高压物理学报

Research on Contact Algorithm between Smoothed Particle Hydrodynamics and Finite Element Method

ZHANG Zhi-Chun, QIANG Hong-Fu, GAO Wei-Ran

2011, 25(2): 97-103 . doi: 10.11858/gywlxb.2011.02.001

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Abstract:
The coupling between smoothed particle hydrodynamics (SPH) and finite element method (FEM) is an effective approach for the simulation of impact dynamics. An alternative algorithm for the treatment of contact problem between SPH particles and finite elements was employed. Background particles were assigned in the position of finite element nodes, and the contact forces on SPH particles and finite element nodes were calculated with the same approach as SPH particles to particle contact algorithm. The contact force was added to the momentum equation for SPH and dynamic equation for FEM respectively. Using the SPH-FEM contact algorithm, the axial impact between two bars and the perforation of a cylindrical steel projectile impacting a plate target were simulated, where the Johnson-Cook material model with damage effect and Grneisen equation of state were employed. The computed results showed good agreement with the experimental data.

High-Pressure Synthesis and Properties Characterization of ZrN-ZrB2 Nanocomposites

LU Feng-Guo, QIU Li-Xia, DING Zhan-Hui, GUO Xing-Yuan, Lü Yang, ZHAO Xu-Dong, LIU Xiao-Yang

2011, 25(2): 104-110 . doi: 10.11858/gywlxb.2011.02.002

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Abstract:
Combining high-energy ball milling and high-pressure high-temperature technique, high-dense ZrN-ZrB2 nanocomposites have been synthesized using Zr and h-BN powders as raw materials. The structures of product materials were studied through X-ray diffraction, high resolution transmission electron microscopy and Raman spectroscopy measurements. The result showed that only ZrNx can be synthesized during mechanical alloying process, which can be explained by the thermodynamics and kinetics of reaction of Zr atoms with N and B atoms. ZrN-ZrB2 nanocomposites synthesized at 5 GPa and 1 300 ℃ using 10 h ball-milled powder mixture show excellent mechanical and electrical properties. The microhardness, thermal expansion coefficient and thermal coefficient of resistivity of ZrN-ZrB2 composites are 17 GPa, 7.5710-6 ℃-1 and 8.84610-4 ℃-1, respectively.

Detonation Synthesis of Carbon-Encapsulated Nickel Nanoparticles

LUO Ning, LI Xiao-Jie, FEI Hong-Lu, MO Fei, ZHANG Cheng-Jiao

2011, 25(2): 111-117 . doi: 10.11858/gywlxb.2011.02.003

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Abstract:
Carbon-encapsulated nickel nanoparticles (CENNPs) with core-shell structure were synthesized by detonation method using homemade composite explosives with negative oxygen balance. The detonation chemical reaction was initiated by a nonel tube detonator in a closed explosion vessel filled with nitrogen gas. X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM) with selected area electron diffraction and Raman spectrum techniques were used to characterize the as-obtained detonation products. The XRD and XRF analysis showed that the detonation products mainly consisted of the well-crystallized face-centered cubic nickel nanocrystals, carbon and other microelement. TEM showed that most nanoparticles are made up of a nickel core with the size of 10~25 nm and a carbon shell with the thickness of 1~2 nm. The Raman spectrum analysis indicated that the coating carbon shell is mainly composed of graphite and amorphous carbon. Furthermore, the possible formation mechanism for CENNPs were also discussed.

Influence of Crystallization Degree of h-BN on Synthesis of c-BN

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

2011, 25(2): 118-122 . doi: 10.11858/gywlxb.2011.02.004

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Abstract:
High pressure and temperature pretreatments were employed for the mixture of Li3N and hexagonal boron nitride (h-BN) powders with different crystallization degrees. Using the pretreated h-BN and Li3N, the cubic boron nitride (c-BN) was synthesized by a cubic-anvil press. According to the X-ray diffraction (XRD) data, both the crystallization degree change of the pretreated h-BN and the microstructure transition from h-BN to c-BN were analyzed. The experimental results indicated that h-BN possessing lower crystallization degree was easier to transform into c-BN.

