There is a significant interest toward the history of tribology in both engineering and historical communities. However, there is a gap between engineers and historians in their approach to the topic, and existing literature sometimes overlooks various cultural influences, in particular, oriental ones, which affected the tribological science and technology. We consider the early history of lubrication and show that while the evidences of usage of lubricants (water, gypsum, and animal fats) in Ancient Egypt in 2nd-3rd millennia BC are hypothetic, rather than established facts, the Hebrew Bible contains earliest records of using oil as a lubricant. In particular, the account of rubbing the shield of King Saul (11th century BC) is discussed as well as other similar cases. These findings allow us to better understand the universal nature of history of science and technology as a multicultural phenomenon.
A concept of integrating more than one tribo-technique, Pin-on-Disc (POD) and Block-on-Ring (BOR), working simultaneously under same test conditions against same counterface is introduced in a new multi-tribo-test-machine. In this machine, different wear modes (adhesive, two-body-abrasive, three-body-abrasive, under dry, lubricated, or slurry conditions) can be conducted. Results of adhesive wear, friction and interface temperature of chopped strand mat glass fibre reinforced polyester composite (CGRP) under wet/dry contact condition are produced at 50 N load for different test durations (10-30 min.) and sliding speeds (1.7-5.6 m/s) using the new machine. Scanning electron microscopy (SEM) observations are carried out on the worn surfaces of the composite to study the mechanism of damage. Wear rates and friction coefficient of CGRP composite were substantially influenced by introducing water as lubricant. Additionally, BOR techniques showed lower wear rate and low friction coefficient compared to POD.
An unbranched perfluoropolyether (PFPE) 815Z is the current ball bearing lubricant for space applications. Measurements of elastohydrodynamic lubrication (EHL) oil film thickness have been carried out to assess the lubricating performance of PFPE with average molecular weight of 9200 using an optical interferometric technique under mean Hertzian pressure 0.45 GPa. The film thickness of 815Z became less than predicted film thickness from Hamrock and Dowson formula for EHL central film thickness. There are two main explanations why PFPE is inferior to mineral oil in their ability to form EHL films, temporary viscosity loss and permanent viscosity loss. In order to elucidate the results, measurements of permanent viscosity loss under mean Hertzian pressure from 0.41 GPa to 2.67 GPa have been carried out using the thrust ball bearing. There results show that the degree of the permanent viscosity loss depends on Hertzian pressure, occurrence of permanent viscosity loss of 36 % with 2.67 GPa and 2 % with 0.41 GPa.
We have developed a simulation method in which grooves are virtually distributed on a slider air-bearing surface instead of on a grooved medium surface and used it to investigate slider flying performance. The characteristics of miniaturized air-bearing flying over a discrete track medium (DTM) with a sufficiently small mesh size are simulated minutely. The simulation results indicated that the air-bearing characteristics do not abruptly change when the DTM's land and groove sizes change from below to above the air mean free path. The “brush” shaped pressure distribution causes a larger shear stress difference between the DTM land and groove, which possibly leads to bigger lube moguls or ripples, and the shear stress on DTM land may make lube move into the groove from the land.
A bis(N,N-dipentylcarbamothioylthio)cadmium additive was synthesized. A four-ball tester was used to evaluate the tribological performance of the additive in mineral oil, and compared with same types of metal additives. The results show that it exhibits better anti-wear and load-carrying capacities. The surface analytical tools such as X-ray photoelectron spectrometer (XPS), Auger electron spectrometer (AES), Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) were used to investigate the topography, the compositions contents and the depth profile of some typical elements on the rubbing surface of worn scar. Smooth topography of worn scar further confirms that the additive showed good anti-wear capacities, the results of XPS, AES and energy dispersive X-ray analyses indicated that tribochemical mixed protective films consists of cadmium atoms, sulfides and sulphates were formed on the rubbing surface, which contribute to improve the tribological properties of lubricants. Particularly, large amounts of sulfur and cadmium atoms play an important role in improving anti-wear properties of oils.