Mixed and Fluid Film Lubrication Characteristics of Worn Journal Bearings

Abstract

The mixed and fluid film lubrication characteristics of plain journal bearings with shape changed by wear are numerically examined. A mixed lubrication model that employs both of the asperity-contact mechanism proposed by Greenwood and Williamson and the average flow model proposed by Patir and Cheng includes the effects of adsorbed film and elastic deformation is applied. Considering roughness interaction, the effects of the dent depth and operating conditions on the loci of the journal center, the asperity-contact and hydrodynamic fluid pressures, friction, and leakage are discussed. The following conclusions are drawn. In the mixed lubrication regime, the dent of the bearing noticeably influences the contact and fluid pressures. For smaller dents, the contact pressure and frictional coefficient reduce. In mixed and fluid film lubrication regimes, the pressure and coefficient increase for larger dents. Furthermore, as the dent increases and the Sommerfeld number decreases, the flow rate continuously increases.

Dynamic of a Flexible Rotor-Bearing System Supported by Worn Tilting Journal Bearings Experiencing Rub-Impact

“…In journal-bearing contact region, the oil film flows between the journal and the bearing surface asperities. This lubrication regime is called mixed-lubrication which was used by Kazama and Naritia [23] to assess the effects of the wear-induced bearing geometrical imperfections on the solid-to-solid contact between a journal and a hydrodynamic plain bearing. They also obtained the oil film pressure distribution and the extent of the effect of bearing wear on a journal-worn bearing behavior at its equilibrium state.…”

“…The other wear signatures can obtain using wear depth measurement on the worn bearings or using other mathematical models for wear. Some examples of other wear signatures are given in [2,23].…”

“…This regime is called the mixed lubrication regime [39]. In this situation, solid-to-solid contact pressure can be obtained by the following relations [23]:…”

“…In Equation (17), 𝑤 * = (𝛽 /𝜎 * )(2𝐻 /𝐸′) is the plasticity index, while 𝐻 represents the hardness of the softer material and 𝑑 , * represents the non-dimensional separation between the two rough surfaces. The separation between the two rough surfaces can be obtained as follows [23]:…”

“…The Gaussian asperity distribution is considered in this research as most of the engineering surfaces have this distribution. 𝜑(𝑠) can be expressed as [23]:…”