Explosion, Shock Wave and Hypervelocity Phenomena in Materials II

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Authors: Akihisa Mori, Kazuyuki Hokamoto, Masahiro Fujita
Abstract: Explosive welding of a thin magnesium plate onto some metal plates was performed by using underwater explosive welding technique developed by some of the authors. The experimental results show that the wavy interface which is typically found in the well-bonded clad was observed. The welding condition is discussed using the welding window based on the numerically simulated results using AUTODYN-2D code.
Authors: Kazumasa Shiramoto, Masahiro Fujita, Yasuhiro Ujimoto, Hirofumi Iyama, Shigeru Itoh
Abstract: The paper describes a numerically simulated result for the explosive welding using reflected underwater shock wave. Through the numerical simulation, the effective use of reflected underwater shock wave was clearly suggested and the method to improve the assembly was demonstrated.
Authors: Akio Kira, Kazuyuki Hokamoto, Yasuhiro Ujimoto, Shoichiro Kai, Masahiro Fujita
Abstract: A new method has been developed to generate an extremely high impulsive pressure by using a metal jet that is discharged when a metal collides with another metal. The high pressure is used to synthesize a new material. When a metal plate was accelerated by the detonation of an explosive, it collides with the concentric circle of the conic surface of a conical concave metal block metal jets are discharged from all parts on the concentric circle. The metal jets fly toward the center while converging and collide with each other at the central axis. Because those collide at high-speed pressure becomes extremely high. The flight direction of the converged metal jet changes downward. The metal jet collides with the bottom of the block. A large hole is formed inside the bottom. The formation process of the hole was examined by the observation of the section of the block. A specimen powder that was rubbed to the conic surface is discharged with the metal jet and become the high pressure. The specimen powder is synthesized to a different material. The synthesized material is held inside the formed hole. The existence of cBN was confirmed by the X-ray diffraction of the synthesized material, in the case that BN was used as the specimen powder. Similarly, the existence of diamond was confirmed in the case of graphite powder.
Authors: Seiichiro Ii, Akio Kira, Ryuichi Tomoshige, Masahiro Fujita
Abstract: In the research center for advances in impact engineering established in Sojo university, advanced materials have been synthesized by using shock wave and their microstructure has been investigated. An extremely high shock pressure and a dynamic hot compaction technique were developed, and the synthesis of the advanced materials and composites was succeeded. Transmission electron microscopy observations revealed unique microstructures of such materials obtained by our original advanced technique.
Authors: Hisaatsu Kato, Kenji Murata, Shigeru Itoh, Yukio Kato
Abstract: To increase largely the performance of shaped charge, it is required to generate detonation velocity much higher than CJ velocity or detonation pressure much higher than CJ pressure of existing high explosives. One solution is the application of overdriven detonation phenomena. In this study, the effects of overdriven detonation in tungsten loaded high density explosive on the performance of shaped charge were demonstrated by experiments and numerical simulation. Sample shaped charge was composed of the inner layer tungsten loaded high density PBX and outer layer high velocity PBX. Concentration of tungsten powder in high density PBX was varied from 20 to 60% in mass. The pressure of overdriven detonation in inner layer PBX was measured by PMMA gauge, and was shown to be higher than 50GPa. The experimental results showed that the initial jet velocity and jet penetration velocity in target plates were largely increased by the effects of the overdriven detonation in tungsten loaded high density PBX.
Authors: Shigeru Tanaka, Kazuyuki Hokamoto, Shigeru Itoh
Abstract: The tungsten carbide - cobalt, (WC-Co) powder is compacted and bonded to on a stainless steel (SUS304) rod by using explosives. In this research, the experiments are conducted using two methods. They are the method of making the pressure of the explosive act directly on the powder and the method of explosively driving a metal pipe with high speed to create high pressure acting on powder. Crack free bulk material was recovered. Heat-treatment was performed on the recovered sample. After heat treatment, the value of hardness was increased compared with commercial material.
Authors: Young Kook Kim, Kazuyuki Hokamoto, Shigeru Itoh
Abstract: In order to achieve an optimal design of shock compaction device, various designs of parts are attempted. For the height of water container that creates an underwater shock wave and a reflected wave, a characteristic of underwater shock wave is evaluated by means of numerical analysis. It is found that the underwater shock wave and the reflected wave became one wave with higher shock pressure in the case of water container (height 21.5 mm). Also, the evaluation for a powder container is experimentally tried in consideration of reuse.
Authors: Young Kook Kim, Kazuyuki Hokamoto, Shigeru Itoh
Abstract: A shock compaction method using an underwater shockwave is used to consolidate the Cu/graphite and Ni/graphite composites. The copper powder (particle size < 45 m) and nickel powder (particle size < 150 m) were respectively mixed with the graphite powder (particle size < 45 m, purity 99.9%). The propagation phenomenon of underwater shock wave is studied by means of numerical analysis (LS-DYNA 3D) in terms of the magnitude and distribution of shock pressure impinged on the powder surface. The shock pressure of underwater shock wave obtained from shock compaction device is approximately 16 GPa. To make a big size material (ø30mm), we changed the inner size of powder container from ø10 mm to ø30 mm. We confirmed that the consolidation possibility of the big size composite materials (Cu/graphite, Ni/graphite) by the shock compaction method using underwater shock wave.
Authors: Shunsuke Tanaka, Yuichi Takemori, Masayuki Tsushida, Hiromoto Kitahara, Shinji Ando, Hideki Tonda
Abstract: In this study, effects of high pulse current (current density :>103 A/cm2, applied time: 15 s) on microstructure of magnesium alloys were investigated. A mild steel was also employed as comparison material. Refinement of microstructure by electropulsing was observed in Mg-3B2O3 and mild steel and micro-Vickers hardness of these alloys were increased by modification of microstructure.
Authors: V.D. Blank, A.A. Deribas, B.A. Kulnitsky, I.A. Perezhogin, A.V. Utkin
Abstract: The results of experiments with shock – loading of graphite bar by sliding detonation wave of HE are presented in this paper. It were revealed the nano – sized onions at the SEM investigation in the preserved sample of Graphite. The estimation of the values of pressures of shock – loading permits to assume that the observed structures were formed directly by solid – solid transformation.

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