نبذة مختصرة : International audience ; Grease is a lubricant used in rolling bearings, composed of a thickener (3-30 wt%), oil (65–95% wt%), and additives (5wt%). It is described as a porous network in which the thickener (typically a polymer or a lithium soap) traps the oil [1,2]. Grease role is to ensure a long life and low friction of the bearing and the rolling element move through the formation of an oil lubricating film between metallic surfaces in contact [1].The dominating mechanism supplying new oil to the lubricated contact is assumed to be “oil bleeding”. Grease acts as a reservoir of oil and by applying mechanical actions such as gravity, pressure force or centripetal body force, the thickener is crushed and releases the oil into the lubricating contact [2]. Experimental data of oil bleeding has been collected by using the apparatus of the ISO 22285:2018F standard procedure [3] for different temperatures. In this procedure, the grease is compacted between a mass and a sieve. Then under the effects of gravity and pressure force, its thickener’s network is retracting and its oil is bleeding out through the sieve.A 1D physical dynamical model of oil-bleeding rate of grease based on both mass and momentum balance equations, has been built. The simulation gives the oil bleeding weight percent with time. By using a parameter estimation procedure, the permeability value, which is a parameter characteristic of the oil bleeding, has been estimated according to the grease type and the experimental conditions. Finally, a good agreement between simulation with estimating permeabilities and experimental results has been observed, as shown in the following figure.
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