Sensitivity Analysis for the Lubricant Film in Bearings Under THD Lubrication

The study about the dynamic characteristics of a great number of mechanical parts has been promoted by the necessity of decreasing the vibrational effects in mechanical systems, as the reduction of superficial fatigue. In this way, the research around, even, a simple part like a hydrodynamic bearing is very important, especially in the automotive industry. In this case, the lubricant acts like a flexible liking element between the journal-bearing surfaces. The lubrication is essential for the engine, because it reduces the wear between the internal parts and prevents the metal contact. Due to the shear stresses present in the lubricant, the temperature rises and, consequently, it changes the lubricant properties. The viscosity is strongly dependent on the temperature and it is the parameter that characterizes the fluid flow and its dynamic behavior. Any temperature change induces a consequent modification in the lubricant behavior. Therefore, a thermohydrodynamics (THD) analysis allows a most accurate prediction of the bearings performance characteristics. It's known that the engine's crankshaft works, partially, in contact with the bearing wall, due to the great force imposed by the combustion. So, this paper aims the study of the limit conditions of the hydrodynamic lubrication for different types of oils and for the THD and HD approach.