高压物理学报

Damage Characteristics of Rear Walls of Aluminum Whipple Shields by Oblique Hypervelocity Impact of Aluminum Spheres

GUAN Gong-Shun, HA Yue, PANG Bao-Jun

2012, 26(1): 1-6. doi: 10.11858/gywlxb.2012.01.001

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Abstract:
In order to simulate and study the oblique hypervelocity impacts of space debris on bumper of spacecrafts, a series of oblique hypervelocity impact experiments of aluminum Whipple shields are carried out by a two-stage light gas gun. The aluminum alloy projectile diameter is 3.97 mm, the impact velocities range from 1.14 to 5.35 km/s, and the impact angles range from 0 to 70. The crater distributions on the rear wall of aluminum Whipple shield obliquely impacted by aluminum spheres are obtained and analyzed. In addition, the forecast equations for crater distribution on the rear wall of aluminum Whipple shield by oblique hypervelocity impact are derived. The results indicate that there are two crater distribution areas on the rear wall under hypervelocity oblique impact. The critical fragmentation velocity of projectile will bring effect on the relationship between the impact damage law of rear wall and impact angle. For aluminum alloy Whipple shield, there exists a critical initial collision angle at which the impact damage on the rear wall is the most severe.

Debris Cloud Characteristics of Non-Spherical Projectile Based on Characteristic Length

XU Kun-Bo, GONG Zi-Zheng, HOU Ming-Qiang, ZHENG Jian-Dong, YANG Ji-Yun

2012, 26(1): 7-17. doi: 10.11858/gywlxb.2012.01.002

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Abstract:
The effects of non-spherical projectile shape on hypervelocity impact are investigated for the cube and flake projectiles, which are the typical shapes of orbital debris in ORDEM2000 and Standard Breakup Model (SBM), by using AUTODYN-3D hydrocode simulations. The characteristics of the debris clouds produced by the hypervelocity impact based on the characteristic length of projectile are analyzed from their shape, mass, velocity and energy distributions, respectively, and are compared with the common used sphere projectile. The simulated results show that the shape and impact orientations of projectile have obvious influences on the debris cloud distribution, and moreover, the point impacts of the cube and flake have the maximum penetration capability, whereas the sphere is minimal. This means that the meteoroids and orbital debris impact risks of spacecrafts would be underestimated using the spherical projectilebased Ballistic Limit Curves (BLC). The projectile shape effects based on the real characteristic length of orbital debris will make more reasonable corrections for the BLC.

Mechanical Characteristics of C-SiC Composite Dual-Wall Shield Structure Subjected to Hypervelocity Impact

SHI Jiao-Hong, LI Yu-Long, LIU Yuan-Yong, SUO Tao

2012, 26(1): 18-26. doi: 10.11858/gywlxb.2012.01.003

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Abstract:
C-SiC composite is a new type of material which is being developed with aerospace technology. C-SiC composite possesses excellent properties and can satisfy the requirements of spacecraft protection system. Therefore it is very significant to study the mechanical behavior of C-SiC composite subjected to hypervelocity impact. Based on current simulations and experiments about C-SiC composite, a set of parameters which are essential for simulating C-SiC composite subjected to hypervelocity impact are derived in this paper. The characteristics of C-SiC composite dual-wall shield under hypervelocity impact and its ballistic limit curve are obtained by numerical simulations with AUTODYN, and furthermore, the ballistic limit equation is also developed.

An in Situ Electrical Conductivity Measurement System in Diamond Anvil Cell

LI Ming, YANG Jie, YANG Wu-Ming, WANG Hui-Xin, LI Li-Xin, GAO Chun-Xiao

2012, 26(1): 27-32. doi: 10.11858/gywlxb.2012.01.004

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Abstract:
In situ resistance measurement in a diamond anvil cell under high pressure and high temperature will be restricted by the thermal insulation. If the ordinary powder heat insulating material is used, it is difficult to introduce the electrode and measure resistance accurately. Here the in situ resistance measurement under high pressure and high temperature is performed successfully using a sputtered alumina film coated onto the surface of the top anvil plate as an insulation layer and a sputtered molybdenum film used as an electrode. With this device, the electrical conductivity of iron magnesium silicate [(Mg0.875,Fe0.125)2SiO4] under 31-35 GPa and 1 500-3 400 K is obtained. It is found that the activation energy increases with pressure, and the activation volume and activation energy are significantly reduced compared to that under the pressure and temperature lower than 15 GPa and 1 200 K.

