Sano, Tomohiko

写真a

Affiliation

Faculty of Science and Technology, Department of Mechanical Engineering (Yagami)

Position

Assistant Professor/Senior Assistant Professor

 

Research Areas 【 Display / hide

  • Natural Science / Mathematical physics and fundamental theory of condensed matter physics

  • Natural Science / Biophysics, chemical physics and soft matter physics

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

Research Keywords 【 Display / hide

  • Structural Mechanics

  • Statistical Mechanics

  • Continuum Mechanics

 

Papers 【 Display / hide

  • Exploring the inner workings of the clove hitch knot

    TG Sano, P Johanns, P Grandgeorge, C Baek, PM Reis

    Extreme Mechanics Letters, 101788 (Extreme Mechanics Letters)  55 2022.08

    Accepted

     View Summary

    We perform a combined experimental and computational investigation of the clove hitch knot. We develop a physical model for the clove hitch by tying an elastic rod onto a rigid cylinder. In the experiments, we characterize the mechanical performance, geometry, and stability conditions of the knot. X-ray tomography allows us to characterize the 3D geometry of the rod centerline. These results also serve to validate our finite element modeling (FEM), which we use to quantify the tension profile, not accessible experimentally, along the knotted rod. We find that the clove hitch comprises alternating segments with two types of contact regions: one where the rod is in single frictional contact with the cylinder, and another with rod self-contact (where a rod segment pinches another against the cylinder). In the first region, the internal tension decays exponentially (akin to the capstan configuration), whereas, in the second, the pinch (nip) regions lead to discontinuous tension drops. We analyze these nip regions with an even simpler model system where an elastic rod is pinched between two rigid cylinders. Despite the complex contact geometry of this pinching experiment, we find that the frictional behavior of our model systems still obeys the classic Amontons–Coulomb law. Ultimately, we can regard the clove hitch knot, if tied correctly, as a functional structure enabling to drop high tension at one extremity of a filament secured onto a rigid post, all the way to zero at the other extremity.

  • An elastic rod in frictional contact with a rigid cylinder

    P Grandgeorge, TG Sano, PM Reis

    Journal of the Mechanics and Physics of Solids 164, 104885 (Journal of the Mechanics and Physics of Solids)  164 2022.07

    Accepted,  ISSN  00225096

     View Summary

    We investigate the load transmission along an elastic rod of finite cross-section in contact with a rigid cylinder, as system often referred to as the generalized capstan problem. In the presence of friction, the idealized classic capstan equation predicts that the tension along a perfectly thin and flexible filament increases exponentially along the contact region. In practical applications, however, the validity of the idealized capstan equation is compromised due to the interplay between finite rod thickness, bending stiffness, and the forces applied at the rod extremities. Here, we combine precision model experiments, finite element simulations, and theoretical modeling to investigate the contact mechanics and the force transmission along an elastic rod in frictional contact with a rigid cylinder. We study two cases when the rod is either static or sliding. First, we focus on the static case, in the absence of friction, by considering equal loads at both extremities of the rod. We show that as the loading force is increased, the nature of contact transitions from a localized region to an extended band at the surface of the cylinder. The latter is characterized by double-peaked contact force distribution. In the sliding case, friction is activated by inducing a relative motion between the rod and the cylinder. We applied a fixed loading force at one rod extremity while pulling the other extremity at a constant velocity. The driving force is monitored during sliding. For increasing loading forces, we find that the force ratio is non-monotonic and displays a local minimum, in contradiction with the constant ideal capstan prediction. This minimum force ratio coincides with the transition from a single contact point to an extended contact region. A theoretical analysis based on Euler's elastica serves to rationalize the results from the physical and numerical experiments. In addition to predicting the nature of the contact region (single point versus extended line), our model provides quantitative predictions for the wrapping angle and the driving-to-loading force ratio. Finally, we leverage our mechanics-based framework to predictively understand the force ratio at the ends of two commercially available engineering belts (spring-steel and polyurethane) in sliding contact with a steel cylinder.

  • Reduced theory for hard magnetic rods with dipole-dipole interactions

    Sano T.G.

