高压物理学报

Several Influential Factors on Numerical Simulated Results for the X-Ray Thermal Shock Waves

ZHANG Ruo-Qi, TANG Wen-Hui, ZHAO Guo-Min

1998, 12(3): 161-167 . doi: 10.11858/gywlxb.1998.03.001

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Abstract:
Taking account of Compton scattering photons transport behavior or not, using what model to describe melting, vaporization and strain rate effect, how to determine free surface difference schemes, mesh size and time step, all of these factors will generate important effect on numerical simulated result for X-ray shock waves. According to the data calculated by thermal shock wave propagation code, the effect of several factors above mentioned are analyzed in this paper. Our results indicate that, for soft spectrum and large fluency of X-ray source, the equations of state, free surface difference schemes, mesh size and time step will influence significantly on calculated results. When X-ray energy spectrum turns to strong, the Compton scattering can cause more influence. At low stress, the constitutive equations and yield strength will control thermal shock wave attenuation along the material thickness basically.

Study on Synthesizing Flaky cBN Crystals and Its Conduction Property

ZHANG Tie-Chen, WANG Ming-Guang, GUO Wei-Li, LIU Jian-Ting, GAO Chun-Xiao, ZOU Guang-Tian

1998, 12(3): 168-173 . doi: 10.11858/gywlxb.1998.03.002

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Abstract:
We synthesized flaky cBN crystals that the grade of which is about 300~500 m by method of controlling temperature and pressure gradient in synthesized cell. The cBN crystal material with semiconductor characteristic is obtained by mixing method in material and in the high temperature-vacuum diffusion process. At the same time its V-A characteristic curves were tested.

A One Dimensional Explicit Magnetic Hydro-Dynamic Model of Electro-Magnetic Implosion

LIAO Hai-Dong, HU Xi-Jing, YANG Li-Bing, FENG Shu-Ping

1998, 12(3): 174-180 . doi: 10.11858/gywlxb.1998.03.003

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Abstract:
In this paper, a one dimensional explicit model for solid density electromagnetic implosion is provided. Its solutions are in agreement with the results of the one dimensional implicit model.

Study on High Pressure-Induced Structural Transformation of KNb0.77Al0.23O2.77

LI Guang-Du, LI Li-Ping, WANG Min-Qiang, FENG Shou-Hua, CUI Qi-Liang, YAO Xi

1998, 12(3): 181-189 . doi: 10.11858/gywlxb.1998.03.004

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Abstract:
Various products including cubic KNb0.77Al0.23O2.77 and orthorhombic KNbO3 were hydrothermally synthesized. Structural evolution behaviors of the cubic were examined by means of X-ray diffraction (XRD), differential scanning calorimeter (DSC), high pressure Raman spectroscopy, Infrared (IR), and X-ray photoelectron spectroscopy (XPS). Another new phase appeared during the pressure-induced structural transition of the cubic at a pressure of 4.49 GPa. High temperature and high pressure treatments resulted in a third new phase by adjusting effectively the number of electrons flowing between Nb-O as well as hybridization between p electrons of oxygen and d electrons of Nb ions. During the structural transition, the reduction of Nb (Ⅴ) to Nb (Ⅳ) occurred as well as oxygen vacncies in the cubic lattice. The stabilization and transition mechanisms are discussed.

A Set of Experimental Device of Preheating Materials under Shock Compression and Shock Response of Stainless Steel with High Temperature

GU Zhuo-Wei, JIN Xiao-Gang, ZHANG Qing-Fu, SUN Yue

1998, 12(3): 190-198 . doi: 10.11858/gywlxb.1998.03.005

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Abstract:
A set of material preheating system used in the light gas gun shock compressed experiment has been built up. The principle of structure and operation of the system are introduced. Using this system, the shock response, including spall strength, Hugoniot elastic limit and unloading sound velocity, of HR-2 stainless steel with initial temperature range 300~980 K under fixed shock amplitude of 8 GPa is obtained, and their variations with temperature are deduced in this paper.

Dielectric Breakdown of Ferroelectric Ceramics PZT-95/5 under Shock Compression

WEN Dian-Ying, LIN Qi-Wen

1998, 12(3): 199-206 . doi: 10.11858/gywlxb.1998.03.006

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Abstract:
Shock loading technique is used to study dielectric breakdown of the PZT-95/5 ferroelectric ceramics caused by compress of shock waves on the direction vertical to the remnant polarization vector Pr in this paper. The character parameters of the dynamic dielectric breakdown with shock wave loading are obtained by means of both experiment and numerical simulation. Finally the breakdown mechanism of the material is discussed.

