高压物理学报

Building of a Constitutive Model for Concrete under Dynamic Impact

WANG Zheng, NI Yu-Shan, CAO Ju-Zhen, ZHANG Wen

2006, 20(4): 337-344 . doi: 10.11858/gywlxb.2006.04.001

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Abstract:
By analyzing both of dynamic behavior and existing constitutive models of concrete, a new constitutive model has been built to simulate dynamic response of concrete. The main factors such as pressure, the third invariant of stress tensor, strain hardening and softening, stain rate and tensile damage have been taken into account in the constitutive model. After calibrating all parameters of the model, simulation of a perforation problem on concrete target has been carried out with the Lagrangian finite element code LTZ-2D. The computed results of residual velocity are well consistent with the test data, and a reasonable figure of fractured concrete target is obtained. Results demonstrated that the built constitutive model could well describe the main characters of concrete under impact loading.

Effective Viscosity Coefficients, Initial Mobile Dislocation Densities and Drag Stresses for Five Materials

ZHANG Wan-Jia, LIU Cang-Li

2006, 20(4): 345-352 . doi: 10.11858/gywlxb.2006.04.002

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Abstract:
Based on the experimental results of the elastic precursor attenuation along with propagation distance, with rate-dependent constitutive relation including dislocation parameters, and according to the thermally activated dislocation motion model proposed by Gilman, the lower bounds of the initial mobile dislocation densities N0 and the drag stresses 0 have been obtained for LY12-aluminum, MB2-magnesium and lead respectively on the order of 106 cm-2 and 0.1 GPa, but for stainless steel, N0 and 0 are on the order of 108 cm-2 and 1.5 GPa. With the elastic precusor decay curve, the upper limits of the effective viscosity coefficient have been given also for LY12-aluminum and magnesium on the order of 103 Pas, and for 2#-iron and stainless steel on the order of 104 Pas.

Numerical Simulation of Hopkinson Spalling of Rock Using Manifold Method

HUANG Tao, CHEN PengWan, ZHANG GuoXin, YANG Jun

2006, 20(4): 353-358 . doi: 10.11858/gywlxb.2006.04.003

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Abstract:
The second-order manifold method (MM) is used to simulate the dynamic Hopkinson spalling process of rock under shock loading through introducing a criterion of crack initiation and crack growth. The attenuation of stress waves and the spalling process caused by a reflected tensile stress wave are reproduced. The simulation results are compared with theoretical analysis. The thickness of the formed scab and its velocity obtained from the simulation are in good agreement with the theoretical values. MM has proven to be an effective method in simulating the dynamic failure process of materials under shock loading and exhibits some advantages to conventional numerical methods in the study of dynamic failure and related issues.

Experimental and Numerical Investigation of Shock Wave Focusing and Reflection

DONG Gang, YE Jing-Fang, FAN Bao-Chun

2006, 20(4): 359-364 . doi: 10.11858/gywlxb.2006.04.004

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Abstract:
The incident shock wave focusing and reflection on the two parabolic reflectors were studied by means of high speed photograph technique and numerical simulation method. The experimental shadow photographs and computational density contours were obtained, and the good agreements between the experimental and computational results were presented. The properties of the gasdynamic focus, formed by shock wave focusing, were analyzed. The results show that for both reflectors studied the gasdynamic focus is formed by the collision of two triple points at the axis, and that this focus is located in the vicinity of the corresponding geometrical focus. The shock-shock structures after shock wave focusing are different for the two reflectors. For the shallow reflector, the bow shock waves form on the surface of reflector before the reflection of incident shock wave; it takes long time to complete the focusing once incident shock wave reflects from reflector; the bow shock waves do not intersect each other during the shock wave focusing and reflection. For the deep reflector, it takes short time to complete the focusing, the bow shock waves have intersected during the shock wave focusing and reflector, and this process leads to the more complex shock-shock structure.

