NAKAO Wataru

Affiliation

Faculty of Engineering, Division of Systems Research

Job Title

Professor

Date of Birth

1974

Research Fields, Keywords

Self-crack-healing, Intelligent material, Ceramic matrix ceramics, Mechanics of fracture, structual ceramics

Mail Address

E-mail address

Web Site

http://www.nakaolab712.blogspot.com

Related SDGs




写真a

Graduating School 【 display / non-display

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    1998

    Tokyo Institute of Technology   Faculty of Engineering   Department of metallgy   Graduated

Graduate School 【 display / non-display

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    2003

    Tokyo Institute of Technology  Graduate School, Division of Science and Engineering  Department of Chemistry and Materials Science  Doctor Course  Completed

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    2000

    Tokyo Institute of Technology  Graduate School, Division of Science and Engineering  Department of Chemistry and Materials Science  Master Course  Completed

Degree 【 display / non-display

  • Doctor of Engineering -  Tokyo Institute of Technology

Campus Career 【 display / non-display

  • 2017.04
    -
    Now

    Duty   Yokohama National UniversityFaculty of Engineering   Division of Systems Research   Professor  

  • 2017.01
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    2017.03

    Duty   Yokohama National UniversityFaculty of Engineering   Division of Materials Science and Chemical Engineering   Professor  

  • 2011.04
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    2016.12

    Duty   Yokohama National UniversityFaculty of Engineering   Division of Materials Science and Chemical Engineering   Associate Professor  

  • 2007.12
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    2011.03

    Duty   Yokohama National UniversityInterdisciplinary Research Center   Specially Appointed Assistant Professor  

  • 2007.04
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    2007.11

    Duty   Yokohama National UniversityFaculty of Engineering   Division of Materials Science and Chemical Engineering   Research Fellow  

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Academic Society Affiliations 【 display / non-display

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    The Japan Institute of Metals

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    The Society of Materials Science, Japan

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    American Ceramics Society

Field of expertise (Grants-in-aid for Scientific Research classification) 【 display / non-display

  • Inorganic materials/Physical properties

  • Structural/Functional materials

  • Materials/Mechanics of materials

 

Research Career 【 display / non-display

  • Development of ceramics having self-crack-healing ability

    Project Year:  -   

Books 【 display / non-display

  • Advances in ceramics matrix composite

    T. Osada, W. Nakao, K. Takahashi, K. Ando (Part: Joint Work , Range: Chapter 17 Self Crack-Healing Behavior in Ceramic-Matrix Composites )

    Woodhead Publisher  2014.02 ISBN: 9780857091208

     View Summary

    自己治癒能力を有するセラミックスの概略を示し,自己治癒性と環境雰囲気との関係性について解説を行った.

  • ENCYCLOPEDIA OF COMPOSITES

    Wataru Nakao (Part: Single Work , Range: one chapter; SiC whisker compsite )

    Wiley-VCH  2012

  • Advanced Ceramics-Charactorization, Raw Materials, Processing, Properties Degradation and healing

    K. Takahashi, K. Ando, W. Nakao (Part: Joint Work , Range: Chapter 18 Crack-Healing Ability of Structural Ceramics and Methodology to Guarantee the Reliability of Ceramic Components )

    INTECH  2011.08 ISBN: 9789533075044

     View Summary

    自己治癒性がセラミックスの機械特性に及ぼす影響を実例を含めて解説を行った.

  • Properties and Applications of Silicon Carbide

    Wataru Nakao (Part: Joint Work , Range: Chapter 11 Effect of Self-healing on Fatigue Behaviour of Structural Ceramics and Influence Factors on Fatigue Strength of Healed Ceramics )

    INTECH  2011.04 ISBN: 9789533072012

     View Summary

    セラミックス疲労挙動に及ぼす自己治癒性の効果について解説を行った.

  • Advanced Nanomaterials

    W. Nakao, K. Takahashi and K. Ando (Part: Joint Work , Range: Chapter 17; Self-healing of Surface Cracks in Structural Ceramics )

    Wiey-VCH  2010 ISBN: 9783527317943

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Papers 【 display / non-display

  • Kinetic Analysis on decarburizing of Spring Steel

    NAKAO Wataru, MIYATA Masaharu, SHIBUYA Nobuhiro, KAI Morimichi, ISHIBASHI Fumiya, NEISHI Yutaka, SU … Show more authors

    Transactions of Japan Society of Spring Engineers ( Japan Society of Spring Engineers )  2021 ( 66 )   97 - 106   2021.03  [Refereed]

