Hirofumi Iyama

An investigation on underwater explosive bonding process

In this paper, we propose a new explosive bonding method for bonding materials by using the underwater shock wave from the explosion of explosives in water. This method is especially suitable to bond the materials with thin thickness and largely dissimilar property. In bonding those materials, the shock pressure and the moving velocity of shock wave on the flyer plate should be precisely managed to achieve an optimum bonding conditions. In this method, the bonding conditions can be controlled by varying of the space distance between the explosive and the flyer plate or by inclining the explosive charge with the flyer plate. We made the experiment of this technique bond the amorphous film with the steel plate. A satisfactory result was gained. At the same time, numerical analysis was performed to investigate the bonding conditions. The calculated deformation of the flyer plate by the action of underwater shock wave was compared with the experimental recordings by high-speed camera under the same conditions. The comparison shows that the numerical analysis is of good reliability on the prediction of the experimental result. Furthermore, the numerical simulation also gives the deformations of the flyer and the base plate, and the pressure and its variation during the collision process.

Computational Simulation of Underwater Shock Wave Propagation Using Smoothed Particle Hydrodynamics

Underwater shock wave phenomenon is applied to various fields such as manufacturing, food processing and medical equipment, and has been investigated with many experiment and numerical analysis. Because of low heat generation and possibility of downsizing of the device which generates shock wave, an application of shock wave induced by gap discharge in food processing has been studied recently. In this study, an ellipsoidal vessel filled with water is modeled in 2D and a computational simulation of underwater shock wave propagation is implemented using Smoothed Particle Hydrodynamics. Then, the computational result is compared with an experimental one and have a good agreement with the experimental one in qualitative. In the simulation, focusing of pressure wave, which is characteristic phenomenon of elliptical vessel, is observed.

Study on Expansion of a Silicon Tube by Underwater Shock Wave

Many studies about the behavior of the structure by shock wave have been researched until now. On those researches, some metals, resin, glass, concrete, wood were handled as a structure, and on many studies it was clarified about processing and behavior by the shock wave. On the other hand, recently, bio-materials have attracted attention on the material dynamics. It is impotant to recognition the behavior of these materials by the shock loading. Therefore, we have investigated the deformation of bio-material by shock wave. As the first approach, the expansion behavior of a silicon tube by underwater shock wave has been investigated and some numerical simulations and experiment have been performed.© 2009 ASME

Piercing process of very thin sheet metal using explosive-impulsive pressure

The characteristics of piercing a hole in amorphous alloy foil with a thickness of 0.025mm using explosive-impulsive pressure were investigated. The effects of the diameter of the die cavity and the impulsive pressure induced by explosion on the piercing of a hole were shown. The quality of the pierced holes was evaluated by means of the contour rate, that is, the ratio of the perfectly sheared contour length to the circumference of pierced holes. The contour rate approached 1.0 with increasing impulsive pressure for all diameters of the die cavity. The error in the diameter of pierced holes to the diameter of the die cavity was within 2%. Even for a small diameter, the optimum impulsive pressure distribution, i.e., the optimum amount of explosive and distance from the explosive to the specimen, enable holes to be pierced perfectly. Introduction The miniaturization of many products, mainly electronic and precision-mechine devices, apparatuses and instruments, is progressing. The formation of parts made of very thin sheets has become increasingly important. Many studies on the methods and techniques of forming precise parts with very low thickness have been performed [1-23]. Kurosaki et al. investigated the mechanical properties of electronic copper foil and sheets ranging from 5μm to 1mm in thickness [1]. Spinning and peen forming have been used to fabricate very small and thin parts [7,8]. Laser forming [2,3], spark forming [4] and incremental forming [5,6] have also been applied for forming metal foil and very thin sheets. For deep drawing, Saotome et al.[11] clarified the effect of the relative punch diameter on the deep drawability of very thin steel sheets. A friction-aided drawing process for very thin sheets was proposed and its effects were presented by Hassan et al.[12]. A technique of the controlling blankholding force by oscillating the blankholder using piezoelectric actuators was also proposed [13]. For the piercing process, Kurosaki et al. [9] developed a method by which many fine holes could be pierced through a thin sheet of 50μm, using a viscoplastic pressure medium. A small press incorporating a piezoelectric actuator was developed for press blanking of metal foil and its good performance was verified [10]. Sano et al. reported a method of punchless blanking in which a plastic material was used instead of a punch [17]. Murata et al. presented a method of punchless piercing using very high-pressure gas for a thin sheet including amorphous alloy foil [18-20]. They also investigated the characteristics of the piercing of holes by the method. An investigation of micropunching of thin sheet metals by an underwater impulsive wave induced using an Materials Science Forum Online: 2004-09-15 ISSN: 1662-9752, Vols. 465-466, pp 337-342 doi:10.4028/www.scientific.net/MSF.465-466.337

The Effect of Pressure Vessel in Explosive Forming

Explosive forming is one of the unconventional techniques, in which, most commonly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the influence of the configuration of the pressure vessel on the deformation of a metal plate, numerical analysis was performed. This paper reports those results.Copyright

Experimental Verification of the Softening of the Pork Using Underwater Shock Waves Generated by Wire Electrical Discharges

The National Institute of Technology, Okinawa College (OkNCT) has developed a food processing machine that generates underwater shock waves through wire electrical discharge. The machine can used for sterilization, milling flour, softening, and extraction among others. In this study, we experimentally examined the conditions for food softening using pork as the food material in experiments. Softness was revealed to be related to the distance of shock wave generation point from meat and the number of shockwave processing.

Shock Wave Propagation Inside of Pressure Vessel Used for Food Processing

In this study, it has aimed at the design of the pressure vessel for food processing using an underwater shock wave. This study aims at the design of a pressure vessel in which the underwater shock wave generated by the underwater explosion of high explosive was experimentally investigated by the optical observation and the pressure measurement. Therefore the pressure vessel is designed so that suitable pressure may apply on food. This designed vessel is evaluated by the numerical simulation. The interaction of the underwater shock wave, the incident wave and the reflected wave are investigated by the numerical simulation.Copyright

NUMERICAL SIMULATION OF EXPLOSIVE FORMING

Explosive forming is one of the unconventional techniques, in which, most com- monly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the influence of the configuration of the pressure vessel on the deformation of a metal plate, numerical analysis was performed. This paper reports those results.

Basic Research on Explosive Forming of Magnesium Alloy Plate

This study has investigated the plastic forming of magnesium alloys plate. It is not easy to perform the cold-worked with the usual plastic forming method although magnesium alloys have the advantages in terms of strength-to-weight ratio. Therefore, explosive forming method which is one of the plastic forming methods with a specific forming mechanism has been applied. At first, numerical simulations have been conducted to clarify the optimal combination conditions, and then we have verified practical effectiveness of this proposed method by using experimental study.

Experimental Study and Computational Simulation for Shock Characteristics Estimation of Okinawa’s Soils “Jahgaru”

To clarify the shock characteristics of Okinawa’s unique soils “ Jahgaru ” that is widely distributed in southern part of Okinawa Main Island, an experimental investigation of dynamics properties such as shockwave propagation, pressure and particle velocity have been performed using impedance matching method. Therefore, we have also obtained the Hugoniot date of “ Jahgaru ”. And then, to reveal a validity of the material characteristics, a computational model for the experimental procedure using ALE simulation have been developed. A comparison between numerical results and experimental ones, the capability of proposed method through the numerical simulations have been confirmed.