高压物理学报

Numerical Modeling of Spallation Experiments of Tantalum

JIANG Song-Qing, LIU Wen-Tao

2007, 21(2): 113-120 . doi: 10.11858/gywlxb.2007.02.001

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Abstract:
A phenomenological model, which includes nonlinear elasticity (equation of state), rate-dependent plasticity, and void nucleation and growth, is provided for modeling the spallation behavior of tantalum. An implicit numerical technique, diagonally implicit Runge-Kutta method, is used to solve the constitutive rate-equations, and some improvements to the stability and accuracy of the solution are obtained. The model developed is used to simulate the plate impact experiments on tantalum. Comparisons are made between the model and the experimental data. Results show that close agreement between model predictions and experimental results is obtained for moderate or high velocity plate impact experiments, but some improvements in the model are necessary to predict the damage evolution and failure in incipient spall fracture of tantalum.

Theoretical Study on the Penetration and Perforation of FRP Laminates Struck by Cone-Nosed Projectiles

QIN Yue, WEN He-Ming, HE Tao

2007, 21(2): 121-128 . doi: 10.11858/gywlxb.2007.02.002

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Abstract:
The penetration and perforation of FRP laminates struck transversely by cone-nosed projectiles has been theoretically investigated. Based upon the assumption that the deformation is localized, the mean pressure offered by the laminate targets to resist the projectiles can be decomposed into two parts: one part is a cohesive quasi-static resistive pressure due to the elastic-plastic deformation of the laminate materials and the other is a dynamic resistive pressure arising from velocity effects. Furthermore, Wen's model has been developed by assuming that the resistance of the FRP laminate is no longer a constant, but a function of penetration velocity. Equations are obtained for predicting the depth of penetration, the residual velocity and the ballistic limit in the case of perforation. It transpires that the theoretical predictions are in good correlation with available experimental data in terms of penetration depth, residual velocity and ballistic limit.

Dynamic Strength of Alumina under Plane Shock Waves

LIU Zhan-Fang, CHANG Jing-Zhen, TANG Lu-Cheng, YAO Guo-Wen, LI Jian-Peng

2007, 21(2): 129-135 . doi: 10.11858/gywlxb.2007.02.003

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Abstract:
The strength expression of material under shock loading has been reviewed. The effects of the hydrostatic pressure and the high strain rate on the strength, has been discussed. A modified form for the Hugoniot elastic limits was given associated with the Drucker-Prager yield criterion. Free surface velocity histories were measured by VISAR in plate impact experiments on alumina with a light gas gun. The experimental determination of the dynamic strength of alumina was discussed and open problems were clarified. By comparing the strength expressions of ceramic materials with the experimental results, the differences were mentioned. Analysis and discussion were made for the experiment phenomenon.

Research of Fragmentation of Nano-Ceramic Powders during Explosive Consolidation Process

ZHANG Yue-Ju, LI Xiao-Jie, YAN Hong-Hao, QU Yan-Dong, TAO Yu-Xiong

2007, 21(2): 136-144 . doi: 10.11858/gywlxb.2007.02.004

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Abstract:
In explosive consolidation of nano-powders, the duration in which the loading changed markedly on nano-particles by shock wave is far longer than the time of stress wave propagating through the character length of the particles; and the ceramic powders behave brittleness during explosive shock consolidation. The elastic hypothesis is put forward based on the two facts mentioned above, and the hypothesis is used to deduce the stress status in particles during the process of consolidation. The three criteria of brittleness fracture of damage (Hugonoit elastic limit, dynamic yield strength and theoretical shear strength) are reviewed. The probability of fracture of ceramic particles is estimated by the intersection value of the three criteria. Based on the calculation, it is concluded that there are two maximal shear positions: one is located in the depth of 0.5 nm in particle from the contact surface, where the shear stress is maximum;the other is located further from the surface. This result offers a reference for interpreting the plasticity and fracture during the process of explosive consolidation.