Propagation of Irreversible Macroscopic Phase Boundaries along a Finite Rod under Dynamic Loading

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

2006, 20(4): 365-371 . doi: 10.11858/gywlxb.2006.04.005

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Abstract:
The rules regarding the propagation of irreversible phase boundaries along a finite rod are investigated with a phase transition constitutive model based on the simple mixture theory. The results show that the boundary and loading/unloading conditions strongly affect the propagation pattern of the phase boundaries, and the final distribution shapes of the volume fraction for the product phase along the rod are different under various end boundaries. The new phenomena observed in the recent Taylor bar tests are explained in this paper, and the possibility for producing symmetric distributed functionally graded materials with impact method is proposed.

Valence Electron Structure Analysis of Catalyst during Diamond Synthesis under HPHT

LI Li, XU Bin, GONG Jian-Hong, LI Mu-Sen

2006, 20(4): 372-378 . doi: 10.11858/gywlxb.2006.04.006

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Abstract:
Experimental results showed that the Me3C (Me means Fe, Ni) pattern carbides produced by the action of catalyst and graphite are main carbon source to form diamond structure under high temperature and high pressure (HPHT). In this paper, based on the empirical electron theory of solids and molecules (EET), the valence electron structure (VES) and interface structure factors of diamond and various carbides are calculated, and the boundary condition of Thomas-Fermi-Dirac-Cheng (TFDC) is applied to the carbide/diamond interfaces. It is found that the electron density of crystal face in Me3C formed by CC bonds is continuous with that of diamond at the first order of approximation, but the continuous intensity of different carbide is different. The VES of plane composed of C atoms in (FeNi)3C and Co3C are more similar to that of diamond, so the energy needed to transform their CC bonds to diamond structure is lower. The catalyst action and catalysis mechanism are explained on the basis of VES concerning the carbides and diamond. This method may be a new way to investigate the mechanism concerning diamond formation.

A Combined Discrete/Finite Element Method in Shock Dynamics

FU Hua, LIU Cang-Li, WANG Wen-Qiang, LI Tao

2006, 20(4): 379-385 . doi: 10.11858/gywlxb.2006.04.007

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Abstract:
A combined discrete element method (DEM) and finite element method (FEM) is presented. A 2D program is developing for application to mesoscale simulation of heterogeneous and homogeneous material under shock loading, and the numerical simulations are testified. The results of simulation are in agreement with those of theory, which verifies that the combined method is viable.

Compression Isentropes of Aluminum and Copper up to 200 GPa

MO Jian-Jun, SUN Cheng-Wei

2006, 20(4): 386-390 . doi: 10.11858/gywlxb.2006.04.008

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Abstract:
The equation of compression isentropes derived from linear and quadratic Hugoniot curves has been obtained by employing the Hugoniot as the reference of Grneisen EOS as well as from p=f(e,v) form EOS directly. The compression isentropes of aluminum and copper are calculated with both Grneisen and Appy EOS. The calculated results show that the compression isentrope of aluminum under 200 GPa calculated with Appy EOS approaches to that with the linear Hugoniot, where the error is less than 1.5%. It is also compared with the ICE data of Shot Z864 at the Sandia Z machine. They agree very well under 200 GPa and derived from both the linear Hugoniot and the Appy EOS, for those where the error is less than 1%. The isentropes of aluminum derived directly from Appy EOS coincides almost with the experimental one.

Synthesis of Large Bulk MgSiO3 Perovskite and (Mg,Fe)O Ferropericlase at High-Pressure and High-Temperature

ZHANG Li, GONG Zi-Zheng, FEI Ying-Wei

2006, 20(4): 391-396 . doi: 10.11858/gywlxb.2006.04.009

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Abstract:
MgSiO3 perovskite and ferropericlase (Mg,Fe)O are generally considered as the most dominant components in the Earth's lower mantle. The experimental data of these phases at high pressures and high temperatures play a key role to constrain the composition of the Earth's lower mantle. However, high pressure experiments at lower mantle conditions, especially the shock wave experiments, are restricted since it is impossible to collect the high-phases of the samples in nature. We introduce the experimental methods to synthesize large bulk MgSiO3 perovskite and ferropericlase (Mg,Fe)O using piston-cylinder and mutli-anvil apparatuses, and the synthesized samples were analyzed by micro electronic probe, Raman spectrum, and X-Ray diffraction. This makes it possible to do shock wave experiments with the large bulk MgSiO3 perovskite and ferropericlase (Mg,Fe)O as starting materials.

