高压物理学报

Planar Explosion Shock Wave Attenuation in Granular Metal

CHEN Ya-Hong, BAI Chun-Hua, WANG Zhong-Qi, LI Jian-Ping

2011, 25(6): 481-486. doi: 10.11858/gywlxb.2011.06.001

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Abstract:
The loading and unloading paths of shock impact on granular metal were analyzed, and the attenuation of planar explosion shock wave in granular metal was investigated using characteristic method. The results showed that the initial peak pressure of the shock wave was determined by the type and property of the metal, porosity and detonation velocity of the explosive. The higher of impact impedance and porosity of metal and higher the detonation velocity were, the higher initial peak pressure was. The attenuation was determined by the length of explosive, impact impedance and porosity of the metal. The higher of impact impedance and porosity of metal and shorter explosive cylinder was, the more quickly the shock wave attenuated.

Characteristics Analysis of Free-Surface Velocity Profiles of Ultra-Pure Aluminum

QI Mei-Lan, LUO Chao, FAN Duan, HE Hong-Liang

2011, 25(6): 487-492. doi: 10.11858/gywlxb.2011.06.002

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Abstract:
A series of plate impact experiments were conducted to probe into the free-surface velocity profiles characteristics of ultra-pure aluminum (Purity:99.999%) by a velocity interferometer system for any reflector (VISAR). Based on the observed differences of pullback signals in amplitude, pulse width, and two sudden changes, the wave profile evolution during fracture process of ultra-pure aluminum from incipient spall to complete rupture is discussed in detail. The reasons for these change behaviors are analyzed with the mesoscopic analysis of soft-recovery sample. This paper points out that these characteristics are possibly related to the release rate of stress wave energy and the fracture behavior of material grain. These analysis results are helpful to understand the evolution process of ductile metal dynamic damage.

An Elastic/Viscoplastic Pore Collapse Model of Double-Layered Hollow Sphere for Hot-Spot Ignition in Shocked Explosives

WEN Li-Jing, DUAN Zhuo-Ping, ZHANG Zhen-Yu, OU Zhuo-Cheng, HUANG Feng-Lei

2011, 25(6): 493-500. doi: 10.11858/gywlxb.2011.06.003

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Abstract:
An elastic/viscoplastic pore collapse model of double-layered hollow sphere, in which the effect of the binder in Plastic Bonded Explosives (PBX) was taken into account, was developed as a hot-spot ignition model in shocked explosives. The space and time distributions of the velocity, strain, temperature and chemical reaction rate in shock compression of the explosive hollow sphere were theoretically calculated. A new expression of reaction rate equation was obtained for the hot-spot ignition. The three-term reaction rate model, consisting of the new hot-spot ignition term, the slow burning term at low-pressure from Kim and the high-pressure reaction term from ZHANG Zhen-Yu, was implemented into the two-dimensional, hydrodynamic finite-element code DYNA2D and used to simulate the one-dimensional shock initiation process of PBX-9501 explosive. The numerical results show that the model can successfully explain the influence of strength and content of the binder in PBX on the shock initiation, and that of particle size and porosity as well.

Study on the Grain-Size Distribution Rule and Influence Factors of Nanocrystalline Copper Fabricated under Explosive Loading

WANG Jin-Xiang, ZHOU Nan, WANG Xiao-Xu, HANG Yi-Fu

2011, 25(6): 501-507. doi: 10.11858/gywlxb.2011.06.004

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Abstract:
Nanocrystalline copper was fabricated by severe plastic deformation of coarse-grained copper at high strain rate under explosive loading. The average grain size of the samples was tested by X-ray diffraction analysis, and the deformation process was simulated recur to LS-DYNA3D finite element program. The influence of strain on the grain refining were analyzed quantitatively. The results show that it is feasible to fabricate nanocrystalline copper by explosively dynamic plastic deformation of coarse-grained copper and the grain size of the NC copper can be controlled less than 100 nm, the higher strain is beneficial to the grain refining, and the distribution of the grain size is not uniform along the loading direction.

Study on Parallel Algorithm of Eulerian Method for Three-Dimensional Multi-Material Plastic-Elastic Hydrokinetics

MA Tian-Bao, FEI Guang-Lei, ZHANG Wen-Yao

2011, 25(6): 508-513. doi: 10.11858/gywlxb.2011.06.005

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Abstract:
Parallel computing of 3D explosion and shock processes on the parallel computer is effective means for the large-scale numerical study of explosion and shock process. Considering the complexity of the parallel programming, the overall strategy for parallel programming of 3D mutil-material hydro-elastoplastic hydrocode MMIC-3D was discussed, and the PMMIC-3D parallel hydrocode was designed based on MPI (Message Passing Interface). In addition, a practical plan of program testing was presented. The speedup, efficiency and scalability of the PMMIC-3D parallel hydrocode were tested on the cluster consisting of 8 nodes based on the numerical example of shaped charge jet, and the effect of the bottlenecks of PMMIC-3D parallel hydrocode was discussed.

