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Lubricants
Special Issues
Recent Advances in Lubricating Greases II
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Recent Advances in Lubricating Greases II

A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 9508

Special Issue Editor

Prof. Dr. Erik Kuhn

E-Mail Website
Guest Editor
TREC, Institute of Engineering Design and Product Development, Hamburg University of Applied Sciences, Berliner Tor 21, 20099 Hamburg, Germany
Interests: tribology; lubricating grease; energetic approach
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Lubricating greases are markedly viscoelastic lubricants with a special tribological behavior, but with a wide range of applications. Our research work has, more or less, two main directions: understanding the behavior of greases during tribology stress, and furthering knowledge of the behavior of greases in concrete machine element applications. In the course of this work, opportunities were also created to develop new lubricants such as biodegradable and completely biogenic lubricating greases.

In recent years, work on the structural degradation of lubricating greases has increasingly been conducted. This has led to a new research focus on lubricating grease tribology. Energetical investigations seem to be an appropriate tool with which to obtain new information.

The success of our previous Special Issue on 'Lubricating Greases in 2017' encouraged us to continue examining this interesting topic. Research on the practical application of lubricating greases is also very welcome.

We hope researchers will accept our invitation and present their research work.

Prof. Dr. Erik Kuhn
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Lubricants is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (4 papers)

