九州大学 研究者情報
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基本情報 研究活動 教育活動 社会活動
山口 哲生(やまぐち てつお) データ更新日:2018.03.12

准教授 /  工学研究院 機械工学部門 設計・生体システム


主な研究テーマ
ソフトマターにおける界面力学現象(接着・摩擦など)
地震現象の模擬実験
キーワード:接着・粘着,摩擦,トライボロジー,破壊,地震,スティック-スリップ,ゲル,粘着剤
2004.10~2015.03.
従事しているプロジェクト研究
科研費 新学術領域研究「スロー地震学」
2016.09~2021.03, 代表者:波多野 恭弘, 東京大学地震研究所, 東京大学地震研究所など
最近,GPSなど観測手法の発達によって,スロー地震とよばれる新しいタイプの地震現象が見つかっている.本研究では,スロー地震のメカニズムを解明すべく,地球物理学および物理学的アプローチに基づいて研究を行っている..
科研費・新学術領域研究「地殻ダイナミクス」公募研究
2015.04~2017.03, 代表者:山口 哲生, 九州大学, 文部科学省
地震発生メカニズムを解明するため,室内実験モデルを構築する.発生過程の可視化を行うことで,詳細にメカニズムを理解する..
光・量子融合連携研究開発プログラム「中性子とミュオンの連携による「摩擦」と「潤滑」の本質的理解」
2013.04~2018.03, 代表者:瀬戸 秀紀, 高エネルギー加速器研究機構 物質構造科学研究所, 文部科学省
摩擦や潤滑といった現象は,私達の身の回りのあらゆる場所で起きている.しかし,摩擦が起きているまさにその場所,物と物が触れ合っている所で実際に何が起きているのかについては,まだわかっていないことがたくさんある.わたしたちは,中性子やミュオンのビーム使って,この摩擦や潤滑という現象を明らかにしようとしている..
科学研究費補助金特別推進研究「極低摩擦・極低摩耗生体関節に学ぶ生体規範超潤滑ハイドロゲル人工軟骨の実用化」
2011.04~2015.03, 代表者:村上 輝夫, 九州大学バイオメカニクス研究センター, 九州大学バイオメカニクス研究センター(日本)
極低摩擦・極低摩耗を長期間にわたって実現している生体関節を規範とし,既存のハードオンハード人工関節に置き換わるハイドロゲル人工関節軟骨を実用化する..
研究業績
主要著書
1. 山口 哲生, 梶谷 忠志, 武居 淳, 竹内 一将, 奥村 剛, ムースの物理学 構造とダイナミクス, 吉岡書店, 2016.11, 本書では,泡,フォームなどの”ムース”の構造と物性について解説をおこなっている.
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2. 山口 哲生, 粘着・剥離のメカニズムとレオロジー特性, 技術情報協会, 2009.01, 粘着・剥離とレオロジーとの関連について基礎から応用までを解説した..
3. Tetsuo Yamaguchi, David Dillard, Special Testing, Springer, Vol.1, pp.533 - 549, 2011.01, 接着・粘着・シールなどの用途における特殊な試験方法について解説を行なった..
主要原著論文
1. Tetsuo Yamaguchi, Tomohiko G. Sano, Hirofumi Wada, Slip Morphology of Elastic Strips on Frictional Rigid Substrates, Physical Review Letters, https://doi.org/10.1103/PhysRevLett.118.178001, 118, 178001-1-178001-5, 2017.04, The morphology of an elastic strip subject to vertical compressive stress on a frictional rigid substrate is investigated by a combination of theory and experiment. We find a rich variety of morphologies, which—when the bending elasticity dominates over the effect of gravity—are classified into three distinct types of states: pinned, partially slipped, and completely slipped, depending on the magnitude of the vertical strain and the coefficient of static friction. We develop a theory of elastica under mixed clamped-hinged boundary conditions combined with the Coulomb-Amontons friction law and find excellent quantitative agreement with simulations and controlled physical experiments. We also discuss the effect of gravity in order to bridge the difference in the qualitative behaviors of stiff strips and flexible strings or ropes. Our study thus complements recent work on elastic rope coiling and takes a significant step towards establishing a unified understanding of how a thin elastic object interacts vertically with a solid surface..
