The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

Iakov A. Lyashenko - One of the best experts on this subject based on the ideXlab platform.

  • Stick–slip Boundary Friction mode as a second-order phase transition with an inhomogeneous distribution of elastic stress in the contact area
    Beilstein journal of nanotechnology, 2017
    Co-Authors: Iakov A. Lyashenko, Vadym N Borysiuk, Valentin L Popov
    Abstract:

    This article presents an investigation of the dynamical contact between two atomically flat surfaces separated by an ultrathin lubricant film. Using a thermodynamic approach we describe the second-order phase transition between two structural states of the lubricant which leads to the stick-slip mode of Boundary Friction. An analytical description and numerical simulation with radial distributions of the order parameter, stress and strain were performed to investigate the spatial inhomogeneity. It is shown that in the case when the driving device is connected to the upper part of the Friction block through an elastic spring, the frequency of the melting/solidification phase transitions increases with time.

  • Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I 7 Friction FORCE FOR Boundary LUBRICATION
    2016
    Co-Authors: Iakov A. Lyashenko
    Abstract:

    A thermodynamic model describing the phase transition of first order between structure states of lubricant material in the Boundary Friction regime is proposed. It is shown that lubricant melts with temperature increase or at shear of rubbing surfaces if the elastic strain (stress) exceeds the critical value. The phase diagram with domains of dry and sliding Friction is constructed. The dependences of Friction force on temperature of lubricant and velocity of shear of rubbing surfaces are analyzed. Key words: ultrathin lubricant film, Boundary Friction, stick-slip regime, phase di

  • Influence of spatial nonhomogeneity on the Boundary Friction regime
    2015 IEEE 35th International Conference on Electronics and Nanotechnology (ELNANO), 2015
    Co-Authors: Iakov A. Lyashenko, Nataliia N. Manko
    Abstract:

    We have analyzed spatial nonhomogeneity of stresses, strain, and temperature of a lubricating layer in synergetic model of Boundary Friction. Firstly, we consider the motion of interacting surfaces in opposite directions with identical velocities, than we consider the situation when the lower surface is rigidly fixed and the upper is displaced with a fixed velocity. We obtain the spatial profiles of stresses, strains, and temperature in both cases and describe the nontrivial non-Newtonian behavior of the effective shear viscosity of the lubricant. Also we analyze the effect of the temperature of the surfaces and the viscosity of the lubricant on the steady-state Friction regime.

  • Analysis of the stability of stationary Boundary Friction modes in the framework of a synergetic model
    arXiv: Mesoscale and Nanoscale Physics, 2014
    Co-Authors: Iakov A. Lyashenko, N. N. Manko
    Abstract:

    A synergetic model describing the state of an ultrathin lubricant layer squeezed between two atomically smooth solid surfaces operating in the Boundary Friction mode has been developed further. To explain the presence of different operation modes of the system for various sets of its main parameters, the mathematical analysis of the synergetic model is carried out. The type of functioning a tribological system is described in accordance with the stability character of singular points, and the diagrams distinguishing various operation modes are obtained. Phase portraits corresponding to different stability types are plotted for all diagram areas. A stick-slip mode of motion that is often observed experimentally is described.

  • Stochastic Oscillations at Stick-Slip Motion in the Boundary Friction Regime
    2013
    Co-Authors: N. N. Manko, Iakov A. Lyashenko
    Abstract:

    In this paper, the further development of the synergetic model describing the ultrathin lubricant film state clamped between two atomically smooth solid surfaces operating under Boundary Friction mode has been done based on the Lorentz model for the approximation of a viscoelastic medium. In all cases, the phase portraits have been built. It has been found that the Friction surfaces' temperature increasing leads to the growth of stochastic-ity in the investigated system. In the phase plane the stochastic oscillation mode can be described as a strange attractor. Also, the behavior of two different types of tribosystems were described using current model. The first was the system with the unidirectional shear of the surfaces and, and the second was the system under an alter-nating external effect. Obtained results agree qualitatively with known experimental data.

Joanna Smith - One of the best experts on this subject based on the ideXlab platform.

