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We give the closed-form solutions for the two-dimensional adhesive contact of a flat-ended wedge with an elastic half-space, including contact pressure distribution and load-contact width relationship. The approach is derived from contact mechanics in plane-strain elasticity and fracture mechanics concepts. The contact pressure has stress singularities both at the edges of contact due to molecular attractive forces and at the wedge corners, and is compared with those without adhesion. Under zero load, we find the contact strip has a finite width which is greater than that of the wedge end, and the central region of contact is under compression, similar to that of a flat punch problem, while the regions near the contact edges are under tension. Unlike the usual experiments with smooth and low modulus materials, we conduct molecular dynamics (MD) experiments via embedded-atom method (EAM), brownian dynamics algorithm and dynamical theory of crystal lattices. The results, including the “pull-off” force for contacting surfaces to peel apart, conform reasonably well with those derived from a continuum model.

The addition of various extreme pressure and anti-wear additives to lubricating oil is an important and effective way of reducing friction and wear. The application of chemico-thermal treatments to material surfaces is another way to improve the tribological behaviour of rubbing pairs. The synergistic effects on the tribological behaviour of a tricresyl phosphate oil additive together with sulphurised, nitrided and oxy-nitrided surfaces of 1045 steel were systematically studied on a ball-on-disc test machine. Good load bearing capacity and reduced friction and wear was obtained as a result. As well as presenting the promising results of this work here, the mechanism of this synergistic effect is discussed, based on micro-analysis of the surface films by AES and XPS.

The analysis of the elastic contact of ideal rough surfaces is presented in this paper. The rough asperities are assumed to be spherical with the same vertical height and spatial distance. The mutual influence of asperities is considered. Numerical results show that for the same load, the contact area is less than the Hertzian prediction, while the pressure distribution is still of a Hertzian type, but is increased to some extent. We find that the asperity interaction is associated with a parameter, called the “loading level,” which combines the surface texture, mechanical properties, and the nominal mean pressure. Of significant importance is the discovery of the variation of the reference plane position with the contact load. In the classical theory of rough contact (Greenwood and Williamson, 1966), the reference plane was in fact assumed to be in the mean line position. We prove that the location of the reference plane is determined by the number of contacting asperities and the loading level, thus making the analysis of the contact of rough surfaces somewhat complex.

The addition of various extreme pressure and antiwear additives in lubricating oil is an important and effective way of reducing friction and wear. The application of chemico-thermal treatments on surface of materials is another effective way of improving the tribological behaviour of rubbing pairs. The synergistic effects of oil additive sulphurized olefin, with sulphurized, nitrided and oxynitrided surfaces of 1045 steel, on the tribological behaviour have been systematically studied on a ball-on-disc testing machine. Increasing load bearing capacity and friction reduction results have been obtained. The mechanism of this synergistic effect is discussed based on the microanalysis of the surface film using AES and XPS.

In order to increase the bonding strength between plating layer and substrate and promote the formation of a transfer film, a new type of Ni-Cu-P brush plating layer with excellent wear resistance was developed on the basis of an Ni-P amorphous plating layer, although it showed different behaviour when the substrate was changed. This paper systematically investigated its tribological behaviour on a “ball-on-disc” testing machine under lubrication with paraffin oil, and analyzed in depth the effect of substrates (conventionally heat treated 1045 steel and nitrided 1045 steel) on its microstructure, hardness, wear resistance and wear mechanism. The results showed that the load bearing capacity of an Ni-Cu-P brush plating layer on a nitrided 1045 steel substrate can be more than ten times that of a 1045 steel without a plating layer, and more than twice that of a 1045 steel substrate without a nitriding layer. The composite coating process can usually offer an immeasurable effect through the interaction between composite layers.

Experiments on and analyses of the waviness and roughness effects in lubricated wear related to running-in were performed. It was found that the ability of a lubricated slider to form an oil film can be determined by surface waviness which can be characterized by a waviness index W n and wavelength parameter λ 0.5 x . The characteristic of contact can be determined by the surface roughness, and in particular by the geometry of the asperity summits which can be characterized by the plasticity index ψ. It seems that W n , λ 0.5 x and ψ taken together provide a good criterion for assessing lubricated wear. Running-in can only improve the surface roughness effect during contact and hardly changes the surface wavelength.

Tribological behaviour of two kinds of scraped surface topography of machine tool guideways — the conventional form named ‘narrow-deep’ scraping and an improved form termed ‘wide-shallow’ scraping — is described. Behaviour is compared under the following conditions: average pressure p = 0.135−0.675 kgf cm−2 and sliding velocity V = 15−600 mm min−1. In comparison with narrow-deep scraping of slideways, wide-shallow scraping may reduce the friction coefficient by about 50–90%, relieve the phenomenon of stick-slip, and increase the amount of table floating. Consequently, the positioning accuracy of the machine tool feed drive system and the wear durability of guideways can be expected to be improved greatly. The amount of scraping work might be decreased to less than 1 2 . An attempt is made to explain the above results from the viewpoint of hydrodynamic lubrication and to summarize the characteristics of the two kinds of scraped surface mentioned above. Based upon a series of experiments, the authors propose that in evaluating the performance of guideway surfaces, the concepts of oil-film-forming ability and oil-film-retaining ability are helpful.