For high performance racing applications as well as to achieve global emission goals, the efficiency of chain drives in vehicles is of great importance. In previous studies research on drive chains for motorcycle transmissions and timing drives of combustion engines is done with regard to efficiency and wear of the entire drive trains. Hence a test rig, the chain joint tribometer, was built. That enables to do wear and friction research on all parts inside of a chain joint like pin and bush. In conventional test rigs for efficiency investigation in circulation mode, the effects of different friction contact points overlap. So, research on the tribological system “chain joint contact” is in the focus. This rig can represent arbitrary load curves, in particular the contact force and the relative motion of a real chain drive. The chain joint tribometer closes the gap between investigations on whole chain drives standard tribometer tests. In this paper, results of friction analysis using drive chain segments in the arrangement of serial production are presented. Differences are distinguished between different chains having deviating surface roughnesses, which proves that the used tribometer is an adequate setup to analyze drive chains with regard to friction.

The tribological behavior of the friction pairs in a high-pressure vane pump under variable working conditions was experimentally studied; in particular, the effects of the varying sliding velocity (1.45–3.61 m/s) and contact pressure (0.11–0.44 MPa) on the friction coefficient and wear rate of the friction pairs in pumps with and without vanes in the vane slot of rotor were investigated. In both cases, the friction coefficient increased with increasing sliding velocity and decreased when the increase of contact pressure in two cases when the contact pressure is 0.22 MPa. Further, the wear rate decreased with increasing contact pressure. With increasing velocity, the friction coefficient was more influenced by the vane compared with wear rate. The main tribological mechanism of wear surface of the valve plate is mechanical ploughing. At a sliding velocity of 2.89 m/s, both with and without vanes, increasing the contact pressure resulted in a reduced friction coefficient and enhanced wear rate. When the contact pressure increased, the vane did not significantly influence the friction coefficient and wear rate. During this time, the wear surface morphology of the valve plate exhibited mainly mechanical plowing and adhesion wear marks.

The Japanese Society of Tribologists is pleased to announce that the 2020 Best Paper Award of the Society was awarded to the following papers from Tribology Online. The Award was presented to the authors by Prof. Joichi Sugimura, the President of the Japanese Society of Tribologists, at the award ceremony in the JAST Annual Meeting on 25th May, 2021, held online.

The titles and the authors of the awarded papers. The pictures are those captured at the award ceremony.

◊ “Intercalation Technology for Preparing a Mica–Organic Hybrid Solid Lubricant and Spectroscopic Evaluation of Its Lubrication Mechanism,” by Kenichiro Oshita, Shinobu Komiyama and Shinya Sasaki, Tribology Online, Vol. 14, No. 5 (2019) 312-320.

◊ “Lubrication Condition Monitoring of Practical Ball Bearings by Electrical Impedance Method,” by Taisuke Maruyama, Masayuki Maeda and Ken Nakano, Tribology Online, Vol. 14, No. 5 (2019) 327-338.

◊ “Effect of Lubrication on Friction and Wear Properties of PEEK with Steel Counterparts,” by Go Tatsumi, Monica Ratoi, Yuji Shitara, Kiyomi Sakamoto and Brian G. Mellor, Tribology Online, Vol. 14, No. 5 (2019) 345-352.

and

◊ “Development of Highly Durable Sliding Triboelectric Nanogenerator Using Diamond-Like Carbon Films,” by Shreeharsha H. Ramaswamy, Ryusei Kondo, Weihang Chen, Ichihiro Fukushima and Junho Choi, Tribology Online, Vol. 15, No. 2 (2020) 89-97.

Congratulations!

The Best Paper Award is given annually to the author(s), either the JAST members or non-members, of the paper(s) judged as the best paper(s) published in Journal of Japanese Society of Tribologists (Toraiborojisuto) and Tribology Online (TROL) for the previous three years. All papers that appeared in Toraiborojisuto and TROL for the three years are reviewed by the JAST Awards Committee.

This study aims to clarify the potential of double network (DN) gel to realize low friction coefficient under water lubrication environment. Friction tests were carried out by using DN gel film and silicon carbide (SiC) disk in water. DN gel shows running-in behavior consists of lowering friction coefficient twice, then friction coefficient shows less than 0.001 under limited experimental conditions. By introducing in-situ test apparatus, self-formation of damaged region is confirmed and external water penetrates into self-formed damaged region. As a result, damaged region becomes water-rich situation more and more and formation of lubricious water layer is enhanced gradually. Thus running-in behavior occurs by friction system using DN gel.

Ionic liquids (ILs) are being considered as novel lubricant additives to improve the friction and anti-wear characteristics of sliding surfaces. Because ILs consist of only cations and anions, their physical and chemical properties can be easily tailored by modifying their combination. These features enable to design of specific ILs for a given tribological system. However, there are few reports on the effect of ILs used as lubricant additives on the friction and anti-wear characteristics of sliding surfaces. Moreover, it is necessary to investigate the synergism between ILs and other lubricant additives to achieve high practical efficiency. Therefore, in this study, two ILs with different cations but similar anions were used in combination with an anti-wear additive, zinc dialkyldithiophosphate (ZDDP), and the resultant wear and friction characteristics of the worn surfaces were analyzed. We found that the tribological performance under steel/steel sliding conditions was dependent on the chemical composition of the ILs. In addition, mixed ZDDP and IL solutions exhibited lower friction and wear when compared to ZDDP alone. It is considered that the excellent lubrication and frictional performance observed with the mixed lubricant solutions is due to the formation of tribofilms comprising of ZDDP and IL on the sliding surface.

Metal-to-metal seals in premium threaded joints (PJs) for Oil Country Tubular Goods are used in severe environments such as high pressure and high temperature. Under the extreme conditions, the thermal degradation of applied grease on the seal surfaces can affect the sealability of metal-to-metal seal. In this study, changes in the sealability of greased metal-to-metal seal due to elevated temperature were investigated by fundamental gas tightness tests. In addition, changes in grease property at high temperature were also investigated. It was found that one of the causes of the loss of the sealability of metal-to-metal seal at high temperature was the decrease in grease viscous resistance against high pressure due to thermal degradation of grease. The decrease in grease viscous resistance was caused by the decrease in the kinematic viscosity of the base oil under 125°C at which the network structure of the thickener was almost maintained. Beyond 150°C, the decrease of complex viscosity of the grease due to the collapse of the network structure of the thickener decreased the grease viscous resistance. The latter significantly affected the loss of sealability of the metal-to-metal seal.