Mechanism of direct contact and numerical model for analysis of line contact mixed elastohydrodynamic lubrication in pure rolling condition

Numerical analyses of mixed EHL (elastohydrodynamic lubrication) are carried out using three different analysis models for line contact between a smooth surface and a rough surface with a single transverse sinusoidal bump. It is demonstrated that the transient Reynolds equation expressed on coordinate system of which origin is fixed to the center of Hertz contact conjunction, which has been used so far in EHL or micro-EHL analyses, has an inadequacy for analyzing of severe asperity interaction in mixed elastohydrodynamic condition. When direct contacts show an inclination to take place, oil mass should travels with asperity conjunction. Therefore, Reynolds equation in such case should be expressed on the moving coordinate system with asperity conjunction. Authors propose a hybrid analysis model for mixed EHL where two kinds of Reynolds equations on different coordinate system are selectively utilized for global and local conjunctions. This model predicts that direct contact asymptotically takes place by squeeze film effect when a sinusoidal bump with large amplitude comes into Hertz conjunction in pure rolling condition.