We believe such compressive-vacuum

component of friction force do in fact exist in practice. We have called this component as compressive-vacuum friction force (F cv). This additional force consists of compressive component arising at the entry of the contact and a vacuum one acting on the contact exit. Therefore, Equation 1 should be rewritten as (2) Figure 1 A sliding tribosystem model: cylindrical roller rotating over the motionless block. Figure 2 Closed volumes formed by valleys between peaks on contacting surfaces. Vacuumization processes not only add to friction force but also increase wear, because produced suction forces along with contact of the naked surface make easier to damage sliding surfaces. In our opinion, wear of sliding contact could be greatly reduced by searching some methods to reduce friction force. These methods may include formation of micro-roughness of special XL184 molecular weight shape on

the surface. Similar approach was successfully used in [7] to reduce friction force in point-contact friction system. Though we use linear contact which differs significantly in properties, specially formed surface can also be used to reduce friction and wear. According to our compressive-vacuum hypothesis of friction, this can be done by preventing vacuumization. This idea is supported by the experimental data obtained during the friction testing of steel surfaces with specially designed micro-roughness [8, 9]. Methods In the present work, the Timken test [6] is chosen as a physical model of a sliding tribosystem. This model corresponds to a rotating shaft on plane bearing system,

selleck products which is the most widespread Branched chain aminotransferase and also the most often friction-damaged unit in engineering. Boundary lubrication is accompanied by wear, so additional care should be taken in experiments. It is important not to allow wear debris to cause micro-cutting damage of the contact zone on the one hand and not to allow formation of simple elastohydrodynamic (contactless) friction on the other hand. In used experimental system, the evolution of wear scar in time is controlled by microscopy, so these precautions are easily satisfied. On the basis of the compressive-vacuum hypothesis described above, we suppose that it is necessary to create special initial three-dimensional (3D) geometry of a sample’s surface roughness which will allow to reduce compressive and vacuum hydrodynamic components of friction force and as a consequence will also reduce contribution of adhesive interaction of surfaces. For this purpose, creation of test samples with specific channels on the surface is suggested. These channels would provide bypass for the lubricant from areas entering the contact to areas leaving the contact, so reduction of vacuum in the exit region becomes possible. Such channels on a surface of test objects can be formed as parallel grooves, like shown in Figure 3.