高压物理学报

Effect of High Pressure Sintering on the Thermoelectric Properties of n-Type PbTe

CHEN Bo, SUN Zhen-Ya, LI Ming-Fa, WANG Shan-Yu, FAN Duan

2012, 26(2): 121-126. doi: 10.11858/gywlxb.2012.02.001

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Abstract:
The n-type nonstoichiometric PbTe (Pb0.55Te0.45) materials were prepared by the high pressure sintering process. The emphasis of the present study is on the influence of the pressure on the thermoelectric properties of the material. The experimental results show that the lattice defects are removed by high pressure sintering process, and it effectively adjusts the carrier concentration and its transport properties. Compared with the melting ingots, the Seebeck coefficient of the high pressure sintering sample obtains enhancement largely, the electric conductivity slightly reduces, simultaneously the thermal conductivity is low, and therefore the figure of merit (T2/) of the high pressure sintering sample is greatly enhanced. Therefore, the maximum the figure of merit of the sample prepared by 2 GPa reaches 0.59 at 700 K, which is about 150% improvement in comparison with the melting ingot.

Experimental Investigation on Resist Capability of Stainless Steel Mesh/Al Multi-Shock Shield by High-Velocity Impact

GUAN Gong-Shun, CHEN Li-Wen, WANG Shao-Heng, PANG Bao-Jun

2012, 26(2): 127-134. doi: 10.11858/gywlxb.2012.02.002

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Abstract:
Stainless steel mesh/Al multi-shock shield was designed by improving Al Whipple shield, and a series of high-velocity impact experiments were conducted by a two-stage light gas gun facility. Impact velocities of Al-spheres varied between 3.93 km/s and 4.25 km/s. The diameter of projectiles was 6.35 mm. For the different shield configurations with the same stainless steel mesh, the same shield configurations with different stainless steel mesh and the filmed stainless steel mesh shield configurations, the structure and material factors affecting on performance of shield were analyzed. The results indicated that when the stainless steel mesh wall was located in the last wall site of the bumper, it could help dispersing debris clouds, reducing the damage of the rear wall. At the same time, when the stainless steel mesh wall was located in the first wall site of the bumper, it did not help comminuting and decelerating projectile. The mesh opening size, wire diameter and separation distance arrangement were the important factors to enhance the protection performance of shields. The filmed stainless steel mesh helped in weakening the kinetic energy of debris cloud.

Numerical Simulation of Temperature Field in Sample Assembly of Cubic Press

LIU Fang, LIU Yong-Gang, XIE Hong-Sen

2012, 26(2): 135-140. doi: 10.11858/gywlxb.2012.02.003

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Abstract:
Numerical simulation for the temperature distribution in sample assembly of cubic press was carried out by using the finite-element method with simplified model and boundary conditions. Based on the adjustment of parameters of the models in simulation, the temperature distribution induced by pressure transmission media, shapes of heater and conductive metal ring were discussed in details. The results indicate that the use of zirconia instead of pyrophyllite as the buffer and thermal insulator can elevate the temperature and at the same time lower the thermal gradient in sample area while reducing power consumption. Different shapes of heater will affect on the temperature distribution. In the case of the metal ring being used in assembly, properly increasing the thickness of the ring will be beneficial to obtain desirable temperature distribution. This work could be a useful reference to optimize the design of sample assembly in cubic press for high temperature and high pressure experiments.

Thermoelectric Properties of Nanoparticle PbTe under Hydrostatic Pressure

ZHANG Xiang-Guo, MU Xin, ZHANG Zeng-Ming, DING Ze-Jun

2012, 26(2): 141-147. doi: 10.11858/gywlxb.2012.02.004

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Abstract:
The thermoelectric properties of PbTe nanoparticles were studied from ambient pressure to 0.8 GPa by using self-built set-up. The electrical conductivity increased while Seebeck coefficient decreased with loading pressure and these properties can be recovered after pressure released. Moreover, Seebeck coefficient is extremely high, up to 565 V/K at ambient pressure. At 0.8 GPa, the electrical conductivity enhances four times, the power factor adds three times and Seebeck coefficient is only reduced by 20% comparing with those at ambient pressure. These results indicate that high pressure can improve the thermoelectric properties of PbTe nanoparticle. The contracted Femi-energy is also calculated based on the First Principle under high pressure from 0.4 to 4.0 GPa. The calculated values agree well with experimental data.