Crystallization Behavior of Polyamide 1010-Single-Walled Carbon Nanotube Nanocomposites under High Pressure

WANG Biao, ZHENG You-Jin, JIA Xiao-Peng, MA Hong-An, ZHANG Xue-Quan

2012, 26(1): 33-40. doi: 10.11858/gywlxb.2012.01.005

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Abstract:
The PA1010 (polyamide 1010)-SWCNT (single-walled carbon nanotube) nanocomposites crystallized at different temperatures and pressures for 30 min are prepared by an XKY-61200MN type high-pressure apparatus. The structure, crystallization behavior and morphological feature of high-pressure crystallized samples are studied by XRD (X-ray diffraction), DSC (differential scanning calorimetry), SEM (scanning electron microscope) and TEM (transmission electron microscope). The results show that high-pressure melt crystallization occurs in the pressure range of 1.0-2.5 GPa, while high-pressure annealing occurs in 3.0 and 4.5 GPa. Both melt crystallization and annealing under high pressure contribute to the thickening of polymer lamellar crystals, and moreover, the effect of high pressure melt crystallization is superior to that of high-pressure annealing. XRD results show that the triclinic form of PA1010 remains unchanged after high-pressure treatment, and both melt crystallization and annealing under high pressure can decrease (100) and (010) crystal plane spacing, and namely the high-pressure treatment results in close packing of polymer molecular chains. DSC results show that elevating the pressure and temperature during melt crystallization under high pressure can lead to the formation of crystals with larger lamella thickness, and the highest value of melting point and crystallinity obtained in the sample crystallized at 2.0 GPa and 350 ℃ are 208.5 ℃ and 64.6%, respectively. The large-sized crystals with c axis thickness exceeding 150 m are detected by SEM and TEM in the sample crystallized at high pressure. The interpenetrating network structure between the SWCNT and PA1010 matrix is formed, and the rigid SWCNT as high pressure nucleating agent can promote growth and thickening of PA1010 crystals under high pressure.

Equation of State of Solid Neon from Quantum Calculation

WU Na, TIAN Chun-Ling, LIU Fu-Sheng, KUANG An-Nong, YUAN Hong-Kuan, ZHENG Xing-Rong

2012, 26(1): 41-47. doi: 10.11858/gywlxb.2012.01.006

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Abstract:
The interaction energy for fcc-neon-crystals at high pressure is calculated by Hartree-Fock method and the atomic cluster theory. The two- and three-body contributions to the static energy are also studied. Incorporating the influence of the zero-point vibration, the equations of state of fcc neon are calculated and compared with the available experimental 300 K isotherm up to the pressure of 208 GPa. It demonstrates that the calculated isotherm is in good agreement with measurements at pressures above 30 GPa. Compared with the recent predictions, the calculated results systematically improve the 300 K isotherm by 3%-5% between 100 and 210 GPa, and imply more static energy-volume relation at high pressure.

Combined Engraving Process of C-Shaped Solid Armature in Electromagnetic Railgun

ZHANG Yi, YANG Chun-Xia, LI Bao-Ming

2012, 26(1): 48-54. doi: 10.11858/gywlxb.2012.01.007

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Abstract:
In order to meet the requirement for initial contact pressure between armature and rails of electromagnetic railgun, by taking the engraving process of C-shaped armature in small caliber electromagnetic railgun as the research object, three engraving modes including uniform loading, impact loading and combined loading are simulated by using finite element method based on the mechanical analysis, and then the changes of radial deformation, stress and shear stress of the elements in the armature arm are compared and analyzed. The results show that the combined loading can obviously decrease the degree of shearing damage during solid armature engraving process and, in addition, improve initial contact pressure effectively in the same condition. The research findings show that combined mode is beneficial to increase the launching efficiency of electromagnetic railgun.

Experimental Investigation of the Influence of Highly Argon Dilution on the Critical Initiation Energy for Direct Initiation of C2H2-2.5O2 Mixtures

ZHANG Bo, Lee John H S, BAI Chun-Hua

2012, 26(1): 55-62. doi: 10.11858/gywlxb.2012.01.008

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Abstract:
Direct initiation is achieved via a high voltage capacitor spark discharge, and the critical energy is accurately estimated from the analysis of the current output. A good agreement is found by comparing the critical initiation energy from experimental measurement and Lee's surface energy model. The influences of highly argon dilution on the critical energy of direct initiation are investigated experimentally for C2H2-2.5O2 and 70% argon diluted C2H2-2.5O2 mixtures. The results show that the critical energy is inversely exponential to the initial pressure for C2H2-2.5O2 mixtures with and without highly argon. Both the experimental and theoretical results indicate that dilution of highly argon in C2H2-2.5O2 enhances the critical initiation energy for direct initiation at the same initial condition. Since the critical initiation energy is proportional to the cube of ZND induction zone length, the dilution of highly argon increases the ZND induction zone length of C2H2-2.5O2 mixture under the same initial pressure, and accordingly the critical initiation energy is raised remarkably.

