In mixed elastohydrodynamic lubrication, it is supposed that asperity conjunctions should interrupt oil flow in advance of the occurrence of a direct contact. The local transient Reynolds equation, which is expressed in the coordinate system travelling with a rough surface, will serve to simulate the interruption process of oil flow. In this paper, we propose a new model for mixed EHL for the rolling-sliding contact of cylindrical bodies with 3-dimensional single-sided roughness considering a periodical boundary condition and oil mass conservation. Under the conditions of pure rolling, as the local Reynolds equation does not include the wedge-film term, direct contact is predicted to occur easily, especially in the case of a single bump. On the other hand, in the case of a sinusoidal wavy surface, oil entrapped in the space between asperities at the entrance of the Hertz conjunction will be compressed up to a considerable pressure in the Hertz region so that direct contact will be prevented unless there is a large amplitude of roughness.
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