    Joint Work

     View Summary

    <p>The guideline as kinetic equation of decarburizing to prevent excess decrease in fatigue strength, which is expressed as temperature the quenching starts, has been proposed from the systematic investigation on decarburizing spring steels;</p><p><i>T</i><sub>Q</sub> = 910 + 44.7<sup>%</sup>Si - 30<sup>%</sup>Mn - 11<sup>%</sup>Cr - 15.2<sup>%</sup>Ni + 31.5<sup>%</sup>Mo - 203√<sup>%</sup>C - (<sup>%</sup>C - <i>C<sub>S</sub></i>) {1 - exp (-(3.29 × 10<sup>8</sup><i>t</i>) / 2<i>d</i> exp (-(3.61 × 10<sup>4</sup>) / (<i>T</i><sub>h</sub>' + 273)))}</p><p>where <sup>%</sup>M[mass%] indicates content of element M in steel, <i>d</i>[m] initial particle size of austenite. Referring the guideline, quenching from above the evaluated temperature, <i>T</i><sub>Q</sub> can prevent excess decrease in fatigue strength the spring steel exposed to high temperature decarburizing atmosphere, whose temperature is <i>T</i><sub>h</sub>'[°C] and decarburizing time is <i>t</i>[s], because the quenching leads to form the quench microstructure without surface ferrite layer. In the case that the exposed atmosphere is excess CO<sub>2</sub> content, as same as the atmosphere of gas combustion furnace, the value of surface carbon content, <i>C</i><sub>S</sub>[mass%] can be employed to be 0.2. Moreover, if the cooling rate is grater than 80 °C/s corresponding to the cooling rate of oil quenching, the guideline can be used to every spring steels. Similarly if temperature rise is slow, the guideline can be acceptable with modification of the term of decarburizing time to <i>t</i> + 0.03<i>t</i><sub>r</sub>, where <i>t</i><sub>r</sub>[s] is the time period of temperature rise.</p>

    DOI CiNii

  • Microstructure-Enhanced Inverse Magnetostrictive Effect in Fe-Co Alloy Wires

    Yamazaki Takahiro, Katabira Kenichi, Narita Fumio, Furuya Yasubumi, Nakao Wataru

    ADVANCED ENGINEERING MATERIALS ( Wiley )  22 ( 10 )   2000026-1 - 2000026-9   2020.06  [Refereed]

    Joint Work

    Web of Science DOI

  • Mechanism of stopping crack propagation in continuous fiber reinforced self-healing ceramic

    Lee Jang-Won, Nam Ki-woo, Nakao Wataru

    JOURNAL OF CERAMIC PROCESSING RESEARCH   21 ( 2 )   200 - 207   2020.04  [Refereed]

    Joint Work

    Web of Science DOI

  • Joining of Al2O3 Rods Using Microwaves and Employing Sic Particles as Adhesive

    Kimura Natsuko, Fujii Takashi, Kashimura Keiichiro, Nakao Wataru

    PROCESSES   7 ( 10 )   750   2019.10  [Refereed]

    Joint Work

    Web of Science DOI

  • Finite Element Analysis of the Size Effect on Ceramic Strength

    Kyohei Takeo, Yuya Aoki, Toshio Osada, Wataru Nakao, Shingo Ozaki

    Materials ( MDPI )  Vol.12 ( 18 )   2019.09  [Refereed]

    Joint Work

    DOI

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Review Papers 【 display / non-display

  • Materials Design Method of Self-healing Materials

    NAKAO Wataru

    Science and industry   90 ( 1 ) 2 - 6   2016.01  [Refereed]  [Invited]

    Introduction and explanation (scientific journal)   Single Work

    CiNii

  • Materials Design Concept of Self-healing Ceramics

      67 ( 9 ) 417 - 421   2015.09

    Introduction and explanation (scientific journal)   Single Work

    CiNii

  • New Innovation Created by Self-healing Materials

      66 ( 10 ) 488 - 493   2014.10

    Introduction and explanation (scientific journal)   Single Work

    CiNii

  • Novel high reliable ceramics having self-healing ability

      64 ( 9 ) 706 - 712   2013.09

    Introduction and explanation (scientific journal)   Single Work

    CiNii

  • Surface Treatment to Improve Tribology Feature of Ceramic Components

      48 ( 9 ) 723 - 726   2013.09

    Introduction and explanation (scientific journal)   Single Work

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Grant-in-Aid for Scientific Research 【 display / non-display

  • Grant-in-Aid for Young Scientists(B)

    Project Year: 2012.04  -   

  • Grant-in-Aid for Scientific Research(B)

    Project Year: 2009.04  -  2011.03 

  • Grant-in-Aid for Scientific Research(C)

    Project Year: 2016.04  -  2019.03 

  • Grant-in-Aid for Young Scientists(B)

    Project Year: 2012.04  -  2015.03 

Other external funds procured 【 display / non-display

  • Development of the novel ceramics having self-healing function for turbine blade

    Offer organization: Japan Science and Technology Agency  Advanced Low Carbon Technology Research and Development Program

    Project Year: 2012.10  -  2020.03  Investigator(s): NAKAO Wataru

Presentations 【 display / non-display

  • Room temperature self-healing function for ceramics using hydration reaction of cement

    SEKINE Nobuhide, NAKAO Wataru

    The Proceedings of the Materials and processing conference  2019   The Japan Society of Mechanical Engineers

