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

Hogenberk, Femke; Osara, Jude A.; Ende, Dirk van den; Lugt, Piet M.

doi:10.1016/j.triboint.2022.108154

Cited by 13 publications

(2 citation statements)

References 16 publications

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“…Under the rotary shear mode, a fixed shear rate of 100 s −1 was applied to the magnetorheological grease, and the viscosity did not change significantly with the shear time, which indicated that the three magnetorheological greases used in the experiments had better storage performances at low shear rates. According to the theory of fluid dynamics, the apparent viscosity of the grease was generated by internal friction, and the external force required to shear the soap fibers was the resistance to flow of the grease [21]. Magnetic particles agglomerating to form a magnetic chain under the action of a magnetic field require drastic changes caused by the temperature field and sustained shear, that is to say, the soap fiber structure suffers great damage, and then the apparent viscosity rises, and the magnetic chain becomes the dominant factor in the composite strength.…”

Section: Rheological Properties In Rotational Shear Modementioning

confidence: 99%

Study of the Effect of Continuous Thermal Effects on the Shear Stability of Magnetorheological Grease

Li,

Pan,

Wang

2023

Applied Sciences

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Magnetorheological dampers in the service of the medium in a project experience continuous thermal effects, frequent reciprocating shear and other complex conditions. Shear stability is an important indicator of the reliability of a magnetorheological media service. Magnetorheological grease (MRG) was prepared using hydroxy iron powder with a mass fraction of 30% and lithium grease of different consistency grades as a continuous phase. The results of magnetic and rheological properties analysis were combined to investigate the mechanism of the continuous thermal effect on the shear stability of MRG. The results show that changes in the temperature field and magnetic field cause significant changes in the magnetic and rheological properties of MRG. At low temperatures and low magnetic fields, the soap fiber structure unique to MRG can effectively inhibit the movement of magnetic particles, with slight changes in the rheological properties and excellent shear stability. When the temperature increases to 80 °C, 00#MRG is damaged by the high temperature. The soap fiber structure is fractured and reorganized, and the rheological properties change significantly. However, the rheological properties of 1#MRG remain largely unchanged during the magnetic field enhancement to saturation, showing better shear stability. The higher consistency continuous phase has excellent heat resistance and better shear performance stability in the face of thermomagnetic coupling conditions, but the fiber breakage caused by continuous reciprocating shear poses a challenge to the service stability of MRG.

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Section: Rheological Properties In Rotational Shear Modementioning

confidence: 99%

Study of the Effect of Continuous Thermal Effects on the Shear Stability of Magnetorheological Grease

Li,

Pan,

Wang

2023

Applied Sciences

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“…Therefore, analyzing the results of section 3.1 where the oil separation rate decreased by more than 30 %, the more critical point obtained is the change in the microscopic fiber structure of the thickener. The oil bleed rate depends internally on the interplay between the oil affinity and permeability of the thickener matrix [10]. These two properties are mainly determined by the fiber diameter and the volume fraction of the fiber.…”

Section: Aging Of Grease Oil Bleed Mechanismmentioning

confidence: 99%

Oil-separation properties of aviation grease under thermal aging

Wang,

Chen,

Liu

et al. 2023

Vib. proced.

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During work or long-term storage, grease is susceptible to thermal oxygen or mechanical aging, which affects the performance of grease or even leads to the destruction of the structural surface of grease lubricated products. As the main mechanism of grease lubrication, grease partitioning can explore the aging law of grease and effectively identify whether the grease fails. In this paper, 7014 aerospace grease was selected as the research object and accelerated test was conducted by high temperature thermal oxygen. The combination of grease separation degree and mass change rate was selected for comprehensive characterization of grease separation performance. The results show that the grease partitioning degree has a significant decreasing trend; the quality change has also decreased and the degradation trajectory is similar to the partitioning degree; it is inferred that the main reason for the decrease of grease partitioning performance may be the loss of base oil and the change of thickener fiber structure.

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A Quantitative Method to Measure Oil-Separation Properties of Lubricating Greases

Hogenberk,

van den Ende,

de Rooij

et al. 2024

Tribol Lett

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The oil-separation properties of lubricating greases are responsible for transporting base oil to the bearing contacts. Therefore, a good understanding of these properties is necessary to predict grease life based on physical grease properties. Currently, oil separation for small, aged grease samples collected from bearings, is studied using so-called maintenance tools. These tools give qualitative insight into the grease properties, e.g., increases or decreases in oil separation after ageing of the grease. In this work, a quantitative, lab-scale method to study oil separation is presented. Using this method, the amount of base oil transferred from a grease sample to a piece of blotting paper is measured based on the difference in light transmission through the oil stain and the dry paper. Translation of transmitted light intensity to oil concentration is accomplished using a modified Lambert-Beer’s law. This enables the determination of the instantaneous bleed rate and oil content. In combination with a physical model, this method can help to improve the understanding of the driving forces behind oil separation, e.g., the affinity pressure and permeability.

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

Cited by 13 publications

References 16 publications

Study of the Effect of Continuous Thermal Effects on the Shear Stability of Magnetorheological Grease

Study of the Effect of Continuous Thermal Effects on the Shear Stability of Magnetorheological Grease

Oil-separation properties of aviation grease under thermal aging

A Quantitative Method to Measure Oil-Separation Properties of Lubricating Greases

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