Papers by Author: Kazuyoshi Takayama

Abstract: Magnesium alloy is the lightest metal that is used as a structural material. It has a higher specific tensile strength and specific stiffness than Iron and Aluminum alloy, and the dent is not caused easily from Iron and Aluminum alloy at the impact. Therefore, Magnesium alloy is widely used in many areas, especially as an external shell of a mobile device and automotive parts which replaces iron and plastic, etc., and its demand is expected to grow in the future. In this paper we studied the hypervelocity impact with a ballistic range to clarify the characteristic of Magnesium alloys which had such a characteristic. The effect of impact velocity, temperature and the size of perforation hole were investigated experimentally. The perforation resistance of Magnesium alloys and their impact behavior were characterized.

Abstract: Shock waves are indispensable tools for medical applications, and hence their interactions with human tissue become one of the most important basic research topics. In this paper, the determination of shock Hugoniot curves for liquids that can model human tissue, namely water, castor oil, and aqueous solutions of sodium chloride, sucrose and gelatin, at 10 and 20 weight percent are presented. Underwater shock waves were generated by ignition of 10 mg silver azide pellets and time variations of over-pressures were measured and simultaneously the shock speed was measured by the time of flight technique. Then shock Hugoniot curves were obtained, by assuming the Tait type equation of state, to relate the estimated density and measured pressure values. Results show in the cases of aqueous solutions that increasing amount of additives into water causes only a very minute decrease in the compressibility of the solution. This difference was more pronounced in the case of sodium chloride, less for gelatin, and almost none for sucrose aqueous solution.

Abstract: This study examined the dynamic penetration phenomena of high-velocity impact of magnesium alloy
 CFRP (Carbon Fiber Reinforced Plastic) composite. Test materials for investigation are magnesium alloy(AZ31B), the heat-treated magnesium alloy (AZ31B-200°C, AZ31B-300°C, AZ31B-430°C), and carbon/epoxy laminated composite materials with fiber direction [0°]8, [0°/45°]4s, [ 0°/90°]4s, [ 0°/45°/90°]3s and [ 0°/45°/-45°/90°]2s. We used a ballistic range (one-stage light gas gun), and the test specimens were set at 0°obliquity at room temperature. A high-speed camera allowed us to capture and analyzed the dynamic penetration phenomena of the test specimen.

Abstract: Recently, high-performance hybrid composites have been used for various applications which require the high strength, high stiffness and low weight. There are growing needs in an automotive, an aircraft, and military applications for composite materials since they have good structural characteristics. They also have good penetration resistance and structural integrity after impact. In order to clarify the mechanism of high-speed destruction for composite materials, this study examined the penetration resistance and the fracture behavior of CFRP (Carbon Fiber Reinforced Plastic) Laminates by using ballistic range (one-stage light gas gun). Test materials for investigation are carbon/epoxy laminated composite materials with fiber direction; [0°]8, [0°/45°]4s, [ 0°/90°]4s, [ 0°/45°/90°]3s and [ 0°/45°/-45°90°]2s. The high speed camera allows us to capture and analyze the dynamic penetration phenomena of the test materials.

Abstract: In this study, dynamic penetration phenomena of high-velocity impact of magnesium alloy were investigated. The surface hardness of magnesium alloy (AZ31B-O) and the heat-treated magnesium alloy (AZ31B-200°C, AZ31B-300°C, and AZ31B-430°C) were examined using Micro Vickers, and the influence of the heat treatment temperature was observed. We analyzed the metal organization using a microscope. We also used a ballistic range (two-stage light gas gun), and the test specimens were set at 0°obliquity at room temperature. A high-speed camera allowed us to capture and analyzed the dynamic penetration phenomena of the test specimen.