The role of nonlinear viscoelasticity in journal bearing lubrication: Insight from the Phan–Thien–Tanner model

This research offers a numerical study of viscoelastic lubrication in journal bearings employing the Phan–Thien–Tanner (PTT) constitutive equation. This equation characterizes the reciprocity between the viscous and elastic properties of materials. Furthermore, it accounts for shear thinning and differences in normal stress. The model records nonlinear elastic effects and simulates complex geometries and flow conditions. This research examines the impact of the following characteristic parameters—the elongational parameter, the Deborah number, and eccentricity ratio, on the pressure distribution, shear stress, the first normal stress difference, load capacity, friction coefficient, and stress ratio. The results indicate that a low elongational property can sustain larger loads while providing a smaller friction coefficient, both of which are desirable features in journal bearing lubricants. As the eccentricity ratio increases, pressure rises, and in high-pressure regions, the lubricant resists deformation, leading to high shear stress. Factors affecting the elasticity of fluids contribute to the accumulation of normal stresses in both shear and extensional flow.