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2008 Volume 22 Issue 4  Published: 2008-12-05
  • Gui-Cun MA , Wei-Feng LIU

    Based on the embbeded atom method (EAM) proposed by Foiles, Baskes and Daw, we have established the EAM potential of copper by using Vinet-Rose universal equation of state. Phonon spectrum and elastic constant of copper at high pressure are calculated by first principle perturbation theory and embedded atom methods. Through proper adjustment of the parameters in EAM potential, we get almostly the same results from the two methods. Furthermore, the spectrum of phonons and the specific heat of lattice are all coincide with the experimental values.

  • Wei ZHANG , Gong-Shun GUAN , Bin JIA , Bao-Jun PANG

    The numerical simulation of projectile shape effects on craters in hypervelocity impact on thick alloy aluminum target at normal angles has been carried out using the AUTODYN hydro-codes. The results of 2D and 3D simulation are given. The effect of projectile with different shapes and aspect ratios as well as impact orientations etc. on damage characteristics sizes and shapes of craters produced by hypervelocity impact on alloy aluminum targets have been investigated at the same mass and velocity. The simulation results are compared with the cratering created by spherical projectiles. It is shown that projectile has a larger aspect ratio, it has a larger crater depth; the damage sizes and shapes of craters created by non-spherical projectiles impact depend on the projectile shapes and impact orientations.

  • Gang WANG , De-Liang ZHANG , Kai-Xin LIU

    Three common chemical reaction models in gaseous detonation numerical simulation have been studied in this work based on an improved space-time conservation element and solution element method. Planar and cellular detonations have been simulated and the numerical results have been compared and discussed. We found that all the cellular patterns simulated by the three chemical reaction models could agree well with the experimental results, though the accuracies of detonation parameters calculated by the three chemical reaction models were rather different. The three chemical reaction models have respective advantage and disadvantage. Adopting which chemical reaction model should consider the specified problems.

  • Jian-Guo NING , Chun LIU , Tian-Bao MA

    When dealing with the problems of multi-material interaction, hydrodynamics numerical methods of Euler is one of the most effective ways. When using unsplit method to deal with pure cells in Euler coordinate, mixed cells are subdivided based on Youngs’ interface reconstruction algorithm which can avoid complicated transport calculation. This paper gives all of the possible distribution modes to eight neighboring cells of both pure ones and subdivided ones. In the end, this unsplit method is added into numerical simulation program of MMIC-2D universal multi-material two-dimension explosion and impact which is developed by ourselves. The simulation results verify that our method can not only improve calculation precision efficiently, but also reduce workload and save computation time.

  • Yan-Shu FU , Yu-Xin SUN , Xiao-Ping WANG , Xiao-Li ZHANG

    Because of the high strength and temperature sensitivity of the metal glass, its lower limit is higher and upper limit is lower than that of crystal metal when bulk metal glass was prepared by amorphous foils explosive welding. In this paper, the surface of foils was coated by copper to decrease surface hardness. Results showed that this method can reduce the lower limit, concentrate the energy of plastic collision mainly on coating layer and remarkably minimize foils heat effect zone. Besides, during the experiment designing, ideas of damage mechanics were used to set defects to accelerate the attenuation of tensile waves, so the tensile strength at welding interfaces can be reduced, in combination with the model of thermo-softening at welding interfaces. The upper limit was obviously increased. Both of upper limit and lower limit were improved, and the welding window was effectively expended, so the purpose of preparing bulk metal glass by explosive welding amorphous foils would be easier to implement.

  • Xun-Cheng LIU , Mei ZHANG , Jun DUAN

    In order to study the effect of expression pattern of high hydrostatic pressure on high plant, a SSH-cDNA library was constructed with rice germinating seeds in this paper. Suppression subtractive hybridization (SSH) in combination with mirror orientation selection (MOS) was performed using the mRNA from rice germinating seeds treated by 75 MPa high hydrostatic pressure as tester and the mRNA from control (seeds untreated by high hydrostatic pressure) as the driver. 580 recombinant clones were picked through blue/white screening. PCR detection of the recombinant clones showed that the size of inserts mainly ranged from 200 bp to 1 000 bp, and the average size of these inserts were about 575 bp. Among the 580 recombinant clones, 542 clones (93.3%) were identified to be effective single band ones. After sequencing some of the recombinant clones, it was found that the genes induced by high hydrostatic pressure were mainly involved in metabolism, stress response and transcriptional regulation. The research paved the way for studying the gene expression patterns of rice seeds responding to high hydrostatic pressure.