Dynamic Analysis of Helium Bubble Growth in the Pure Al under High Strain-Rate Loading

QI Mei-Lan, HE Hong-Liang, WANG Yong-Gang, YAN Shi-Lin

2007, 21(2): 145-150 . doi: 10.11858/gywlxb.2007.02.005

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Abstract:
Based on the dynamic process of helium bubble growth under high strain-rate, the dynamic equation of helium bubble growth has been presented. The effects of internal pressure of helium bubble, inertia, viscosity, surface tension of base material and environment temperature on helium bubble with 1 nm radius have been considered respectively. Results indicate that: (1) At high strain-rate loading, the original internal pressure may help to accelerate the growth of the helium bubble. When the radius of helium bubble is larger than 1 m, the internal pressure is too small and it may be omitted. (2) The effect of surface tension is very weak in the whole process of helium bubble growth. (3) The growth of helium bubble may be restrained by the inertia. And this effect will be more obvious with the growth of diameter. (4) While all the above effects are important, the effect of temperature needs to be particularly emphasized. With the temperature rising, the viscosity will decrease and the internal pressure will increase, the growth of helium bubble will be accelerated.

Numerical Investigations of Detonation Induced by Implosion Flame inResonator Cavity

GUI Ming-Yue, FAN Bao-Chun, DONG Gang, YU Lu-Jun

2007, 21(2): 151-156 . doi: 10.11858/gywlxb.2007.02.006

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Abstract:
Based on the two-dimensional axisymmetric Euler equations coupling with chemical reactions, the phenomena of implosion combustion for hydrogen-air mixture were numerically studied by using wave propagation algorithm with Superbee limiter in resonator cavity. The effects of resonator shapes on initiation and detonation were discussed. Results show that the shock wave induced by combustion firstly reflected back and forth from walls and the axis of the resonator cavity, which led to multiple the shock-flame interactions and enhanced the flame combustion. Then the reflected shock wave produced by the parabolic reflector in resonator cavity frequently penetrated the flame, which led to continuous flame excitation. Finally, DDT occurred. Simultaneously, the repeated shock-flame interactions caused the instability and distortion of the flame, and then formed asymmetrical collapsing of the flame front. The different shapes of reflector caused the change of focus, which could influence the shock-flame interaction and made detonation onset change, even not occurred.

Failure Modes of Ductile Metal Plates under Normal Impact by Flat-Ended Projectiles

PAN Jian-Hua, WEN He-Ming

2007, 21(2): 157-164 . doi: 10.11858/gywlxb.2007.02.007

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Abstract:
This paper examines the failure modes of ductile metal plates subjected to impact by rigid flat-ended projectiles at normal incidence. General speaking, there are two failure modes which can occur in a ductile metal plate: simple shear failure with global deformation, and localized adiabatic shear plugging. Based on the thermoplastic constitutive relationship of Bai and Johnson, an adiabatic shear plugging model is first proposed. When combined with the Wen-Jones model which describes simple shear failure with global response, a critical condition for the change in these two failure modes is obtained. It transpires that the present theoretical predictions are in good agreement with available experimental observations in terms of failure modes and ballistic limits.

Three-Dimensional Numerical Simulation of the High Velocity Rod-Shaped Projectile

LI Cheng-Bing, PEI Ming-Jing, SHEN Zhao-Wu

2007, 21(2): 165-172 . doi: 10.11858/gywlxb.2007.02.008

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Abstract:
The software of LS-DYNA was applied to simulate the formation process of a high velocity rod-shaped projectile from the modified hemispherical liner. Its formation mechanism was analyzed. It was demonstrated that the initiation methods such as center point initiation, four-point initiation and peripheral initiation had an effect on the formation and the performance parameters of the high velocity rod-shaped projectile. The results of numerical computation indicate that the shaped charge with the modified hemispherical liner can form the rod-shaped penetrator with high velocity, large slenderness and rational mass distribution. Its formation mechanism combines that of the shaped jet and the over-turned explosively formed projectile, i. e. the upper half of liner directly collapses along the axial line and the lower half of liner is gradually overturned when closing the axial line. There are some differences of the shape and performance parameters of the rod-shaped penetrators formed under the different initiation methods. The peripheral initiation is the best excellent initiation method. The experimental result shows a good agreement with results of numerical simulations.