Study on High-Pressure Phase Transition of Hexagonal B-C-N Compound

YANG Jie, LI Ming, LIN Peng, YU Dong-Li, HE Ju-Long

2011, 25(2): 123-127 . doi: 10.11858/gywlxb.2011.02.005

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Abstract:
Using in situ high-pressure synchrotron X-ray diffraction and diamond anvil cell (DAC) techniques, the phase transition and physical characteristics of B0.47C0.23N0.30 compound were observed in the pressure range of 1.4~30 GPa. The experimental results showed that the B-C-N compound experiences a phase transition from hexagonal structure to wurtzite phase at 14.9 GPa. The pressure dependences of the lattice parameters and volume of wurtzite-type B-C-N were calculated. By fitting the Brich-Murnaghan equation of state to the pressure-volume data, the bulk modulus of wurtzite-type B-C-N compound was obtained as (27526)GPa, which is very close to the value of (28215)GPa for the cubic BC2N.

Sound Velocity Measurement of Mesoscale Objects Using Laser Ultrasonics Technique

MA Yun, ZHANG Yi, LI Jia-Bo, CAI Ling-Cang, LI Jian-Feng, WANG Xiang, WENG Ji-Dong, LI Jun, JING Qiu-Min

2011, 25(2): 128-132 . doi: 10.11858/gywlxb.2011.02.006

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Abstract:
A laser-based ultrasound system was designed and built to measure the sound velocity of mesoscale (tens of micrometer- to millimeter-sized) objects. The system uses a Q-switch laser with 6.3 ns pulse width for excitation of broadband ultrasonic waves, and an optical fiber displacement interferometer for detection. The longitudinal acoustic wave velocities of the copper foils with different thicknesses were presented, which exhibit a relatively high degree of accuracy.

Application of Laser Velocity Interferometry in Interior Ballistic Projectile Velocity Measurement

WANG De-Tian, PENG Qi-Xian, LIU Jun, MENG Jian-Hua, LIU Shou-Xian, CHEN Guang-Hua, LIU Qiao, DENG Xiang-Yang

2011, 25(2): 133-137 . doi: 10.11858/gywlxb.2011.02.007

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Abstract:
Using a laser velocity interferometer system for any reflector (VISAR) and a fiber displacement interferometer (FDI), the interior ballistic projectile velocity for rifle cannon was measured. According to the interference signal obtained directly from VISAR and FDI, whose persistence time is 491 s, the projectile velocity history ranging from 0 to 140 m/s was acquired. Therefore, the measurable displacement of projectile is 20.7 mm. In addition, the shot velocity at the muzzle was also obtained as 817 m/s. The experimental results showed that muzzle smoke is the dominant influencing factor. The research results will provide a valuable reference for the practical application of laser interferometer to interior ballistic measurement.

One-Dimensional Gas-Phase Reaction Model of Laser-Induced Ignition of RDX

TIAN Zhan-Dong, ZHANG Zhen-Yu, LU Fang-Yun, TAN Fu-Li

2011, 25(2): 138-142 . doi: 10.11858/gywlxb.2011.02.008

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Abstract:
Based on the work of Liau et al., a one-dimensional gas-phase reaction model of laser-induced ignition of RDX was established by considering the variations of physical parameters with temperature and component concentration. Using this gas-phase reaction model and finite difference method, the ignition characteristics of RDX ignited by laser radiation of 400 W/cm2 power density at 0.1 MPa and 300 K were investigated. The calculated results showed that about 90% RDX transform to gas phase by evaporation and the remaining 10% decompose in condensed phase. With the accumulation of reactant and increase of temperature, the reaction rate increases gradually and finally the gas phase is ignited at about 10 ms, which is consistent with the results reported in previous literatures.

