The Grease Worker and Its Applicability to Study Mechanical Aging of Lubricating Greases for Rolling Bearings

Abstract

Mechanical degradation by shear is one of the mechanisms that limits the life-time of lubricating grease in a rolling bearing. It results in a change of the micro-structure of the thickener-oil system, leading to a change in bleed and consistency. The resistance to degradation can be quantified using a grease worker. In this paper a novel approach is described, where the grease worker is used to measure the rheological properties of a grease in-situ, while aging the grease. Mechanical energy and pressure losses are calculated using the measured force that is required to push the plate with holes through the grease in the cylinder of the grease worker. A pipe flow model in combination with a power law rheology model are used to analytically determine the power-law fluid consistency index and exponent while aging the grease. The model validity is verified using CFD simulations and measurements using a rheometer with plate-plate geometry.

On the evolution of oil-separation properties of lubricating greases under shear degradation

“…The grease worker used in this study, shown in Fig. 1, was described by Meijer and Lugt [12]. Its dimensions are given in Table 2.…”

“…Using the load cell data from the grease worker, the energy input, i.e., the total mechanical work to which the grease sample was subjected, can be calculated. According to Meijer and Lugt [12], the instantaneous power density to move the perforated grease plate through the grease is given by Eq. ( 1) and the supplied energy density 𝐸 𝑔 is given by Eq.…”

“…Controlled shear ageing is performed in a grease worker, instrumented with a load cell for monitoring the imposed force, as originally designed by Rezasoltani and Khonsari [11]. The data obtained from the grease worker are used to calculate the energy imposed on the grease [12]. Previous works showed that the yield stress (13) and viscosity (12) of the grease change significantly with the degree of shear ageing, using the same grease worker set-up.…”

“…The data obtained from the grease worker are used to calculate the energy imposed on the grease [12]. Previous works showed that the yield stress (13) and viscosity (12) of the grease change significantly with the degree of shear ageing, using the same grease worker set-up.…”

Rheological characteristics and behaviour prediction of lubricating grease for RV reducer across a wide temperature range

“…Ideal operating temperatures allow the reducer to exhibit appropriate efficiency and service life during service [1][2][3]. At low temperatures, grease viscosity is high and the internal frictional resistance of the flow process is high, requiring the aid of sufficient external force to overcome the resulting resistance [4][5][6]. In the high-speed operating conditions of the RV reducer, due to the friction between the parts, the working temperature will rise rapidly.…”