Tribology Online
Online ISSN : 1881-2198
ISSN-L : 1881-218X
Volume 9 , Issue 2
Showing 1-7 articles out of 7 articles from the selected issue
Short Communication
  • Saroj Bala, Amit Chauhan
    2014 Volume 9 Issue 2 Pages 31-36
    Published: April 15, 2014
    Released: April 15, 2014
    JOURNALS FREE ACCESS
    In the present simulation study, the performance characteristics of vertical offset non-circular journal bearing have been evaluated. During study, the thermal pressures have been found of increasing nature with increase in speed in both the lobes of the bearing. A considerable rise in oil-film temperature and thermal pressure has been found in lower lobe and comparatively a low rise in oil-film temperature and thermal pressures has been found in upper lobe of the bearing. The trend for variation of oil-film temperature with speed has been found of increasing nature. The load capacity, power loss in the bearing and bearing characteristics Sommerfeld number has been observed to be of increasing nature with speed. It has been concluded that more than one lobe have been reported in the bearing profile under study, thus the profile can be considered as an alternate to circular journal bearing for better stability applications.
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Article
  • Miki Nakano, Koji Miyake, Atsushi Korenaga, Yasuhisa Ando
    2014 Volume 9 Issue 2 Pages 37-44
    Published: April 15, 2014
    Released: April 15, 2014
    JOURNALS FREE ACCESS
    The tribological properties of nanostripe surfaces were investigated to examine the effects of lubricant additives. The authors fabricated a nanostripe structure by depositing an Au-Cr multilayer film on a microscale slope array and mechanical polishing. Au and Cr flat surfaces were also prepared for comparison. Friction tests were performed using a pin-on-plate tribometer. After the friction tests the surfaces were analyzed using X-ray photoelectron spectroscopy (XPS). Poly-alpha-olefin (PAO) and PAO with acid phosphate ester (APE) were used as the lubricants, and the pins were made of glass. The results of the friction tests showed that APE effectively reduced the friction coefficients and wear for the Au-Cr nanostripe surface, Au flat surface and Cr flat surface.
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Short Communication
  • Hitoshi Washizu, Shi-aki Hyodo, Toshihide Ohmori, Noriaki Nishino, Ats ...
    2014 Volume 9 Issue 2 Pages 45-50
    Published: April 30, 2014
    Released: April 30, 2014
    JOURNALS FREE ACCESS
    The no-slip boundary condition widely used in the macroscopic fluid mechanics has not been explained from the molecular level. This letter describes all atom molecular dynamics simulation to study boundary slip of hydrocarbon oil film under shear of a submicron thickness confined between solid walls. The large time-space scale simulation under the realistic interactions of fluid atoms, solid-fluid interaction and sliding speed has shown the no-slip of the oil film. The difference between the nanoscale film and the submicron thick film is explained from the viewpoint of the anisotropic viscosity rise in the vicinity of the solid wall and the correlation length of the momentum up to several tenths of nanometers. The results of the present simulation coincide with the experiments of fluid flow through nanometer-scale channels.
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Article
  • Robert J. Waltman
    2014 Volume 9 Issue 2 Pages 51-62
    Published: April 30, 2014
    Released: April 30, 2014
    JOURNALS FREE ACCESS
    Infrared specular reflection spectra of the TA-30, D-4OH and C4-4OH perfluoropolyether liquid films on gold substrates are simulated and studied experimentally. The simulated spectra were obtained using a classical dispersion analysis coupled with solutions of Maxwell's equations for transmission and reflection of electromagnetic radiation. The simulated spectra, which are based on a randomly oriented sample, provide excellent fits for the perfluoropolyethers over a wide film thickness range. Spectroscopic data are provided for TA-30, D-4OH and C4-4OH. The differences in the transverse and longitudinal optical IR spectra are discussed for off-normal reflection spectra in the thin film limit. Corrections to the IR reflection spectra for sub-monolayer coverage using effective medium theory are also discussed.
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Editorial
  • Masabumi Masuko
    2014 Volume 9 Issue 2 Pages ii
    Published: April 30, 2014
    Released: April 30, 2014
    JOURNALS FREE ACCESS
    Volume and issue: Vol.6, No.7 (2011)
    Page: pp.317-322
    Title: Contribution of Slip and Cleavage in Friction and Wear at (10-14) Surface of Magnesite (MgCO3) Crystal
    Author(s): Kaori Niki, Mai Kobayashi and Hitoshi Shindo

    Volume and issue: Vol.7, No.1 (2012)
    Page: pp.8-12
    Title: Frictional Asymmetry and Wear Pattern Formation by Slip and Cleavage Detected at Directional r {10-14} Face of Calcite (CaCO3)
    Author(s): Kaori Niki, Mai Kobayashi and Hitoshi Shindo
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Article
  • Naohiro Kado, Chiharu Tadokoro, Ken Nakano
    2014 Volume 9 Issue 2 Pages 63-70
    Published: May 31, 2014
    Released: May 31, 2014
    JOURNALS FREE ACCESS
    Using a novel anti-vibration tribometer with a yaw angle misalignment, Kado et al. (Trans. Jpn. Soc. Mech. Eng. C79: 2635—2643, 2013) have recently shown experimentally that frictional vibration in tribotesting causes considerable error, e.g., a 35% underestimation of the kinetic friction coefficient for the sliding contact between a steel ball and a steel plate lubricated with glycerol. In this paper, it is shown that their experimental results can be numerically simulated based on a purely mechanical model, which confirms that their experiments were carried out properly and also that in conventional tribotesting, the “measured kinetic friction coefficient” (obtained from the time-averaged spring force) is not the “inherent kinetic friction coefficient” (determined by the inherent nature of materials in contact as a function of the relative velocity) but the “effective kinetic friction coefficient” (determined by the mean energy consumption rate as a function of the driving velocity). The effective kinetic friction coefficient depends on the mechanical properties of the tribometer used in the test, and it corresponds to the inherent kinetic friction coefficient when the measurement is carried out with no frictional vibration.
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  • Fumihiko Yokoyama, Yuka Iwama
    2014 Volume 9 Issue 2 Pages 71-79
    Published: June 15, 2014
    Released: June 15, 2014
    JOURNALS FREE ACCESS
    While formation of deposits in machinery used under high temperature conditions is inevitable, it needs to be minimized as much as possible. Desorption of deposits, though rarely reported, also needs to be addressed, as it could cause secondary damage. There have been a number of reports on the formation of high-temperature deposits and the effects of additives, none of which, however, addresses the desorption phenomenon as part of the deposit formation mechanism. Paying attention to the polar properties of lubricating oils and evaluating the formation, dissolution, and desorption of deposits by lubricating oils, the formation mechanism of high-temperature deposits was considered. Taking notice also of the changes in polar characteristics of oils with the progress of oxidative degradation of oil, we examined the influence of oxidative degradation of oils on the tendency to form high-temperature deposits. Furthermore, the countermeasure to prevent from deposit formation is also considered.
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