Updated on 2025/04/20

写真a

 
SAKAMOTO Junji
 
Organization
Faculty of Environmental, Life, Natural Science and Technology Assistant Professor
Position
Assistant Professor
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Degree

  • 博士(工学) ( 2013.3   九州大学 )

Research Interests

  • Fracture mechanics

  • Fatigue

  • Vibration

  • Fracture

Research Areas

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Social systems engineering

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Safety engineering

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Mechanics of materials and materials

Education

  • Kyushu University   工学府   機械工学専攻

    2010.4 - 2013.3

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    Country: Japan

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  • Kyushu University   工学府   機械科学専攻

    2009.4 - 2010.3

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    Country: Japan

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  • Kyushu University   工学部   機械航空工学科

    2005.4 - 2009.3

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    Country: Japan

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Research History

  • Okayama University   学術研究院環境生命自然科学学域   Assistant Professor

    2023.4

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    Country:Japan

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  • Okayama University   学術研究院自然科学学域   Assistant Professor

    2021.4 - 2023.3

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    Country:Japan

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  • Yokohama National University   リスク共生社会創造センター

    2018.12 - 2019.3

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    Country:Japan

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  • Okayama University   Graduate School of Natural Science & Technology   Assistant Professor

    2018.9 - 2021.3

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    Country:Japan

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  • Yokohama National University   Institute of Advanced Sciences   Assistant Professor

    2017.6 - 2018.8

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    Country:Japan

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Professional Memberships

  • THE IRON AND STEEL INSTITUTE OF JAPAN

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  • THE JAPAN SOCIETY OF MECHANICAL ENGINEERS

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  • THE SOCIETY OF MATERIALS SCIENCE, JAPAN

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Committee Memberships

  • 日本機械学会 マイクロ・ナノ工学部門   広報委員会 幹事  

    2025.4   

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    Committee type:Academic society

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  • 日本材料学会 破壊力学部門委員会   幹事  

    2024.4   

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    Committee type:Academic society

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Papers

  • Crystal plastic homogenization finite element analysis of Ti-6242 alloy subjected to in-plane reverse loading Reviewed

    Takeshi Uemori, Naoya Tada, Junji Sakamoto

    Mechanical Engineering Journal   12 ( 2 )   24-00340 - 24-00340   2025.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Mechanical Engineers  

    DOI: 10.1299/mej.24-00340

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  • Effect of artificial defect on tensile properties of thin titanium alloy wire Reviewed

    Junji Sakamoto, Naoya Tada, Takeshi Uemori, Koyo Oishi

    Mechanical Engineering Journal   11 ( 6 )   24-00129 - 24-00129   2024.12

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    This study investigated the effects of artificial defects, introduced via focused ion beam (FIB) processing, on the tensile properties of thin titanium alloy wires (Ti-6Al-4V). Results indicated that the defective wires fractured when the net-section nominal stress reached the ultimate tensile strength of the smooth wires, probably because of localized stress concentrations relaxing due to plastic deformation around the defects. The effect of defects on tensile properties was classified into three regions based on the size of the defect area. In the case of small defects, wires fractured at the smooth area away from the defects where the cross-sectional strength was lower. In this case, the defects minimally affected the tensile properties. This is attributable to variations in the cross-sectional strength of the wire, which resulted in some sections with lower strength as compared with the defect area. In the case of medium-sized defects, the fracture strain decreased gradually as the defect area increased. Finally, in the case of large defects, the fracture strain was extremely small. The boundary between the medium-sized and large defects indicates the transition from plastic deformation to no plastic deformation in the smooth area.

    DOI: 10.1299/mej.24-00129

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    Other Link: https://www.jstage.jst.go.jp/article/mej/advpub/0/advpub_24-00129/_pdf

  • Crystal Grain Rotation during Tensile Test of Polycrystalline Pure Titanium Thin Sheet Based on Surface Height and Crystal Orientation Reviewed

    Naoya Tada, Hiroaki Ohashi, Takeshi Uemori, Junji Sakamoto

    Journal of Physics: Conference Series   2892   012002   2024.11

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1088/1742-6596/2892/1/012002

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  • Fracture Morphology of Ti-6Al-4V Thin Wire Under Load-Controlled Fatigue Test

    坂本惇司, 多田直哉, 上森武

    チタン   72 ( 3 )   39 - 43   2024.7

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    Authorship:Lead author, Corresponding author   Language:Japanese  

    J-GLOBAL

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  • Relationship between cyclic tensile properties of cellulose nanofiber reinforced natural rubber and volume fraction of bound rubber obtained from swelling tests Reviewed