Experiment Research of Nano Manganese Ferrite Powders Prepared by Detonation Method

WANG Xiao-Hong, LI Xiao-Jie, ZHANG Yue-Ju, QU Yan-Dong, SUN Gui-Lei, XIE Xing-Hua

2007, 21(2): 173-177 . doi: 10.11858/gywlxb.2007.02.009

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Abstract:
Nanometer-sized MnFe2O4 powders were synthesized by detonation of two kinds of emulsion explosives with different oxygen balance (OB) values. The phase structure and the different components of the two samples obtained from the emulsion explosives were characterized and compared by X-ray diffraction (XRD). According to the results of DSC and XRD, the samples were heated at 200 ℃, 260 ℃, 280 ℃, 500 ℃ for 1 h and 360 ℃ for 40 min respectively. And at 280 ℃, pure nanometer-sized MnFe2O4 powders were obtained, their morphology was observed by transmission electron microscopy (TEM). The results of the experiments indicate that detonation powders of the EE with negative OB value are relatively purer than those of the EE with zero OB value, and 280 ℃ is a suitable temperature for thermal treatment. Detonation method has the advantages of convenience and rapidness for nano-particles synthesis and simplity for post-thermal treatment.

Discussion on Shear Modulus of Materials at Solid-Liquid Phase Region

RAN Xian-Wen, TANG Wen-Hui, TAN Hua, DAI Cheng-Da

2007, 21(2): 178-182 . doi: 10.11858/gywlxb.2007.02.010

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Abstract:
From theoretical and experimental aspects, the shear modulus of material at the solid-liquid phase region was discussed when the material has attained its phase transition equilibrium and concluded that the shear modulus did not equal to zero as soon as the material began to melt. Using percolation theory, the connectivity of solid phase in solid-liquid phase region was calculated and the critical melting mass fraction is 0.687 when the shear modulus of material equal to zero. The melting unstable factor of material, presented by us, can represent qualitatively the change of correlative physical parameters in melting process.

Non-Fourier Energy Transport in Silicon Thin Films during Femtosecond Laser Heating

LIU Guo-Dong, LUO Fu, WANG Gui-Bing

2007, 21(2): 183-187 . doi: 10.11858/gywlxb.2007.02.011

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Abstract:
A numerical model which is based on the hyperbolic two-step model is developed to investigate the microscopic energy transport in silicon thin films during ultra-fast laser heating. It is observed that, electrons dominate energy transport within a few picoseconds. The coupling processes between electrons and phonons are non-local due to the ballistic transport of electrons, and the coupling coefficient is found to be much more strongly dependent on electron temperature than lattice temperature. The speed of heat wave propagation is the same magnitude as that of the electron energy transport. Predictions from the numerical model agree with available experimental data during ultra-fast laser heating.

Dynamic Behavior of -Zirconium at Low Pressure

LI Ying-Hua, CAI Ling-Cang, ZHANG Lin, LI Ying-Lei

2007, 21(2): 188-192 . doi: 10.11858/gywlxb.2007.02.012

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Abstract:
The stress-strain curves of the -zirconium which strain rate ranges from 3.310-4 s-1 to 1.5103 s-1 under room temperature were obtained, and the parameters of Johnson-Cook model were determined through these experiments. The computed free-surface velocity profiles using dynamic damage and fracture model consist with the experimental measurements at 4.3 GPa and 5.1 GPa peak pressure. The comparison indicates that the determined dynamic parameters of -zirconium are valid.

Simulation of Combustion Process in the Electric Squib

ZHU Ming-Shui, HE Bi, JIANG Xiao-Hua, JIANG Ming

2007, 21(2): 193-198 . doi: 10.11858/gywlxb.2007.02.013

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Abstract:
Based on two phase flow model of interior ballistics, considered that the weight of ignition charge is comparable with the secondery charge and many of its products are solid, the so called four phase flow model of interior ballistics adaptive to the combustion process in the electric squib has been established. In the model, gas products, solid products, ignition charge and secondery chare, all be taken as a phase, each of them is described by mass, momentum and energy equation, and they are related by mutual actions, which are the source terms in the before-mentioned equations. Caculated result by the model is in agreement with the test of the electric squib. This shows that the model describes reasonably the combustion process in the electric squib, and can be as an assistant tool for evaluating of the performance of electric squib.