  • Wet but not slippery: Boundary Friction in tree frog adhesive toe pads
    Journal of the Royal Society Interface, 2006
    Co-Authors: Walter Federle, W. J. P. Barnes, Werner Baumgartner, Patrick Drechsler, Joanna Smith
    Abstract:

    Tree frogs are remarkable for their capacity to cling to smooth surfaces using large toe pads. The adhesive skin of tree frog toe pads is characterized by peg-studded hexagonal cells separated by deep channels into which mucus glands open. The pads are completely wetted with watery mucus, which led previous authors to suggest that attachment is solely due to capillary and viscous forces generated by the fluid-filled joint between the pad and the substrate. Here, we present evidence from single-toe force measurements, laser tweezer microrheometry of pad mucus and interference reflection microscopy of the contact zone in Litoria caerulea, that tree frog attachment forces are significantly enhanced by close contacts and Boundary Friction between the pad epidermis and the substrate, facilitated by the highly regular pad microstructure.

Massimiliano Pau - One of the best experts on this subject based on the ideXlab platform.

  • estimation of wheel rail adhesion coefficient under wet condition with measured Boundary Friction coefficient and real contact area
    Wear, 2011
    Co-Authors: Hua Chen, Koan Sok Baek, Tsunamitsu Nakahara, Akira Namura, Bruno Leban, Makoto Ishida, Massimiliano Pau
    Abstract:

    Abstract This paper describes how to improve the prediction method of the adhesion coefficient by means of the experimentally estimated Boundary Friction coefficient obtained by two kinds of twin-disc rolling contact machines and the ratio of real contact area to nominal contact area ( RCA / NCA ) obtained by ultrasonic measurement. The previous prediction method that the authors had already proposed in the last paper was based on Greenwood–Tripp's rough surface contact model; however, in this study, the authors adopted Lee & Ren's rough surfaces contact model and focused on the RCA / NCA measured by ultrasonic wave in order to predict the adhesion coefficient under wet conditions with the actual surface contact conditions. As a result, regarding the tendency of adhesion coefficient decreasing with an increase of running speed, a good agreement has been obtained between the results obtained by the prediction method proposed in this study and the measured results obtained by the field-test of Japanese Shinkansen vehicle (series 200).

  • Estimation of wheel/rail adhesion coefficient under wet condition with measured Boundary Friction coefficient and real contact area
    Wear, 2010
    Co-Authors: Koan Sok Baek, Massimiliano Pau, Akira Namura, Bruno Leban, Hua Chen, Makoto Ishida, Tsunamitsu Nakahara
    Abstract:

    This paper describes how to improve the prediction method of the adhesion coefficient by means of the experimentally estimated Boundary Friction coefficient obtained by two kinds of twin-disc rolling contact machines and the ratio of real contact area to nominal contact area (RCA/NCA) obtained by ultrasonic measurement. The previous prediction method that the authors had already proposed in the last paper was based on Greenwood-Tripp's rough surface contact model; however, in this study, the authors adopted Lee & Ren's rough surfaces contact model and focused on the RCA/NCA measured by ultrasonic wave in order to predict the adhesion coefficient under wet conditions with the actual surface contact conditions. As a result, regarding the tendency of adhesion coefficient decreasing with an increase of running speed, a good agreement has been obtained between the results obtained by the prediction method proposed in this study and the measured results obtained by the field-test of Japanese Shinkansen vehicle (series 200).

Tsunamitsu Nakahara - One of the best experts on this subject based on the ideXlab platform.

  • estimation of wheel rail adhesion coefficient under wet condition with measured Boundary Friction coefficient and real contact area
    Wear, 2011
    Co-Authors: Hua Chen, Koan Sok Baek, Tsunamitsu Nakahara, Akira Namura, Bruno Leban, Makoto Ishida, Massimiliano Pau
    Abstract:

    Abstract This paper describes how to improve the prediction method of the adhesion coefficient by means of the experimentally estimated Boundary Friction coefficient obtained by two kinds of twin-disc rolling contact machines and the ratio of real contact area to nominal contact area ( RCA / NCA ) obtained by ultrasonic measurement. The previous prediction method that the authors had already proposed in the last paper was based on Greenwood–Tripp's rough surface contact model; however, in this study, the authors adopted Lee & Ren's rough surfaces contact model and focused on the RCA / NCA measured by ultrasonic wave in order to predict the adhesion coefficient under wet conditions with the actual surface contact conditions. As a result, regarding the tendency of adhesion coefficient decreasing with an increase of running speed, a good agreement has been obtained between the results obtained by the prediction method proposed in this study and the measured results obtained by the field-test of Japanese Shinkansen vehicle (series 200).

