Stability evaluation of three-layered journal bearing with slip/partial slip

This paper aims to present stability of a three-layered journal bearing considering magnitude of the layers’ thicknesses and viscosities with slip/partial slip on the bearing surface.

Modified Reynolds equation based on one-dimensional analysis is derived for a three-layered journal bearing with slip/partial slip. Dynamic coefficients are derived based on infinitesimal perturbation method. Linearized stability analysis is presented taking into account slip/partial slip on bearing surface; thicknesses and viscosities of bearing surface layer; and core layer and journal surface layer.

Results of threshold speed and critical whirl frequency ratio coefficients (C_ω, C_Ω), stiffness (K_ij for i = x,y) and damping (B_ij for i = x, y) coefficients and threshold speed (ω_s) and critical whirl frequency ratio (Ω_s) are presented. The bearing surface is analyzed for slip (total surface with slip) and partial slip (partial surface with slip). The slip-on bearing surface reduces stability, while partial slip improves bearing stability. The threshold speed coefficient (C_ω) decreases with slip on bearing surface. The threshold speed (ω_s) and critical whirl frequency ratio (Ω_s) are influenced by the variation of threshold speed coefficient (C_ω) and critical whirl frequency ratio coefficient (C_Ω), respectively. A three-layered journal bearing with partial slip and thick high viscosity bearing surface layer results in higher threshold speed coefficient and has a potential to improve stability of journal bearing. The analyses indicate that optimal angular extent of partial slip region (θ_s) enhances the stability of journal bearing.

The paper presents parametric study of stability coefficients (C_ω and C_Ω) and evaluation of threshold speed (ω_s) and critical whirl frequency ratio (Ω_s) of a three-layered journal bearing with slip/partial slip.