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Tetsuo Yamaguchi Last modified date:2020.01.29

Associate Professor / Machine elements and design engineering laboratory
Department of Mechanical Engineering
Faculty of Engineering

Graduate School
Undergraduate School

Machine Elements and Design Engineering Laboratory, Kyushu University .
Personal Website .
Academic Degree
ph. D
Country of degree conferring institution (Overseas)
Field of Specialization
Soft matter physics, statistical physics, experimental seismology
Total Priod of education and research career in the foreign country
Outline Activities
I have been working on interfacial and dynamical properties of soft visco-elastic solids, such as adhesion of soft rubber and sliding friction of gels. I have also been interested in fracture of network-like materials and mechanical meta-materials.
Research Interests
  • Large deformation behavior of mechanical metamaterials
    keyword : mechanical metamaterial, large deformation, buckling, fracture, non-affin deformation
  • Topology and toughening of sparse elastic networks
    keyword : network-like material, topology, fracture, toughening
  • Studies on intersonic sliding friction
    keyword : friction, contact, intersonic, subsonic, fracture
  • Laboratory experiments of earthquakes
    keyword : Earthquake, experiment, visualization
  • Interfacial mechanics in soft matter (adhesion & friction)
    keyword : adhesion, friction, tribology, fracture, gel, pressure sensitive adhesives
Current and Past Project
  • In this study, we investigate the relationship between topology and toughening of network-like structures, and develop new type tough materials.
  • Our objectives of this study are to understand the mechanisms for transient mechanical responses like scuffing or running-in processes.
  • Recently, a new type of earthquake, called slow earthquake, has been discovered due to the development of new observation techniques like GPS. In this project, we have been studying slow earthquakes to understand the basic mechanisms based on geophysical or physical approaches.
  • In order to understand the basic mechanisms of earthquake occurrence, we develop laboratory models. We try to elucidate the details by performing In-situ visualization during the processes.
  • By mimicking ultra-low friction and wear articular cartilages, we develop hydrogel-based artificial articular cartilages.
Academic Activities
1. Les Mousses Structure et Dynamique.
2. 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..
1. Tetsuo Yamaguchi, Costantino Creton, Masao Doi, Simple model on debonding of soft adhesives, Soft Matter, 10.1039/c8sm00723c, 14, 30, 6206-6213, 2018.01, We propose a simple theoretical model describing the debonding process of soft adhesives in the probe-tack test. In this model, the expansion dynamics of interfacial cavities is determined by the balance between the strain energy release rate and the rate-dependent fracture energy. As a result, we obtain analytical solutions for the cavity size, stress-strain curve, peak stress, strain at the peak stress, maximum strain, as well as the adhesion energy. Furthermore, we discuss the validity of our theoretical results by comparing them with experiments..
2. Tomohiko G. Sano, Tetsuo Yamaguchi, Hirofumi Wada, Slip Morphology of Elastic Strips on Frictional Rigid Substrates, Physical Review Letters, 10.1103/PhysRevLett.118.178001, 118, 17, 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..
3. 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, 2016.12, 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..
4. Tetsuo Yamaguchi, Hiroyuki Muroo, Yutaka Sumino, Masao Doi, Asymmetry-symmetry transition of double-sided adhesive tapes, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 10.1103/PhysRevE.85.061802, 85, 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..
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, 12, 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. Nick Gravish, Matt Wilkinson, Simon Sponberg, Aaron Parness, Noe Esparza, Daniel Soto, Tetsuo Yamaguchi, Michael Broide, Mark Cutkosky, Costantino Creton, Kellar Autumn, Rate-dependent frictional adhesion in natural and synthetic gecko setae, Journal of the Royal Society Interface, 10.1098/rsif.2009.0133, 7, 43, 259-269, 2010.02, Geckos owe their remarkable stickiness to millions of dry, hard setae on their toes. In this study, we discovered that gecko setae stick more strongly the faster they slide, and do not wear out after 30 000 cycles. This is surprising because friction between dry, hard, macroscopic materials typically decreases at the onset of sliding, and as velocity increases, friction continues to decrease because of a reduction in the number of interfacial contacts, due in part to wear. Gecko setae did not exhibit the decrease in adhesion or friction characteristic of a transition from static to kinetic contact mechanics. Instead, friction and adhesion forces increased at the onset of sliding and continued to increase with shear speed from 500 nm s-1 to 158 mm s-1. To explain how apparently fluid-like, wear-free dynamic friction and adhesion occur macroscopically in a dry, hard solid, we proposed a model based on a population of nanoscopic stick-slip events. In the model, contact elements are either in static contact or in the process of slipping to a new static contact. If stick-slip events are uncorrelated, the model further predicted that contact forces should increase to a critical velocity (V*) and then decrease at velocities greater than V*. We hypothesized that, like natural gecko setae, but unlike any conventional adhesive, gecko-like synthetic adhesives (GSAs) could adhere while sliding. To test the generality of our results and the validity of our model, we fabricated a GSA using a hard silicone polymer. While sliding, the GSA exhibited steady-state adhesion and velocity dependence similar to that of gecko setae. Observations at the interface indicated that macroscopically smooth sliding of the GSA emerged from randomly occurring stick-slip events in the population of flexible fibrils, confirming our model predictions..