  • Estimation of wheel/rail adhesion coefficient under wet condition with measured Boundary Friction coefficient and real contact area
    Wear, 2010
    Co-Authors: Koan Sok Baek, Massimiliano Pau, Akira Namura, Bruno Leban, Hua Chen, Makoto Ishida, Tsunamitsu Nakahara
    Abstract:

    This paper describes how to improve the prediction method of the adhesion coefficient by means of the experimentally estimated Boundary Friction coefficient obtained by two kinds of twin-disc rolling contact machines and the ratio of real contact area to nominal contact area (RCA/NCA) obtained by ultrasonic measurement. The previous prediction method that the authors had already proposed in the last paper was based on Greenwood-Tripp's rough surface contact model; however, in this study, the authors adopted Lee & Ren's rough surfaces contact model and focused on the RCA/NCA measured by ultrasonic wave in order to predict the adhesion coefficient under wet conditions with the actual surface contact conditions. As a result, regarding the tendency of adhesion coefficient decreasing with an increase of running speed, a good agreement has been obtained between the results obtained by the prediction method proposed in this study and the measured results obtained by the field-test of Japanese Shinkansen vehicle (series 200).

  • Estimation of coefficient of Boundary Friction under mixed lubrication in refrigerant atmosphere
    Japanese journal of tribology, 1999
    Co-Authors: Shinji Tanaka, Satoshi Momozono, Keiji Kyogoku, Tsunamitsu Nakahara
    Abstract:

    A Falex block on ring-type test machine that is capable of performing Friction tests under lubrication in refrigerant atmosphere is manufactured with the purpose of determining the Boundary Friction coefficient of sliding parts in refrigerant compressors under the mixed lubrication condition. Attempts were made to estimate the Boundary Friction coefficient by measuring Friction characteristics, sliding component materials, and lubricants and by comparing these with the analysis of mixed lubrication conditions presented earlier. The obtained results showed that the Boundary Friction coefficient under the mixed lubrication condition, estimated by comparing experimental results with those obtained by the analysis of mixed lubrication, either coincided with the coefficient of Friction in the Boundary lubrication region or is lower. The application of the present technique allowed more accurate evaluation of lubricating properties of lubricants and Friction materials of real machines that operate mainly under the mixed lubrication conditions and showed the possibility of evaluating the surface roughness simultaneously. It is found that the effect of the difference in composition of HFC refrigerants on the Frictional characteristics is rather weak.

Koan Sok Baek - One of the best experts on this subject based on the ideXlab platform.

  • estimation of wheel rail adhesion coefficient under wet condition with measured Boundary Friction coefficient and real contact area
    Wear, 2011
    Co-Authors: Hua Chen, Koan Sok Baek, Tsunamitsu Nakahara, Akira Namura, Bruno Leban, Makoto Ishida, Massimiliano Pau
    Abstract:

    Abstract This paper describes how to improve the prediction method of the adhesion coefficient by means of the experimentally estimated Boundary Friction coefficient obtained by two kinds of twin-disc rolling contact machines and the ratio of real contact area to nominal contact area ( RCA / NCA ) obtained by ultrasonic measurement. The previous prediction method that the authors had already proposed in the last paper was based on Greenwood–Tripp's rough surface contact model; however, in this study, the authors adopted Lee & Ren's rough surfaces contact model and focused on the RCA / NCA measured by ultrasonic wave in order to predict the adhesion coefficient under wet conditions with the actual surface contact conditions. As a result, regarding the tendency of adhesion coefficient decreasing with an increase of running speed, a good agreement has been obtained between the results obtained by the prediction method proposed in this study and the measured results obtained by the field-test of Japanese Shinkansen vehicle (series 200).

  • Estimation of wheel/rail adhesion coefficient under wet condition with measured Boundary Friction coefficient and real contact area
    Wear, 2010
    Co-Authors: Koan Sok Baek, Massimiliano Pau, Akira Namura, Bruno Leban, Hua Chen, Makoto Ishida, Tsunamitsu Nakahara
    Abstract:

    This paper describes how to improve the prediction method of the adhesion coefficient by means of the experimentally estimated Boundary Friction coefficient obtained by two kinds of twin-disc rolling contact machines and the ratio of real contact area to nominal contact area (RCA/NCA) obtained by ultrasonic measurement. The previous prediction method that the authors had already proposed in the last paper was based on Greenwood-Tripp's rough surface contact model; however, in this study, the authors adopted Lee & Ren's rough surfaces contact model and focused on the RCA/NCA measured by ultrasonic wave in order to predict the adhesion coefficient under wet conditions with the actual surface contact conditions. As a result, regarding the tendency of adhesion coefficient decreasing with an increase of running speed, a good agreement has been obtained between the results obtained by the prediction method proposed in this study and the measured results obtained by the field-test of Japanese Shinkansen vehicle (series 200).