  • Jin-Zhong XU , Wen-Hui TANG , Zhi-Hong XU

    The characteristics of debris clouds produced by hypervelocity impacts are simulated and analyzed by smoothed particle hydrodynamics (SPH). The variational laws of the diameter of holes, the width of debris clouds, the cumulative percentage of fragments, the dimensionless momentum MD/M0 and the residual velocity are given. By fitting computational data, the cumulative percentage of fragments as a function of the fragment mass and the impact velocity is presented. The computational results show that the function agrees with SPH results very well.

  • Yun MA , Lin ZHANG , Qi-Xian PENG , Xiang WANG , Jian-Feng LI , Ling-Cang CAI , Jia-Bo LI , Xiao-Song WANG , Ji-Dong WENG , Hong CHEN

    Four experimental approaches were developed to measure the velocity-per-fringe constants of VISAR. In particular, owing to the high accuracy and the wide applicable range, the integrated VISAR and DISAR should be a versatile method to measure arbitrary velocity-per-fringe constants of VISAR. In the absence of the integrated VISAR and DISAR system, the velocity-per-fringe constants of VISAR can also be measured through the measurement of the VISAR’s delay time, a relatively standard velocity source produced by the symmetric impact of fused silica with a window, or the calibrated VISAR.

  • Feng LIN , Wei JIANG , Ji-Fu FENG , Li-Wei LI , Hai-Bo LÜ

    The wear ratio, resistance, integrality and hardness of polycrystalline diamond compacts (PDC) are investigated. The high pressure sintering processes are optimized using orthogonal experiments. According to our experimental results, the optimized parameters for the high pressure sintering of PDC are determined as below: pressure 5.5 GPa, temperature 1 350 ℃, temperature rising rate 200 ℃/min, cooling time 14 min, and sintering time 16 min. It is found that the wear ratio and micro-hardness can be improved by increasing sintering temperature. The temperature distribution in the sample cell is reduced and PDC microstructure becomes more uniform by prolonging the heating time. The residual stress is also found to be decreased by prolonging the cooling time.

  • Gui-Lei SUN , Xiao-Jie LI , Hong-Hao YAN , Xiao-Hong WANG , De-An JIANG

    N2 adsorption/desorption isotherms and pore diameter distribution of the porous graphite nanopowders, prepared by detonation splitting technique with different acid content in raw materials, were analyzed using Brunauer-Emmet-Teller (BET) equation and Barrett-Joyner-Halenda (BJH) method. The results indicate that there exists hysteresis phenomenon in the product isotherms and the corresponding BET surface area is 5.3~9.2 times of the natural flake graphite which is increasing with the acid content in raw materials. The difference of the BET surface area among the detonation soot is mainly caused by the pore of which diameter distributes between 3 nm and 7 nm. Moreover, the amount of the pore size at about 4 nm arrived at the maximum after detonation. In addition, the research provides sorption capacity information for application and at the same time it also proves that acid has perfect impact on preparing graphite nanopowders.

  • Zi-Jian FAN , Zhao-Wu SHEN , Xue-Yan LIAO , Yuan-Dong LIU

    The elastic shell strain of the cylindrical vessel produced by the inner underwater explosion shock wave was analyzed and evaluated, according to the thin shell and underwater explosion theory. The relationship between the elastic shell strain and three main factors, i.e. the vessel diameter, the shell thickness and the mass of the inner explosion, is revealed by numerical simulation, and is examined by detailed experiments. The experimental results show a better consistency with the numerical results.

  • Qing-Song WANG , Qiang LAN , Jing WU

    The expressions of Hugoniot parameters of preheated metal were obtained by simplification of M-G EOS model, which made it more easily to determine Hugoniot parameters of metal at various initial temperatures using M-G model. The EOS of Mo at 1 400 ℃ had been studied by Miller and Duffy, which was not agree with M-G EOS model. Some problem need to research further.

  • Jin-Liang GUO , Fu-Sheng LIU , Gao-Yu HAO , Ming-Jian ZHANG , Dai-Yu ZHANG , Xue-Dong XUE

    The iron sample is symmetrically impacted by a high speed flyer of the same material, which is launched by use of two-stage light-gas gun. The temperature of the interface between iron and sapphire is determined by measuring the spectra illuminaton. In experiment, a new technique is applied to prepare the bulk-iron/sapphire interface, and an improved in-situ method is used to calibrate the pyrometer. As a result, the “peak radiation” from the directly contacted interface is effectively diminished, and the stable emission from the ideally intacted interface of Fe/Al2O3 is observed. The result shows that the Fe/Al2O3 interface temperature corresponding to the shock pressure of 164 GPa is (3 950±180) K.

