JOURNAL OF JAPANESE SOCIETY OF TRIBOLOGISTS
Online ISSN : 2189-9967
Print ISSN : 0915-1168
ISSN-L : 0915-1168
Volume 66, Issue 7
Special Issue on Intellectual Property for Engineer
Displaying 1-16 of 16 articles from this issue
Announcement
Contents
The Inaugural Address by the President
Special Issue on Intellectual Property for Engineer
Explanation
Explanation
Original Contribution on Science
  • Kiyoshi HATAKENAKA, Aoi HONDA
    2021 Volume 66 Issue 7 Pages 548-569
    Published: July 15, 2021
    Released on J-STAGE: July 15, 2021
    Advance online publication: May 13, 2021
    JOURNAL FREE ACCESS

    This paper proposes a new THL bearing design method based on an improved version of a precedent method. The precedent method used a model expression prepared in advance to easily and quickly find a crucial predicted data of the maximum bearing temperature. Three expressions were prepared for three different values of journal eccentricity ratio, 0.25, 0.5, and 0.75. Which one of the three should be used was determined, based on the preliminarily obtained value of journal eccentricity ratio derived from the initially assumed bearing specifications. Two dimensionless temperature-rise parameters κ1 and κ2 were introduced for the common variables of the expression. On the other hand, the new improved method uses a single expression, which is obtained by applying multiple regression analysis and t-test, for the crucial temperature for any value of journal eccentricity ratio. Furthermore, the new expression explicitly includes the four well-known dimensionless numbers used in THL analysis, that is, Sommerfeld number, bearing width-to-dimeter ratio, Peclet number and Khonsari number. The model expressions for other bearing characteristic performances were obtained in the same way. Compared with some measurements in test rigs of cylindrical bearings, the new improved method is confirmed to predict reasonably accurate bearing performances of cylindrical bearings faster and more easily than the precedent method over a wide range of operating conditions.

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  • Takumi KANI, Takayuki TOKOROYAMA, Noritsugu UMEHARA, Motoyuki MURASHIM ...
    2021 Volume 66 Issue 7 Pages 570-578
    Published: July 15, 2021
    Released on J-STAGE: July 15, 2021
    Advance online publication: June 09, 2021
    JOURNAL FREE ACCESS

    In general, several mechanical parts are subjected to friction and wear. To prevent wear and high friction coefficient under lubrication, additives can work to reduce friction force, to build up thin film on surfaces which is so-called tribofilm. Recently, Diamond-Like Carbon (DLC) is focused because it has excellent low friction and high wear proof as solid lubricant. However, several researchers already reported that tetrahedral amorphous carbon (ta-C) showed abnormal wear when it rubbed with glycerol mono-oleate (GMO) that is a kind of additive, although it showed very low friction coefficient. To improve tribological properties, new additives were developed that had both phosphate-oxide structure derived from ZnDTP which had high wear resistance and hydroxyl group derived from GMO in one structure. To clarify the effects of the additives, friction tests were performed fixed-roller-on-disk type rotating friction tester. In the friction tests, hydrogenated amorphous carbon (a-C:H) disks, and a-C:H coated rollers were used under boundary lubrication condition at 20-80°C. Friction tests were conducted in Poly-α-olefin (PAO) oil with each GMO and the additives. The results exhibited that a-C:H gave ultra-low friction with the additive. Elemental analysis of the surface showed that tribofilm of phosphorus and oxygen was detected on the a-C:H surface in the additive used condition.

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