Study on the Development Mechanism of Detonation Wave for the Hydrogen-Oxygen Mixture in a Shock Tube

WANG Jian, DUAN Ji-Yuan, ZHAO Ji-Bo, WEN Shang-Gang, TAN Duo-Wang

2011, 25(6): 514-518. doi: 10.11858/gywlxb.2011.06.006

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Abstract:
This paper mainly focuses on the experimental investigation of the gaseous detonation wave build-up mechanism for hydrogen-oxygen mixture in shock tube. Five pressure sensors were used to record the pressures and a high-speed camera was used to capture velocities of flame, shock, or detonation wave. The high-speed camera records the transformation of flame, shock in the ignition phase and the attenuation of detonation wave. The experimental results show that the diagnostic system can effectively measure the DDT. The images of flame propagation show that the flame front is curving and dispersive. It is found that the interaction of shock and turbulent flame is a dominant factor for the onset of explosion. In the smooth tube, experiments indicate that the intensity of shock wave continually increases due to the acceleration of flame. The local explosion occurs in the reaction zone when the intensity of shock wave arrives at a critical pressure pc when some hot spots form in the local explosion centers. At that time, an unsteady detonation wave is formed immediately, and after a period of the propagation or attenuation process, it eventually evolves into a steady detonation wave.

First-Principles Study of Al, N Codoped p-Type ZnS

LI Sheng-Zhi, LIU Jin-Chao, YANG Xiang-Dong, JIANG De-Qiong

2011, 25(6): 519-525. doi: 10.11858/gywlxb.2011.06.007

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Abstract:
The electronic structures of pure ZnS, N-doped and Al-N codoped zinc-blende ZnS were calculated by using first-principles ultrasoft pseudo-potential approach of the planar wave based upon the density functional theory, and the band structure, density of states and Mulliken charge population were studied. The calculated results revealed that N-doped ZnS caused formation of deep N acceptor levels in the band gap and the carriers (hole) which were provided by N 2p states were localized near the top of the valence band. But the codoping calculation revealed that the acceptor levels showed broadening and non-localizing, and the concentration of impurities, the stability of the system were enhanced. Our calculations indicate that codoping of Al and N is in more favor of the formation of p-type ZnS.

Failure Characteristics of Alumina Penetrated by Shaped Charge Jet

REN Hui-Lan, GUO Ting-Ting, NING Jian-Guo

2011, 25(6): 526-532. doi: 10.11858/gywlxb.2011.06.008

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Abstract:
A theory model to calculate the target resistance is established to evaluate the ballistic properties; the parameters used in the numerical simulations were determined by simulating the experiment of long rod penetration into alumina ceramic target; the theoretical model is proved to be reasonable by simulating the penetration of shaped charge jet into alumina ceramic. The impact of the geometric size of the shaped charge on the jet velocity and penetration results was studied. It can be concluded that the bigger the angle and the thickness of the shaped charge are, the lower the jet velocity is, and the impact of the thickness on the velocity gradient is severe; the angle of the shaped charge has a significant influence on the penetration depth.

Experiments and Numerical Simulations of Concrete Dynamic Mechanical Properties

ZHANG Zhu, ZHAO Hui, YU Hui

2011, 25(6): 533-538. doi: 10.11858/gywlxb.2011.06.009

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Abstract:
A light gas gun was used to conduct the dynamic mechanical properties experiments of plain concrete material under three different impact velocities, getting the time-stress curves. Then, numerical calculations were used to simulate concrete's light gas gun experiments, comparing the simulation results with experimental results. In this paper the propagation of wave in flyer and target was formulated. Further analysis shows that concrete material has obvious rate-related properties, lag effect and stress wave's attenuation features, and all of this is closely related to the evolution of internal damage in material. Concrete material finally forms macro fracture under the interaction of compression wave, side release effect and reflected tensile wave of left and right free surface. The size of target in the experiment is reasonable, avoiding the effect of side releasing on the test signals of manganin piezoresistive transducer.