Influence of the Parameter of Explosive Welding Caused by the Slope of Fly Plate at Static Load

FU Yan-Shu, SUN Yu-Xin, WANG Jin-Xiang, RONG Guang

2007, 21(2): 199-204 . doi: 10.11858/gywlxb.2007.02.014

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Abstract:
Explosive welding is a solid state fusion welding process in which the joining of two metals is accomplished by the application of the pressure released by the detonation of an explosive layer. It is widely used to manufacture material sandwich components. But when explosive was set on a thin fly plate, the deflection would take place because of the weight of explosive and the fly plate itself. In this paper, based on the analysis of the deflection of the big and thin plate which is supported by smooth cylindrical pin at four boundaries, the slope of the fly plate which endured uniform pressure of weight was developed. Combined with the explosive welding subsonic speed limit and fluid limit, the minimal thickness was calculated to make sure explosive welding can be successful. At last, the formula of the minimal thickness was gained in the conditions that the material, length, width of fly plate were all confirmed.

Does There Exist a Solid-Solid Transformation in Shocked Iron at around 200 GPa?

HUANG Hai-Jun, CAI Ling-Cang, TIAN Xu

2007, 21(2): 205-209 . doi: 10.11858/gywlxb.2007.02.015

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Abstract:
A theoretical Hugoniot curve of iron has been calculated based on Grneisen equation of state and internal energy conservation consideration, using a set of optimized or thermophysical parameters and both - and liquid-iron models. This determined Hugoniot curve is well in accord with the revised Hugoniot data [J Appl Phys, 2000, 88: 5496] on the whole, and could be further divided into two parts. The first one can well describe the revised data below ~200 GPa with -phase model, while the second can approximately replicate the revised data above ~260 GPa with liquid-phase model. It is thus convinced that the range between ~200 GPa and ~260 GPa should be in solid/liquid mixed state, i. e, a small kink appearing on the revised Hugoniot at ~200 GPa is due to a solid-liquid transition, rather than a solid-solid transition at ~200 GPa that was inferred from Brown's analysis [Geophys Res Lett, 2001, 28: 4339].

Shock Compression Behavior of Nd2Fe14B

LI Qiao-Yan, SHI Shang-Chun, YANG Jin-Wen, SUN Yue

2007, 21(2): 210-214 . doi: 10.11858/gywlxb.2007.02.016

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Abstract:
The shock compression properties for permanent magnet Nd2Fe14B were studied in the shock pressure range of 19~78 GPa, using a two-stage light-gas gun. The Hugoniot data of Nd2Fe14B with initial average density 7.346 g/cm3 were measured by the impedance matching method. The experiment results indicate a good linearity between the shock wave velocity and the particle velocity, i. e. C0, are obtained as 3.686 km/s, 1.059. Shock compression curve in the Nd2Fe14B shows a stable compression course and there is no evidence phase transition in present pressure range. The small displays that the Nd2Fe14B material leans to loosen state and is prone to compression. At the same time, it also provides corresponding experiment parameters for calculation of EOS and application of pulse power resource.

Raman Scattering Study of Colloidal MoS2 under High Pressure

ZHAO Ya-Jun, ZHANG Zeng-Ming, DING Ze-Jun, ZHANG Quan

2007, 21(2): 215-219 . doi: 10.11858/gywlxb.2007.02.017

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Abstract:
Raman spectra of colloidal MoS2 powder with the average diameter of 4 m under high pressures were measured. The experimental results indicate that the Raman bands shift to higher wavenumbers with the increase of pressure, while the intensity decreases and the FWHM increases. The mode Grneisen constants for E12g and A1g modes were obtained through the data analysis of the Raman bands shift with pressure.

Electric Properties of ZnO Nanowires under High Pressure

LI Jin-Lai, WU Zhen-Yu, BAO Zhong-Xing, ZOU Bing-Suo, FENG Ya-Qing

2007, 21(2): 220-224 . doi: 10.11858/gywlxb.2007.02.018

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Abstract:
The R-p and C-p relationship of ZnO nanowires were determined by diamond anvil cell (DAC), and compared with those of ZnO nanocrystals and bluk materials in the previous experiments. Our results show that a phase transition began at the pressure of 5.0 GPa. The resistance under pressure decreased and the capacitance increased at the exponential speed before the phase transition, while after that, the resistance increased and the capacitance descended rapidly, which reveal the differences between ZnO nanowires and general nanocrystals.

2007 Vol. 21, No. 2

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