Elastohydrodynamic analysis of double-layered journal bearings lubricated with couple-stress fluids

Abstract

Elastohydrodynamic (EHD) analysis of a journal bearing with a realistic model for the bearing made of two distinct layers is extended to include couple-stress effects in lubricants blended with polymer additives. Based on the Stokes microcontinuum theory, a transient pressure differential equation (modified Reynolds' equation) is derived from the fluid motion equations and solved numerically. The elegant and powerful semi-analytical approach based on the complex variable theory developed in an earlier work is extended to solve linear elastostatics problems for a double-layered journal bearing. The EHD solution in isothermal conditions is obtained numerically by means of an iterative procedure. By the finite perturbation technique, the eight fluid-film stiffness and damping coefficients are determined. At the threshold of instability, the dynamic coefficients are used as input data for studying the linear stability of the rotor-bearing system. According to the results obtained, the influence of couple-stress parameter on the static and dynamic performance characteristics of the compliant journal-bearing system is physically apparent and not negligible. Compared with the Newtonian lubricants case, lubricants with couple-stresses provide an increase in the load-carrying capacity and stability, a reduction in the attitude angle and the friction factor. It is also found that the fluid -solid interaction effect on the performance characteristics is more important, especially for high values of couple-stress parameter and relative rigidity of liner-bush assembly.

Nonlinear analysis of a rub-impact rotor supported by turbulent couple stress fluid film journal bearings under quadratic damping

“…It was found that the combined effects of couple stress and surface roughness can improve the load carrying capacity and decrease the attitude angle and friction parameters. Recently, Lahmar [17] studied the elastohydrodynamic analysis of double-layered journal bearings based on the Stokes microcontinuum theory. He found that the lubricants with couple stress would increase the load carrying capacity and stability and decrease the friction factor and the attitude angle.…”

Bifuraction Analysis of Hydrodynamic Plain Journal Bearing Lubricated With Couple Stress Fluid

“…In 2003, Hsu et al [10] investigated the effects of surface roughness on the dynamic response of short journal bearings lubricated with a couple stress fluid and showed that the combined effects of the couple stress and the surface roughness improved the load-carrying capacity of the journal bearing system and reduced both the rotor attitude angle and the values of the friction factors. In a recent study, Lahmar [11] conducted an elastohydrodynamic analysis of double-layered journal bearings and demonstrated that the use of a couple-stress lubricant increased the load-carrying capacity and stability of the bearing system and reduced the friction effects and attitude angle of the rotor. There are some prominent literatures about non-linear dynamics of rotor-bearing systems.…”

Nonlinear Dynamic Response of an Unbalanced Flexible Rotor Supported by Elastic Bearings Lubricated with Piezo-Viscous Polar Fluids

“…The new material constant  is responsible for couple-stress property. In the literature, the effects of couple-stresses on the behavior of journal bearings are studied by defining the dimensionless Owing to its relative mathematical simplicity, the couple-stress fluid model has been widely applied to analyze various hydrodynamic lubrication problems: hydrostatic thrust bearings, slider bearings, rolling bearings, squeeze film bearings, layered journal bearings, and dynamically loaded engine journal bearings [27][28][29][30][31][32][33]. The theoretical results obtained showed that the presence of the couple-stress provides an enhancement in the load carrying capacity, improve the dynamic performance characteristics and the stability of journal bearings, and lengthens the response time of the squeeze film action of the system as compared to the Newtonian lubricant case.…”