著者
橋村 真治 小松 恭一 大津 健史 関戸 裕二郎
出版者
一般社団法人 日本トライボロジー学会
雑誌
トライボロジスト (ISSN:09151168)
巻号頁・発行日
vol.62, no.3, pp.205-216, 2017-03-15 (Released:2017-03-16)
参考文献数
12

In recent years, self-loosening detail mechanisms of bolted joints had been revealed using three dimensional FE analysis in which the bolts and the nuts have almost perfect configurations geometrically. However the configurations of actual bolts and nuts have certainly errors. Wear on contact surfaces also occurs in the actual bolted joint. Hence it is not easy to accurately simulate the actual bolted joint by only FEM. In this study, an influence of lubricants on self-loosening characteristics have been investigated in order to understand actual phenomena in self-loosening process. The self-loosening tests for a hexagon head cap screw M10 due to transverse vibration were performed under lubricated conditions by Machine oil ISO VG46, Molybdenum disulfide grease and Polyisobuthylene which is used as a special lubricant for bolt tightening. A bearing surface configuration of the bolt was controlled in this study. The results showed that the bolted joints lubricated by Polyisobuthylene had a higher resistance for self-loosening than the bolted joints lubricated by Molybdenum disulfide grease and Machine oil ISO VG46. The number of cycle until loosening depended on bearing surface configurations.
著者
村木 正芳 中村 健太 鈴木 真 瀬上 高博 山本 賢二
出版者
一般社団法人 日本トライボロジー学会
雑誌
トライボロジスト (ISSN:09151168)
巻号頁・発行日
vol.59, no.8, pp.507-514, 2014-08-15 (Released:2018-02-23)
参考文献数
11

Tribological performances of the oils containing polylaurylacrylates with and without hydroxyethyl group were studied under elastohydrodynamic lubrication (EHL), partial EHL and the boundary lubrication conditions. The base oil was polyalphaolefin and the viscosity of polymer solutions and the concentration of polymer was adjusted at the same level. Under the partial elastohydrodynamic contacts using a ball-on-disk type tribometer, polylaurylacrylatehydroxyethylacrylate (PLA/HEA) showed a greater oil film thickness while lower traction coefficient at low rolling speeds than polylaurylacrylate (PLA). This can be interpreted that adsorption of hydroxyethyl group of PLA/HEA reduced traction under the partial EHL condition. Under the boundary lubrication conditions using a pin-on-disk type tribometer, PLA/HEA exhibited the flat friction-velocity relation while PLA showed a large negative gradient of friction-velocity relation. Finally, PLA/HEA was superior to PLA in terms of the antiwear properties with a reciprocating friction tester. It is inferred that these better performances of PLA/HEA under the boundary lubrication conditions were brought about by formation of a tribofilm based on reaction of hydroxyethyl group and the sliding surface.
著者
木之下 博 政安 亮祐 藤井 正浩
出版者
一般社団法人 日本トライボロジー学会
雑誌
トライボロジスト (ISSN:09151168)
巻号頁・発行日
vol.59, no.9, pp.577-585, 2014-09-15 (Released:2018-02-23)
参考文献数
12

It is thought that sandfish skink, living in desert, has scales that have low friction and high wear resistance properties. In previous study, we investigated the tribological properties of sandfish's scales under micro newton loads. It is found that the scales have low adhesion forces, which would lead to the low friction property. In this study, a tribological property of sandfish's scales was investigated under milli newton loads (of 3, 5, 10 mN) to investigate wear resistance property mainly. Tribological tests were also carried out using polytetrafluoroethylene (PTFE) and polyimide (PI) for comparison with the scales. Using a SUJ2 ball with a diameter of 1 mm, wear of sandfish scale was not occurred or much lower than those of PTFE and PI. When wear was not happened for sandfish's scale in the relative low contact pressure, a friction coefficient of the sandfish's scale was lower than those of PI and PTFE. When a tungsten probe with an apex diameter of 5 μm was used in which contact pressure was huge with compare to that using the SUJ2 ball, wears on all samples were observed. In the relative high contact pressure, the friction coefficient of sandfish's scale was higher than that of PI. Under the milli newton loads, the microstructure of the sandfish's scale did not affect its tribological property.
著者
石崎 啓太 中野 冠
出版者
一般社団法人 日本トライボロジー学会
雑誌
トライボロジスト (ISSN:09151168)
巻号頁・発行日
pp.18-00002, (Released:2018-06-21)
参考文献数
43

This paper presents a study of the environmental performance impact of a comprehensive set of conventional viscosity lubricants and latest low viscosity lubricants, considering the use for average fuel economy passenger vehicle (118.1 g-CO2/km in 2016). The vehicle is assumed to be equipped with either automatic transmission (AT) or contentiously variable transmission (CVT) with a lifetime mileage of 150 000 km. Engine oil, transmission fluid as well as oil filter were identified as requiring servicing (replacement) in use phase. It was found that the analyzed engine oil, AT fluid and CVT fluid with different formulations show almost identical CO2 emissions per weight from the lubricants production, and the contribution of the oil filters and the transmission fluids to CO2 emissions in maintenance phase accounts for over 20%. The latest low viscosity lubricants improve vehicle fuel economy by up to 4.0% compared to conventional viscosity lubricants. As a consequence, latest lubricants have the potential to save the vehicle life cycle CO2 emissions by up to 630 kg-CO2 even when subtracting the produced CO2 emissions in maintenance phase, with comparison of conventional viscosity lubricants.
著者
大津 健史 西田 一樹
出版者
一般社団法人 日本トライボロジー学会
雑誌
トライボロジスト (ISSN:09151168)
巻号頁・発行日
vol.61, no.2, pp.127-136, 2016-02-15 (Released:2016-05-23)
参考文献数
27

This paper describes that the behavior of growth of cavitation formed in the journal bearing and the effect of cavity growth on the bearing performance. The journal bearing test apparatus in which the bearing was made of transparent acrylic plastic was used, and cavitation in lubrication film was observed by the fluorescent method in this study. Results show that the cavity is formed by the bubble occurred at the edge of bearing, and the angle of start and end position of cavity depends on applied weight. The cavity grows with time at a constant load of 45 N because the cavity coalesces with small cavities occurred at the edge of bearing, and the eccentricity ratio and the attitude angle are also changed during the time of growth. It is also shown by a numerical analysis that the cavity growth is related with the oil flow generated by the negative pressure at the outlet of the cavity.