7. 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, 20, 2009.05, 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..
8. Tetsuo Yamaguchi, K. Koike, M. Doi, In situ observation of stereoscopic shapes of cavities in soft adhesives, EPL, 10.1209/0295-5075/77/64002, 77, 6, 2007.03, By using a new visualization technique, we succeeded in the in situ observation of the stereoscopic shape of cavities formed in a thin film of soft adhesives in the debonding process of the probe-tack test. We found that the cavity shape and the interfacial fracture behavior are strongly influenced by the cross-linking density of the soft adhesives: for soft adhesives, the cavity is nearly spherical, and the fracture slows down basically due to the blunting of the cavity edge, while for hard adhesives the cavity becomes pancake-like, and the fracture is due to the coalescence of cavities at the adhesive-probe interface..
9. Tetsuo Yamaguchi, H. Morita, M. Doi, Modeling on debonding dynamics of pressure-sensitive adhesives, European Physical Journal E, 10.1140/epje/i2005-10078-6, 20, 1, 7-17, 2006.05, We propose a simple mechanical model describing viscoelasticity and cavitation during the debonding process in pressure-sensitive adhesives (PSA). Our calculation qualitatively reproduces typical stress-strain curves in the probe-tack test, such as the steep stress maxima and the following plateau region. It is shown that in the thin-film geometry the stress-strain curve is essentially determined by the cavities created by the large negative pressure. Effects of pre-existent air bubbles due to surface roughness are also discussed..
1. Tetsuo Yamaguchi, Sliding friction of polymer gels at various sliding speeds
, Okinawa Colloids, 2019.11, Polymer gels are sparsely cross-linked polymers with a large amount of solvent. When polymer gels are slid against their counterparts, the system exhibits a variety of frictional behavior, depending on the combination between the materials and the sliding conditions. In this talk, we will focus on the sliding speed dependence on the frictional behavior. We will firstly give an overview of the sliding mechanisms for polymer gels, and then will introduce several results at various sliding speeds, from 10-6 to 10 m/s. In such a wide range, the dominant mechanisms switch from molecular adsorption, diffusion-mechanical coupling, hydrodynamics to inertia, and the targets are spanning from laboratory experiments of giant earthquakes, articular cartilage in hip or knee joints, to high-speed braking of Formula-1 car. Throughout these topics, we will stress the importance of “softness” of polymer gels in sliding friction..
2. Tetsuo Yamaguchi, Yudai Onoue, Yoshinori Sawae, Fracture of Model Polymer Networks, The 7th Pacific Rim Conference on Rheology, 2018.06, [URL], Toughening of crosslinked polymers like rubbers or gels is one of the most important problems in polymer science. While novel types of tough gels have been developed in the last decade, the toughening mechanism is not well understood: for example, it is not still so clear whether heterogeneous structures enhance the fracture toughness or weaken the system. In this study, we focus on geometrical aspects of crosslinked polymers (how the molecular weight distributions of partial chains affect toughness) as well as topological ones (how the spatial structure of connectivity between crosslinking points controls toughness). We created macroscopic crosslinked polymers made of rubber strings and connecters, and performed fracture experiments of such model polymers with various degrees of molecular weight variations and different topological structures. We found that small degrees of heterogeneity of molecular weight contribute to weakening while large variations to slowing down of crack propagation and significant toughening. We also found that small change in network topology results in great improvement in toughness due to weakening of stress concentrations. In our talk, we will explain the details of our experiments and discuss the results by comparing with numerical simulations. .
3. 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..
4. Tetsuo Yamaguchi, Sliding friction of sticky gels, Gordon Research Conference on Tribology, 2014.07, 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. .
5. 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..
6. 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. .
7. 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. .
Membership in Academic Society
  • American Geophysical Union
  • Japanese Society of Tribologists
  • The Adhesion Society of Japan
  • The Japan Society of Mechanical Engineers
  • The Seismological Society of Japan
  • The physical society of Japan
  • Best Presentation Award was awarded in the Malaysian International Tribology Conference, held in Penang Island, Malaysia.
  • He has been working on experimental and theoretical studies on adhesion phenomena based on his original view points.
Educational Activities
I have been giving lectures for 5 courses to undergraduate students and 2 courses (including Soft Matter Engineering) to graduate students.