高压物理学报

Detonation Shock Dynamics Calibration of JB-9014 Explosive at Ambient Temperature

TAN Duo-Wang, FANG Qing, ZHANG Guang-Sheng, HE Zhi

2009, 23(3): 161-166 . doi: 10.11858/gywlxb.2009.03.001

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Abstract:
Detonation shock dynamics (DSD) is an approximation to the reactive Euler equations that allows numerically efficient tracking of curved detonation waves. The DSD parameters are the velocity curvature relation and the boundary angle. A computer code was developed to facilitate the calibration of these parameters for JB-9014 insensitive high explosive using the generalized optics model of DSD. Calibration data were obtained from measurements of the detonation velocities and fronts in JB-9014 rate sticks at ambient temperature, with diameters of 10~30 mm. The steady state detonation velocities and fronts predicted by these DSD parameters are in very good agreement with experiment.

Numerical Simulation of Hypervelocity Launch of Flier Plate with Gradual Change Impedance

CHEN Lang, LIU Qun, LU Jian-Ying, GONG Zi-Zheng, GUO Xin-Wei

2009, 23(3): 167-172 . doi: 10.11858/gywlxb.2009.03.002

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Abstract:
A graded density flier plate with gradual change impedance was designed to launch the secondary flier plate in hypervelocity on a light gas gun. The impact surface of graded-density flier plate was made of magnesium, the base surface was made of tungsten, and the middle part was made of the mixture of magnesium, copper and tungsten. A calculating model of hypervelocity launch was developed. The numerical simulations of hypervelocity launch with graded density flier plate were conducted.The effects of change law of impedance, diameter of secondary flier plate and thickness of buffer on the secondary flier plate velocity were analyzed. The calculated results indicated that the maximum velocity of the secondary flier plate exceeded 16 km/s in the condition of optimizing the change law of impedance of graded density flier plate, diameter of secondary flier plate, and thickness of buffer.

Computational Design of Graded Density Impactors for Shock Loading

BAI Jing-Song, LUO Guo-Qiang, TANG Mi, HU Jian-Bo, DAI Cheng-Da, MA Yun, TAN Hua, WU Qiang

2009, 23(3): 173-180 . doi: 10.11858/gywlxb.2009.03.003

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Abstract:
The method of 1D elastic plastic hydrodynamic calculations, the mixing model of different material constituents, and the shock dynamics code of compressible fluids were verified through the overall comparisons of the calculated results with the experimental data from Lawrence Livermore National Laboratory (LLNL). A Mg-W system prepared for graded density impactor (GDI) for quasi-isentropic compression was proposed by means of numerical simulations. By considering the actual material fabrication, the technical restrictions of minimum thickness of discrete layer, and the limitation of maximum mixing rate of the two individual constituents, a model GDI of a novel Mg-W system was designed to actualize the required loading traces and anchor the structural characteristics of GDI. Numerical calculations show that the loading path and intensity are highly sensitive to the distribution of wave impedance of GDI. The experimental designs and predictions for different complicated loading/unloading processes can be realized through model calculations.

Isothermal Equations of State of Au and Pt at Room Temperature: Implication for Pressure Scales

JIN Ke, WU Qiang, LI Xin-Zhu, CAI Ling-Cang, JING Fu-Qian

2009, 23(3): 181-188 . doi: 10.11858/gywlxb.2009.03.004

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Abstract:
Isothermal equations of state at room temperature of Au, Pt were investigated to the relative volume change of 0.5~0.6. The isothermal bulk modulus B0 K, its first pressure derivative B0 K, and the specific volume v0 K at zero pressure and temperature were derived directly from the experimental shock wave data with a simple method, independent of any assumption on the behavior of Grneisen parameter at high pressures and temperatures. Based on the derived parameters, the isothermal equations of state for the four pressure standard materials were calculated, which show excellent agreements with the available quasi hydrostatic measurements in diamond-anvil-cell experiment. Comparison of the calculated results with the previous theoretical investigations was also performed. The crosscheck on independent data and the excellent agreements with experimental data confirm that the present isothermal equations of state for Au and Pt can be used as high-pressure scales for future static DAC experiments.

