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An analytical EHL model suitable for highly loaded point contacts operating in mixed and boundary regimes of lubrication is presented. The results are compared and validated with the experimental measurements of friction coefficient from an MTM tribometer. Measurements are carried out upon a PAO40 oil at medium to high temperatures. In general, a good agreement in trend and magnitude over a wide range of operating conditions is observed. Both the experimental findings and the model predictions show an inverse relationship between friction and contact load in mixed and boundary regimes of lubrication, an effect not hitherto reported in literature. [ABSTRACT FROM AUTHOR]

The (cyclopentadienyl)molybdenum(dicarbonyl)(nitrosyl) complex as a metal-organic precursor and acetylene gas were used to produce the MoC x /a-C:H film by the PECVD. When the acetylene gas is mixed with a vaporized metal-organic precursor, the friction coefficient and hardness would be superior for the MoC x /a-C:H film, whereas the specific resistivity slightly high. The friction coefficient measurements by the ball-on-disk wear tester dramatically reduced from 0.25 to 0.06 as the acetylene flow rate increased. The electrical specific resistivity slightly high from 5.74 mΩ-cm to 203.32 mΩ-cm following the increasing acetylene partial pressure. XPS analysis indicated that the Mo-C bond in the Mo3d peaks diminished, and the sp3/sp2 ratio in the C1s peaks reached 0.37 in the condition of acetylene gas addition. [ABSTRACT FROM AUTHOR]

Frictional behaviour of mixed Elasto-hydrodynamic lubrication (EHL) arises from the coupling of the lubricant fluid and asperity interaction frictions. Due to the difficulties in modelling asperity interaction friction, existing approaches often use a constant friction coefficient obtained in boundary lubrication to approach the asperity interaction friction coefficient in mixed EHL. In this study, the asperity interaction friction is, for the first time, considered to result from either the boundary film friction or solid-to-solid ploughing and adhesion friction depending on the local contact and deformation conditions. The friction of mixed EHL was predicted by the combination result of lubricants fluid, boundary film, and solid-to-solid frictions. This development provides an alternative and cost effective method to estimate friction coefficient in mixed EHL. [ABSTRACT FROM AUTHOR]

The tribological interaction between patterned running surfaces and an ice track was investigated. The friction coefficient was analyzed according to the patterned running surface type, ambient temperature, and rotational track velocity. The results were analyzed based on the structural characteristics of the patterned running surface in terms of average height and skewness. Generation of the water layer was visualized using transparent replicas of the patterned running surfaces. The water layer ratio was then calculated and compared with the friction coefficient. We found that the water layer either functioned as a lubricant or offered frictional resistance depending on the water layer ratio and the type of patterned running surfaces as the lubricating friction regime changed. • The friction force between the commercially available patterned running surfaces of jumping ski and ice is measured. • The water layer is visualized to elucidate the effect of the surface patterns on ice friction coefficient. • The lubricating friction regime varies by surface patterns , resulting either increases or decreases frictional drag. [ABSTRACT FROM AUTHOR]