Dynamic Brazilian Test and Simulation of Plastic-Bonded Explosives

FU Hua, LI Jun-Ling, TAN Duo-Wang

2012, 26(2): 148-154. doi: 10.11858/gywlxb.2012.02.005

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Abstract:
Dynamic Brazilian test of plastic-bonded explosives was investigated by split Hopkinson pressure bar (SHPB). The tensile strengths of three PBXs were acquired under different strain rates. The evolution of crack on sample surface was captured using high-speed camera. The strain field was calculated by digital speckle correlation method before samples occurred to crack. The simulation on dynamic Brazilian test was performed using discrete element method, and the simulation model considering meso-structure was acquired.The simulation results show the produce and evolution process of damage and crack, and the simulation results are in accordance with the experimental results.

Numerical Simulation of Cylindrical Shell Loaded by Explosive Rods (Ⅰ): Fluid-Structure Interaction Simulation

MAO Yong-Jian, LI Yu-Long, CHEN Ying, HUANG Han-Jun, ZHANG Qing-Ping, MIAO Ying-Gang

2012, 26(2): 155-162. doi: 10.11858/gywlxb.2012.02.006

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Abstract:
A loading test by explosive rods to simulate mechanical effects of pulsed X-ray was numerically simulated by fluid-structure interaction method. The 2-D numerical model including a cylindrical shell, two layers of rubbers, nineteen explosive rods and a layer of air was built. Therein, the two rubber materials were described by Ogden hyperelastic models, the explosive rods and their explosion product were described by High Explosive Burn model and JWL equation of state, and the air was described by polynomial equation of state. The numerical simulation was performed by the multi-material ALE method. The physical images, load transmission and structural responses were obtained. The results show that, in the loading test of 265 mm cylindrical shell by 19 explosive rods to simulate a cosine-distributed load induced by X-ray, the stress responses at typical locations are basically equivalent. Furthermore, the additive two rubber layers can affect the response characteristics of the shells, and tightly glued interactions can distort the structural responses of shells with small mass and/or low stiffness.

Investigation on the Ballistic Resistance of Double-Layered A3 Steel Targets Against Blunt Projectile Impact

ZHANG Wei, XIAO Xin-Ke, GUO Zi-Tao, MU Zhong-Cheng, WEI Gang

2012, 26(2): 163-170. doi: 10.11858/gywlxb.2012.02.007

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Abstract:
Steel plates are widely used to construct resistant structures, and a lot of literature report on the ballistic resistance of metallic monolithic target. However, few reports can be found for double-layered target (DLT), especially the one with large gap space. Experimental study was conducted on the DLTs of both in contact (I-DLT) and with 200 mm gap space (S-DLT) by using a gas gun to fire blunt projectiles. Each DLT was made of two A3 steel plates with the thickness of 5 mm. From the experiments, initial-residual velocity curves were obtained. The experimental observations are as follows. Firstly, both configurations of DLT suffer from shear plugging. Secondly, the ballistic limit of I-DLT is 1.92 times of that of 5 mm thick monolithic target. Thirdly, the ballistic resistance of S-DLT yield to large divergence. The large divergence, according to the high speed photograph and the recovered targets, is caused by the two classical different trajectory statuses of the projectile after perforation of the first plate. Fourthly, there are two ballistic limits for S-DLT. Finally, the ballistic limit of I-DLT is close to or greater than that of S-DLT. Parallel numerical simulations were conducted by ABAQUS/EXPLICIT, and the experimental phenomena and results were well predicted.

Experimental Investigation on the Yield Behavior of Aluminum Foams under Combined Stress States

ZHOU Zhi-Wei, WANG Zhi-Hua, ZHAO Long-Mao, SHU Xue-Feng

2012, 26(2): 171-176. doi: 10.11858/gywlxb.2012.02.008

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Abstract:
The initial yield behavior of Alporas closed-cell aluminium foams with relative density 8.5% under biaxial loading has been experimentally investigated using the Arcan apparatus and the universal testing machine (INSTRON 5544). The experimental yield surfaces measured from biaxial experiments are compared with various proposed phenomenological yield surface models. The comparison result indicates that the experimental data are consistent with both Miller and Deshpande and Fleck criteria. Biaxial experiments have been carried out on aluminium foams at various loading velocities to study the effect of strain rate on the initial yield surface. The results showed that the initial yield stresses of Alporas closed-cell aluminium foams are not sensitive to the equivalent strain rate ranged from 7.010-3~1.010-1 s-1.

Model for the Deceleration of Secondary Debris Produced by Hypervelocity Impact on Pressure Vessels

GAI Fang-Fang, PANG Bao-Jun, GUAN Gong-Shun

2012, 26(2): 177-184. doi: 10.11858/gywlxb.2012.02.009

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Abstract:
According to characteristic of secondary debris, initial models of secondary debris are built. The models of secondary debris are classified as three patterns. The first patten is that the projectile is not fragmentated. The second patten is that the projectile is not entirely fragmentated. The third patten is that the projectile is entirely fragmentated. The secondary debris deceleration process is analyzed based on hydrodynamics theory and gas-solid two phase flow theory. The computational model of secondary debris deceleration is built. The computational results are consistent with numerical results very well. The model of secondary debris deceleration is validated.