A Dynamic Friction Analysis Method of Charge Survivability during Supersonic Penetration of Concrete Targets

ZHANG Xu, CAO Ren-Yi, TAN Duo-Wang

2012, 26(1): 63-68. doi: 10.11858/gywlxb.2012.01.009

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Abstract:
Based on the assumption of elastic deformation of charge, a novel theoretical analysis method for charge survivability in the process of penetration is proposed by using relative displacement between projectile body and internal charge, friction work, hot spot theory, and principle of thermal dynamics. The resistance function during penetration is based upon the cavity expansion theory in the analysis. The radial stress on the projectile surface is obtained utilizing mass and momentum conservation equation and Hugoniot jump condition. In addition, the resistance forces in the supersonic penetration of concrete targets are calculated with finite difference method and Newton's Second Law. The important design parameters of charge affecting the charge survivability in the penetration are revealed from the elastic theoretical analysis, which provide a theoretical basis for the survivability design of housing explosive.

An Experimental Study of Thin Steel Plates Perforated by Conical-Nosed Projectiles

SUN Wei-Hai, JU Gui-Ling, CHEN De-Min, YANG Ban-Quan

2012, 26(1): 69-75. doi: 10.11858/gywlxb.2012.01.010

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Abstract:
Both quasi-static and impact loading experiments of thin steel plates are performed using conical-nosed projectiles with cone angle of 90. Load-deflection curves and different failure modes are acquired from the quasi-static tests. Membrane analysis and plastic collapse model with pure bending are investigated and compared with the experimental data. It is shown that the membrane force dominates the deformation process for the large deformation of thin plate; with increase of the thickness of plate, the bending moment becomes more and more important. In the impact experiments, the initial and residual velocities with different failure modes are obtained for four plates with different thicknesses, and the critical perforation energies are evaluated. In addition, the experimental data of quasi-static and dynamic tests are compared and discussed.

Numerical Simulation on the Effect of Surface Concrete Layer on Inner Explosion of Runway

KANG Yan-Long, JIANG Jian-Wei, WANG Shu-You, MEN Jian-Bing

2012, 26(1): 76-82. doi: 10.11858/gywlxb.2012.01.011

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Abstract:
The explosion damage of runway is numerical simulated using a hydro code of AUTODYN based on TCK damage model considering tensile failure. The effects of charge and surface concrete layer thickness on the explosion crater diameter are obtained when the detonation is at the bottom of surface concrete layer. The results indicate that the model describes well the process of concrete fracture and crater formation in surface concrete. According to the simulation results, the dimensionless expression relating crater radius, cavity radius and the thickness of the surface concrete layer is established to predict the crater parameters during inner explosion in runway. A good agreement is achieved between the crater sizes measured by experiment and that predicted using this empirical equation.

An Abrasion Algorithm for Ogive-Nose Steel Projectile Penetrating Concrete Target

YANG Yang, HE Tao, WEN He-Ming

2012, 26(1): 83-88. doi: 10.11858/gywlxb.2012.01.012

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Abstract:
A finite difference program is developed to predict the mass loss, nose shape change, and penetration depth of a steel projectile which penetrates into concrete targets based on the modified empirical equation of nose surface abrasion velocity and the assumption that the density of the projectile is constant. The model predictions are compared with the experimental results available in the literature, and good agreements are found between the present calculations and the experimental observations in terms of nose shape and mass loss.

Numerical Simulation Analysis of Particle Impacting Breaking Rock

REN Jian-Hua, XU Yi-Ji, ZHAO Jian, ZHAO Xu-Long, ZHANG Meng

2012, 26(1): 89-94. doi: 10.11858/gywlxb.2012.01.013

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Abstract:
The three-dimensional nonlinear dynamics of particle impacting breaking rock is simulated with LS-DYNA3D. The energy conversion curves and the process of rock breaking under steel particle are obtained, and the mechanism of rock breaking is also analyzed. The simulation results agree with the experimental observations basically. Therefore, this simulation is feasible and can be used as a good reference for optimizing hydraulic parameter for oil well drilling.

