高压物理学报

Numerical Simulations of Anti-Penetration of Confined Ceramic Targets by SPH/FEM Coupling Method

BIAN Liang, WANG Xiao-Jun, ZHANG Jie

2010, 24(3): 161-167 . doi: 10.11858/gywlxb.2010.03.001

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Abstract:
Numerical simulations of tungsten long rod penetrating into confined ceramic target was carried out by inserting the constitutive models of ceramic and metal in the SPH/FEM coupling method. The penetration pattern was reproduced and the property of anti-penetration of ceramic targets was discussed. The computational results for different impact velocities were compared with the experiments. The penetration depths of computations are in good agreement with the experiments and so that the coupling method is validated.

Numerical Study on Bubble Motion near the Wall

LI Jian, RONG Ji-Li

2010, 24(3): 168-174 . doi: 10.11858/gywlxb.2010.03.002

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Abstract:
The volume-acceleration model was introduced to determine the initial condition for bubble motion of underwater explosion. From the basic phenomenon of the interaction between bubble and rigid wall, the dynamic behavior of bubble near wall, including ring rebound of bubble and jet flow, was simulated and analyzed using MSC.DYTRAN finite element analysis software with developed subroutine defining the initial value and boundary condition of fluid field. The computational result of the behavior of bubble was compared with the experimental result. The comparison of results show that the former is consistent with the latter. The dynamic behavior of bubble near rigid wall and velocity of jet flow were studied systematically. It is summarized that the dynamic behavior near bottom rigid wall is close relevant to depth and distance. The research is of value to relevant theory modelings and engineering calculations.

Numerical Computation and Analysis on Anti-Penetration Capability of Rock, Concrete and Soil

WANG Zheng, LOU Jian-Feng, YONG Heng, LIANG Long-He

2010, 24(3): 175-180 . doi: 10.11858/gywlxb.2010.03.003

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Abstract:
Using LS-DYNA3D to compute the problem of projectile penetrating into rock, concrete and soil targets, we analyze anti-penetration capability of these three materials. We choose HJC concrete constitutive model for target materials in numerical computations. Under the lower and intermediate impact velocities such as from 200 m/s to 900 m/s, rock is evidently more stronger than concrete for anti-penetration. The peak value of deceleration of the projectile penetration into rock is as twice as into concrete. And it is 6 times into concrete than soil. The energy of the projectile dissipated rapidly when the projectile has greater peak value of the deceleration and the steady penetration process is shorter. When the impact velocity is above 1.5 km/s, the effect of material strength on depth or diameter of the penetration becomes gradually decreased. For rock, concrete and soil targets, with gradual decrease of strength, density and compressibility, the depth or diameter of the penetration slowly increased. The maximum of penetration depth increases by 41%~62%, and that of penetration diameter increases by 16%~25%.

A Calculation Study on the Effect of the Heat Conduction on the Safety of the Solid-Liquid Mixed Charge

DUAN Yun, ZHANG Qi, XIANG Cong, PANG Lei, LI Wei, HE Ning

2010, 24(3): 181-186 . doi: 10.11858/gywlxb.2010.03.004

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Abstract:
The physical parameter of the solid-liquid mixed charge is one of the main factors of the charge safety. Several typical ratios of composite charges were calculated by applying the calculation method of composite explosive physical parameter, and the different physical parameters of charge were numerically simulated based on the energy conservation equation. According to calculations, the temperature response with the different physical parameters has obvious differences at the same temperature load. Further analysis showed that the influence of different parameters of solid-liquid mixed charge on safety should be considered enough in order to truly explain the process of hot spot energy evolution, which provided theoretical basis for anglicizing solid-liquid mixed charge safety.

Research on EOS at Extremely High Pressure Using a Three-stage Gas Gun Hypervelocity Launcher Techniques

WANG Qing-Song, WANG Xiang, DAI Cheng-Da, BO Jin-Song, TAN Hua, HU Jian-Bo

2010, 24(3): 187-191 . doi: 10.11858/gywlxb.2010.03.005

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Abstract:
A new material system for fabricating graded-density impactors was designed based on the standard design principle of graded wave-impedance materials and numerical simulation method for hypervelocity launching. The secondary Ta flyer-plate was accelerated over 9 km/s by a three-stage gun and used to study equation of state (EOS) of Ta at extremely high pressure. The particle velocity and shock velocity were measured simutaneously in EOS experiments. The obtained Hugoniot data were well consistent with the corresponding experimental data published previously. It shows that the three-stage gas gun hypervelocity launcher technique is suitable to research on EOS at extremely high pressure.

