高压物理学报

The Constitutive Relationship between High Pressure-High Strain Rate and Low Pressure-High Strain Rate Experiment

CHEN Da-Nian, LIU Guo-Qing, YU Yu-Ying, WANG Huan-Ran, XIE Shu-Gang

2005, 19(3): 193-200 . doi: 10.11858/gywlxb.2005.03.001

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Abstract:
It is indicated that the constitutive equations at high strain rates proposed by Johnson-Cook(J-C), Zerilli-Armstrong (Z-A) and Bodner-Parton (B-P) collapse the data of flow stress in compression, tension, torsion, and shear into simple curve with the scalar quatities 'effective' stress and 'effective' strain, however, the collapsed data of flow stress did not include the data in the planar shock wave tests. The SCG constitutive equation proposed by Steinberg et al for the planar shock wave tests is discussed, which describes the coupled high pressure and high strain rate effects on the plastic deformation of materials. Basing on the recent experiments at elevated temperatures and high strain rates and the shear strength measurements during shock loading, the flow stress for tungsten at high pressure and high strain rates is estimated with J-C and SCG constitutive equations, respectively. It is concluded that the J-C, Z-A and B-P constitutive equations may not be appropriate to describe the plastic behavior of materials at high pressure and high strain rates, comparing with SCG constitutive equation. It is emphasized that the physical background of the constitutive equation at high pressure and high strain rates is different from that at low pressure and high strain rates.

A New Statistical Meso-Scopic Damage Model and Its Applications in Spalling Processes

ZHOU Hong-Qiang, QIN Cheng-Sen, ZHANG Shu-Dao, ZHANG Feng-Guo, LIU Wen-Tao, WANG Pei

2005, 19(3): 201-205 . doi: 10.11858/gywlxb.2005.03.002

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Abstract:
A new damage evolution equation for ductile materials is presented based on the statistical meso-scopic damage mechanism, which consistent well with the results of analysing the mechanical responses for the spherical cell containing a single central spherical void. The model presented is incorporated in a hydrodynamic one-dimensional finite-difference computer code, to simulate the process of spallation of OFHC copper. The calculation is in good agreement with the experimental data.

Study on Sound Velocity and Unloading Path for Single Crystal LiF under Shock Compression

YU Jin-Quan, XIAO Ya-Bin, ZHOU Xian-Ming, TAN Hua

2005, 19(3): 206-212 . doi: 10.11858/gywlxb.2005.03.003

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Abstract:
Symmetrical impact experiments for single crystal LiF were conduced at two-stage light-gas gun with a VISAR diagnostic. Longitudinal and bulk sound velocities, and unloading path of LiF were obtained up to 79.1 GPa shock pressure. Experimental results indicate a good linearity between the Lagrangian longitudinal sound velocity and the particle velocity. There is no evidence of shock-induced melting or phase transition for LiF in the present pressure range. The LiF unloading path and velocity profiles show a clear transformation from the elastic release to the plastic unloading.

Microstructure Fractural Characteristics of Energetic Materials under Compressive Loading

WU Hui-Min, LU Fang-Yun, LU Li, WANG Zhi-Bing

2005, 19(3): 213-218 . doi: 10.11858/gywlxb.2005.03.004

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Abstract:
The fractural surfaces of the compression tested specimens have been observed by scanning electron microscope (SEM). Microstructure fractural characteristics of three energetic materials under compressive loading at different strain rates are obtained. Based on the material composition, the fractural mechanisms of the PBX and Comp.B under the loading are discussed, respectively, which attempts to explain differences of the fractural characteristics between the two explosives.

