Papers by Author: Satoshi Kishimoto

Abstract: Metallic closed cellular materials containing polymer were fabricated by the penetrating polymer into metal foam. The aluminum and stainless steel foams were selected for the metal foam and epoxy resin and polyurethane resin were selected for the penetrated polymer. The many kinds of mechanical properties of this material were measured. The results of the compressive tests show that these materials have different stress-strain curves among the specimens that containing different materials in the cells. Also, this metallic closed cellular materials containing polymer have higher compressive strength, higher Young’s modules, higher energy absorption and higher internal friction than that of metallic closed cellular material without any polymer.

Abstract: New methods to fabricate a metallic closed cellular material for smart materials using an isostatic pressing and penetrating method are introduced. Powder particles of polymer or ceramics coated with a metal layer using electro-less plating were pressed into pellets and sintered at high temperature. These powder particles were sintered by spark plasma sintering (SPS) method. Closed cellular materials including polymer were fabricated by penetrating polymer into metallic foams. Many kinds of metallic closed cellular materials including different materials from that of cell walls were tried to fabricate. The physical and mechanical properties of these materials were measured. The results of the compressive tests show that this material has high-energy absorption and the result of measuring the internal friction show that the internal friction of these materials is larger than that of pure aluminum.

Abstract: In this paper, scanning electron moiré method is used to measure the mechanical behavior of Ferro-based shape memory alloys(SMA). The moiré patterns are formed by the interference between a 1000 lines/mm cross-type specimen grating (which is fabricated using electron beam lithography) and the scanning lines of Scanning Electron Microscope (SEM). When the specimen is subjected to uniform tension load at the room temperature, the unloading residual strain values in the different regions under the same tensile load and the values in the same region under different tensile loads are compared respectively. The shape memory effect is also studied. From the experimental results, it can be concluded that the proposed moiré method is highly accurate to measure the mechanical behavior of microscopic field.

Abstract: A method for measuring the stress and strain distribution in the composite materials and residual stress at the interface in the fiber reinforced composite has been developed. The strains are measured using an electron Moiré method and then the stresses are calculated from these strains. A very fine model grid with frequencies up to 10,000lines/mm can be fabricated using the optical and electron lithography techniques on the surface of the specimen and an electron beam scan which spaces are almost same as that of model grid the can be used for master-grid. The difference of the amount of secondary electrons per a primary electron makes Moiré fringes that consists bright and dark parts. Micro-creep deformation and residual strain and stress near the fibers of composite materials were measured by this method.

Abstract: A method to fabricate the metallic closed cellular material has been developed. Powder particles of polymer or ceramics coated with a metal layer using electro-less plating were pressed into pellets and sintered at high temperatures by heating and spark plasma sintering (SPS) method. A metallic closed cellular material containing different materials from that of cell walls was then fabricated. The mechanical and Thermal properties of this material were measured. The results of the compressive tests show that this material has the different stress-strain curves among the specimens that have different thickness of the cell walls and the sintering temperatures of the specimens affect the compressive strength of each specimen. Also, it seems that the results of the compressive tests show that this material has high-energy absorption and Young’s modulus of this material depends on the thickness of the cell walls. Also thermal properties of this material were measured.

Abstract: Several methods of fabricating metallic closed cellular materials a spark plasma sintering (SPS) system have been developed. Powdered polymer particles coated with a nickel-phosphorus alloy layer using electro-less plating were pressed into pellets and sintered at high temperatures in a furnace using SPS system. Metallic closed cellular materials containing different materials from the cell walls were then fabricated. The physical, mechanical and damping properties of these materials were measured. The results of the compressive tests show that this material has different stressstrain curves among the specimens that have different cell wall thicknesses and the sintering temperatures of the specimens affect the compressive strength of each specimen. Also, it seems that the results of the compressive tests show that this material has a high-energy absorption. The internal friction of this material was measured and the results show that this internal friction is the same as that of pure aluminum. These results suggest that this material can be utilized as an energy absorbing and passive damping material.

Abstract: The electron moiré method uses a high frequency grating to measure microscopic deformation. Finer and finer gratings are being pursued to meet higher and higher resolution requirements in microscopic stress analysis. In this study, the techniques of fabricating electron grid by means of a scanning electron microscope are improved. The use of a low accelerating voltage shows a better effect than the high accelerating voltage in fabricating a superfine grid. A new group of parameters is suggested based on this consideration. A cross-line grid with a frequency of 10,000 lines/mm and a parallel grating with a frequency of 13,000 lines /mm have been successfully fabricated.