Oshikawa Wataru

写真a

Title

Professor

Researcher Number(JSPS Kakenhi)

80224228
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Current Affiliation Organization 【 display / non-display 】

  • Duty   University of the Ryukyus   Faculty of Engineering   School of Engineering_Energy and Environment Program   Professor  

  • Concurrently   University of the Ryukyus   Graduate School of Engineering and Science   Material,Structural and Energy Engineering   Professor  

  • Concurrently   University of the Ryukyus   Graduate School of Engineering and Science   Solid Mechanics and Materials Engineering   Professor  

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Academic degree 【 display / non-display 】

  • The University of Tokyo -  Doctor of Engineering

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External Career 【 display / non-display 】

  • 2005.07
    　
    　

     

  • 2005.07
    　
    　

    - , University of the Ryukyus, Faculty of Engineering, Department of Mechanical Systems Engineering, Engineering Materials,Design and Processing, Associate Professor  

  • 2005.07
    　
    　

    University of the Ryukyus, Faculty of Engineering, Energy and Environment Program, Professor  

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Research Areas 【 display / non-display 】

  • Nanotechnology/Materials / Material processing and microstructure control

  • Nanotechnology/Materials / Material processing and microstructure control

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Published Papers 【 display / non-display 】

  • Effect of Soil Particle Diameter on Soil Corrosion

    Fujihashi Kenta, Nakagami Ryosuke, Oshikawa Wataru

    Zairyo-to-Kankyo ( Japan Society of Corrosion Engineering )  72 ( 1 ) 22 - 30   2023.01

    Type of publication: Research paper (scientific journal)

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    <p>The main foundation structure of photovoltaic power generation facilities is a steel pile foundation. Soil corrosion rate is regarded as 0.02 mm/year regardless of the soil. However, it is considered that corrosion rates of each soil are difference. In this study, we estimated the soil corrosion environment by measuring the physical properties of soil and evaluated the charge transfer resistance of each soil environment by AC impedance method that regarded soil as electrolyte, in order to investigate the effect of soil particle size on soil corrosion.</p><p>Glass beads of uniform sphere haven't been packed close-packed structure, and porosity of soil with particle size distribution was nearly equal to regardless of particle size. But in case of the soil that included particles less than 50μm in a large quantity, porosity of the soil was increase. Porosity of soil that had similar particle size distribution was nearly equal regardless of water content. Therefore, it is suggested that the change of soil water content was replacement liquid phase and gas phase. The charge transfer resistance of soil corrosion decreased with decrease of gas phase ratio in soil. Therefore, it is suggested that the charge transfer resistance of soil corrosion might be estimated from the soil particle size distribution and water content.</p>

  • Cracking Process in Delayed Fracture of High-Strength Steel after Long Atmospheric Exposure

    Homma T.

    ＩＳＩＪ　Ｉｎｔｅｒｎａｔｉｏｎａｌ ( 一般社団法人 日本鉄鋼協会 )  62 ( 4 ) 776 - 787   2022.04

    Type of publication: Research paper (scientific journal)

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    <p>This paper is the first microscopic observation of the entire cracking process in delayed fracture of high-strength steel bolt after long-term atmospheric exposure. A sufficiently fresh fracture surface exhibits the initiation of the propagating crack in a thin zone beneath the screw groove, resulting from the merging of multiple cracks nucleated therein. The fracture morphology is initially intergranular, exhibiting the three-dimensional shape of prior austenite grains, but the stress and strain states at the nucleation sites are not uniquely specified. The fracture morphology alters as the crack extends from intergranular to quasi-cleavage and fine dimples, associated with increasing stress intensity under a constant-displacement condition. The change from inter- to trans-granular fracture is continuous, implying affinity among different morphologies associated with the increased density and the distribution of potential crack nucleation sites in the crack front. The crack propagation in the quasi-cleavage and fine dimple regions is step-wise of about 50 <i>µ</i>m per step. Recent studies about the function of hydrogen in embrittlement are referred to in respect of the accumulation of strain-induced damage. The enhanced generation of strain-induced vacancies is the presumable function of hydrogen compatible with the present findings.</p>

  • Universities and Academic Associations in COVID-19

    Oshikawa Wataru

    Zairyo-to-Kankyo ( Japan Society of Corrosion Engineering )  71 ( 3 ) 61 - 62   2022.03

    Type of publication: Research paper (scientific journal)

  • A case study of exam preparation course for mechanical design engineer 3rd grade

    SUEYOSHI Toshiyasu, GIMA Satoru, UEZATO Eiho, TERUYA Isao, OSHIKAWA Wataru, MIYAZAKI Tatsujiro

    The Proceedings of the Tecnology and Society Conference ( The Japan Society of Mechanical Engineers )  2022 ( 0 ) 331   2022

    Type of publication: Research paper (scientific journal)

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    <p>This report is a case study of a preparatory course for the Mechanical Design Engineer Examination conducted at the University of the Ryukyus. The Mechanical Design Engineer 3rd grade is an examination to evaluate and certify one's technical level. The subjects of the examination correspond to the required subjects of mechanical engineering. Examinees can check their own learning level, which is expected to improve their motivation for learning. The contents of this report include the method of implementation of the preparatory course, the number of examinees, and the passing rate. In addition, opinions from the students will also be presented.</p>

  • Evaluation of corrosion properties of steel with Zn-30mass% Al thermal-spray coating using accelerated atmospheric exposure test

    Nakano A.

    MATERIALS TRANSACTIONS ( 公益社団法人 日本金属学会 )  62 ( 7 ) 1001 - 1008   2021.07

    Type of publication: Research paper (scientific journal)

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    <p>A four-year atmospheric exposure test was performed on steel with a Zn–30 mass%Al thermal-sprayed coating using an accelerated atmospheric exposure test, and then the atmospheric corrosion properties were evaluated. X-ray diffraction results showed that the corrosion products formed on the coating owing to the accelerated atmospheric exposure test were the same as those formed in a typical atmospheric exposure test. The corrosion weight loss of the thermally sprayed coatings in the accelerated atmospheric exposure test was promoted by approximately 1.5 to 2.0 times compared to the atmospheric exposure test.</p><p> </p><p>This Paper was Originally Published in Japanese in Zairyo-to-Kankyo <b>68</b> (2019) 187–193.</p>

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