・ゲル室内地震実験
Stick-slip friction of soft elastic bodies and laboratory earthquake experiments
弾性体同士を摩擦させたとき，しばしば，固着とすべりを繰り返す，スティックスリップ運動を示す．スティックスリップ運動は，機械システムのみならず，プレート同士のすべりによって引き起こされる地震や，ワイパーのビビリなど，さまざまな状況で現れる日常的な現象である．当研究室では，スティックスリップ運動を詳細に観察するため，高分子ゲルとよばれるやわらかくて透明な弾性体を用いて摩擦実験を行なっている．すべり素過程や応力・ひずみ場の可視化を通して，メカニズムの解明や挙動の制御を目指す．
When two elastic bodies are slid against each other, they often exhibit stick-slip motions repeating lock and sliding. The stick-slip motions are seen in various systems such as machinery, earthquakes, wiper chattering, etc. In order to observe the behavior in detail, we have been conducting stick-slip experiments using soft and transparent polymer gels. We are now aiming at understanding mechanisms and controlling the behavior through in-situ visualization of elementary slip processes, and stress/strain fields.
References
[1] T. G. Sano, T. Yamaguchi, H. Wada, Phys. Rev. Lett. 118 (17), 178001 (2017).
[2] T. Yamaguchi, Y. Sawae, S. M. Rubinstein, Extreme Mech. Lett. 9, 331-335 (2016).
[3] T Yamaguchi, Y Himeno, Y Sawae, Proc. Malaysian Int. Tribol. Conf. 78-79 (2015).
[4] T. Yamaguchi, M. Morishita, M. Doi, T. Hori, H. Sakaguchi, J.- P. Ampuero, J. Geophys. Res, 116, B12306-1-8 (2011).
[5] M. Morishita, M. Kobayashi, T. Yamaguchi, M. Doi, J. Phys.: Cond. Matt., 22, 365104-1-6 (2010).
[6] T. Yamaguchi, S. Ohmata, M. Doi, J. Phys.: Condens. Matter, 21, pp.205105-1-7 (2009).
・メカニカルメタマテリアル
Toughening of sparse elastic networks and mechanical metamaterials
紐や梁が連結してできた疎な弾性ネットワーク構造は，高分子ゲルや網，発泡材など，我々の身の周りに数多く存在する．このような疎な弾性ネットワーク構造の高靭化は極めて重要な課題であるものの，研究例は非常に少ない．本研究では，とくにネットワークトポロジーとメタマテリアル構造に着目し，高靭ネットワークの設計指針の確立を目指している．
The toughening of sparse elastic networks, such as hydrogels, foams, or meshes against fracture is one of the most important problems in materials science. However, the principles of toughening have not yet been established despite urgent engineering requirements and several efforts made by materials scientists. Here we tackle with the abovementioned problem by focusing on the topology and the matamaterial structure of a network.
References
[1] T. Yamaguchi, Y. Onoue, Y. Sawae, Topology and Toughening of Sparse Elastic Networks, Physical Review Letters 124 (6), 068002 (2020).
・超音速すべり摩擦
Studies on sliding friction at intersonic sliding velocities
通常のすべり摩擦においては，すべり速度は物体中を伝ぱする弾性波速度に比べて極めて小さく，動弾性の効果は無視できる．本研究では，すべり速度が弾性波速度と同等な条件下で生じる摩擦挙動を観察することで，超高速での接触・摩擦機構を明らかにする．
In normal situations during sliding friction, the sliding velocity is much smaller than the Rayleigh wave velocity or Secondary wave velocity of the objects, and there have been very few studies on the friction at intersonic sliding velocities. Here we study the intersonic sliding friction to understand the mechanisms behind such an abnormal situation.
References
[1] T. Yashiki, T. Morita, Y. Sawae, T. Yamaguchi, Subsonic to Intersonic Transition in Sliding Friction for Soft Solids, Physical Review Letters 124 (23), 238001 (2020).
