Papers by Author: Kenji Higashi

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Authors: Hajime Iwasaki, Toru Mori, Mamoru Mabuchi, Kenji Higashi
681
Authors: Koichi Makii, Seiya Furuta, Kazuo Aoki, Atsumichi Kushibe, Tsutomu Tanaka, Kenji Higashi
497
Authors: Tokuteru Uesugi, Masanori Kohyama, Masahide Kohzu, Kenji Higashi
49
Authors: H. Takahara, Y. Motoyama, Masato Tsujikawa, Sachio Oki, Sung Wook Chung, Kenji Higashi
375
Authors: T. Kobayashi, Junichi Koike, Toshiji Mukai, Mayumi Suzuki, H. Watanabe, Kouichi Maruyama, Kenji Higashi
231
Authors: Atsumichi Kushibe, Yorinobu Takigawa, Kenji Higashi, Kazuo Aoki, Koichi Makii, Toshiaki Takagi
Abstract: As a new damping material, the authors first developed a Zn-22wt.%-Al eutectoid alloy with ultra-fine grains exhibiting superplasticity at room temperature by means of thermomechanical controlling processes (TMCPs). The Zn-Al alloy has a few advantages such as low work-hardening rate and high ductility over a conventional seismic damping material, for instance, a low-yield-point steel. In addition, Zn-Al alloys are environment-conscious because of no harmful metal like Pb. However, when Zn-Al alloys are subjected to plastic deformation, since its work hardening is small, plastic deformation proceeds locally so that required absorption energy cannot be sufficiently obtained, and local fracture and local deformation instability can take place easily, which is the intrinsic characteristic of superplastic materials. Therefore we attempted to develop a shear panel type, a brace type damper for tall buildings and a bending type damper for Japanese wooden houses using FEM analysis in order to minimize localized strain and local deformation and to determine the optimum shape for this Zn-Al superplastic seismic damper. As a result, an ecological and high-energy absorption seismic dampers, so-called “maintenance-free seismic damper,” was successfully developed.
583
Authors: Atsumichi Kushibe, Koichi Makii, L.F. Chiang, Tsutomu Tanaka, Masahide Kohzu, Kenji Higashi
Abstract: High strain rate superplasticity has been realised at room temperature for the first time with a ultra fine grained Zn-22wt%Al alloy. Zn-Al alloys have some advantages over low-yieldpoint steels in their low work-hardening rate and high ductility. In addition, Zn-Al alloys are environment-conscious because of no harmful metal like Pb. However, when Zn-Al alloys are subjected to plastic deformation, the strain is localised and local fracture can take place because of their low work-hardening property. In this study, a seismic damper was designed with a Ultra fine grained Zn-Al alloy. As a result, an ecological and high performance seismic damper, the so-called “maintenance-free seismic damper”, has been successfully developed.
3055
Authors: Tokuteru Uesugi, Masanori Kohyama, Kenji Higashi
599
Authors: Tokuteru Uesugi, Yorinobu Takigawa, Kenji Higashi
Abstract: We investigated the contribution to the high yield strength due to the solid solution strengthening in nanocrystalline Al-Ti alloys produced by a vapor quench method. The misfit strain due to solute Ti atom in aluminum was obtained from the first principles calculation. Then, the theoretical result of the contribution to the yield strength due to the solid solution strengthening was estimated from the misfit strain using the Friedel’s theory. In dilute Al-Ti alloy, the theoretical results of the solid solution strengthening from the misfit strain was in good agreement with the analytical result using the measured grain size and yield stress.
977
Authors: Hiroyuki Hosokawa, Hajime Iwasaki, Toru Mori, Mamoru Mabuchi, Tsutomu Tagata, Kenji Higashi
699
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