Hideki Hamashima

Research on the JWL Parameters of Several Kinds of Explosives

A warhead requires the most suitable HE (High explosives). It is necessary to determine the optimal casing and HE in the development stage of the warhead by repetition of a series of process design, trial production, and testing. Accuracy of the simulation (Hydro-code) results also requires a practically usable level. However, we have asked for the JWL (Jones-Wilkins-Lee) parameters numerically by using KHT (Kihara-Hikita-Tanaka) code, since we have not experimental instruments like a streak camera and these experiments spend great deal of time and cost. For this reason, the simulation result was different from the experiment one slightly. Recently, we can ask for the JWL parameters experimentally, using the image converter camera of Kumamoto University by the joint research activities. We hope that the accuracy of these simulations might be raised by these studies. As sample explosives, PBX (Plastics bonded explosives) which used RDX or HMX, and Comp.C-4 were chosen. Further, new explosive of which detonation velocity was decreased by adding GMB (Glass micro balloon) to Comp.C-4 was made. These explosives were studied by KHT code and experiment, and JWL parameters were also gotten. As the result we could get several information, so it would be reported in this paper.

Behavior of Bubble in Small Water Tank Used for Food Processing Using Underwater Shock Wave

The food processing technology using a shock wave can prevent deterioration of the food by heat because it can process food in a short time. Generally, since the shock wave used for food processing is generated by underwater explosion, the load of a shock wave to the food becomes very complicated. Therefore, in order to process safely, it is important to clarify the behaviors of the shock wave and the bubble pulse generated by underwater explosion. In this research, in order to investigate the behavior of the shock wave in the water tank used for food processing, the optical observation experiment and the numerical simulation were performed. In the experiment, the shock wave generated by underwater explosion was observed with the high-speed video camera. The numerical simulation about the behavior of bubble pulse was performed using analysis software LS-DYNA. Comparing and examining were performed about the experimental result and the numerical simulation result. The result of the numerical simulation about the behavior of the shock wave generated by underwater explosion and the shock wave generated by the bubble pulse and the bubble pulse was well in agreement with the experimental result.

Numerical Simulation and Experiment for Underwater Shock Wave in Newly Designed Pressure Vessel

Modern eating habits depend in large part on the development of food processing technology. Thermal treatments are often performed in the conventional food processing, but it can cause discoloration and loss of nutrients of the food by thermal processing or treatment. On the other hand, food processing using an underwater shock wave has little influence of heat and its processing time is very short, preventing the loss of nutrients. In this research optical observation experiment and the numerical simulation were performed, in order to understand and control the behavior of the underwater shock wave in the development of the processing container using an underwater shock wave for the factory and home. In this experiment a rectangular container was used to observe the behavior of the underwater shock wave. In the experiment, the shock wave was generated by using explosive on the shock wave generation side. The shock wave, which passed through the phosphor bronze and propagated from the aluminum sidewall, was observed on the processing container side. Numerical simulation of an analogous experimental model was investigated, where LS-DYNA software was used for the numerical simulation. The comparative study of the experiment and the numerical simulation was investigated. The behavior of a precursor shock wave from the device wall was able to be clarified. This result is used for development of the device in numerical simulation.

Synthesis of TiCx Powder via the Underwater Explosion of an Explosive

In this study, a novel approach to the explosive synthesis of titanium carbide (TiC) is discussed. Nonstoichiometric TiCx powder was produced via the underwater explosion of a Ti powder encapsulated within a spherical explosive charge. The explosion process, bubble formation, and synthesis process were visualized using high-speed camera imaging. It was concluded that synthesis occurred within the detonation gas during the first expansion/contraction cycle of the bubble, which was accompanied by a strong emission of light. The recovered powders were studied using scanning electron microscopy and X-ray diffraction. Submicron particles were generated during the explosion. An increase in the carbon content of the starting powder resulted in an increase in the carbon content of the final product. No oxide byproducts were observed within the recovered powders.

Propagation of Underwater Shock Wave and Gas Bubble Behavior Induced by Electrical Discharge in Water

The basic behavior during underwater electrical discharge up to 10 kJ stored energy is investigated through both numerical analysis and optical-observation experiments. Since the authors have been investigating the use of underwater exploding phenomena for food processing and other applications, it is necessary to know the whole process which may affect the quality of the samples recovered. In the present investigation, the propagation of underwater shock wave was measured using a high-speed camera and compared with the numerically simulated results using LS-DYNA. Also, the motion of gas bubble, which is induced quite after the propagation of the shock wave, was measured and compared with the numerical simulation using the same code. The pressure of the bubble is not such high as the shock wave, but it is known that the impulse is not possible to be ignored due to its relatively long duration of the pressurization. Through a series of optical-observation experiments, it is confirmed that the numerical simulation is potentially possible to predict the whole phenomena for processing foods and other materials.

Numerical Simulation of Oblique Collision of Flier Plate

The metal jet that is flowed out by the oblique collision between a metal flier plate and a metal block becomes a high velocity. We have been developing the device that makes a material extremely high pressure by using the metal jet. The flier plate of the previous device had been accelerated by using a high explosive. There were several problems in the collection and analysis of the material that had been made the high pressure. Therefore we thought up the new device of which the flier plate was accelerated by a powder gun. The collision process was examined by a numerical simulation because the collision process of the flier plate of this device differs from that of the previous device. LS-DYNA was used for a numerical simulation and the difference of the collision process was clarified.