  • Xue-Ping ZHENG , Fu-Sheng LIU , Ming-Jian ZHANG , Xian-Meng CHEN , Yue SUN

    The cryogenic target technique and an optical analysis technique are combined to measure multi-shock Hugoniot equations of state of liquid carbon monoxide. The measured first, second, and third shock pressures are respectively 19 GPa, 60 GPa, and 71 GPa. The maximum compression ratio of volume reaches three point five and higher by twenty percent than that of ever reported one. The measured results for specific volume are less by nearly twenty percent than the predicted ones by molecular fluid theory, which is attributed to the molecular dissociation reactions of carbon monoxide under shock compressions. The detail of the measurement technique and calculation method are described, and such a scheme can be applied to other molecular fluids to achieve higher pressures and larger compression ratios.

  • Xian-Wen RAN , Wen-Hui TANG , Hua TAN , Zhi-Hong XU

    The material strength in shock-induced melting region was analyzed with renormalization group theory, and it indicates that the material strength begin to decrease as soon as the melting mass fraction reaches 0.300 798, corresponding to the point at which the longitudinal sound velocity initiates the transformation to bulk sound velocity.

  • Research Note
  • Shi-Xia WANG , Hai-Fei ZHENG

    The Raman spectra of gypsum in the pressure range of 200~1 100 MPa is studied at ambient temperature, and the dissolvability and phase transition of gypsum are observed. It shows that gypsum is stable at the pressure less than 407 MPa; and then gypsum begins to dissolve with the increasing pressure. Gypsum stops dissolving and phase transition happens (gypsum-bassanite) to some degree. After phase transition, bassanite disappears with the rising pressure. It implies that geological disasters will happen because of dissolvability and phase transition of minerals in the inner of earth.

  • Research Note
  • Shu-Hua SUN , Jie LI , Rui XU , Hai-Li ZHAO , Ri-Ping LIU

    The microstructures of hypoeutectic and hyper-eutectic Al-Cu and Al-Si alloys solidified at high pressure (5 GPa) were investigated. The results showed that high pressure had an evident influence on the morphologies and the dimensions of the solidified microstructures. This influence is directly related to the temperature interval of the liquid-solid region in the phase diagram. When the temperature interval is increased by pressure, the solidified microstructure will be coarsened. When the temperature interval is decreased by pressure, the solidified microstructure will be refined. Moreover, a new method is proposed to easily evaluate the sizes of the cellular and the dendritic microstructures.

  • Research Note
  • Jie WAN , Cheng-Mei LIU , Hai-Jun LAN , Zong-Cai TU , Wei LIU

    The enzymolysis rates of cellulase on dietary fiber under dynamic instantaneous high pressure (IHP) were studied. Utilizing the Microfluidizer machinery as the carrier of Instantaneous High Pressure treatment to deal with dietary fiber from bean dregs, we got dietary fiber of different granularities and densities under different pressures and different times under the same pressure. The corresponding enzymolysis rates of cellulase on dietary fiber were different. The hydrolysates of cellulase on dietary fiber were of some reducing sugars, such as cellobiose and glucose. The enzymolysis rates could be estimated by measuring the contents of the reducing sugars in the dietary fiber of different granularities and densities. The results indicated that with the increase of the pressure in the range of 40~90 MPa, the granularities of the materials reduced drastically, the densities of the materials and the enzymolysis rates increased. And the granularity of the materials was in minimum of 202.4 nm; when the pressure went on increasing, the granularities of the materials tended to increase because of the occurrence of expanding in the system, but the densities started to decrease and the enzymolysis rates kept increasing. The density of the materials was in minimum of 1.027 g/mL, the contents of the reducing sugars after enzyme hydrolysis was maximal at this time. When the pressure was higher than 140 MPa, the granularities and density of the materials increased, the enzymolysis rates decreased. It could be due to the reuniting of particles in the system. When the materials were treated separately with instantaneous high pressure between 90 MPa and 140 MPa for several times, the granularities of the materials increased with the increase of dealing times, the density decreased first and then increased, and the enzymolysis rates decreased.

  • Research Note
  • Ru-Jiang LI , Zhao-Wu SHEN , Feng-Ying WANG

    Shock heating can cause temperature rise prior to the porous liner collapse process because of its porous nature, which is possible to increase the jet temperature and enhance the jet ductility. The temperature rise calculation method was presented, and the porous effect on the jet behavior was studied with the pulse X-ray photograph. It was shown that the jet ductility increased with the initial porosity within some value, and the jet diameter became smaller with increasing initial porosity.