Study on the Damping Properties of Nitrile Rubber under Pressure by Modified WLF Equation

LIU Hai-Lu, ZHAO Xiu-Ying, SONG Zhen-Yu, WU Si-Zhu, ZHANG Li-Qun

2010, 24(3): 192-200 . doi: 10.11858/gywlxb.2010.03.006

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Abstract:
According to time-temperature superposition, it is shown that at certain frequency, the higher temperature the lower modulus. At a certain temperature, the lower frequency the lower modulus, which indicates that elevated temperature and reduced frequency has the equivalent effects. Based on this, the mechanical properties of rubber materials at wide frequency can be obtained by the data in different temperatures. For studying the basic theory of the damping properties of rubber, a modified Williams-Lendel-Ferry (WLF) equation under pressure has been proposed in this work. According to the loss factor tan from DMTA experiments, the shift factors under different pressures might be calculated. Then, the mast curve of loss factor versus frequency could be plotted, in which the range of frequency spanned about ten orders of magnitude. The result showed that the peak of tan appeared below the reference temperature. With the increasing pressure, the glass transition temperature moved towards higher frequency, and enhenced by 1.5 orders of magnitude. This method offered the theoretical basis to quantitatively characterize the damping properties of rubber materials.

Experimental Study on Sound-Speed of Overdriven-Detonation Product and the Thermodynamic CJ State

CHEN Jun, ZENG Dai-Peng, TAN Duo-Wang, WANG Rong-Bo

2010, 24(3): 201-205 . doi: 10.11858/gywlxb.2010.03.007

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Abstract:
Sound-speed data of overdriven-detonation product are fundamental to model EOS, and CJ data are important to manifest detonation properties of explosive. Using rarefaction wave chasing technique, the sound-speeds in overdriven detonation product at different pressures are measured with optic-fiber probes, which are used to monitor the process of rarefaction wave chasing shock wave in the trichloromethane behind explosive. The thermodynamic CJ state is determined by the intersection point of the steady detonation velocity and the sound-speed line Lc. The thermodynamic CJ pressure is evaluated 28.8 GPa by this method. There is only a slight difference of 0.3 GPa between the thermodynamic CJ pressure and the ordinarily measured value 28.5 GPa. The method to measure velocity and planarity of detonation driving flyer with optic-fiber probes is also introduced. The velocity and planarity of the flyer are obtained using this method, which possesses good precision of measurement.

Ultrasonic Velocity Measurement and Pressure Calibration of Single Crystal MgO under Hydrostatic Pressure Load

ZHANG Yi, BI Yan, CAI Ling-Cang, XU Ji-An

2010, 24(3): 206-212 . doi: 10.11858/gywlxb.2010.03.008

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Abstract:
By measuring the sound velocity of single crystal MgO at high pressures and using the high pressure Brillouin scattering data, the pressures point by point (the oil-pressure points range from 15 MPa to 51 MPa with step of 2 MPa) in a wide pressure range in the cubic pressure cell under hydrostatic loading environment were calibrated. Furthermore, a novel pressure calibration technique for the large volume pressure cell was established. This new calibration method is more reliable than the traditional one which only depends on 2 or 3 phase transition points. As an example, the measured sound velocity in LY12 aluminum under this hydrostatic loading is in good agreement with published literature data, which further confirms that the novel pressure calibration method is feasible and reliable. Comparing the pressure in the high-pressure cell based on the solid-liquid hybrid assembly with that based on the all-solid one, it was found that the cell-pressure in the former is systematically lower. The analysis suggested that this phenomenon is due to the shear effect in all-solid assembly which makes the pressure scale much higher.

Study on Phase Transition and Spallation of Pure Iron under Given Pressure

CHEN Yong-Tao, LI Qing-Zhong, TANG Xiao-Jun, LU Qiu-Hong

2010, 24(3): 213-218 . doi: 10.11858/gywlxb.2010.03.009

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Abstract:
By means of VISAR and metallography, phase transition and spalling behavior in pure iron under the given pressure were studied through symmetric and same thickness flyer/sample experiments. In combination with the experimental results from references, and the loading and unloading histories and phase structure in iron sample are obtained. The given pressure is beyond the phase transition pressure of 13 GPa about 2~5 GPa and 10 GPa, respectively. Abnormal multiple spalling behavior happens in the pure iron sample as the impact pressure beyond the phase transition pressure of 13 GPa about 2 GPa. From the interaction process of stress waves, the contacting mechanism among the spalling behavior, the phase transition and the reverse phase transition have been studied.

