Of rubbed surfaces

Figure 8 Left Schematic graph of the setup for the simulation of rubbing surfaces. Upper and lower walls are separated by a fluid or a boundary lubricant of thickness D. The outermost layers of the walls, represented by a dark color, are often treated as a rigid unit. The bottom most layer is fixed in a laboratory system, and the upper most layer is driven externally, for instance, by a spring of stiffness k. Also shown is a typical, linear velocity profile for a confined fluid with finite velocities at the boundary. The length at which the fluid s drift velocity would extrapolate to the wall s velocity is called the slip length A. Right The top wail atoms in the rigid top layer are set onto their equilibrium sites or coupled elastically to them. The remaining top wall atoms interact through interatomic potentials, which certainly may be chosen to be elastic.

Mixed Film Ijibrication. Mixed film lubrication is almost invariably the true state ol affairs when boundary and EP lubrication are encountered, i.c.. an appreciable fraction of the load is carried by the fluid film in the valleys" of the surface w hile the asperities in contact are permitted to carry the halancc of (he load without seizure through ihe beneficent intervention of the boundary or EP lubricant. The very important hreakin process of rubbing surfaces consists in the controlled induction of the number and die size of the surface asperities so that fluid lubrication will prevail for must of ihe lime. 

Catalytic activity of rubbing surfaces (a) By reference to Table 5.5, find the metal hydroxides, oxides and nitrides that illustrate their highest exoelectrons emission intensity (I, cps), (b) Calculate the tribochemical energy (TribEn) TribEn = (AHf - WF) for the listed compounds and correlate them with measured exoelectrons emission intensity (I, cps). Explain differences. 

The next chapter is a review of current practice in lubrication of internal combustion engines and lubricant design. The role of individual lubricant components and their use in mineral and synthetic formulations is covered. This is followed by a discussion of the tribochemical effects of additive interactions. The heart of the manuscript is chapters, "Tribochemical nature of antiwear film , "Surface tribochemistry and activated processes", and "Analytical techniques in lubricating practices". Topics covered include tribofilm formation, organomolybdenum compounds in surface protection, catalytic activity of rubbing surfaces, introduction of some techniques for evaluation of tribofilms composition and analytical techniques for evaluation of lubricant degradation. Examples of the application of basic concepts are introduced, eg., acidity and basicity in the process of lubricant deterioration. 

We study the evolution of the topologieal features of rubbed surfaces of samples imdergoing various aging processes. The approaeh is similar to creep experiments that are widely employed in the study of segmental relaxations in bulk polymers, but with two distinctions. One is that here the stress due to the Laplace Pressure (LP) from the surface topographic features, such as ditches and ridges ereated by rubbing, is present at all time until... 

Tribological system peg-and-disk apparatus, pressure (P) = 1.0 MPa, rubbing velocity (V) = 0.5 m/s, temperature of rubbing surfaces 40°C, mating material steel 100 Cr 6 700 HV (Vickers Hardness) 10, no lubricant. 

In the cases where full film lubrication is difficult to maintain because of severe working conditions such as low speed or high Hertzian pressure, the asperities of rubbing surfaces will come in contact with each other. This is known as the boundary lubrication regime. Because there is a sparse lubricant film between the surfaces, the physical properties of the lubricant such as viscosity are not as important as the chemical properties of the lubricant. The chemical additives added to the lubricant help in forming the protective thin film between the rubbing surfaces. These films have low... 

---