An Issue in the Numerical Simulation for Non-Ideal Detonation Propagation in Body-Fitted Coordinate Systems

ZHONG Min, CHEN Sen-Hua, LI Ping

2006, 20(4): 397-402 . doi: 10.11858/gywlxb.2006.04.010

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Abstract:
The Level Set method in body-fitted coordinate for propagation of non-ideal detonation is studied. According to the Hamilton-Jacobi formulation of the Godunov's scheme, we studied finite difference method for the propagation equation of non-ideal detonation in non-orthogonal body-fitted coordinate systems and presented an algorithm. We have shown a few calculations and compared with analytical and other numerical results.

Study of Pulsed Large Current Out-Put of Shock-Activated Energy Transducer

DU Jin-Mei, ZHANG Fu-Ping, ZHANG Yi, WANG Hai-Yan

2006, 20(4): 403-407 . doi: 10.11858/gywlxb.2006.04.011

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Abstract:
The PZT 95/5 ferroelectric ceramics with niobium doped was assembled into the shock-activated energy transducer. Based on the explosive to electric energy transfer theory, the large pulse of electrical current output was investigated under the action of shock wave in normal mode, and the electrical response of LRC load was discussed, especially for the small resistance (R) and small inductance (L) load. Several shock wave tests were conducted, and the PZT 95/5 ceramic stacks in parallel were devised to generate large pulses of electrical current. The maximum output current reaches above 5 kA, and the rising rate of the initial current is to 10~20 GA/s. The experimental results accord very well with the calculations.

Numerical Simulations of the Penetration of Aluminum Targets by Ogive-Nosed Steel Projectiles

HE Tao, WEN He-Ming

2006, 20(4): 408-414 . doi: 10.11858/gywlxb.2006.04.012

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Abstract:
Numerical simulations are conducted herein on the penetration of aluminum targets by ogival-nosed steel projectiles using the commercial FEM code ABUQUS. In the simulations, the response of the targets are represented by a forcing function, which is derived from spherical cavity expansion theory. This methodology eliminates the need for discretizing the targets as well as the need for a contact algorithm. It is shown that the numerical simulations are in good agreement with the available experimental data for the penetration of 6061-T6511 aluminum targets struck by VAR 4340 steel projectiles, reported in the literature. It is also shown that pitch and yaw or inclination angle has significant effects on the depth of penetration as well as projectile response.

Structure Evolution and Transport Properties of La2-xSmxCuO4 at High Pressure

WU Yun-Long, SONG Chun-Mei, XIONG Yu-Feng, LI Lai-Feng

2006, 20(4): 415-420 . doi: 10.11858/gywlxb.2006.04.013

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Abstract:
The structure evolution and transport properties of La2-xSmxCuO4 synthesized both at atmosphere pressure and high pressure have been studied. The crystal structure changed from T phase to the T phase. Following treatment in high pressure of 6 GPa in 850 ℃, a slight modification in the lattice constants was observed. The results also showed that oxygen pressure tended to stabilize the T structure. The pressure caused the sample density increasing. The high oxygen pressure treatment for the T structure resulted in a drastic decrease of the resistivity at low temperature, indicating a superconductivity with Sm concentration0.5.

Research on Mutation in Rice (Oryza Sativa L.) Induced by High Hydrostatic Pressure

LI Gui-Shuang, BAI Cheng-Ke, DUAN Jun, PENG Chang-Lian

2006, 20(4): 421-428 . doi: 10.11858/gywlxb.2006.04.014

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Abstract:
Seeds of three rice (Oryza sativa L.) cultivars, Yuexiangzhan, Yuefengzhan and Ce 64, were soaked for 10 h, and then were treated by high hydrostatic pressure (78 MPa) for 12 h. The seedlings of high-pressure treatment and control were transplanted in the field after sowing of 30 d. Mutation type of characters and selection of excellent varieties were investigated. The results indicated that: (1) In M1 generation, grain numbers per panicle of Yuexiangzhan, Yuefengzhan and Ce 64 treated by high hydrostatic pressure (HHP) increased by 5.2%, 1.2% and 17.0%, respectively. Ce 64 delayed 10 d but Yuexiangzhan and Yuefengzhan advanced 5 d and 2 d in period of duration. (2) There were quality and quantity traits among the mutation traits by HHP. For instance, dominant mutation in leaf sheath made green leaf sheath become purple leaf sheath, while recessive mutation in the node length below panicle made node length of treatment longer than that of control. Mutation in plant height, awn length and grain numbers per panicle belonged to mutation of quantity traits. (3) Mutation frequency and the time from mutant to stable mutation lines varied among species. Mutation frequency of Ce 64 in M1 generation was 8% while that of Yuefengzhan and Yuexiangzhan was 1 and 5, respectively. (4) Currently one hundred mutants were found in the field. Twenty two mutants had no significant separations and seven of them displayed remarkable advantages in comprehensive traits than their control.