    OKUI Kento, TADA Naoya, UEMORI Takeshi, SAKAMOTO Junji, SAKAKIBARA Keita

    Transactions of the JSME (in Japanese)   90 ( 932 )   24-00008 - 24-00008   2024.4

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    In recent years, environmental concerns have led to a demand for sustainable materials, and natural rubber (NR) reinforced with cellulose nanofibers (CNFs) has been attracting attention as one such material. When CNFs are added to NR, the elastic modulus is greatly improved. This is considered to be caused by deformation constraint of NR by reinforcing CNFs. On the other hand, it is known that there exists a region around reinforcing fibers where the rubber is tightly connected to the surface of fibers, which is called bound rubber. The volume fraction of the bound rubber is usually measured by swelling tests using organic solvent. In this paper, we focused on the relationship between the tensile properties of NR reinforced with CNFs and the volume fraction of bound rubber. Firstly, cyclic tensile tests were performed using plate specimens of CNF-reinforced NR and the effect of reinforcing CNFs on the tensile properties of CNF-reinforced NR and their change with loading cycles were investigated. Then, the swelling tests were conducted for similar specimens and the volume fraction of the bound rubber was evaluated. It was found from a series of experimental results that tensile deformation resistance of NR increased largely by adding 5 phr (4.8 mass%, 3.2 vol.%) of CNFs but that this increase decreased from the second loading cycle. Moreover, a clear relationship was found between the tensile deformation resistance of CNF-reinforced NR and the volume fraction of bound rubber. These results suggest that the tensile deformation resistance of CNF-reinforced NR can be evaluated by swelling tests.

    DOI: 10.1299/transjsme.24-00008

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Books

  • Creep-Fatigue Fracture: Analysis of Internal Damage

    Weisheng Zhou, Naoya Tada, Junji Sakamoto

    Springer  2024.4 

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  • 水素利用技術集成 Vol.5 ~水素ステーション・設備の安全性~

    坂本惇司, 三宅淳巳( Role: Contributor ,  第3章 第7節)

    エヌ・ティー・エス  2018.12 

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  • リスク共生学 先端科学でつくる暮らしと新たな社会

    三宅淳巳, 坂本惇司( Role: Contributor ,  6.4節)

    丸善  2018.6 

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MISC

Presentations

  • Investigation on Deformation Constraint Near Fiber/Rubber Interface in Cellulose-Nanofiber-Reinforced Natural Rubber by Swelling Test

    奥井健斗, 多田直哉, 上森武, 坂本惇司, 増田廉, 榊原圭太

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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    Event date: 2023

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  • Study on Fatigue Damage under Bending Vibration in Aluminum Alloy

    坂本惇司, 多田直哉, 上森武

    日本材料学会学術講演会講演論文集(CD-ROM)  2023 

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    Event date: 2023

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  • Surface Height Change at Grain Center and Near Grain Boundaries in Pure Titanium Plate Specimen with Circular Notch under Elastic and Plastic Tensions

    緒方隆太, 多田直哉, 上森武, 坂本惇司

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2023 

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    Event date: 2023

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  • Changes in Crystal Orientation and Surface Height after Unloading in Stepwise Load Increasing Repeated Tensile Test of Pure Titanium Thin Sheet Specimen

    大橋弘晃, 多田直哉, 上森武, 坂本惇司

    日本機械学会M&M材料力学カンファレンス(CD-ROM)  2023 

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    Event date: 2023

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  • Effect of Fine Particle Peening on Bending Vibration Life of Titanium Alloy

    畑昂輝, 坂本惇司, 多田直哉, 上森武, 杉澤拓海

    日本機械学会中国四国支部総会・講演会講演論文集(CD-ROM)  2023 

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    Event date: 2023

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Research Projects

  • 材料損傷による振動モード変化を応用した非破壊検査・長寿命化手法の開発

    Grant number:24K07235  2024.04 - 2028.03

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    坂本 惇司

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    Grant amount:\4550000 ( Direct expense: \3500000 、 Indirect expense:\1050000 )

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  • Prediction of deformation localization and fracture in polycrystalline titanium alloy based on 3D measurement of ultra-small inhomogeneous deformation

    Grant number:21H01214  2021.04 - 2024.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    多田 直哉, 上森 武, 坂本 惇司

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    Grant amount:\17810000 ( Direct expense: \13700000 、 Indirect expense:\4110000 )