A Study on the Spallation Behavior of Silicon Nitride

XIAO Gui-Feng, TANG Zhi-Ping, ZHOU Chang-Guo, HU Xiao-Jun, CAI Jian

2005, 19(3): 219-224 . doi: 10.11858/gywlxb.2005.03.005

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Abstract:
Shock behavior of silicon nitride ceramic was investigated by using a onestage light gas gun facility. A new technique is developed to measure the spall characteristics of materials with embedded electro-magnetic particle velocity gauges in the sample. This method measures the particle velocity profiles inner the sample and particularly, the gauge located behind the spalling plane will disclose clearly the message of spallation of the sample, which differs from the usual methods such as VISAR and manganin gauge. By this method, we obtained experimentally the spall strength of silicon nitride ceramic of density 3.12 g/cm3 as 0.73 GPa, which fit the data of Nahme et al. The scab thickness was almost equal to the flyer thickness in the experiments, since the symmetry impact was used. The experimental results indicate that the particle velocity gauge method can be used to study the spllation behavior of non-electromagnetism materials. Since we used three gauges in one shot to record velocity profiles at different locations, so the Hugoniot data up to 3.6 GPa (as in elastic range) was also obtained.

Equation of State of Cassiterite at Room Temperature and up to 13 GPa

JIANG Xi, ZHOU Wen-Ge, LIU Yong-Gang, XIE Hong-Sen, ZHANG Huan, LIU Jing, MA Mai-Ning, LI Xiao-Dong, LI Yan-Chun

2005, 19(3): 225-229 . doi: 10.11858/gywlxb.2005.03.006

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Abstract:
At room temperature and up to 13 GPa, in situ energy dispersive X-ray diffraction measurements for a natural cassiterite, collected from Gejiu tin deposits, Yunnan, were performed by using diamond anvil cell instrument with synchrotron radiation at BSRF. The results show that cassiterite is stable up to 13 GPa and its parameters of unit-cell decrease with increasing pressure. On the other hand, the parameters of unit-cell we calculated are bigger than these of former experiments with synthetical cassiterite. According to Birch equation of state, KT(0)＝228 GPa. For natural cassiterite crystal, it is believed that Zr replacing to Sn may be the reason for expansion of unit-cell.

Experimental Investigation on the Detonation Cellular Structure Caused by C5~C6 Cloud Fuel Mixtures

HE Xiao-Bo, XIE Li-Feng, PENG Jin-Hua

2005, 19(3): 230-234 . doi: 10.11858/gywlxb.2005.03.007

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Abstract:
The detonation cellular structures caused by C5~C6 cloud fuel mixtures are studied under the initial atmospheric pressure and room temperature by improved soot foil technique. Sharp cellular patterns are obtained. Meanwhile, the effect of equivalence ratio and initiation energy on the detonation cell size are also discussed respectively. The experimental results show that the detonation cell size of C5~C6 increases almost linearly with the increase of the equivalence ratio, but the detonation cell size increases first then decreases with the increase of the initiation energy. Moreover, when the initiation energy gets high enough, the fine structures in cellular structures are observed.

Activities of Antioxidative Enzymes and the Responds to Cold Stress of Rice Treated by High Hydrostatic Pressure

BAI Cheng-Ke, LI Gui-Shuang, DUAN Jun, PENG Chang-Lian, WENG Ke-Nan, XU Shi-Ping

2005, 19(3): 235-240 . doi: 10.11858/gywlxb.2005.03.008

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Abstract:
Rice seeds (Oryza sativa L. cv. Yuexiangzhan) were soaked for 10 h or not soaked, then exposed to 75 MPa high hydrostatic pressure (HHP) for 12 h. The seeds treated by HHP and their control were sowed in the field. Activities of antioxidative enzymes (SOD, AsA-POD) in the leaves, Rubisco content, Fv/Fm and PSⅡ were measured to evaluate the effect of HHP on the growth and development of rice. Results indicated that HHP inhibited the increasing of pigment and protein content in the early growth stage (12 d). Activities of antioxidative enzymes were lower than that of the control at the moment. With days after sowing increasing, the content of pigment and protein in the treatment were higher than that of the control (Yuexiangzhan). Antioxidative ability of rice treated by HHP was stronger than that of the control at the 32th days after sowing. The content of Rubisco, including Rubisco large subunit and Rubisco small subunit, was higher in the treated rice than that of the control at the natural low temperature. Fv/Fm and PSⅡ of treatment and control decreased at noon but can recover at evening, and recovery of treatment was better than that of the control. These results suggested that difference in growth between the treatment and control was due to the effect of HHP on the activities of antioxidative enzymes of rice possibly. Furthermore, HHP may enhance rice's resistance to low temperature.