2. Tetsuo Yamaguchi, Yoshinori Sawae, Shmuel M. Rubinstein, Effects of loading angles on stick–slip dynamics of soft sliders, Extreme Mechanics Letters, 10.1016/j.eml.2016.09.008, 9, 331-335, 2016.10, When soft gels move across a hard surface, stick–slip frictional sliding is mediated by propagation of adhesion and detachment fronts. Here we experimentally investigate the sliding dynamics of an extended frictional interface between soft Silicone gel and hard PMMA and identify three distinct sliding regimes. We directly visualize the interface and show that a minute manipulation of the initial loading angle results in a sharp bifurcation between the different sliding states. The phase diagram as well as universal scaling relations governing the dynamics is presented..
3. Tetsuo Yamaguchi, Yoshimi Tanaka, Risa Shimazaki, Solvent effects on fracture of chemically crosslinked gels, Soft Matter, 10.1039/C6SM01645F, 12, 8135-8142, 2016.10, We have investigated how the fracture behavior of a polyacrylamide hydrogel is affected by different types of solvents poured into its crack tips. We obtained the following results: first, when water (good solvent or reaction solvent for the polyacrylamide gel) is poured, the fracture energy Gamma becomes smaller than that measured in air for small crack velocities. Second, when good solvents other than water are poured, Gamma is enhanced for a large V region, but this effect is not observed for smaller V; Gamma(V) in good solvents converges to that in water as V approaches 0. Third, when ethanol (poor solvent for polyacrylamide) is poured, stick–slip-like crack propagation appears in the entire V range, and Gamma calculated from the time-average of the oscillating tearing forces is larger than that in air or in other solvents. We discuss the results on the basis of diffusion dynamics around the crack tips of the gel..
4. Tetsuo Yamaguchi, Satoshi Ohmata, Masao Doi, Regular to chaotic transition of stick-slip motion in sliding friction of an adhesive gel-sheet, Journal of Physics: Condensed Matter, 10.1088/0953-8984/21/20/205105, 21, 205105-1-7, 2009.04, Spatio-temporal pattern of the stick–slip motion of a gel-sheet pulled on a glass substrate is observed. The sliding takes place via the propagation of the wave of detachment (Schallamach wave). At large pull velocity, the detached region is a stripe which moves regularly with constant speed and the frictional force shows a periodic time dependence. As the pull velocity is decreased, the detached region is separated into bubbles which move around irregularly. In the irregular state, the frictional force shows chaotic time dependence and the statistics of the event of the force drop obeys a power law similar to the Gutenberg–Richter law known in
earthquakes. In the regular region, the detachment wave is analyzed theoretically and the velocity and lengths are obtained as a function of the pull velocity. The transition from the regular to chaotic behavior is shown to be related to the spontaneous wetting of the gel..
5. Tetsuo Yamaguchi, Masatoshi Morishita, Masao Doi, Takane Hori, Hide Sakaguchi, Jean-Paul Ampuero, Gutenberg-Richter’s law in sliding friction of gels, Journal of Geophysical Research, Solid Earth, 10.1029/2011JB008415, 116, B12306-1-8, 2011.12, We report on experimental studies of spatio-temporally heterogeneous stick-slip
motions in the sliding friction between a hard polymethyl methacrylate (PMMA, plexiglass)
block and a soft poly-dimethyl siloxane (PDMS, silicone) gel plate. We perform
experiments on two PDMS gels with different viscoelastic properties. For the less viscous
gel, large and rapid events are preceded by an alternation of active and less active periods.
For the more viscous gel, successive slow slip events take place continuously. The
probability distributions of the force drop, a quantity analogous to seismic moment, obey a
power law similar to Gutenberg-Richter’s empirical law for the frequency-size statistics of
earthquakes, and the exponents of the power law vary with the plate velocity and the
viscosity of the gel. We propose a simple model to explain the dependence of the power law
exponent on the plate velocity, which agrees with experimental results..
6. Tetsuo Yamaguchi, Hiroyuki Muroo, Yutaka Sumino, Masao Doi, Asymmetry-symmetry transition of double-sided adhesive tapes, Physical Review E, 10.1103/PhysRevE.85.061802, 85, 061802-1-6, 2012.06, We report on the debonding process of a double-sided adhesive tape sandwiched between two glass plates.
