Some rheological properties of plastic greases by Carreau-Yasuda model

Various greases are often used for lubrication of various roller bearing and more seldom for slide bearings operating under rather lower speed values, when the mixed or boundary friction occur, for example, during operation in the start-stop regime. Three various commercial greases were tested, differing in the value of the kinematic viscosity of the base oils used in them, measured at temperature 40 degrees C and 100 degrees C, and the resulting different dropping point temperature. The rheological properties of such greases have been determined using the rotary rheometer. Based on the resulted dependencies of the apparent viscosity on the shear rate the parameters of the Carreau-Yasuda rheological model chosen, have been estimated. The prediction of rheological parameters for three plastic greases studied obtained with particularly good accuracy. Among the tested greases, the grease with the highest drop point temperature turned out to be a mechanically stable grease. The differences in pa-rameters values could be affected by differences in the compounds of the greases studied.