Numerical Study on Effect of Covered Water in Thawing Frozen Soil by Explosive Load

It is known to be able to expect the improvement of the harvest if the cropping time can be made early in a cold region such as Russia, Norway, Sweden and Hokkaido in Japan. Therefore, for the purpose of making cropping time early as much as possible, we researched the destruction of the frozen soil by the explosive. In the simple experiment, as compared with the experiment which placed the explosive directly on top of the frozen soil, it broke greatly in the experiment which poured out water 20 mm in height after placing an explosive directly on top of the frozen soil. Furthermore, it was found that the thawing time of residual frozen soil in the experiment using water is shorter than without water. In this research, in order to investigate the effect of the covered water in thawing frozen soil by explosive load, the numerical simulation was performed. The result of the numerical simulation was well in agreement with the experimental result, and it was clarified that destruction effect is increased by covering with water.

The Design of Rice Powder Production Vessel and the Pulverization of the Rice Using Numerical Simulation

In recent years, the food self-support rate of Japan is 40%, and this value is the lowest level of major advanced country. The stable supply of food is a big subject that Japan has. Therefore, rice powder attracts attention for improvement of the food self-support rate in Japan. Previously, the rice powder is produced by two methods. One is dry type, and the other is wet type. However, these systems have a fault of the heat damage of the starch and the consumption of a large quantity of water. In our laboratory, as solution of those problems, production of the rice powder by using the underwater shock wave is considered. Shock wave is the pressure wave which is over velocity of sound by discharging high energy in short time. Propagating shock wave in water is the underwater shock wave. This food processing using an underwater shock wave has little influence of heat and its processing time is very short, preventing the loss of nutrients. In this research optical observation experiment and the numerical simulation were performed using trial vessel, in order to understand the behavior of the underwater shock wave in the development of the rice powder production vessel using an underwater shock wave at the factory. In addition, in order to understand the rice powder production and to develop it, the numerical simulation about pulverization of rice is performed. By this method, the pressure which takes for rice at the time of pulverization, and its pulverization phenomenon are solved. Analysis soft LS-DYNA was used for these numerical simulations. The comparative study of the experiment and the numerical simulation was investigated. The behavior of the shock wave in the device and transformation of rice were able to be clarified.

The Basic Research for Pulverization of Rice Using Underwater Shock Wave by Electric Discharge

In recent years, the food self-support rate of Japan is 40%, and this value is the lowest level in major developed countries. This reason includes decreasing of diverting rice consumption in Japan and increasing abandonment of cultivation. Therefore, these problems are solved by using rice powder instead of expensive flour, and we manage to increase the food selfsupport rate. Previously, the rice powder is manufactured by two methods. One is dry type, and the other is wet type. The former is the method getting rice powder by running dried rice to rotating metal, and has a problem which that starch is damaged by heat when processing was performed. The latter is performed same method against wet rice, and has a problem which a large quantity of water is used. As a method to solve these problems, an underwater shock wave is used. Shock wave is the pressure wave which is over speed of sound by discharging high energy in short time. Propagating shock wave in water is underwater shock wave. The characters of underwater shock wave are long duration of shock wave because water density is uniform, water is low price and easy to get and not heat processing. Thinking of industrialization, the electric discharge is used as the generating source of underwater shock wave in the experiment. As the results, the efficiency of obtaining enough grain size, 100im, of rice powder was too bad only using the simple processing using underwater shock wave. Therefore, in Okinawa National College of Technology collaborating with us, obtaining rice powder with higher efficiency by using converged underwater shock wave is the goal of this research. In this research, the underwater shock wave with equal energy of the experimental device of underwater shock wave is measured by the optical observation. In addition, the appearance converging underwater shock wave is simulated by numerical analysis, and the pressure appreciation rate between the first wave and converged underwater shock wave is calculated by using the pressure history of 2nd focal point.

Newly Developed Unsteady Wave Sensing System for Polycarbonate

Stress-strain relationships of polycarbonate (PC) were determined over a very wide range of strain rates including shock wave regime. High-velocity plate impact tests, drop-weight tests, and quasi-static tests using universal and Instron testing machines were used for the high strain rate (107 s-1), medium strain rate (102 s-1) and low strain rate (10-4 s-1) tests, respectively. The revised unsteady wave sensing system (UWSS) for plate impact tests was newly developed to determine the stress-strain relationships and Hugoniot linear relation of PC. The system consists of a powder gun for plate impact tests and three polyvenylidene fluoride (PVDF) gauges embedded in the PC utilizing a newly developed nanosecond UWSS. As originally proposed, UWSS is aimed in obtaining experimental inputs for the Lagrangian analysis used to determine the dynamic behavior of materials. The new method to determine also the shock Hugoniot stress-strain curves is proposed for PC at medium particle velocities up to about 1 km/s. The revised, unsteady wave sensing system (M-UWSS, which we proposed before) using plate impact experiment with three PVDF gauges embedded is applied to construct stress-strain curves under shock loading up to Hugoniot stress σH and Hugoniot strain εH. Linear relationship between shock velocity Us and particle velocity Up: Us = C0 + S x Up, where C0 and S are material constants, is used to determine the constant S, since the constant C0 is determined as bulk sound velocity at ambient pressure. By using the momentum conservation and the mass conservation relations, S = (1 - C0 / CH) /εH, is derived from the linear relationship described above, where , ρ is density and CH ≈ Us.