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402 results on '"Nomura, Naoyuki"'

191. Materia Japan

Author

Suzuki, Teppei, primary, Matsumoto, Hiroaki, additional, Nomura, Naoyuki, additional, and Hanada, Shuji, additional

Published
2002
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195. Correlation between cyclic fatigue and the bending properties of nickel titanium endodontic instruments.

Author

Jindan PIAO1, MIYARA, Kana, EBIHARA, Arata, NOMURA, Naoyuki, HANAWA, Takao, and SUDA, Hideaki

Subjects
CYCLIC fatigue, ENDODONTICS, TITANIUM, NICKEL, DENTAL adhesives, FRACTOGRAPHY
Abstract

The effects of cyclic fatigue on bending properties of NiTi endodontic instruments were investigated. Sixteen Profiles® were divided into two groups (A, and B). The sequence of cantilever bending test and cyclic fatigue test was alternated repeatedly until file separation occurred. In the cyclic fatigue test, the instrument curvature was 19° in group A and 38° in group B. Fractographic examination was performed to determine fracture patterns. In group A, there were significant differences between the bending load values measured before the cyclic fatigue test and the last cantilever bending test before instrument fracture at each deflection (p<0.05). Fractographic examination showed the specific patterns of cyclic fatigue fracture. The stress required to induce martensitic transformation might be reduced due to the softening behavior caused by the cyclic fatigue under the relaxation condition of the superelasticity range (group A). The SEM images were able to display specific patterns indicating cyclic fatigue fracture. [ABSTRACT FROM AUTHOR]

Published
2014
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199. Three-dimensional quantification of susceptibility artifacts from various metals in magnetic resonance images.

Author

Imai, Haruki, Tanaka, Yoji, Nomura, Naoyuki, Tsutsumi, Yusuke, Doi, Hisashi, Kanno, Zuisei, Ohno, Kikuo, Ono, Takashi, and Hanawa, Takao

Subjects
MAGNETIC resonance imaging, THREE-dimensional imaging, MAGNETIC susceptibility, IMAGING phantoms, AGAROSE, COLLOIDS
Abstract

Susceptibility artifacts generated in magnetic resonance (MR) images were quantitatively evaluated for various metals using a three-dimensional (3-D) artifact rendering to demonstrate the correlation between magnetic susceptibility and artifact volume. Ten metals (stainless steel, Co–Cr alloy, Nb, Ti, Zr, Mo, Al, Sn, Cu and Ag) were prepared, and their magnetic susceptibilities measured using a magnetic balance. Each metal was embedded in a Ni-doped agarose gel phantom and the MR images of the metal-containing phantoms were taken using 1.5 and 3.0T MR scanners under both fast spin echo and gradient echo conditions. 3-D renderings of the artifacts were constructed from the images and the artifact volumes were calculated for each metal. The artifact volumes of metals decreased with decreasing magnetic susceptibility, with the exception of Ag. Although Sn possesses the lowest absolute magnetic susceptibility (1.8×10−6), the artifact volume from Cu (−7.8×10−6) was smaller than that of Sn. This is because the magnetic susceptibility of Cu was close to that of the agarose gel phantom (−7.3×10−6). Since the difference in magnetic susceptibility between the agarose and Sn is close to that between the agarose and Ag (−17.5×10−6), their artifact volumes were almost the same, although they formed artifacts that were reversed in all three dimensions. [ABSTRACT FROM AUTHOR]

Published
2013
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200. Microstructures and mechanical properties of Co–29Cr–6Mo alloy fabricated by selective laser melting process for dental applications.

Author

Takaichi, Atsushi, Suyalatu, Nakamoto, Takayuki, Joko, Natsuka, Nomura, Naoyuki, Tsutsumi, Yusuke, Migita, Satoshi, Doi, Hisashi, Kurosu, Shingo, Chiba, Akihiko, Wakabayashi, Noriyuki, Igarashi, Yoshimasa, and Hanawa, Takao

Subjects
MICROSTRUCTURE, MECHANICAL properties of metals, TERNARY alloys, SCANNING electron microscopy, X-ray spectroscopy, DENDRITIC crystals, ANISOTROPY
Abstract

Abstract: The selective laser melting (SLM) process was applied to a Co–29Cr–6Mo alloy, and its microstructure, mechanical properties, and metal elution were investigated to determine whether the fabrication process is suitable for dental applications. The microstructure was evaluated using scanning electron microscopy with energy-dispersed X-ray spectroscopy (SEM-EDS), X-ray diffractometry (XRD), and electron back-scattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test. Dense builds were obtained when the input energy of the laser scan was higher than 400Jmm−3, whereas porous builds were formed when the input energy was lower than 150Jmm-3. The microstructure obtained was unique with fine cellular dendrites in the elongated grains parallel to the building direction. The γ phase was dominant in the build and its preferential 〈001〉 orientation was confirmed along the building direction, which was clearly observed for the builds fabricated at lower input energy. Although the mechanical anisotropy was confirmed in the SLM builds due to the unique microstructure, the yield strength, UTS, and elongation were higher than those of the as-cast alloy and satisfied the type 5 criteria in ISO22764. Metal elution from the SLM build was smaller than that of the as-cast alloy, and thus, the SLM process for the Co–29Cr–6Mo alloy is a promising candidate for fabricating dental devices. [Copyright &y& Elsevier]

Published
2013
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