    研究の初年度に当たる本年度では,3D測定レーザー顕微鏡を導入し,試験片表面における微小な変形を測定する準備をするとともに,純チタン試験片の引張に関して,既存の走査型電子顕微鏡およびデジタルホログラフィック顕微鏡も併用して試験片表面の観察を行った.本研究では,試験片に小さな引張負荷を段階的にかけながら結晶方位や応力分布を測定する薄膜試験片を用いた試験と,段階的に引張荷重をかけながら,各引張荷重を除荷した後に残留応力を測定する試験の2種類の試験を実施した.いずれも結晶粒にすべり線が発生するまで試験を実施し,微視的変形レベルにおいて弾性変形と塑性変形の関係について検討した.まず,前者の試験では,引張負荷によって生じる各結晶粒のすべりは,試験片が完全な弾性変形段階にあると見なせる小さな負荷において測定される各結晶粒の応力分布および想定されるすべり系に関するせん断応力成分と,そのすべり系の臨界分解せん断応力を用いることによりかなり高い確率で予想できることが明らかとなった.また,後者の試験からは,除荷後の各結晶粒の残留応力分布から計算できる活動すべり系のせん断応力の勾配が,発生したすべり線の方向に近い傾向にあることが明らかになった.再現性と理由については,今後,検討する予定である.
    結晶塑性有限要素法に関しては,多結晶体モデルを作成するプログラムを導入し,少結晶粒モデルに関しては解析が可能であるとの感触を得た.結晶粒数や要素分割に関する検討にはさらに時間を要すると考えられる.

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  • ネッキング型破壊の抑制とコーキシング効果の応用による微小金属材料の耐疲労特性向上方法の開発

    2021.04 - 2022.03

    公益財団法人JKA  2021年度機械振興補助事業 個別研究 

    坂本 惇司

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    Authorship:Principal investigator 

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  • Investigation of vibration fatigue crack growth behavior and vibration fatigue strength improvement by peening

    Grant number:20K14610  2020.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists  Grant-in-Aid for Early-Career Scientists

    坂本 惇司

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    Grant amount:\4160000 ( Direct expense: \3200000 、 Indirect expense:\960000 )

    本研究では,①振動疲労き裂進展時のき裂先端近傍の力学場の状態とそれがき裂進展とともにどう変化するのかを明らかにすること,および,②ピーニングによる振動時の疲労強度向上技術を構築することを目的とする.それぞれの目的に対して,本年度に推進した主な実施内容を以下に示す.
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    ①試験片切欠き部の表面と裏面にひずみゲージを貼付し,試験片の表面と裏面のひずみを測定することで,振動試験時のマクロな力学状態を検討した.その結果,曲げ振動試験においては,純粋な曲げに加えて遠心力による引張が加わるが,今回の試験片においては,遠心力による引張ひずみは,曲げで付与される最大引張ひずみに比べて無視できる程度であることが分かった.また,昨年度に確認された疲労損傷とともに振動モード(曲げ振幅)が変化する現象について,高速度カメラを用いた観察,ひずみゲージによる破断部近傍のひずみの測定,プラスチックレプリカ法を用いたき裂進展挙動の観察を行うことで検討した.その結果,疲労損傷とともに試験片がわずかに伸びることおよび疲労き裂が進展することにより,固有振動数が変化することが考えられた.
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    ②振動疲労強度を向上させるピーニング手法として,本年度はニードルピーニングを検討した.その結果,振動疲労寿命をわずかに増加させる可能性はあるものの,顕著な変化は確認できなかった.その原因として,圧縮残留応力の付与や硬さの向上等の疲労寿命を向上させる影響と,表面粗さの増加等の疲労寿命を低下させる影響が同程度であるためだと考えられる.そのため,次年度は,微粒子ピーニングを用いてピーニングの影響について検討する予定である.

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  • 繰返し硬さ試験による疲労寿命の簡易評価法の確立とその微小材料の疲労寿命の向上探索への応用

    2019.04 - 2020.03

    公益財団法人村田学術振興財団  研究助成 

    坂本 惇司

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    Authorship:Principal investigator  Grant type:Competitive

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Class subject in charge

  • Experiments in Mechanical Engineering (2024academic year) Other  - [第1学期]火5~8, [第2学期]不開講, [第3学期]火5~8, [第4学期]火5~8

  • Experiments in Mechanical Engineering (2024academic year) Other  - [第1学期]火5~8, [第2学期]不開講, [第3学期]火5~8, [第4学期]火5~8

  • Experiments in Mechanical EngineeringⅡ (2024academic year) 3rd and 4th semester  - 火5~8

  • Experiments in Mechanical EngineeringI (2024academic year) 1st semester  - 火5~8

  • Research Works for Mechanical and Systems Engineering 1 (2024academic year) Prophase  - その他

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