When the glass plates are separated from each other at a constant rate, a highly asymmetric extension of top and
bottom adhesive layers and bending of the inner film are observed first. As the separation proceeds, the elongation
of both layers becomes symmetric, and the inner film becomes flat again. When this happens, there appears a
local maximum in the force-displacement curve. We explain this asymmetry-symmetry transition and discuss
the role of the bimodal force-displacement relation of each adhesive layer.We also discuss the effect of the inner
film thickness and the separation rate on the debonding behavior, which causes undesirable early detachment of
the double-sided adhesive tape in a certain condition..
主要総説, 論評, 解説, 書評, 報告書等
1. 山口 哲生, 粘着性のある物質の粘着と摩擦, トライボロジスト, 2008.03, やわらかい粘弾性体の粘着・剥離・摩擦現象に関して解説を行なった..
2. 山口 哲生, 土井 正男, 高分子の粘着と剥離ーミクロ・メソの視点から-, 成形加工, 2007.04, 高分子の粘着・剥離現象について,非専門家に対して解説を行なった..
主要学会発表等
1. Tetsuo Yamaguchi, Effects of electric fields on sliding friction of hydrogels, IUMRS-ICA2014, 2014.08, Frictional properties of hydrogels have attracted much attention due to its low friction. In particular, friction coefficient of polyelectrolyte hydrogels can be as small as 0.001. In this talk, we report our studies on friction of polyelectrolyte hydrogels and electric field effects, i.e., 1) friction control of polyelectrolyte hydrogels using electric fields and 2) preparation of polyelectrolyte hydrogels under electric fields. Through the discussions, we will point out the importance of electric charges for reduction or control in friction of hydrogels..
2. Tetsuo Yamaguchi, Sliding friction of sticky gels, Gordon Research Conference on Tribology, 2014.07, [URL], When a soft and sticky gel is slid against a smooth surface, stick-slip motion does not occur grobally but in a localized manner.
As slip regions propagate, they move randomly: they start to move and arrest suddenly, coalesce with each other, break into several parts, or even wander around the frictional interface in backward direction. Furthermore, the slip size statistics follows the power law, like Gutenberg-Richter law for earthquakes. In this talk, we discuss why and how such complexity emerges during friction through the in-situ visualization of frictional stresses. .
3. Tetsuo Yamaguchi, Sliding friction of polymer gels: from slippery to sticky surfaces, Joint Symposium of ISPMS'12 & OUMS'12, 2012.11, In this presentation, we introduce our two different topics discussing low friction and high friction in polymer gels. The first topic is the effects of stress-diffusion coupling (“biphasic lubrication” in biomechanics society) in sliding friction of PVA (poly-vinyl alcohol) hydrogels, where frictional behavior is dominated by transient diffusive process of water. In the second part, we discuss spatio-temporally heterogeneous stick-slip motions in sliding friction of adhesive gel-sheets. The system shows formation of the inchworm-like detachment waves (Schallamach waves) in the frictional interface and exhibits regular-chaos transition of the detachment wave patterns, dependent on the driving velocity. Through these two examples, we will stress the importance of coarse-grained or mesoscopic description on frictional properties for polymer gels..
4. Tetsuo Yamaguchi, Non-linear Mechanics in Debonding of Pressure-Sensitive Adhesives, The Adhesion Society Annual Meeting, 2013.03, We report on the debonding process of a double-sided adhesive tape sandwiched between two glass plates as an example showing the importance of non-linear mechanics in pressure-sensitive adhesives. .
5. Tetsuo Yamaguchi, Sliding friction of sticky gel-sheets, The Adhesion Society Annual Meeting, 2013.03, We report our recent results on the image analyses of the spatio-temporal patterns of the stick-slip motions. .
学会活動
所属学会名
アメリカ地震学会
アメリカ地球物理学連合
日本トライボロジー学会
日本接着学会
日本機械学会
日本地震学会
日本物理学会
学協会役員等への就任
2009.04~2010.04, 日本物理学会, ソフトマター物理分野世話人.
学会大会・会議・シンポジウム等における役割
2017.03.09~2017.03.11, YITP Workshop on non Gaussian fluctuation in solids, 座長(Chairmanship).
2016.11.03~2016.11.05, 第3回 非線形現象の捉え方, 座長(Chairmanship).
2016.09.11~2016.09.14, 日本機械学会年次大会, 座長(Chairmanship).
2015.09.16~2015.09.20, ITC Tokyo 2015, 座長(Chairmanship).
2015.03.21~2015.03.24, 日本物理学会第70回年次大会, 座長(Chairmanship).