    Journal of Physics A: Mathematical and Theoretical (Journal of Physics A: Mathematical and Theoretical)  55 ( 10 )  2022.03

    ISSN  17518113

     View Summary

    Hard magnetic elastomers are composites of soft elastic foundations and magnetic particles with high coercivity. We formulate a theoretical framework to predict the large deformation of a hard magnetic elastomeric rod. In the previous work, the magnetic Kirchhoff rod equations, which constitute a framework for analyzing instabilities for hard magnetic rods, have been developed and validated experimentally for negligible dipole-dipole interactions. Building on previous studies, we derive the magnetic Kirchhoff rod equations with dipole-dipole interactions. The derived equations are integro-differential equations, representing the force and moment balance along the rod centerline that include long-ranged dipole-magnetic force and torque. On the basis of its discrete numerical simulation, we systematically study the effect of the the dipole-dipole interactions strength on the large deformation of hard magnetic rods. In addition, we find that our theory can predict previous experimental results without any adjustable parameters.

  • A Kirchhoff-like theory for hard magnetic rods under geometrically nonlinear deformation in three dimensions

    TG Sano, M Pezzulla, PM Reis

    Journal of the Mechanics and Physics of Solids 160, 104739 (Journal of the Mechanics and Physics of Solids)  160 2022.03

    Accepted,  ISSN  00225096

     View Summary

    Magneto-rheological elastomers (MREs) are functional materials that can be actuated by applying an external magnetic field. MREs comprise a composite of hard magnetic particles dispersed into a nonmagnetic elastomeric (soft) matrix. Hard MREs have been receiving particular attention because the programmed magnetization remains unchanged upon actuation. Motivated by a new realm of applications, there have been significant theoretical developments in the continuum (three-dimensional) description of hard MREs. In this paper, we derive an effective theory for MRE rods (slender, mono-dimensional structures) under geometrically nonlinear deformation in three dimensions. Our theory is based on reducing the three-dimensional magneto-elastic energy functional for the hard MREs into an one-dimensional Kirchhoff-like description (centerline-based). Restricting the theory to two dimensions, we reproduce previous works on planar deformations. For further validation in the general case of three-dimensional deformation, we perform precision experiments with both naturally straight and curved rods under either constant or constant-gradient magnetic fields. Our theoretical predictions are in excellent agreement with both discrete simulations and precision-model experiments. Finally, we discuss some limitations of our framework, as highlighted by the experiments, where long-range dipole–dipole interactions, which are neglected in the theory, can play a role.

  • Wetting dynamics of viscoelastic solid films

    T Yamaguchi, M Morishita, TG Sano, M Doi

    Soft Matter  2022

    Accepted

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Reviews, Commentaries, etc. 【 Display / hide

  • Stochastic Mean Field Model of Heat Engine partitioned by Fluctuating Piston

    Tomohiko G. Sano, Hisao Hayakawa

     2014.12

     View Summary

    We propose a stochastic mean field model of heat engine partitioned by a<br />
    finite-mass piston. The time evolution equations for the density and the<br />
    temperature of the enclosed gas are proposed, taking into account the<br />
    stochastic equation of motion of the piston, and the energy conservation for<br />
    the gas. Though the heat cycle consisting of finite-time heating and cooling<br />
    processes is under strong non-equilibrium situations, i. e., the ratio of<br />
    temperatures of two reservoirs is large, we analyze the efficiency and the<br />
    power, and derive the semi-analytical expression for the efficiency. We find<br />
    that the obtained efficiency at the maximum power operation is close to the<br />
    Chambadal-Novikov-Curzon-Ahlborn (CNCA) efficiency, if the piston is<br />
    sufficiently heavy and elastic for collisions with particles, even when the<br />
    system is far from equilibrium. However, the extra heat due to the finiteness<br />
    of the piston-mass or its inelasticity lowers the efficiency from the CNCA<br />
    efficiency. The results of our stochastic mean field model are consistent with<br />
    those for our event driven molecular dynamics simulation.

  • 9aAY-6 Granular rotor : Is is possible to infer athermal granular fluctuation from the dynamics of the rotor?