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Research

22 pages, 12061 KiB  
Article
Influence of Rheological Properties of Lithium Greases on Operating Behavior in Oscillating Rolling Bearings at a Small Swivel Angle
by Iryna Slabka, Sören Henniger, David Kücükkaya, Michael Dawoud and Hubert Schwarze
Lubricants 2022, 10(7), 163; https://0-doi-org.brum.beds.ac.uk/10.3390/lubricants10070163 - 19 Jul 2022
Cited by 4 | Viewed by 2050
Abstract
In this study, the behavior of greases during oscillating bearing operation with a small oscillation angle and high frequency was investigated. This mode of operation entails demands on the lubrication system that differ significantly from those for continuously rotating bearings. In order to [...] Read more.
In this study, the behavior of greases during oscillating bearing operation with a small oscillation angle and high frequency was investigated. This mode of operation entails demands on the lubrication system that differ significantly from those for continuously rotating bearings. In order to determine the variables influencing the suitability of a lubricating grease for small angle oscillating operation, the grease samples were examined with particular regard to their rheological properties. The focus of this investigation was to find a relationship between the rheological parameters and the real behavior in the bearing. Therefore, rheological and physical parameters, which influence the long-term structural changes and lubrication conditions, were identified. For this purpose, the viscosity was measured over a wide shear-rate range. The storage and loss modulus, the work of deformation, and the adhesion force jump are also determined. Afterward, rotational transient flow measurements were performed. These allowed us to analyze the development of the shear stress over time, at a constant shear rate, and to examine the internal friction behavior by evaluating the energy density. Subsequently, grease-lubricated four-point bearings were used in component tests, while the frictional torque was measured. These bearings operated in oscillating motion. Moreover, the yield point of mechanically aged greases was measured and compared with that of fresh greases to examine the influence of the oscillating operation on the lubricant condition. Finally, correlations between grease composition, rheological measurements, and component tests were investigated. Thereby, parameters influencing the frictional behavior of greases in rolling bearings during oscillating operation at small swivel angles were identified. Full article
(This article belongs to the Special Issue Recent Advances in Lubricating Greases II)
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14 pages, 4762 KiB  
Article
Study on Factors Influencing Film Formation of Grease and Calculation Model for Grease Film Thickness
by Zhe Zhang, Yanshuang Wang, Jianghai Lin and Dongfeng Wang
Lubricants 2022, 10(6), 123; https://0-doi-org.brum.beds.ac.uk/10.3390/lubricants10060123 - 12 Jun 2022
Cited by 5 | Viewed by 1860
Abstract
The grease film thickness was measured in fully flooded elastohydrodynamic lubrication, and the influence of rolling speed, load, consistency, base oil type and thickener type on grease film thickness was analyzed. A new calculation model for grease film thickness was established. The results [...] Read more.
The grease film thickness was measured in fully flooded elastohydrodynamic lubrication, and the influence of rolling speed, load, consistency, base oil type and thickener type on grease film thickness was analyzed. A new calculation model for grease film thickness was established. The results show that the grease film thickness increases with the increasing rolling speed, and then levels off with the amount of thickener in the contact region reaching an equilibrium. The degree of grease film enhancement comparing to its base oil will depend on thickener type and consistency. The larger the atmospheric viscosity and pressure-viscosity coefficient of the base oil, the higher the film thickness of the greases with the same thickener. The grease film thicknesses with the same base oil and different thickeners are determined by the size of thickener particles at the same consistency or concentration. The larger the consistence of the grease, the larger the effective viscosity of the grease at the contact and the thicker the grease film thickness whose base oil has the same type and viscosity along with the same type of thickener. The calculated values by the new model are in good agreement with the measured values. Full article
(This article belongs to the Special Issue Recent Advances in Lubricating Greases II)
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18 pages, 5870 KiB  
Article
Influence of Mechanical, Thermal, Oxidative and Catalytic Processes on Thickener Structure and Thus on the Service Life of Rolling Bearings
by Markus Grebe and Michael Ruland
Lubricants 2022, 10(5), 77; https://0-doi-org.brum.beds.ac.uk/10.3390/lubricants10050077 - 22 Apr 2022
Cited by 6 | Viewed by 2400
Abstract
Constant further developments in application technology with the aim of higher economic efficiency and power density place ever greater demands on mechanical components and construction elements and thus on the lubricating greases used. This is particularly true in the area of roller bearings, [...] Read more.
Constant further developments in application technology with the aim of higher economic efficiency and power density place ever greater demands on mechanical components and construction elements and thus on the lubricating greases used. This is particularly true in the area of roller bearings, in which lubricating greases are sometimes used with high mechanical stress and in wide temperature ranges. A current example is the rolling bearings in the assemblies of hybrid vehicles, which are subjected to extreme thermal and mechanical loads due to engine downsizing, high speeds and the radiant heat from the combustion engine. Investigations at the Competence Center of Tribology Mannheim (KTM) show that the grease service life for roller bearing lubrication, even at high temperatures, does not only depend on classic oil aging. In numerous roller bearing tests and by means of rheological measurements, it could be shown that the loss of the lubricating effect is a consequence of the change in the thickener structure. Mechanical, thermal, oxidative and catalytic processes play a decisive role here. In this article, a scientific method is presented for the first time as to how these individual influencing factors can be examined and evaluated independent from one another. For this purpose, the first results of an ongoing DGMK project are presented and evaluated. Full article
(This article belongs to the Special Issue Recent Advances in Lubricating Greases II)
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10 pages, 7220 KiB  
Article
On the Flow Dynamics of Polymer Greases
by Josep Farré-Lladós, Lars G. Westerberg, Jasmina Casals-Terré, Johan Leckner and René Westbroek
Lubricants 2022, 10(4), 66; https://0-doi-org.brum.beds.ac.uk/10.3390/lubricants10040066 - 13 Apr 2022
Cited by 5 | Viewed by 2509
Abstract
In this paper, the flow dynamics of polymer greases was investigated using micro-particle image velocimetry. Polymer greases have a different thickener structure, compared to widely used lithium-based greases, and they have the well-known ability to release oil. How these properties affect grease deformation [...] Read more.
In this paper, the flow dynamics of polymer greases was investigated using micro-particle image velocimetry. Polymer greases have a different thickener structure, compared to widely used lithium-based greases, and they have the well-known ability to release oil. How these properties affect grease deformation and its ability to flow is investigated and compared to the corresponding behavior of a lithium complex grease with the same consistency. Two main tests were carried out, where velocity profiles in a straight channel were measured and analyzed, and velocity evolution during the transition period from a no-flow to a fully-established flow was measured, respectively. It was found that the polymer grease flow dynamics is different from that of the lithium grease. This indicates that the internal structure of the grease and the grease ability to bleed oil have a strong influence on the deformation on a global scale, which in turn entails other lubricating abilities for the two grease types. Full article
(This article belongs to the Special Issue Recent Advances in Lubricating Greases II)
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