Applicability of Winkler and FEM models for elastohydrodynamic analysis of deformable oil and water-lubricated journal bearings

Abstract

This article explores the elastohydrodynamic analysis of journal bearings with deformable surface. An iterative solver is developed, coupling the Reynolds equation for hydrodynamic lubrication with the open-source FEM software, CalculiX. The steady-state Reynolds equation is solved using FDM with Reynolds boundary conditions, while the displacement field of the bearing bush is obtained via FEM and compared to the Winkler model. Both oil and water-lubricated bearings are examined, and the validity of the Winkler model is investigated, pointing out the circumstances under which it provides satisfactory results. While fluid-solid interaction and EHD analysis of journal bearings are well-documented in the literature, few studies offer a cross-domain comparison between FEM and Winkler models. This study aims at assessing the bearing performance over a range of operational conditions, including different loads, values of bush thickness, and shaft misalignment conditions. The model results are compared and validated against existing literature results. Furthermore, in water-lubricated bearing bush materials, a phenomenon occurs where negative values of radial displacements (opposite to the applied pressure) are observed in the divergent region of the fluid film. This effect is closely linked to the poisson ratio and the incompressibility of the material, and it is thoroughly illustrated and discussed in detail.