A Master Curve for the Shear Degradation of Lubricating Greases with a Fibrous Structure

Zhou, Y.; Bosman, Rob; Lugt, Piet M.

doi:10.1080/10402004.2018.1496304

Cited by 34 publications

(51 citation statements)

References 19 publications

(15 reference statements)

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“…According to Zhou et al [21], the mechanical degradation of grease is caused by pressure and shear stresses. According to Reference [22], grease may soften during aging and leak out of the bearing systems.…”

Section: Degradation Systems Of Greasesmentioning

confidence: 99%

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The Effect of Addition of Nanoparticles, Especially ZrO2-Based, on Tribological Behavior of Lubricants

Rylski

Siczek

2020

Lubricants

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The aim of the paper was to discuss different effects, such as, among others, agglomeration of selected nanoparticles, particularly those from zirconia, on the tribological behavior of lubricants. The explanation of the difference between the concepts of ‘aggregation’ and ‘agglomeration’ for ZrO2 nanoparticles is included. The factors that influence such an agglomeration are considered. Classification and thickeners of grease, the role of additives therein, and characteristics of the lithium grease with and without ZrO2 additive are discussed in the paper. The role of nanoparticles, including those from ZrO2 utilized as additives to lubricants, particularly to the lithium grease, is also discussed. The methods of preparation of ZrO2 nanoparticles are described in the paper. The agglomeration of ZrO2 nanoparticles and methods to prevent it and the lubrication mechanism of the lithium nanogrease and its tribological evaluation are also discussed. Sample preparation and a ball-on disc tester for investigating of spinning friction are described. The effect of ZrO2 nanoparticles agglomeration on the frictional properties of the lithium grease is shown. The addition of 1 wt.% ZrO2 nanoparticles to pure lithium grease can decrease the friction coefficient to 50%. On the other hand, the agglomeration of ZrO2 nanoparticles in the lithium grease can increase twice the friction coefficient relative to that for the pure grease.

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Section: Degradation Systems Of Greasesmentioning

confidence: 99%

“…Zhou et al [21] studied the mechanical aging behavior of fibrous structured greases, such as the lithium complex soap with poly-alpha-olefin (PAO) base oil and the polyurea-thickened grease with ester base oil. They reported that in the absence of oxygen no chemical reactions occurred.…”

Section: Degradation Systems Of Greasesmentioning

confidence: 99%

The Effect of Addition of Nanoparticles, Especially ZrO2-Based, on Tribological Behavior of Lubricants

Rylski

Siczek

2020

Lubricants

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“…This shear degradation will contribute to the mobility of the grease (Cann and Lubrecht (38)). It was shown in (Zhou et al (28)) that PU/E is an aging sensitive grease (low shear stability). Albeit its relatively low bleeding rate, a good film recovery can be observed after the churning phase (Fig.…”

Section: Overall Film Thickness Profilementioning

confidence: 99%

An Experimental Study on Film Thickness in a Rolling Bearing for Fresh and Mechanically Aged Lubricating Greases

Zhou

Bosman

Lugt

2019

Tribology Transactions

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The lubricating film formation of greases has been widely studied using single contact ball-on-disc configurations. However, other than for oil, the film formation with grease is governed by starvation, which in a full bearing is clearly different from that of the single contact. In this paper, film thickness measurements for various greases in a shielded deep groove ball bearing will be presented. The results were obtained using an in-house-made film thickness measurement rig based on the 'electric capacitance method'. It will be shown that the film thickness may deviate from the theoretical elastohydrodynamic film thickness calculated from the base oil and that the film thickness is not constant in time. It will also be shown that the film thickness for longer times is not only determined by the classical properties such as oil viscosity and grease bleed but also by shear degradation of its microstructure.

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“…Changes in base oil content (due to evaporation) and additive content (due to oxidation) can be established by infrared spectroscopy [8,41], but its use is limited in monitoring mechanical degradation. Rather, it can be used as a justification that mechanical degradation is dominant by finding that chemical reactions do not take place [13,36].…”

Section: Infrared Spectroscopymentioning

confidence: 99%

“…For these greases especially, a model that includes other forms of degradation-particularly oxidation-is essential. A promising start to incorporating thermal effects (without oxidation) into mechanical degradation models has been introduced by Zhou et al [36]. Additionally, Osara and Bryant [23] provide a DEG-based approach that incorporates thermal effects with high accuracy, and this proves a step forward in the development of a complete model.…”

Section: Future Directionsmentioning

confidence: 99%

The Use of Entropy in Modeling the Mechanical Degradation of Grease

Gurt

Khonsari

2019

Lubricants

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Recent theoretical developments linking degradation to the thermodynamic concept of entropy have allowed a new approach to modeling all types of degradation. The theory has been successfully applied to wear, fatigue, and numerous other forms of degradation and experimentation has confirmed its applicability to modeling the mechanical degradation of lubricating grease. This paper overviews the mechanical degradation of grease, discusses past and present modeling techniques, shows how new techniques can be used to predict grease life, and provides suggestions for future research.

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A Master Curve for the Shear Degradation of Lubricating Greases with a Fibrous Structure

Cited by 34 publications

References 19 publications

The Effect of Addition of Nanoparticles, Especially ZrO2-Based, on Tribological Behavior of Lubricants

The Effect of Addition of Nanoparticles, Especially ZrO2-Based, on Tribological Behavior of Lubricants

An Experimental Study on Film Thickness in a Rolling Bearing for Fresh and Mechanically Aged Lubricating Greases

The Use of Entropy in Modeling the Mechanical Degradation of Grease

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