Papers by Author: Hajime Hirose

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Authors: Katsuhiro Seki, Hashimoto Munetoh, Masahide Gotoh, Hajime Hirose
Abstract: Recently, the study of fine grain steels aimed at achieving into high strength has become active. Welding is one of the most effective methods for connecting the structural components. For those cases, the negative influence of any residual tensile stress induced during the welding process must be considered. It has been proved that shot-peening can effectively solve this problem. However, the influence of the Shot-Peening process on fine grain steels after welding has only been briefly reported up to now. In this study, fine grain steels were used, and specimens were obtained after heat treatment. Residual stress distributions near the surface of the fine grain steel after shot-peening were measured by X-ray diffraction technology. Moreover, the effect of hardness on distributions near the shot-peened surface was also estimated.
Authors: Hajime Hirose, Shinya Suzuki, Masahide Gotoh, Toshihiko Sasaki
Abstract: In depositing the TiN thin films to the substrate by Physical Vapor Deposition (PVD), it influences the substrate interface. Change of the residual stress and the full-width at half maximum (FWHM) in each process of the TiN deposition of thin film was measured by the X-ray stress measurement. As a result of the X-ray stress measurement, there are no changes in the residual stress and the FWHM. It is thought that there is a difference in the penetration depth to the substrate of X-rays and Ti ion.
Authors: Masahide Gotoh, Katsuhiro Seki, M. Shozu, Hajime Hirose, Toshihiko Sasaki
Abstract: The fine-grained rolling steels NFG600 and the conventional usual rolling steels SM490 were processed by sand paper polishing and mechanical grinding to compare the residual stress generated after processing. The average grain size of NFG600 and SM490 is 3 μm and 15μm respectively. Therefore improvement of mechanical properties for such fine-grained steels is expected, it is important to understand the residual stress state of new fine-grained materials with processing. In this study, multi axial stresses of two kinds of specimens after polishing and grinding were measured by three kinds of analysis methods including cos-ψ method. As a result, as for σ33, the stress of NFG was compression, though that of SM490 was tension.
Authors: Masahide Gotoh, Hajime Hirose, Toshihiko Sasaki
Abstract: Thin films deposited by physical vapor deposition (PVD) were studied in terms of residual stress by the authors. The final purpose of our study is to evaluate the stress state at the interface between a substrate and a thin film. In this study, JIS-SKH55 tool steel without thin-film deposition was used as the specimen. SKH55 is a dual-phase steel consisting of martensite a’Fe and alloyed carbide M6C2. The specimens were heated to 573K, 798K, 843K and 893K. Recently, the relationship between the misfit of plastic strain and stress obtained by X-ray stress measurement has been proposed by the authors using the Eshelby/Mori-Tanaka model (EMT model). The residual stress and the misfit of plastic strain were determined by X-ray stress measurement using the EMT model. Results showed that as annealing temperature increased, the compressive residual stress remained nearly constant up to about 800K, and decreased above 800K in both phases. The misfit of plastic strain also remained nearly constant up to about 800K, and reached zero above 800K.
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