2014.11.05~2014.11.08, トライボロジー会議2014 秋, 座長(Chairmanship).
2014.10.15~2014.10.17, 第62回レオロジー討論会, 座長(Chairmanship).
2014.09.07~2014.09.11, WCARP 2014, 座長(Chairmanship).
2013.09.25~2013.09.27, 第61回レオロジー討論会, 座長(Chairmanship).
2013.06.06~2013.06.08, 第36回バイオレオロジー学会年会, 座長(Chairmanship).
2014.03.27~2014.03.30, 日本物理学会第69回年次大会, 座長(Chairmanship).
2013.09.25~2013.09.28, 日本物理学会2013年秋季大会, 座長(Chairmanship).
2012.09.18~2012.09.21, 日本物理学会2012年秋季大会, 座長(Chairmanship).
2012.06.29~2012.06.30, 日本接着学会第60回年次大会, 座長(Chairmanship).
2012.06.06~2012.06.08, 平成24年度繊維学会年次大会, 座長(Chairmanship).
2016.12.05~2016.12.06, JSPS-HAS Worshop on Granular Physics, 主催者.
2016.03.07~2016.03.09, Avalanches, plasticity, and nonlinear response in nonequilibrium solids, 組織委員として研究会の企画・運営に参加した..
2015.09.17~2015.09.17, International Tribology Conference Tokyo, セッション”Science of Friction”を企画した..
2010.09.13~2010.09.18, The International Conference on Science of Friction, Organizing Comittee.
2012.11.06~2012.11.08, 京大・基研研究会「摩擦、レオロジー、地震の新展開-異なる階層と舞台をつなぐ-」, 実行委員.
学会誌・雑誌・著書の編集への参加状況
2008.04~2010.04, 日本物理学会誌, 国内, 新著紹介小委員会委員.
学術論文等の審査
年度 外国語雑誌査読論文数 日本語雑誌査読論文数 国際会議録査読論文数 国内会議録査読論文数 合計
2017年度
2016年度 11 
2015年度
2014年度
2013年度 11 
2012年度 10  10 
2011年度
その他の研究活動
海外渡航状況, 海外での教育研究歴
Universite de Lyon 1, France, 2016.09~2016.10.
Stanford University, UnitedStatesofAmerica, 2016.03~2016.03.
Ecole Polytechnique Federale de Lausanne, Switzerland, 2015.11~2015.12.
Harvard University, UnitedStatesofAmerica, 2015.01~2015.01.
California Institute of Technology, UnitedStatesofAmerica, 2010.03~2013.03.
パリ市立工業物理化学高等専門学校(ESPCI Paris Tech), France, 2007.04~2007.10.
受賞
Best Presentation Award, Malaysian Tribology Society, 2015.11.
Papers of Editors’ Choice, The Physical Society of Japan, 2010.05.
日東電工賞・ベストポスター賞, 日本接着学会, 2006.06.
進歩賞, 日本接着学会, 2011.05.
研究資金
科学研究費補助金の採択状況(文部科学省、日本学術振興会)
2016年度~2021年度, 新学術領域研究, 分担, スロー地震学C02班:非平衡物理学に基づくスロー地震と通常の地震の統一的理解.
2015年度~2016年度, 新学術領域研究, 代表, 断層面の不均一性と地震発生過程に関する実験的研究.
2013年度~2014年度, 新学術領域研究, 代表, ヤモリ模擬構造への材料力学的アプローチ.
2013年度~2014年度, 挑戦的萌芽研究, 分担, 機能性表面創成のための多層・多段階インプリントプロセス.
2012年度~2015年度, 挑戦的萌芽研究, 代表, すべり摩擦現象における時空間揺らぎと自己組織化.
共同研究、受託研究(競争的資金を除く)の受入状況
2015.03~2016.02, 代表, ABS制動距離予測および短縮に関する研究.
寄附金の受入状況
2017年度, 株式会社ブリヂストン, 高分子、及びその複合体の摩擦・摩耗 .
2016年度, 株式会社ブリヂストン, 高分子、及びその複合体の摩擦・摩耗 .
2015年度, 株式会社ブリヂストン, 高分子、及びその複合体の摩擦・摩耗.
学内資金・基金等への採択状況
2015年度~2015年度, P&P特別枠第3回, 代表, 座屈・破壊・地震等の非線形力学現象の発生予測に関する研究.

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