Structure and Properties Modulation of RMnO3 Multiferroic Materials by Average Ionic Radius at A-Site

FENG Shao-Min, WANG Li-Juan, ZHU Jin-Long, LIU Qing-Qing, LI Feng-Ying, JIN Chang-Qing

2011, 25(2): 143-146 . doi: 10.11858/gywlxb.2011.02.009

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Abstract:
The effects of internal chemical pressure produced by A-site ionic radius were investigated for the Ho1-xDyxMnO3 system. It is found that the hexagonal HoMnO3 is gradually transformed to orthorhombic perovskite structure as reducing A-site ion size, forming three regions which contain pure hexagonal phase, mixture of hexagonal and orthorhombic phases and pure orthorhombic phase respectively. Using Rietveld method, the crystal structures were refined, and moreover, the correlations between lattice parameters and unit cell volume as a function of Dy3+ ion content x were obtained. The properties of the temperature dependence of the magnetization and specific heat were also studied. It is suggested that Dy3+ doping would increase the ordering temperature T2 of rare earth elements.

A Preliminary Study on Conductivity of Serpentinite at High Pressure and High Temperature

LIU Zai-Yang, WANG Duo-Jun, LI He-Ping, GUO Ying-Xing, YU Ying-Jie

2011, 25(2): 147-152 . doi: 10.11858/gywlxb.2011.02.010

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Abstract:
Using an AC impedance spectroscopy within the frequency ranges of 0.1～106 Hz, the electrical conductivities of serpentinite were determined from 373 K to 933 K and at 2.0 GPa and 4.0 GPa respectively. The conduction mechanisms of serpentinite before and after dehydration were also analyzed. The experimental results show that complex impedance depends on the variation of frequency, and the electrical conductivity of serpentinite is highly dependant on temperature but only slightly on pressure. The activation enthalpies derived are ~0.6 eV before dehydration and up to 2.0 eV after dehydration. The dehydration of serpentinite, occurred at 690～761 K, causes the jump of the electrical conductivity and alters conduction mechanism. The analysis results indicate that the charge carriers in serpentinite are probably electrons transferred between Fe2+ and Fe3+ before dehydration and are dominated by ions after dehydration.

Phase Transition and Reverse Transition in FeMnNi Alloy

CHEN Yong-Tao, LI Qing-Zhong, TANG Xiao-Jun, LIU Wen-Tao

2011, 25(2): 153-158 . doi: 10.11858/gywlxb.2011.02.011

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Abstract:
By means of VISAR, the phase transition and reverse phase transition in FeMnNi alloy under different pressures were studied through direct impact and reverse impact experiments. As the difference between shock pressure and phase transition threshold is larger than reverse transition threshold, namely 0p-tn, it may lead to an occurrence of the phase transition in FeMnNi alloy, and produces a multi-wave structure consisting of an elastic wave, a plastic wave and a phase transition wave. Under the release process, the rarefaction wave reflecting by the plastic wave from the free surface induces the complete reverse phase transition , and forms a multi-wave structure comprising a rarefaction wave, a rarefaction shock wave and another rarefaction wave. As p-tn, it may produce a multi-wave structure with phase interface reflection (PIR) wave. During the release process, the rarefaction wave reflecting by the residual phase wave causes the reverse phase transition , and forms a two-wave structure consisting of a rarefaction wave and a rarefaction shock wave.

Research on the Dynamic Behavior of a PBX Explosive

LI Jun-Ling, LU Fang-Yun, FU Hua, ZHAO Yu-Gang, TAN Duo-Wang

2011, 25(2): 159-164 . doi: 10.11858/gywlxb.2011.02.012

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Abstract:
PBX explosive is the main charge of modern weapons, so its mechanical behavior determines the survival ability of weapons. To study the dynamic behavior of PBX explosive, a series of split Hopkinson pressure bar (SHPB) tests for PBX explosive have been carried out. With combination of the semiconductor strain gauge and quartz crystal transducer, the validity of the experimental data was obtained. In addition, the stress equilibrium of the specimen and constant strain rate loading were realized experimentally using wave shaping technique. The stress-strain curves of PBX explosive under different strain rates (90~410 s-1) were acquired. According to the variations of the dynamic modulus, failure strength and failure strain with strain rate, a constitutive model of the PBX explosive under uniaxial compression was proposed. The fitted curves derived from the developed model agree well with the experimental results.