Effect of High Pressure on Seed Germination and Seedling Growth of Wheat

LIANG Ling, ZHANG Zheng-Mao, DUAN Xu-Chang, YANG Gong-Ming, LI Guo-Long

2005, 19(3): 241-246 . doi: 10.11858/gywlxb.2005.03.009

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Abstract:
Using the wheat seed of Yumai No.18 as material, the effect of high pressure on seed germination and seedling growth of wheat was preliminary studied, and seedling growth of wheat that treated under 95 MPa pressure in various time was investigated.Results showed that, in 50~95 MPa pressure, all vacuum-packed seeds could not germinate; the germination of seeds that packed in water was inhibited significantly; the germination power and germination rate of seeds soaked for 6 h and packed in water were slightly inhibited. These indicated that water could alleviate the harm of high pressure to wheat seed. The average seedling height and seedling fresh weight of wheat seeds treated by 95 MPa pressure in various time both exceed CK.

Behaviors of Initiation and after-Initiation for Homogeneous Explosives

LI Yin-Cheng

2005, 19(3): 247-256 . doi: 10.11858/gywlxb.2005.03.010

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Abstract:
Campbell's experimental studies of behaviors of initiation and after-initiation for homogeneous explosives were introduced and analyzed, but initiation conditions were not dealt with. Campbell's experimental results showed that detonation originated at the gap-explosive interface some microseconds of induction time later after the shock entered the nitromethane (NM). In other words, detonation is initiated by shock not instantaneously but directly (namely, not to pass through other processes, such as deflagration). The experimental data were newly treated, then they showed obviously that after initiation of detonation in NM the net detonation velocity is less than the normal detonation velocity. The experimental values of induction time decrease from 3.06 s to 0.705 s if the efficient pressures of shock wave increase from 8.82 GPa to 12.14 GPa. The two-phase repulsive-translation (A, m) equation of state was used to describe states of detonation product, and formularies of estimating induction time were derived newly and strictly from the thermal initiation theory. The calculated values of induction time estimated by the new formularies decrease from 248 s to 0.99 s if the efficient pressures of shock wave change in the same region. The calculated values of induction time are markedly higher than the experimental values. Thus this indicates that the thermal initiation theory is not applicable to describe the behaviors of shock initiation of NM. The cause is that the explanation of behaviors of shock initiation for homogeneous explosives with the thermal initiation theory does not accord with microscopic motion image of substance. Therefore, the thermal initiation theory is not the applicable one to describe behaviors of shock initiation for homogeneous explosives.

Analysis of High-Velocity Tungsten Rod on Penetrating Brittle Target

WANG Yan-Bin, LI Jiu-Hong, WEI Xue-Ying, YU Mao-Hong

2005, 19(3): 257-263 . doi: 10.11858/gywlxb.2005.03.011

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Abstract:
Brittle materials can be pulverized near the tip of the penetrator under high-velocity impact. This paper considers the pulverization of brittle materials and divides the target into the pulverized, cracked and elastic regions, and derived the cavity expansion pressure, viz. target resistance Rt of A-T model (modified hydrodynamic model) based on static cylindrical cavity expansion theory. The influences of the pressure-shear coefficient on Rt and stress fields are discussed. The depth of penetration is calculated using A-T model for a tungsten long rod impacting brittle target at 1.5~4.5 km/s. The calculated results of this model are compared with the experimental data and the results of other models.

