## 1 Introduction
[22] examined the tribo performance in the starved lubrication condition on a non-conforming contact between laser-textured medium carbon steel surfaces. There are many works in the literature that explore the rheological behavior of lubricating oil and grease. Using a coupled simulation model of fluid-structure interaction (FSI) based on the computational fluid dynamics method (CFD), [PERSON] et al. [23] analyzed the lubricating characteristics of oil flow in bearings according to the increase of lubricating oil viscosity and its velocity, the angle and number of the fluid inlet nozzle. [PERSON] et al. [24] investigated the grease-lubricated region of bearings operating at low speed to devise a method that better considers the lubrication quality parameter according to the effects of the grease thickener and not only on the viscosity of the base oil. [PERSON] et al. [25] analyzed the connection between various grease components (thickener and base oil) applied in bearings with the sliding friction generated in lubricated contacts. [PERSON] et al. [26] introduced a CFD approach for solving EHL lubrication in metal-on-metal contact using the freely available package OpenFOAM. They considered the isothermal and thermal cases under moderate loads and steady-state conditions, the phenomenon of cavitation under constant velocity, different viscosities, and slide-to-roll ratios. [PERSON] et al. [27] studied the friction properties of a range of modifier-containing oils in an engine bearing under a hydrodynamic regime using a combined experimental and modeling approach (a journal bearing machine (JBM) supplied by PCS Instruments and a finite difference-based 3D thermal hydrodynamic lubrication model). [PERSON] et al. [28] investigated the influence on the tribological parameters of lubricated contact parts due to the presence of diamond-like carbon coatings. Their finite element numerical model considered variables such as drag velocity and infinite sliding conditions, generating temperature and thermal viscosity profiles for analysis and discussion about film thickness and friction. [PERSON] [29] evaluated the emergence of super-low frictional forces that occur in fluid-structure interactions when applying representative normal velocities and loads by simulating lubricated contacts as they exist in real life, which involved engineered surfaces and materials, EHL and EHD lubrication, and Stripbeck diagrams. Several experimental and numerical studies using the Finite Element Method (FEM) have been performed to analyze fatigue damage in rolling contacts. [PERSON] et al. [30] verified the influence of microcavities on the surface texture and surface fatigue on a non-conforming contact under a mixed lubrication regime. [PERSON] et al. [31] and [PERSON] et al. [32] analyzed how roughness parameters such as mean roughness, mean square roughness, skewness, and kurtosis interfere with the fatigue life of rolling contacts under a mixed EHL lubrication regime. [PERSON] et al. used a continuous damage mechanics (CDM) FEM model to estimate the fatigue life of machine elements. [PERSON] et al. [33], using a non-Gaussian surface simulation technique and FEM stress analysis, calculated the relative fatigue life of bearing with a particular roughness profile subjected to high speed and loads. Finally, [PERSON] et al. [34], through numerical simulation of a three-dimensional dynamic and cyclic loading model and experimental comparison, evaluated the damage caused by contact fatigue of bearings. This paper aims to present a 3D microscopic scale computational model implemented in a finite element program (Abaqus(r)) and to analyze, through fluid-structure Interaction (FSI) method, stresses, pressures, and friction between the bearing parts in contact. The work by [PERSON] et al. [17] is closer to this one in terms of methodology, but we can highlight as a main difference the fact that they have dedicated mainly to mixed lubrication conditions while this paper seeks to elucidate the differences between the two regimes: hydrodynamic and mixed.