01.003

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Abstract:
With a simple multi-phase mixture model proposed by TANG Zhi-Ping et al earlier, we have studied the propagation of the elastic and plastic waves as well as the macroscopic phase boundary in the targets by characteristic line method, and the mechanism of the abnormal spall phenomena mentioned above are explained theoretically. The investigation shows that (reverse) phase transition can strongly affect the profiles of the shock waves, leading to the so called three-wave structure and the release shock waves, and the static phase boundary may appear somewhere in the plates. The more complex interactions of the waves in the plates may cause some special spall phenomena.

The Effect of Thickness of Diamond Layer on Residual Stresses in Polycrystalline Diamond Compact

XU Guo-Ping, CHEN Qi-Wu, YIN Zhi-Min, XU Gen

2009, 23(1): 24-30 . doi: 10.11858/gywlxb.2009.01.004

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Abstract:
The effect of thickness of diamond layer on the residual stresses in polycrystalline diamond compact (PDC) was investigated through XRD measurement and finite element analysis (FEA) method. The results show that as the thickness of the diamond layer increases from 0.5 mm to 2.0 mm, the residual compressive stress on the surface of the diamond layer at the center decreases from 1 800 MPa to about 700 MPa, but the stress on the edge changes gradually from compression into tension, and the tensile stress region on the edge of the diamond layer becomes wider. At the same time, the vertical tensile stress on outer edge of the cutter and shear stress near the interface increase significantly. These two stresses are the main factors that cause cracks near the interface of the PDC with a thicker diamond layer. Based on the measured results, the equations of the stresses at the centers and on the edges of the PDC as a function of the thicknesses of diamond layers have been deduced.

Properties of Sr8CaRe3Cu4O24 with Perovskite Structure under Pressure

LI Sheng-Ai, WANG Wei, LIU Su, WAN Xian-Gang

2009, 23(1): 31-36 . doi: 10.11858/gywlxb.2009.01.005

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Abstract:
We have investigated the mechanism and electromagnetic properties of new compound Sr8CaRe3Cu4O24 under the hydrostatic pressure by the mean of local spin density approximation and mean field theory. Then we have discussed the internal mechanisms of the high magnetic transition temperature (TC) and the regularity of TC with the variety of hydrostatic pressure of this compound. Our calculation shows that the value of the magnetic transition temperature increases and the width of gap around Fermi level in DOS of this material descreases with the increasing of pressure. Our results show that a simple Heisenberg model and the theory of orbital order is suitable for this compound.

Micro-Analysis of the Void Growth of Aluminum under Shock Loading

CUI Xin-Lin, LI Ying-Jun, ZHU Wen-Jun, QI Mei-Lan, WANG Hai-Yan, HE Hong-Liang, LIU Jian-Jun

2009, 23(1): 37-41 . doi: 10.11858/gywlxb.2009.01.006

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Abstract:
The distribution of micro-voids in aluminum under shock loading has been investigated by means of SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope). Results show that plenty of nano-voids have been produced in the shocked aluminum. Most of the void sizes are hundred nanometers. They distribute inhomogeneity, and connect together as a band. Further analysis of the micro-voids indicate that a lot of dislocations are generated around the voids, and the emission direction is in the {111} planes, which are the closed-packed planes of the face-centered cubic metal. The emission direction of the dislocations is excellently agreement with the molecular dynamics (MD) simulation.

Synthesis and Electric Transport Properties of Na-Filled CoSb3 at High-Pressure

DONG Nan, JIA Xiao-Peng, SU Tai-Chao, JIANG Yi-Ping, GUO Jian-Gang, DENG Le, MA Hong-An

2009, 23(1): 42-45 . doi: 10.11858/gywlxb.2009.01.007

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Abstract:
Skutterudite compounds Na-filled CoSb3 were successfully synthesized at high-pressure using powders of Co, NaN3 and Sb as starting materials. The X-ray diffraction (XRD) results indicate that all samples have the single phase CoSb3. No secondary phase is found when Na content wNa80%. The composition-dependent electric transport properties of Na-filled CoSb3 have been studied at room temperature. The Seebeck coefficient decreases with increasing Na content. The electrical resistivity decreases with increasing Na content. In this study, the obtained maximum power factor reaches 8.72 Wcm-1K-2 when Na content is 40%.

Constitutive Model of Pure Zirconium under High Temperature and High Strain Rate

XIAO Da-Wu, LI Ying-Lei, HU Shi-Sheng

2009, 23(1): 46-50 . doi: 10.11858/gywlxb.2009.01.008

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Abstract:
The thermo-mechanical response of zirconium has been investigated under temperature ranging from normal temperature to 1 073 K and strain rate from 4.110－4 s－1 to 2.8103 s－1. Results show that the flow stress and strain hardening rate of zirconium are very sensitive to the changes of temperature and strain rate. The flow stress and strain hardening rate increase with the increase of strain rate, and decrease with the increase of temperature. Based on the concept of dislocation kinematics, a physically based constitutive model is developed, and the model is modified by taking into account of the effect of developing twins during deformation. The modified model could be used to predict the flow stress of zirconium over a wide range of temperature and strain rates. The experimental results are in good agreement with the predictions.