The Least Absolute Value Linear Fitting of D-u Line

CHEN Xiu-Fang, CHEN Gao-Bo, GONG Zi-Zheng

2005, 19(3): 264-268 . doi: 10.11858/gywlxb.2005.03.012

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Abstract:
The Linear relationship between shock wave velocity D and particle velocity u is very important to obtain high pressure equation of state and dynamic properties of materials under shock loading. In this paper, the least absolute value method is adopted to fit the D-u line of several kinds of materials, and comparing with the generally accepted least square method. Results show that for the experimental data which scatter small (e.g., non-porous samples), the two methods obtain almost the same results; but for the experimental data which scatter large (e.g., porous samples), the two methods obtain different results. Anyway, the least absolute value method has small average absolute error than the least square method. The reason of the different result between the two methods was addressed.

Study on the Technique of Electric Gun Loading for One Dimensionally Planar Strain

WANG Gui-Ji, ZHAO Jian-Heng, TANG Xiao-Song, TAN Fu-Li, WU Gang, LIU Hai-Tao, KUANG Xue-Wu

2005, 19(3): 269-274 . doi: 10.11858/gywlxb.2005.03.013

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Abstract:
The designing principles are discussed based on the analyses of discharging circuit of electric gun. According to those, an electric gun with the energy of 14.4 kJ is designed and established. The measuring results show that the parameters of the electric gun, for example, the inductance is less than 40 nH, the discharging period is 7 s, the flatness of the flyer is less than 40 ns, and the rising ratio of the initial current is to 750 GA/s. Compared with the same type of devices at home and abroad, the electric gun is high level and with good performances. Based on the above discussions and analyses, the common requirements are presented for electric gun in order to attain the one dimensionally planar strain.

Review on the Simulation of Detonation Products Equation of State by Monte Carlo Method

MA Yi-Gang, LI Sheng-Cai

2005, 19(3): 275-278 . doi: 10.11858/gywlxb.2005.03.014

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Abstract:
In this paper, the background and progress of Monte Carlo method, which is used to simulate the equation of state of detonation products directly at atoms level, is reviewed. The expression of the macroscopic values, the computation of the statistical average, the selection of the potential functions and the boundary condition are described in detail. Monte Carlo method is different from the traditional treatments that are primarily based on spherical potentials and it is more accurate for the mixture of products.

Broad Pulse Forming Circuit and Its Application

WANG Xiang, JIA Lu-Feng, FU Qiu-Wei, MA Yun

2005, 19(3): 279-283 . doi: 10.11858/gywlxb.2005.03.015

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Abstract:
A measurement technique of electrical shorting pins based on broad pulse forming circuit is described here. The problem of pins shorting advance can be solved with this technique in place of the conventional narrow pulse forming circuit. The results of simulations and experiments show that the arrival time of shock-wave, flyer or free-surface can be determined precisely and reliably from the pins' signal with broad pulse forming circuit regardless of shorting advance somewhat.

The Time Response Character of Two Types of Fiber-Optic Pin under Shock Wave Loading

WANG Rong-Bo, HE Li-Hua, TIAN Jian-Hua, WU Ting-Lie, YE Yan, LI Ze-Ren

2005, 19(3): 284-288 . doi: 10.11858/gywlxb.2005.03.016

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Abstract:
Two types of fiber-optic pin have been developed for measuring shock wave physics characters in strong electromagnetic environment and low shock pressure experiments. One is the shock self-luminescene fiber-optic pin, and the other is the flash-gap fiber-optic pin. The physical mechanism of the fiber-optic pins is the quartz and the argon (or air) gap can luminesce under shock compressed. The dynamic time response character of the fiber-optic pins have been tested under shock loading. The response time of self-luminescene fiber-optic pin signals are less than 3 ns, which obtained in experiments that shock pressure was higher than 70 GPa. The response time of flash-gap fiber-optic pin signals are between 2 ns and 7 ns under 10～30 GPa shock pressures.

2005 Vol. 19, No. 3

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