    Sano Tomohiko, Kanazawa Kiyoshi, Sagawa Takahiro, Hayakawa Hisao

    Meeting abstracts of the Physical Society of Japan (The Physical Society of Japan (JPS))  69 ( 2 ) 160 - 160 2014.08

    ISSN  1342-8349

  • 29pBD-11 Microscopic derivation of non-Gaussian Langevin equations

    Kanazawa Kiyoshi, Sano Tomohiko, Sagawa Takahiro, Hayakawa Hisao

    Meeting abstracts of the Physical Society of Japan (The Physical Society of Japan (JPS))  69 ( 1 ) 356 - 356 2014.03

    ISSN  1342-8349

  • 29pBD-12 Fluctuating Heat Engine under Dry Friction

    Sano Tomohiko, Hayakawa Hisao

    Meeting abstracts of the Physical Society of Japan (The Physical Society of Japan (JPS))  69 ( 1 ) 356 - 356 2014.03

    ISSN  1342-8349

  • Application of Adiabatic piston problem with dry friction to Heat Engine

    Sano Tomohiko, Hayakawa Hisao

    Meeting abstracts of the Physical Society of Japan (The Physical Society of Japan (JPS))  68 ( 2 ) 249 - 249 2013.08

    ISSN  1342-8349

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • Designing principles of mechanical metamaterials based on the studies of heterogeneous elastic materials

    2018.04
    -
    2024.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists , Principal investigator

     View Summary

    複雑な内部自由度をもつ構造物の力学応答をデザインする指針を明らかにする。一般に、自然な構造物では通常起こり得ない特異な力学特性を示す材料は、メカニカルメタマテリアルと呼ばれる。構造を圧縮すると通常は圧縮方向に垂直にふくらむ(ポアソン比が正)が、逆に垂直にも縮むもの(ポアソン比が負)が例として挙げられる。メカニカルメタマテリアルは対称性の高い内部構造を用いて開発されており、その非対称性や乱れが全体に与える影響は明らかにされていない。本研究は構造の乱れと不均一性がメカニカルメタマテリアルに与える影響を系統的に考察することにより、力学応答を自在にデザインするための指針を解明する。
    本研究はくしゃくしゃに丸めた紙に代表される内部構造を持つ弾性材料の力学特性を明らかにすることを目的にしている。初年度は、丸めた紙の皺を系統的に生成する方法を確立し、皺が発生する過程での力学的性質を実験的に明らかにした。同じ直径の金属柱を二つ用意し、一つをリニアステージに取り付ける。そしてもう一つをロードセルと共に光学定盤に固定する。金属柱に紙(Mylar sheet)を巻きつけ、巻きつけた紙を金属柱より少し大きな直径をもつアクリル円筒内に入れ、紙のもう一端を光学定盤に固定した金属柱に固定する。リニアステージの変位制御により、巻きつけた紙に対して圧縮と伸張を繰り返し、その際に発生する力を変位の関数として測定した。この繰り返しにより系統的に皺を発生することができる。ロードセルで測定した力変位曲線の結果から、皺を発生させる力にも先行研究で知られている「皺の全長」と圧縮伸張回数の関係に類似した関係式が実験的に得られた。紙に皺を発生させるという一見乱雑な過程にも普遍的な数理構造があることが示唆された。研究成果は未だ公表に至っていないが、共同研究者との議論を重ね解析を続けている。またアメリカ物理学会に参加し関連研究の情報収集を行なった。
    内部構造を持つ弾性材料の簡単な問題として、円筒に切れ込みを入れたシェル構造体の力学特性を定量的にあきらかにした。切れ込みの入った円筒は、切れ込みのない円筒の場合と比べ、変形の緩和長が大きくなることがわかった。切り紙のような構造デザインを考える際の指針になりうると考えている。

 

Courses Taught 【 Display / hide

  • SPECIAL LECTURE SERIES ON MULTIDISCIPLINARY AND DESIGN SCIENCE

    2022

  • INDEPENDENT STUDY ON INTEGRATED DESIGN ENGINEERING

    2022

  • GRADUATE RESEARCH ON INTEGRATED DESIGN ENGINEERING 2

    2022

  • GRADUATE RESEARCH ON INTEGRATED DESIGN ENGINEERING 1

    2022

  • FACTORY VISITING

    2022

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