Thermodynamic Analysis of Diamond Growth with Catalyst at HPHT

XU Bin, LI Li, TIAN Bin, FAN Xiao-Hong, FENG Li-Ming

2009, 23(3): 189-195 . doi: 10.11858/gywlxb.2009.03.005

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Abstract:
The diamond growth with Fe-based catalyst at high pressure and high temperature (HPHT) was analyzed with the determinant method of G0 in thermodynamics theory, and the changes of volume with temperature and pressure were involved in the calculation. The results show that the Fe3C phases have been formed before diamond nucleation; at the temperature and pressure range of the diamond synthesis with catalyst, the Gibbs free energies of Fe3CC(diamond)+3-Fe and graphitediamond are all negative, but the former's absolute value is much larger than the latter's, which means the former will take place more easily.Therefore, from the viewpoint of thermodynamics the formation of Fe3C reduces the potential energy of the transformation from graphite to diamond, and the diamond crystal growth with Fe based catalyst comes from the decomposition of Fe3C instead of the direct transformation from graphite. Moreover, the p-T (Pressure-Temperature) equilibrium of peq(GPa)=1.036+0.00236T (K) was gained, which was closer to that presented by F.P.Bundy. Thereby the thermodynamic calculation used in this paper is feasible.

Study on Strain Rate Sensitivities of FCC Metals Based on Multi-Scale Analysis

QIN Kun, YANG Li-Ming, HU Shi-Sheng

2009, 23(3): 196-202 . doi: 10.11858/gywlxb.2009.03.006

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Abstract:
Dislocation theory and molecular dynamics simulation were used to investigate the effect of atom properties on the strain-rate sensitivity of FCC metals. A method to analyze such effect is proposed. The stress dependence on dislocation velocity is identified as the key of such study and is obtained via 2-D MD simulations on the motion of an individual dislocation in FCC metals. Combining the simulation results with Orowan's relationship, it is concluded that strain rate sensitivities of FCC metals are mainly dependent on their atomic mass rather than the interatomic potential. The order of strain rate sensitivities of five FCC metals obtained by multi-scale analysis is consistent with the experimental results available.

Study on the Physical Explosion Character and Ejection Effect of the High-Pressurized Hydrogen Transport Device

LI Wei, ZHANG Qi

2009, 23(3): 203-208 . doi: 10.11858/gywlxb.2009.03.007

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Abstract:
High-pressured hydrogen's ejection caused by the structural failure of transport device could result in overpressure and mass fraction within the explosion limits. External flow field characters, hydrogen jet pressure, and mass fraction in the field were numerically simulated by using physical and calculation model in case of external flow field with or without obstacle. Hazardous area after hydrogen explosion and effect of obstacle on preventing hydrogen leakage and diffusion were obtained. The drawn conclusion could be the reference for prevention and treatment of hydrogen explosion accidents.

The High Pressure Structure and Isothermal Equation of State of NiO up to 67 GPa

LIU Lei, LI Xiao-Dong, LI Yan-Chun, TANG Ling-Yun, LIU Jing, BI Yan

2009, 23(3): 209-214 . doi: 10.11858/gywlxb.2009.03.008

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Abstract:
The high-pressure structure and isothermal equation of state of NiO were investigated up to 67 GPa by in situ synchrotron X-ray diffraction in a diamond anvil cell using argon as the pressure medium. No phase transition was found in this pressure range, nor the the pressure coefficient of axial ratio c/a became larger suddenly at about 60 GPa which was predicted by T.Sasaki. Our experiments showed that the distortion of the structure under pressure was slacker than previous results. We fit the data points to the three-order Brich-Murnaghan EOS, which resulted in a bulk modulus of B0=195(4) GPa with its pressure derivative B0=5.3(2).

