Approaching mixed elastohydrodynamic lubrication of smooth journal-bearing systems with low rotating speed

When a conformal interface is under low velocity and heavy load conditions, solid contact (or dry contact) may occur even in a system with smooth surfaces. This paper presents two approaches for solving steady-state and transient mixed elastohydrodynamic lubrication problems of journal bearings with smooth surfaces under low rotating speed. The first approach uses the reduced Reynolds equation with a combined finite element-backward finite difference scheme and the second applies a zero film thickness equation to describe the mechanical behavior of mating surfaces at solid contact points. The major advantages of these two approaches are (1) no division of the solution domain into a lubricated area and a solid contact area is necessary and (2) the solid contact pressure, lubricant pressure, and eccentricity ratio can be solved simultaneously. Numerical examples are presented for the application of these approaches. For the steady-state cases under low velocity studied in this work, pressure distributions approach those found in a dry contact state. This comparison confirms that the contact treatments are proper. Moreover, a transient case under sinusoidal loading was analyzed with these two approaches, and the results showed good agreement. This comparison further supports the use of these approaches.