Calculation of the Angle Deformation in Explosive Welding Based on the Ideal Fluid Model of Symmetrical Colliding

ZHANG Xiao-Li, WANG Jin-Xiang, LI Xiao-Jie, LIU Jia-Cong

2009, 23(1): 51-58 . doi: 10.11858/gywlxb.2009.01.009

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Abstract:
An ideal fluid model of symmetrical colliding was taken to analyze the physical deformation on streamlines in explosive welding, and a theoretical formula of the angle deformation was deduced. The language of Visual C++ was adopted to make a program to calculate the angle deformation numerically. The size of the angle deformation is obtained as well as the change law of it. The result shows that, near the stagnation point, the angle deformation is always increasing along the coming fluid to the outing fluid, and the changing rate near the stagnation point is maximum. Along the outing fluid the angle deformation increases with the augment of the velocity at given impact angle, and decreases with the increasing of the impact angle at the given velocity. The contrast and verification of the calculated results are in agreement with the theory and the experiment of others' indirectly. Based on it, the influence on the formation of the wavy interface in explosive welding by the strain rate field near the stagnation point was discussed.

Models for Momentum of Debris Cloud and Ejecta Produced by Hypervelocity Impacts of Aluminum Spheres with Thin Aluminum Sheets

CHI Run-Qiang, GUAN Gong-Shun, PANG Bao-Jun, ZHANG Wei, TANG Qi

2009, 23(1): 59-64 . doi: 10.11858/gywlxb.2009.01.010

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Abstract:
Debris clouds produced by the normal impact of an aluminum alloy sphere with an aluminum alloy sheet can scatter flying downrange, as well as an ejecta veil is produced at the same time. The momentum of debris clouds and ejecta are necessary to create the debris clouds and ejecta theoretical models. 54 numerical simulations were performed using the SPH (smoothed particle hydrodynamics) technique in AUTODYN-2D, in which 6.35 mm diameter of 1100-O aluminum spheres impacted six thicknesses of 6061-T6 aluminum sheets at velocities ranging from 1.0 km/s to 5.0 km/s. Using the data from the numerical simulations, two respective regression models are developed for characterizing the momentum of debris clouds and ejecta produced by impacts with 1.0 km/sv5.0 km/s, 0.5 mm3.0 mm. In the two models, the independent variables are the impact velocity, v, and the thickness of the sphere, t, while the dependent variables are the momentum ratios (ratios of debris clouds momentum and ejecta momentum to sphere momentum). The effects of v and on the momentum of debris clouds and ejecta are investigated. Seven additional numerical simulations in the same way as above were carried out and values obtained are compared with the experimental data of NASA to evaluate the performance of the simulation.

Numerical Study on Penetration of Semi-Infinite Aluminum Alloy Targets by Tungsten Alloy Rod

LOU Jian-Feng, WANG Zheng, HONG Tao, ZHU Jian-Shi

2009, 23(1): 65-70 . doi: 10.11858/gywlxb.2009.01.011

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Abstract:
Used the LS-DYNA procedure to set up numerical model on penetration of semi-infinite aluminum alloy targets by tungsten alloy rod over a wide velocity range has been discussed. The mass of penetrator is about 46.7 g with a length over diameter ratio of 15. Based on experiment results from the reference, distinguished analytical models were used individually in case of relative high impact velocity and low one, and parameters of constitutive equations including failure parameters for aluminum alloy 7020 and tungsten alloy were calibrated. Penetration experiments within the impact velocity from 200 m/s to 2500 m/s were numerically simulated, and the numerical results were in good agreement with experiments. In addition, the effect of projectile nose to penetration was investigated, and the relationship between length over diameter ratio and penetration was obtained. In the case of high impact velocity, the nose shape has little effect on penetration. Numerical results indicate that dimensionless penetration decreases as length over diameter ratio increases.

Synchrotron Radiation X-Ray Diffraction of Carbon Nitride under High Pressure

LI Xue-Fei, ZHANG Jian, LIU Wei, MA Hong-An, CUI Qi-Liang, ZOU Guang-Tian

2009, 23(1): 71-74 . doi: 10.11858/gywlxb.2009.01.012

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Abstract:
In situ synchrotron radiation X-ray diffaction studies under high pressures and room temperature on the CN samples produced under 1 200 ℃ and 6.0 GPa have been carried out via the diamond anvil cell (DAC) technique. The results show that at room temperature and up to 44 GPa, both graphitic C3N4 and the unidentified orthogonal CN phase are stable.p-V data of both the two materials have been fitted to Murnaghan equation of state by using the least square method.

Research on Behavior of Composite Material Projectile Penetrate Concrete Target

ZHONG Wei-Zhou, SONG Shun-Cheng, ZHANG Fang-Ju, ZHANG Qing-Ping, HUANG Xi-Cheng, LI Si-Zhong, LU Yong-Gang

2009, 23(1): 75-80 . doi: 10.11858/gywlxb.2009.01.013

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Abstract:
Projectiles made of carbon fiber composite material shell and metal warhead have penetrated concrete targets at the speed of 336, 447 and 517 m/s, respectively. The angles are 0 and 30 between the perpendicular of target surface and projectile axes. The thickness of concrete target is 200 mm and its compression strength is 30 MPa. The experimental results indicate that the strength of composite material structure is strong. The composite projectile can go through the concrete target without fiber segregation and breakage. Given the same size of the projectile, the mass percent of filler is 18.5% in the composite material projectile, which is about twice of the metal (density of metal is takes as 7.8 g/cm3) projectile. Comparing to metal projectile, little density, high strength composite material projectile can lessen weight, improve charge-weight ratio of powder and enhance specific damage powder.

2009 Vol. 23, No. 1

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