Papers by Author: Yoshihisa Tanaka

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Authors: Sergey V. Dmitriev, Ju Li, Nobuhiro Yoshikawa, Yoshihisa Tanaka, Yutaka Kagawa, Takayuki Kitamura, Sidney Yip
Abstract: We apply the lattice instability analysis to homogeneously strained single crystal with a flat or defected surface to demonstrate that, in the process of emission of dislocation by an unstable surface, prior to the breaking of atomic bonds, a vibrational mode localizes, foretelling the location and the manner of the impending microscopic catastrophic event.
Authors: Qing Hua Wang, Shi En Ri, Hiroshi Tsuda, Satoshi Kishimoto, Yoshihisa Tanaka, Yutaka Kagawa
Abstract: Multi-scale grid is an essential deformation carrier in optical methods for multi-scale deformation measurement. In this study, several new-type multi-scale grids were designed and fabricated by electron beam lithography. Each pattern includes several periodically distributed dots with the same spacing but different sizes. As a consequence, the grayscale of the whole grid pattern periodically changes. The peak parts of the grayscale generate a secondary grid, i.e., the large-scale grid. The ratio of the large-scale grid pitch to the small-scale grid pitch can be easily adjusted according to the requirement. The natural integration between the small-scale grid and the large-scale grid works well in eliminating the mutual disturbance between the different-scale grids. Besides, this type of grid has a very high success rate in fabrication owing to the small differences in size between the big dots and the small dots. The proposed multi-scale grid pattern is expected to serve as the deformation carrier in moiré methods and geometric phase analysis for multi-scale deformation measurement.
Authors: Satoshi Kishimoto, Yoshihisa Tanaka, Yong Ming Xing, Gyu Chang Lee
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.
Authors: Satoshi Kishimoto, Toru Shimizu, Fu Xing Yin, Kimiyoshi Naito, Yoshihisa Tanaka
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.
Authors: Yoshihisa Tanaka, Yu Fu Liu, Yutaka Kagawa
Abstract: The surface nano-deformation behavior in metal matrix composite during tensile loading was investigated by in-situ atomic force microscope (AFM) observation. The composite material used was aluminum matrix reinforced with 10 and 20 percent volume fraction of SiC particles. The average size of the reinforcement was 3 μm. Tensile test and in-situ observations were conducted using a loading device equipped with an AFM. Surface morphologies of the composite specimens were acquired before the loading and at various stages of the loading. The microstructural damage and the evolution of surface roughness were studied. The effect of volume fraction of the reinforcement on the nano-deformation behavior and damage evolution process of the composite based on nanoscale in-situ AFM observation will be discussed.
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