Research on Performance of the Underwater Air Buffer Weakening Shock Wave

YAO Xiong-Liang, YANG Wen-Shan, CHU Wen-Hua, ZHANG A-Man

2011, 25(2): 165-172 . doi: 10.11858/gywlxb.2011.02.013

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Abstract:
Based on the characteristics of the damage on the ship caused by the torpedo, the numerical model of multi-medium underwater explosions was established, where the methods of treating interface and calculating generalized smooth length were presented. According to this new model, the programs of multi-medium underwater explosions were worked out, and a quantitative analysis was made on the performance of the underwater air buffer weakening shock wave. The results show that the shock wave can be significantly attenuated by the air buffer, whether in contact explosions or non-contact explosions. And the attenuation effect of the air buffer in contact explosions is better than that in non-contact explosions. The pressure peak of the shock wave can be decreased by nearly 55% by the air buffer in contact explosions. When the ratio between the thickness of the air buffer and explosion equals 1, the effect of the air buffer on weakening shock wave is obvious, and further increasing the thickness of the air buffer has little influence on the attenuation effect. The research results will provide reference for the structure design of the ship protection system and torpedo defense cabin.

Numerical Simulation of the Oblique Collision in Explosive Welding

LI Xiao-Jie, MO Fei, YAN Hong-Hao, ZHANG Cheng-Jiao

2011, 25(2): 173-176 . doi: 10.11858/gywlxb.2011.02.014

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Abstract:
Using the software of ANSYS/LS-DYNA 11.0 and the method of smoothed particle hydrodynamics (SPH), the formation process of the oblique collision in explosive welding was simulated, where the elastic-plastic hydrodynamic model with the material strength was used. The simulation results showed that the shapes of the interface wave and the metal jet were consistent with the practical phenomena of explosive welding. Therefore, it is valuable to research the formation process of the oblique collision in explosive welding with SPH method.

An Application of PIV Technique in Gas Interfacial Instability Experiment

GAO Ning, ZHANG Guang-Sheng, LIN Jun

2011, 25(2): 177-182 . doi: 10.11858/gywlxb.2011.02.015

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Abstract:
An experimental investigation on gas interfacial instability was carried out with particle image velocimetry (PIV) technique. The evolution images and two dimensional velocity field of a shock-accelerated heavy gas cylinder in air were experimentally measured utilizing glycol fog droplets as tracking particle. The results exhibited the typical characteristics and fine structure of instability flow field, which were consistent with the numerical and experimental results published previously. Therefore, the PIV technique is feasible to measure the gaseous interface evolution process, and also is a advanced and accurate diagnostic technology for gaseous interfacial instability experiment.

Void Growth and Local Temperature Rise in Necking Region of OFHC Ring

GUI Yu-Lin, SUN Cheng-Wei, ZHANG Guang-Sheng, LI Qiang

2011, 25(2): 183-187 . doi: 10.11858/gywlxb.2011.02.016

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Abstract:
The fragmentation tests of high-conductivity oxygen-free copper (M-state TU1) rings have been carried out by the electromagnetically driven expanding ring technique. Using a metallographic microscope, the void growth and coalescence were observed in the necking region of recovery fragment. The void growth conditions in the thin ring were analyzed with a spherical void model. The results showed that the circumferential deviatoric stress is more suitable for describing the void growth in necking zone of the expanding ring. Moreover, the local temperature rise effect of necking region was also discussed. This work may be helpful for the further meso-mechanics studies on necking instability of expanding metal ring.

Experimental Study on the Influences of Defects on Expanding Fracture of a Metal Cylinder

JIN Shan, ZHANG Shi-Wen, LONG Jian-Hua

2011, 25(2): 188-192 . doi: 10.11858/gywlxb.2011.02.017

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Abstract:
By means of high-speed frame photography, clear images of the expanding fracture of two metal cylinders with and without a notch were obtained. The experimental results showed that the notch defect would significantly accelerate the fracture process of the cylinder. For the metal cylinder containing a prefabricated notch, the leakage time of detonation products (5.5 s) is earlier than that without a notch, which can be satisfactorily explained by stress or strain concentration. Furthermore, using Mott wave theory, it is well explained that the fragments of the metal cylinder with a notch defect are smaller and more abundant than that without defect.

2011 Vol. 25, No. 2

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