Against the backdrop of increased needs for longer operating life of turbine oils, there is a tendency to use amine

Fretting wear is often the case when ball-and-roller bearings oscillate under grease lubrication. Against the backdrop of fretting wear on the wheel bearings of automobiles caused by rail transportation, the ASTM D4170 fretting test method was developed to evaluate the fretting protection property of lubricating grease. The ASTM test is conducted under a fixed load, but the load condition for industrial machines usually fluctuates. Currently, there is no international standard to evaluate the fretting wear under fluctuating load. In this study, using thrust ball bearings the authors examined 14 kinds of commercially produced greases and three kinds of originally prepared greases on fretting protection evaluation under both the ASTM test and the impact fretting test. Consequently, the authors found out the inversion of the order of fretting protection superiority between the ASTM test and the impact fretting test. As for the kinematic viscosity of base oil of grease, the amount of wear of ASTM test increases with increasing the kinematic viscosity, on the other hand the wear of impact fretting test decreases with increasing the kinematic viscosity.

To meet with the latest environmental regulation, as environmentally acceptable lubricant (EAL) in marine field, biodegradable oils based on synthetic ester oils, have been applied to stern tube bearings of many new building vessels since the end of 2013, when the US EPA * effectuated the 2013 VGP ** regulation. These synthetic ester oils are of the same viscosity grade, ISO VG100, as commonly used mineral oil. However, up to now, there has been no report on verification of tribological characteristics to use them for stern tube bearings, including the 2013 VGP regulation. Therefore, physical properties of them were measured in tribological aspects, and load carrying capacities while mooring trial condition were clarified by the tests using 100 mm inner diameter plain bearing, comparing to mineral oil. As the result, the following are derived. 1) There are three major differences in viscosity characteristics of synthetic ester oils depending on temperature, shear stability and pressure, which gives them lower load carrying capacity. 2) Sliding velocities at friction rising points of synthetic ester oils in Stribeck curve are larger than the one of mineral oil by the effects above, which also indicates lower load carrying capacity of them. *) EPA: Environmental Protection Agency **) VGP: Vessel General Permit

This paper investigates the friction and friction heat of the micronscale iron under the influences such as the velocity of the slider and temperature of the substrate by using the smoothed particle hydrodynamics simulations. It is found that in the velocity range of 10–100 m/s, the sliding velocity–friction coefficient relationship well complies with the fitted exponent or hyperbolic tangent function, and the friction coefficient approaches a stable value of 0.3 at around the velocity of 50 m/s after a rapidly increasing situation. The steady friction coefficient maintains over the temperature range of 200–400 K. The friction heat is detailed analyzed versus the sliding time. The sliding time–system temperature relationship is well fitted by the sigmoidal functions, except the interfacial particle layers. The layer causing friction shows the highest steady temperature and largest temperature rise. The increment between the initial temperatures of the slider and the substrate strongly results in the temperature rise while it does not affect the configuration of the sliding time–system temperature curves.