Numerical Simulation for Formation Flight and Penetration of Sphericity EFP

YANG Jun, JIANG Jian-Wei, MEN Jian-Bing

2006, 20(4): 429-433 . doi: 10.11858/gywlxb.2006.04.015

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Abstract:
With AUTODYN-2D code, the formation, flight and penetration processes of sphericity explosively formed projectile (EFP) are simulated. The influence of curvature of liner impose on formation of EFP is studied, and the flight velocity field of EFP is revealed. By analyzing the v-t curve, the attenuation coefficient could be obtained, and then the penetration process of EFP to armor plate are simply analyzed.

Expanding Fracture of Beryllium Bronze Cylinder Shell

JIN Shan, TANG Tie-Gang, LI Qing-Zhong, SUN Xue-Lin, XU Yong-Bo, SHA Gui-Ying

2006, 20(4): 434-438 . doi: 10.11858/gywlxb.2006.04.016

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Abstract:
High-speed camera and optical microscope were used to study the expanding fracture characteristic of the beryllium bronze (QBe2) cylinder shell under detonation loading. The experimental result show that the static mechanics characteristics and the dynamic fracture characteristic of the material depend on the material's microcosmic structure. When the microcosmic structure of the material has evident difference, the static mechanics characteristics and the dynamic fracture characteristic of the material will be evident changed. When the basic structure of the material have no evident difference while the number of the strengthen phase in the basic structure is changed, the static mechanics characteristics of the material can be evident different, but the dynamic fracture characteristic of the material will be not greatly changed. A reason for such a behavior might be that the strengthen phase which occurs to the difference of the static mechanics characteristics of the material tends to the identical under detonation loading.

SEM Observation of Large Polymer Extended-Chain Crystals in High-Pressure Crystallized PET/PC Blends

Lü Jun, HE Yang, LI Liang-Bin, HUANG Rui

2006, 20(4): 439-444 . doi: 10.11858/gywlxb.2006.04.017

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Abstract:
Large polymer extended-chain crystals have an important role that cannot be replaced in the study on low dimensional systems of physics. However, the small size of polymer extended-chain crystals that formerly had to be obtained through a long time confined their effect. Adding 10% (mass fraction) PC to PET, we obtained plenty of polymer extended-chain single crystals with C axis thickness exceeding 100 m during the study on the high-pressure crystallization behaviors of PET/PC blends with a self-made piston-cylinder apparatus. For the first time, scanning electron microscope was employed to analyze them in a deep-going way. Large extended-chain crystals with various morphologies were observed by SEM, i. e. perfect extended-chain crystals, extended-chain crystals fractured along or perpendicular to C axis, extended-chain crystals with cohesive fracture surfaces, different wedge-shaped extended-chain crystals on different fracture surfaces and bending extended-chain crystals. Some mechanisms were also put forward for the formation of the observed large crystals.

Study on Compression Stage in Two-Stage Light Gas Gun

WU Jing, LAN Qiang, WANG Qing-Song, XIAN Hai-Feng, JIA Lu-Feng, FU Qiu-Wei

2006, 20(4): 445-448 . doi: 10.11858/gywlxb.2006.04.018

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Abstract:
Experiment was done to study on the effect of big diaphragm between powder chamber and pump tube in two-stage light gas gun with diameter of 25 mm. The differences of interior ballistics with diaphragm and diaphragmless are observed at the same filling parameters. Theoretical calculation and experimental result indicate that the effect of big diaphragm on interior ballistics is not evident.

2006 Vol. 20, No. 4

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