Overpressure Comparison of Blasting in Air and Special-Made Hemispherical Structure

QU Yan-Dong, YAN Hong-Hao, LI Xiao-Jie, LIU Hua-Xin

2012, 26(1): 95-101. doi: 10.11858/gywlxb.2012.01.014

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Abstract:
The explosive welding process always accompanies with explosive vibration, shock waves, overpressure, hazardous gases and noises. A method of designing a hemispherical structure with 36 m in diameter, whose entrance and smoke extraction opening are 8 m in height and 8 m in diameter respectively, is proposed to decrease the influence of overpressure during the explosive welding process. In order to evaluate the rationality and efficiency of the special-made hemispherical structure, the overpressure comparative experiments of blasting are carried out in air and in the special-made hemispherical structure with a 1/6 scale factor. The experimental results prove that the hemispherical structure with a 1/6 scale factor reduces the overpressure efficiently, especially for the propagation distance longer than 20 m. Furthermore, the overpressure along the tangent direction (perpendicular to the entrance of the hemispherical structure) is lowered more than that along the radial direction (the entrance of the hemispherical structure) for the same propagation distance. Considering the characteristics of propagation and reflection of shock waves, the possible reasons for the overpressure decreasing of blasting in the hemispherical structure are also discussed.

Mathematical Model and Numerical Simulation of Two-Phase Flow Interior Ballistics of Variable Burning-Rate Propellant

MA Zhong-Liang, LIU Lin-Lin, XIAO Zhong-Liang

2012, 26(1): 102-106. doi: 10.11858/gywlxb.2012.01.015

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Abstract:
In order to describe the combustion and interior ballistics processes of variable burning-rate propellant more accurately, the model of two-phase flow interior ballistics of variable burning-rate propellant is established, which consists of one center hole and double layers. In the charge condition of 30 mm cannon, Lax-Wendroff difference scheme with second order accuracy is used to get the numerical solutions of the model. The pressure and velocity profiles calculated are in good accordance with the actual ones. Therefore this numerical model can truly and accurately reflect the real physical process of interior ballistics. The simulation results show that it is very effective to restrain the pressure waves in the bore of variable burning-rate propellant, which is great benefit for fire safety. The analysis of the calculation parameters, such as phase velocity and bore pressure, plays a guiding role in the further research of the interior ballistics process of variable burning-rate propellant.

1 064 nm Laser Damage on Indium Tin Oxide Films

LI Yang-Long, WANG Wei-Ping, LUO Yong-Quan, WANG Hai-Feng, ZHANG Da-Yong

2012, 26(1): 107-112. doi: 10.11858/gywlxb.2012.01.016

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Abstract:
Liquid crystal optical elements have important applications in laser facility, and the indium tin oxide (ITO) films are generally used in liquid crystal optical elements as transparent conductive electrodes. Laser induced damage of ITO films leads to failure of liquid crystal optical elements. The laser damage model of ITO films which simulates the temperature distribution and thermal stress distribution was established. The laser damage of ITO films was experimented through pump-probe technology, and the power density producing damage at a probability of 50% (i.e., damage threshold) was obtained by 1-on-1 testing, and the square resistance of the film after laser irradiation was also measured. The experimental data basically agree with the simulated results. The results show that 1 064 nm laser damage of ITO film occurs mainly by thermal stress. The damage of ITO film begins from K9 glass substrate after CW laser irradiation, while the damage begins from the surface of ITO film after pulsed laser irradiation. Furthermore, the laser damage thresholds decrease with the increase of thickness of ITO films. The square resistance of ITO films increases with the increase of laser intensity unless the ITO films have been damaged completely. The optimal thickness of ITO film in liquid crystal optical element depends on the factors of laser damage, transparence and square resistance.

Numerical Simulation of Microchannel of Dynamic High-Pressure Microfluidization Based on FLUENT

LIU Wei, LI Huo-Kun, LIU Cheng-Mei, LIU Wei-Lin

2012, 26(1): 113-120. doi: 10.11858/gywlxb.2012.01.017

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Abstract:
In order to analyze the flow field within the microchannel of dynamic high-pressure microfluidization, the geometric model and mesh model are established, and the pressure and velocity distributions of the flow field in interactive chamber are obtained with SIMPLEC solution algorithm and RNG k- model using FLUENT software. The simulated results show that the high-speed jet flow impinging increases the acting force field, and the sharp increment of the flow velocity rapidly increases the velocity gradient and shear stress. All these ensure the excellent effect of the high-pressure microfuidization. In addition, because of the opposite change of the static pressure and velocity in the oscillating chamber, the dramatic changes of static pressure greatly enhance the effect of gas cavity and pressure release, which corrode the material of the interactive chamber. It is desirable to appropriately decrease feeding speed, reduce the fluid separation inlet corner angle, and choose a short discharge nozzle on the condition of ensuring the impinging speed when designing the internal microchannel of interactive chamber.

2012 Vol. 26, No. 1

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