This scheme represents an intermediate state between boundary lubrication and hydrodynamic mechanism by which all pass before reaching this condition. In this case, part of the surface roughness of both mechanisms are inserted so that only part of the burden is borne by the hydrodynamic action and the other by the boundary film that covers the irregularities of both surfaces.
An incorrect selection of oil, as well as a decrease in viscosity, may lead to the mechanism is operating under these conditions. In this case, the lubricant film thickness is equal to the average roughness of both surfaces and not enough to obtain a laminar flow. See Fig. (A) and (b). For
cylinder internal combustion engine, where the present conditions of boundary and mixed film in the top and bottom dead spots, respectively, the incorporation of additives to oils unctuous base (during the manufacturing process) to ensure a better fixing of the oil film on the surfaces, or use of solid film lubricants (graphite or molybdenum disulfide), relatively insensitive to temperature and can form resistant layers and good rubbing permanence, can reduce a significant proportion wear in regime (fully loaded) and adhesive wear at startup. The figure shows these decreases in wear from five successive trials in a single-cylinder gasoline engine, the addition of graphite or MoS2 to a pure mineral oil and oil additives.
course, the benefit obtained with the addition of a solid film lubricant base oil, in terms of adhesive wear should not be offset by the potential risks that would result from a greater tendency to deposit formation as a result of insufficient stability of the suspension of solid lubricant base oil to be centrifuged at the elbows of crankshaft or passing through the filters of the lubrication circuit. However, current techniques of preparation and selection of these products and stabilization of suspensions suitable dispersant additives, SENCIBLES reduce these dangers. Whenever these conditions are met, these products can provide effective protection during the shooting and lead to surfaces that have a low coefficient of rubbing and whose subsequent wear are weak.
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