Numerical and Experimental Study on Explosively Formed Projectile with Fins

LIN Jia-Jian, REN Hui-Qi, SHEN Zhao-Wu

2009, 23(3): 215-222 . doi: 10.11858/gywlxb.2009.03.009

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Abstract:
It is a new method to produce an explosively formed projectile (EFP) with fins by attaching aluminum cover on the liner. Experimental and numerical research were performed using this new method. Furthermore, the mechanism of forming fins was discussed. The new method of forming EFP with fins was simulated by LS-DYNA, and a contrastive analysis was carried out on three typical liners, including big-cone shaped, imperfect-sphere shaped and arccone shaped. The results from 3D numerical simulations and experiments were also analysed. Comparison of results show that three kind of liners could form obvious fins by this new method,and the results of numerical simulations are in agreement with the experiment data. The research provides a new reference method for designing EFP with fins.

Numerical Investigation on the Characteristics of Debris Clouds Produced by Hypervelocity Impact on Pressure Vessels

GAI Fang-Fang, PANG Bao-Jun, GUAN Gong-Shun

2009, 23(3): 223-228 . doi: 10.11858/gywlxb.2009.03.010

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Abstract:
SPH methods in AUTODYN-2D was used to investigate the characteristics of debris clouds propagation inside the gas-filled pressure vessels for hypervelocity impact on the pressure vessels. The effect of equation of state on debris cloud was examined. A better correlation between experimental and numerical results was obtained. The result shows a strong interaction between cloud debris and pressurized gas. The pressurized gas in vessel reduces strongly the radial and axial velocity of the debris cloud. Spike of the debris clouds and shock wave are shown to be important factors governing the damage of pressure vessel.

Effects of Liner Curvature Radius on Formation of Double-Layered Spherical Segment Charge Liner into Tandem Explosively Formed Projectile (EFP)

ZHENG Yu, WANG Xiao-Ming, LI Wen-Bin, LI Wei-Bing

2009, 23(3): 229-235 . doi: 10.11858/gywlxb.2009.03.011

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Abstract:
In order to study the influences of liner curvature radius on the formation of double layer shaped charge liner (DLSCL) into tandem explosively formed projectile (EFP), the numerical simulations on the mechanical phenomenon of DLSCL forming into tandem EFP were carried out by using two-dimensional finite element dynamic code AUTODYN. The formation mechanisms of DLSCL and the influence of curvature radius on the formation of DLSCL were studied. After tests on the formation of DLSCL were performed, the X-ray pictures were obtained. Comparisons between experimental results and numerical simulation results show a good agreement. It can be concluded from the results that DLSCL can form tandem EFP and the liner curvature radius has great influence on the velocity, shape and l/D radius of tandem EFP.

Study on the Influence of Magnetism of Synthetic Diamond Single Crystal on Their Mechanical Performances

LUO Zhong-Ping, YAO Ya-Lin, XIA Zhi-Hua, HE Bing

2009, 23(3): 236-240 . doi: 10.11858/gywlxb.2009.03.012

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Abstract:
Static-pressure strength, toughness index (IT) and thermal-toughness index(ITT) of each sample were analyzed on the basis of the experimental studies on the magnetic separation of diamond single crystal. The results show that the magnetism of synthetic diamond single crystal has an obvious influence on the mechanical performance. With the increase of magnetism, synthetic diamond single crystal becomes darker and darker in appearance color, and have more bubbles, impurities and defects inside the particles. Furthermore, their surface fineness observed under the microscope becomes worse. Meanwhile, the static-pressure strength, the IT under the normal temperature and ITT become lower and lower. The influence of magnetism on the static-pressure strength and the IT is slight, however, the influence on ITT is serious.

2009 Vol. 23, No. 3

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