Difference Scheme for Modifying the Experimental Temperature in High-Temperature SHPB Test

SHANG Bing, WANG Tong-Tong, ZHUANG Zhuo

2010, 24(3): 219-224 . doi: 10.11858/gywlxb.2010.03.010

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Abstract:
The governing equations of the waves transmitting in the waveguide bar with temperature gradient were dispersed using difference scheme, and then the strain information of any point in the bar was calculated through one point's strain information using computer procedure. One experiment was designed to prove this method. This method can be used in high-temperature split Hopkinson press bar (SHPB) experiment: the guide bar contacts the specimen in high-temperature area. The strain information of this area is calculated through the strain information of the room-temperature point, where a stain gauge is glued. Then the high temperature stress-strain curve of the specimen can be obtained through the strain information of the points, which connect the specimen and the waveguide bar.

First-Principles Study of Structural Stabilities, Electronic and Optical Properties of CaF2 under High Pressure

YANG Xiao-Cui, ZHAO Yu-Wei, GAO Zhong-Ming, LIU Xin, ZHANG Li-Xin, WANG Xiao-Ming, HAO Ai-Min

2010, 24(3): 225-230 . doi: 10.11858/gywlxb.2010.03.011

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Abstract:
An investigation on the structural stabilities and electronic properties of CaF2 under high pressure was conducted using first-principle calculation based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. Our results demonstrate that the sequence of the pressure-induced phase transition of CaF2 is the fluorite structure (Fm3m) to the PbCl2-type structure (Pnma), and to the Ni2In-type phase (P63/mmc). The energy gap increases with pressure in the Fm3m and Pnma phases, then begins to decrease in the P63/mmc phase. The band gap overlap metallization does not occur up to 210 GPa. It is predicted that the metallization pressure of CaF2 should be over 300 GPa. The pressure effect on the optical properties is discussed.

The Coloration Process Study on the Synthesis of cBN by hBN-LiH/hBN-Li3N-B System

JI Xiao-Rui, YANG Da-Peng, YANG Xiao-Hong, ZHANG Tie-Chen

2010, 24(3): 231-236 . doi: 10.11858/gywlxb.2010.03.012

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Abstract:
Using hBN-LiH or hBN-Li3N-B as starting materials, we synthesied black cBN crystals under high pressure and high temperature. The results of Raman spectrum show that the reason why cBN crystals become black is that the redundant B atoms get into them. The cBN crystal is synthesized in hBN-Li3N-B system, and then we observe a trigonal shadow is formed clearly. This phenomenon indicates that there are more B atoms from center to apex in cBN crystal, and the B atoms content gradually decrease from center to edge. However, the color of cBN crystal which is synthesized in hBN-LiH system was from transparent black to opaque black directly, and the trigonal shadow does not be formed. This phenomenon indicates that the B atoms as impurity diffuse equably in cBN crystals. The two circumstances illustrate that as an impurity atom, B has two kinds of distributions when it enter into cBN crystal: one is centeral symmetric distribution, the other is uniform distribution. In this paper, we analyze the reason why cBN crystals have different phenomenon above according to its growth environment and its ability of excluding impurity.

The High-Pressure Synthesis of Cubic Boron Nitride Crystals with Various Shapes in Li-Based System

YANG Da-Peng, JI Xiao-Rui, LI Ying-Ai, ZHANG Tie-Chen

2010, 24(3): 237-240 . doi: 10.11858/gywlxb.2010.03.013

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Abstract:
By high pressure and high temperature (HPHT) method, we used hexagonal boron nitride (hBN) as raw materials, Li3N, Li3N+LiH, LiH, LiH+LiNH2, Li3N+LiNH2 as catalyst, and successfully prepared thick plate, spherical, octahedron or hex-octahedron, flat cone and flaky hexagon morphology cubic boron nitride (cBN) crystals with relevant growth conditions. It was summarized that various Li-based catalysts/additives had distinct effects on the cBN crystal morphologies synthesized.

2010 Vol. 24, No. 3

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