The High Pressure Synthesis and Properties of La0.3Sr0.7CrO3

Lü Yu-Xi, LI Feng-Ying, JIN Chang-Qing

2012, 26(2): 185-188. doi: 10.11858/gywlxb.2012.02.010

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Abstract:
We synthesizedLa0.3Sr0.7CrO3 Mott compound by using high pressure and high temperature sintering method; and studied the crystal structure and magnetic properties. It is shown that La0.3Sr0.7CrO3 adopts a cubic perovskite structure at room temperature. Above 170 K La0.3Sr0.7CrO3 is paramagnetism with the (T) curve being fitted by Curie-Weiss law, while a spin glass transition was found in La0.3Sr0.7CrO3 below 20.7 K.

Study on Leakage Model of Gas Blowout and Its Numerical Simulation

ZHENG Yuan-Pan, SU Xiao-Ke, LIU Xin-Xin, ZHANG Ya-Li, SUN Ken

2012, 26(2): 189-198. doi: 10.11858/gywlxb.2012.02.011

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Abstract:
Blowout is one of the most serious accidents of gas wells during drilling. To investigate leakage and dispersion of gas blowout and to provide scientific guidance for on-site emergency response, it is necessary to identify what model should be used to describe the leakage source. Leakage source model of gas blowout was theoretically analyzed by fluid dynamics and aerodynamics, and was also numerically demonstrated by computational fluid dynamics. Distributions of temperature, static pressure and Mach number were obtained from simulation based on theoretical analysis. These numerical results agree well with both theoretical results and related experimental results done by other researchers. The present study shows that leakage source of gas blowout during drilling stage can be characterized by model of choked flow and gas blowout can be recognized as under-expanded jet flow.

Research on the Damaging Ability of EFP Warhead at Different Incidence Angle

FAN Fei, LI Wei-Bing, WANG Xiao-Ming, LI Wen-Bin, HAN Yu

2012, 26(2): 199-204. doi: 10.11858/gywlxb.2012.02.012

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Abstract:
Using LS-DYNA simulation software, we studied the relationship of the EFP's damaging ability with the penetration incidence angle of explosively formed projectile (EFP). It was found that, with the incidence angle changing from 0 to 40, the depth of vertical penetration of EFP reduced 34.2%, and the pore size of openings increased 18.2%. During the penetration, the head velocity of EFP changed as lines with time, and with the incidence angle increasing, the head velocity of EFP decreased more quickly. At first, the depth of vertical penetration of EFP changed as lines with time, then it showed slow upward trend. The relationship between penetration parameters and time was consistent under different penetration incidence angles. Based on 0 penetration theory of EFP and oblique penetration theory of rod projectile, according to fitting curve of simulation, the correction formula of depth of vertical penetration of EFP and angle was obtained.

Slitting Mechanism and Numerical Simulation Experiments of Complex Ligamented Charge Holders

XIE Hua-Gang, RUAN Huai-Ning, WU Ling-Li

2012, 26(2): 205-210. doi: 10.11858/gywlxb.2012.02.013

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Abstract:
According to the theries of explosion mechanics and rock fracture dynamics mechanics, we found that the slits location shear stress of the complex ligamented charge holders is about 1.59 times of that of the conventional ligamented charge holders. The finite element software ANSYS10.0/LS-DYNA was employed to numerically compare the blasting effects of three kinds of seam cartridge, and it was found that the blasting effect of the complex ligamented charge holders is the best. Through comparing the effective plastic strain in the slits direction and vertical slits direction of the complex ligamented charge holders, we obtained that the effective plastic strain is the slits direction is 2.93 times of that in the vertical slits direction. After companing the pressure of surrounding rock in the far zone, we observed that the blasting pressure in the far zone of the complex ligamented charge holders is the lowest, which may lead to the minimum degree of injury to the surrounding rock and full use of the energy.

Experimental Investigation of Door-Explosion with Short-Delay Controlled Blasting in the Counterterrorism

YAN Hong-Hao, WANG Li-He, LI Xiao-Jie, WANG Bin

2012, 26(2): 211-215. doi: 10.11858/gywlxb.2012.02.014

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Abstract:
The counterterrorism personnel commonly use the methods of the concentrated charge and multi-spot explosion to open fast track, rescue the hostage and capture the terrorists. The peak overpressures of the blast wave produced by above two methods are very high, which may easily cause unnecessary damage to the counterterrorism personnel. A new multi-spot short-delay controlled blasting technique is proposed in this paper. The experimental results show that the expansion bolts could be considered as the weakness of the burglarproof door in the door-explosion, and the peak overpressure of shock wave is effectively reduced by this new method. Moreover, the best dosage and safe distance in the blasting are obtained.