Study on Big Entry Hole Bidirectional Shaped Charge

LI Lei, SHEN Zhao-Wu, MA Hong-Hao

2011, 25(6): 539-548. doi: 10.11858/gywlxb.2011.06.010

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Abstract:
A shaped charge model, in which the biconical liner with the two-way charging structure was combined, was designed. Its jet formation mechanism was studied by means of numerical simulations, and the jet parameters were calculated. The obtained results were shown as follows: First, the small cone angle of the liner formed shaped charge jet, and the large cone angle formed explosively over-turned projectile. Second, the velocity of the jet tip and the projectile were respectively 6 250 m/s and 1 620.9 m/s. Third, the length and average diameter of the projectile were 26.1 mm and 8.6 mm. Based on the numerical results the jet penetrate formula was amended and then used to calculate the penetration depth of the shaped charge, and the calculated value was 69.6 mm. Finally, an experiment was carried out according to the model, the length and average diameter of the projectile were 28.1 mm and 8.8 mm. Furthermore, the penetration depth and hole size were 70 mm and 17 mm. Good agreement is among the numerical, theoretical calculation and the experimental results. In addition, the superior penetration performance is proved by the experimental results.

2-D GEL Coupling Method and Its Numerical Simulation on Vessel to Explosion Impact Load

LI Lei, BAI Jin-Song, LIU Kun, LI Ping

2011, 25(6): 549-556. doi: 10.11858/gywlxb.2011.06.011

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Abstract:
MF PPM (Piecewise-Parabolic Method) code based on Euler method and DEFEL (2-D Finite Elements Code) code based on Lagrange method were coupled according to the pressure and normal velocity consecutive rule. GEL (Ghost-fluid Euler-Lagrange) method was developed. This method has the advantage of performing large strain fluid field while small strain shell, complicated flow and interactions of many objects. A 2-D example was simulated and compared with the results in reference to prove the validity of the coupling code. Simulations on global and ellipsoidal explosion vessel yielded consistent results with experiments, proving that this program was valid to simulate the flow structure loaded by a blast wave from a central charge.

A Novel Design of a Hypervelocity Launcher Based on Two-Stage Gas Gun Facilities

ZHAO Shi-Cao, SONG Zhen-Fei, JI Guang-Fu, GONG Zi-Zheng, ZHAO Xiao-Ping

2011, 25(6): 557-564. doi: 10.11858/gywlxb.2011.06.012

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Abstract:
A new scheme of hypervelocity launcher was put forward in this paper by means of strong detonation. An explosive ring was fixed internally in a specially designed third-stage barrel in which the projectile launched by two-stage gas gun at velocity ranging from 6 to 7 km/s was able to be accelerated subsequently to a hypervelocity of 10 km/s or so. Based on hydrocode simulations, the shape of flyer and explosive ring was optimally designed. In addition, through the encapsulation of the sphere projectile by epoxy resin, the projectile damages resulted both from detonation-induced jet and spalling due to the characteristic of short pressure pulse imposed on centimeter-sized projectiles would be suppressed. The simulations illustrate that the optimized hypervelocity launcher has the capability of accelerating 1.03 g aluminum alloy projectile with a velocity of 6 km/s to 9.6 km/s, keeping the sphere-like shape with the velocity amplification ratio of 1.6.

Study on Characteristics of Partial Penetration of Projectile into Steel Panel

DONG Yong-Xiang, FENG Shun-Shan, WU Guang, DUAN Xiang-Jie, XIAO Li-Xing

2011, 25(6): 565-571. doi: 10.11858/gywlxb.2011.06.013

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Abstract:
Study on partial embedment of projectile (PEP) is put forward with the development of modern science and technology. The outer part of PEP standing stably can form an obstacle or induce the selective object to attack it by waiting for the proper chance, or act as the loading point to realize the special application. The research on a new nose shape projectile was carried out by the numerical analysis on process and characteristics of PEP and material testing of rheological behavior. Meanwhile, the main dimensionless group parameters were obtained by dimensional method. The deformation of target and energy evolution of the whole system in the forward and rebound phases of projectile were analyzed. The exploratory development work on mechanics of the PEP action was performed. Ultimately, PEP on steel panel was verified by artillery experiment.

Influence of FeMn Powder Catalyst on the Synthesis of Diamond

LIU Wan-Qiang, MA Hong-An, JIA Xiao-Peng

2011, 25(6): 572-576. doi: 10.11858/gywlxb.2011.06.014

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Abstract:
FeMn powder catalyst was employed to synthesize diamond in China-type cubic high-pressure apparatus. Fine single crystal diamond was successfully obtained in the graphite-FeMn system at 5.7 GPa and 1 550 ℃. The optical imaging microscopy observations show that all the synthesized diamond is in light yellow octahedral crystals with grain size of 0.3-0.5 mm. Moreover, there is plenty of white substance in the crystals. The surface morphology of crystals is checked by SEM, and craters can be found in the crystal surface. Mossbauer spectrum is used to detect the impurity in the diamonds. FeMn alloy and independent state Fe are the two states in catalysts, and inclusions in diamond mainly contained Fe and Fe3C. Fe and Mn were detected in the sample using X-ray fluorescent spectrum.

2011 Vol. 25, No. 6

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