Effect of the Crystal Size Distribution on the Compression Wave Velocity in Rocks at High Pressure: A Preliminary Result

ZHOU Wen-Ge, XIE Hong-Sen, ZHAO Zhi-Dan, LI Yu-Wen, GUO Jie, XU Zu-Ming, XU Ji-An

1998, 12(3): 207-211 . doi: 10.11858/gywlxb.1998.03.007

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Abstract:
The olivine crystal size distribution and compression wave velocity of trachybasalt from the Qinling-Dabie orogenic belt are measured. The samples are divided into two groups. Although the samples of each groups show similar chemical composition, mineral assemblage and mineral orientation, their olivine crystal size distributions are different. However, the compression wave velocities of trachybasalt at high pressure are similar. Based on the experiment data, it is believed that if 94% minerals in a rock is less than 0.54 mm in diameter, the crystal size distribution has no effect on the compression wave velocity measured by used the lead zirconate titanate transducer (PZT) with the resonant frequency of 1 MHz. Therefore, the compression wave velocity in rock measured at laboratory can be compared with the results gained by the seismic method (such as seismic refraction survey and seismic reflection survey).

Synthetic SiO2 Glass at 2.0~5.5 GPa

DING Dong-Ye, XIE Hong-Sen, SU Gen-Li, ZHANG Yue-Ming, GUO Jie, JIANG Da-Yong, XU Zu-Ming

1998, 12(3): 212-217 . doi: 10.11858/gywlxb.1998.03.008

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Abstract:
A series of SiO2 glasses are synthesized at 355～445 ℃ and 2.0～5.5 GPa, making use of silica (99.99% purity). The infrared spectra of these SiO2 glasses are similar to that of densified SiO2 glass. The relations between natural logarithm of pressure and index of SiO2 glass or densified SiO2 glass are linear. These SiO2 glasses contain a little water which exists in the form of OH- ion. It is possible that a little water results in amorphization of silica.

Rigid Plastic Deformation of a Sphere Driven by an Explosive

TAN Duo-Wang, SUN Cheng-Wei

1998, 12(3): 218-222 . doi: 10.11858/gywlxb.1998.03.009

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Abstract:
A method of calculating the deformation of a sphere as a result of divergent or convergent detonation of an explosive is presented. This method bases on the conservation of mass and momentum, and assumes the sphere material is incompressible and rigid plastic. The accelerated movement of a sphere calculated with this method is in good agreement with the experiment and the numerical result performed with the finite element hydrocode DYNA.

Electrical Properties and Phase Transitions in P(VDF-TrFE) (80/20 mol%) at High Pressure Using a DAC

BAO Zhong-Xing, Pinto N J, Schmidt V H, Tu C S

1998, 12(3): 223-227 . doi: 10.11858/gywlxb.1998.03.010

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Abstract:
Capacitance-pressure (C-p) and resistance-pressure (R-p) relationships for the ferroelectric eopolymer poly (vinylidenefluoride/trifluoroethylene), P(VDF-TrFE) (80/20 mol%) at room temperature up to 14 GPa were investigated in a diamond anvil cell (DAC) using capacitance and resistance measurements. These results indicate that P(VDF-TrFE) with 80 mol% VDF undergoes two phase transitions below 14 GPa. The first apparent transition occurs near 1.1 GPa and the second apparent transition which is more sharply defined occur in the 5 to 6 GPa range.

Free-Lagrangian Method for Simulating Shock Wave Propagation

YUE Zong-Wu, TANG Wen-Hui

1998, 12(3): 228-232 . doi: 10.11858/gywlxb.1998.03.011

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Abstract:
In this paper, a hydrodynamic code is written according to the free-Lagrangian method. Both examples of the shock tube and impact of flyer on target are simulated by this code. The results are in good accord with that obtained by traditional Lagrangian code.

Pressure-Induced Structure Phase Transitions of Sr2Bi4Ti5O18

HAN Jie, ZOU Guang-Tian, CUI Tian, LIU Bing-Bing, PAN Yao-Wu, GAO Chun-Xiao, YANG Hai-Bin

1998, 12(3): 233-235 . doi: 10.11858/gywlxb.1998.03.012

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Abstract:
The in situ high pressure Raman spectra and the pressure-induced structure phase transitions of layered ferroelectrics Sr2Bi4Ti5O18 have been studied in the range of 0~27 GPa with diamond anvil cell (DAC), using methanol-ethanol (4:1) mixture as transmission medium. We assigned the internal modes of Sr2Bi4Ti5O18 according to internal mode approach. It is found Sr2Bi4Ti5O18 experienced a structure phase transition at 8.31 GPa. Over 23.13 GPa, Sr2Bi4Ti5O18 displayed a clear indication of amorphous phase transition.

A Simple Method for Manganin Piezoresistance Measurement

WANG Xiang, WANG Yuan-Jun, FU Qiu-Wei, WANG Wei

1998, 12(3): 236-240 . doi: 10.11858/gywlxb.1998.03.013

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Abstract:
A method for manganin piezoresistance measurement that uses a D. C. power supply is described. This technique is very simple and easy to match. Compared with the conventional technique which uses pulse power supply, it not only omits the trigger system, but also can reduce the electromagnetic disturbance which is caused by the magnetic field derived from the current traversing in the gauge, because the current flowing over the gauge is very weak (about 20 mA). Furthermore, the technique is also a low cost method for dynamic pressure measurement.

1998 Vol. 12, No. 3

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