Back Propagation Neural Networks of Base Bleed Propellant Burning Rate under High Pressure Condition

ZHANG Ling-Ke, YU Yong-Gang, LI Zhi-Feng, LIU Dong-Yao

2012, 26(2): 216-220. doi: 10.11858/gywlxb.2012.02.015

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Abstract:
To investigate the combustion characteristics of base bleed propellant moving with the projectile in the gun bore, the closed bomb semi-physical and experimental simulation technology was employed. The combustion property under the condition of simulative high pressure in the gun bore was studied. Two average pressure-time curves corrected by heat loss were obtained under different charge density of the closed bomb. The correlation data between burning rate and pressure (8－150 MPa) were processed by smoothing, filtering and data transformation. The burning rate model adopting back propagation (BP) neural networks describing, which is suitable for high combustion pressure condition, was built based on training data samples. Comparing with the exponential burning rate model, the BP neural networks burning rate model of base bleed propellant has higher fitting precision and stronger robust.

The Propagation Law of Shock Wave Overpressure in Nuclear Explosion Fusion Power Plant

TAO Jun-Lin, LI Ze-Peng, CHEN Xiao-Wei

2012, 26(2): 221-226. doi: 10.11858/gywlxb.2012.02.016

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Abstract:
The shock wave will be created in the process of generating electricity in the nuclear explosion fusion power plant, whose propagation law of overpressure is an important foundation for the design of cavity wall. However, there is a certain lack of describing the peak overpressure of shock wave in the existing equations (for example, relative error is great). A new equation of the peak overpressure of shock wave, the time of positive pressure + and the propagation coefficient of shock wave are suggested by theoretical analysis, from which we get the propagation law of shock wave. The comparative result indicates that the new equation is more suitable than the existing equations for solving the peak overpressure of shock wave in the power plant.

Influence of Steam Explosion on Physical-Chemical Characteristic of Corn Stalk

REN Tian-Bao, XU Gui-Zhuang, MA Xiao-Qin, YU Zheng-Dao, SONG An-Dong, ZHANG Bai-Liang

2012, 26(2): 227-234. doi: 10.11858/gywlxb.2012.02.017

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Abstract:
In the research fields of lignocellulosic materials, the physical-chemical properties are an important foundation for the resource conversion. Employing thermal gravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy methods, physical-chemical properties changes of steam exploded corn stalk were studied. The results of analysis showed that pyrolysis region of steam exploded corn stalk had a wider temperature range compared with the control substance, during which the maximum self-heating rate increased significantly and activation energies (E) decreased by 16.25%. The characteristic peak absorption intensity was significantly different. The hierarchical structure of the cell wall was completely destroyed, and crystallinity of lignocellulose decreased by 14.57%. Based on this analysis, a mechanism model of steam explosion pretreatment was constructed. The results indicate that physical-chemical properties of corn stalk are significantly affected by steam explosion pretreatment.

Effect of High Pressure Processing on Polyphenol Oxidase from Trametes Trogii

CHEN Xiao-Qiang, ZHANG Yin-Jun, ZHANG Shi-Kang, LI Jian-Rong, JIN Jian-Chang, ZHENG Na, YANG Xiu-Fang

2012, 26(2): 235-240. doi: 10.11858/gywlxb.2012.02.018

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Abstract:
The activity of polyphenol oxidase (PPO) produced from Trametes Trogii was determined through using tea polyphenols as substrate. The pH value and the substrate concentration of strongest activity of PPO are 5.0 and 4 mg/mL, respectively. The activity of PPO processed by ultrahigh pressure of 100, 300 and 500 MPa for 10 min accounted for 93%, 87% and 86% of that of untreated one. The CD spectra of PPO processed by 100 and 300 MPa pressure respectively displayed folding shape and tillering shape of Cotton effect peak located in 190－210 nm, while the retention time of the first peak fraction(i.e., the maximum molecular weight fraction) of the two processed PPO on HPGPC profiles were advanced to 1.514 and 2.296 min, respectively from 6.678 min. Compared with control, CD spectrum and HPGPC of PPO treaded by 500 MPa showed more significant difference with only one positive Cotton effect peaks on CD spectra and reduced peak area of main components on HPGPC profiles (ie, the response value of 280 nm decreased). The disparity of CD and HPGPC of PPO treated by various UHPP showed the corresponding difference in the degree.

2012 Vol. 26, No. 2

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