     View Summary

    <p>In this research, a new type of self-healimg mechanism for ceramics is developed. This mechanism is using hydration reaction of cement as a self-healing mechanism and the effictivness of this mechanism is assessed. We developed advanced CMC(Ceramic Matrix Composites) which has self-healing ability. Ceramic matrix is mainly composed of SiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> and self-heling agent which causes chemical reaction is mainly composed of CaO and Al<sub>2</sub>O<sub>3</sub>. This self-healing agent is generally called calcium aluminate cement. When water comes into cracks and contact with the cement, hydration reaction occurs and hydrates fill up the cracks. Self-healing phenomenon can be divided into 3 stages. At the first stage, chemical reaction starts. At the second stage, cracks are filled with products. At the third stage, strength is recoverd. According to this devision, chemical reaction used in the self-healing mechanism can be divided into three elementary reaction. With this idea, a model of self-healing mechanism using hydration reaction is established. As a result, it is suggested that with some additional condition, strength recover is possible. Howevr, full sterength recover seems to be impossibe unless drying shrinkage of hydrates is supressed.</p>

    DOI CiNii

  • Investigation on dynamic fracture behavior of ceramics using silicon nitride

    Sakata Anan, Nakao Wataru

    The Proceedings of the Materials and processing conference  2019   The Japan Society of Mechanical Engineers

     View Summary

    <p>Foreign object damage(FOD) in ceramic materials is a complicated damage mode that occurs when a foreign object collides with a peripheral blade. In order to investigate this damage mode, an experiment was conducted in which a steel ball collides with fine ceramics silicon nitride using a light gas gun and a ring bending jig. An experiment was conducted to make it collide until it broke, and the condition and number of breaks were investigated. As a result, cracks were damaged at a rate of 55% to 71% of the rate of fracture due to a single impact. In addition, the conditions under which radial cracks were generated by changing the mass of the steel balls were investigated. As a result, it was found that the energy required for destruction increases as the projectile becomes smaller. In considering the resistance to FOD, it is necessary to evaluate ceramic materials not at the speed at which a single collision breaks but at the speed at which radial cracks on the lower speed are introduced.</p>

    DOI CiNii

  • Construction of alloy design technology for hydrogen storage alloy actuator:(About the effect of external load on deformation behavior of hydrogen storage alloys)

    OKAMURA Issei, GOTO Kenta, NAKAO Wataru

    The Proceedings of the Materials and processing conference  2019   The Japan Society of Mechanical Engineers

     View Summary

    <p>The deformation behavior of Pd powder as a hydrogen storage alloy when hydrogen was introduced and exhausted while changing the external load was investigated. As a result, it was found that the maximum displacement decreased linearly as the external load increased due to the accumulation of strain energy inside the alloy by the external load. In addition, the deformation behavior inside the particle is thought to exist in three stages, and the deformation rate of the particle is greatly influenced by the rate-limiting reaction inside the particle at each stage. As the external load increased, the first stage displacement during hydrogen discharge decreased, suggesting that the hydrogen solid solution in the hydride decreased due to the increase in external load.</p>

    DOI CiNii

  • Prediction of plastic strain in Fe-Co magnetostrictive alloy using magnetic Barkhausen effect

    YAMAZAKI Takahiro, FURUYA Yasubumi, NAKAO Wataru

    The Proceedings of Mechanical Engineering Congress, Japan  2019   The Japan Society of Mechanical Engineers

     View Summary

    <p>Structural health monitoring techniques play a significant role in pre-service and in-service inspection of infrastructure, machinery, plant and equipment. In particular, in order to quickly detect fatal damage to a structure after an earthquake, the nondestructive and simple measurement of the local plastic strain and the internal damage of the structure is strongly desired. When a steel material is plastically deformed, the microstructures such as vacancies and dislocations, which affect the local magnetic properties, are drastically changed. Here, we focused on a noise-like magnetic signal called Barkhausen noise which is caused by the interaction between magnetic domain walls and microstructures in magnetization process. In this study, the waveform or the root-mean square value of Barkhausen noise depending on the plastically strains were investigated by an interrupted tensile test using tough and high magnetostrictive Fe-Co alloys. From the relationship between Barkhausen noise and dislocations, we propose a quantitative evaluation method of strain damage, which makes it possible to prolong the life of infrastructure structure.</p>

    DOI CiNii

  • Fiber -reinforced Self-healing Ceramics and Its Original Structural Integrity

    W. Nakao  [Invited]

    ISHOC2018  2018.10.21  

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Preferred joint research theme 【 display / non-display

  • R&D on novel self-healing ceramics used at high temperatrue

  • Development of advance ceramics having self-crack-healing ability-development of ceramics spring for high temperature use

 

Social Contribution(Extension lecture) 【 display / non-display

  • 4th International Conference on Self-healing Ceramics

    2013.06
     
     

  • 5th International Conference on Self-healing Ceramics

    2015.06
     
     

  • ICM&P2011

    2011.06
     
     

  • ICM&P2014

    2014.06
     
     

  • ASMP2015

    2015.08