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Lubricants
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Tribological Studies of Roller Bearings
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Tribological Studies of Roller Bearings

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

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 9076

Special Issue Editors

Dr. Markus Grebe

E-Mail Website
Guest Editor
Competence Center for Tribology, Mannheim University of Applied Sciences, Paul-Wittsack-Straße 10, 68163 Mannheim, Germany
Interests: tribometry; laboratory tests; false brinelling; standstill marks; fretting; greases; machine learning; polymers; coatings
Dr. Henrik Buse

E-Mail Website
Guest Editor
Tribologie Engineering Mannheim GmbH, Dietrich-Bonhoeffer-Straße 22, 76744 Wörth am Rhein, Germany
Interests: tribometry; laboratory tests; fretting; machine learning; polymers; sensors

Special Issue Information

Dear Colleagues,

Lubricants is planning a Special Issue on the subject of roller bearings.

With over 4 billion units sold worldwide, roller bearings are one of the most important machine elements [source: nbr.eu], and we encounter them in all dimensions, from miniature roller bearings in precision instruments to huge roller bearings in wind turbines.

The importance of rolling bearings has continued to increase in recent years because energy efficiency and precision are of essential importance, for example, in electric drive trains.

Although roller bearings have a very long history (in approx. 1500 AD Leonardo da Vinci invented the roller bearing cage, which is one of the reasons for the low friction of this type of bearing), there is always further potential for optimization, as the requirements continue to increase. While conventional electric motors used to run at a maximum of 3000 revolutions per minute, today in the vehicle sector 18,000 revolutions are required and the trend is increasing. In addition, the subject of noise is becoming increasingly important, since the masking noises of combustion engines are no longer present. Another big issue is electrical current. The risk of parasitic currents increases due to the increasing use of converters for speed and power control in all industrial and automotive sectors. If the lubricant insulates between the rolling elements and the raceways, voltages can build up, which then lead to electrical breakdowns. These lead to damage and material removal, as in the case of electrical discharge texturing. If the lubricant conducts electricity, ohmic currents occur, which in turn can damage the lubricant.

The new requirements for rolling bearings also result in new requirements for lubricants and testing technology. Established test benches such as the FE8 or the FE9 can no longer map the speed range that is now required. Validation and service life tests must be adapted in accordance with the new requirement profiles in order to simulate realistic load situations and generate reliable statements. The lubricants have to withstand high mechanical and thermal loads, and should guarantee lifetime lubrication as far as possible.

We invite you to submit an original research article on the subject of rolling bearings, rolling bearing lubrication or rolling bearing testing technology. Articles that deal with the aforementioned new requirements for rolling bearings and their lubricants are particularly welcome.

We look forward to receiving your contributions.

Dr. Markus Grebe
Dr. Henrik Buse
Guest Editors

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.

Keywords

  • roller bearings
  • e-mobility
  • greases
  • high-speed applications
  • energy efficiency
  • noise behavior
  • electrical issues

Published Papers (5 papers)

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Research

18 pages, 9873 KiB  
Article
Comparison of Different Standard Test Methods for Evaluating Greases for Rolling Bearings under Vibration Load or at Small Oscillation Angles
by Markus Grebe and Alexander Widmann
Lubricants 2023, 11(7), 311; https://doi.org/10.3390/lubricants11070311 - 24 Jul 2023
Cited by 1 | Viewed by 1446
Abstract
Rolling bearings operated at small oscillation angles or exposed to vibrations during standstill show typical damage after only a short period of operation. This can be false brinelling damage, so-called standstill marks or classic fretting damage (fretting corrosion, tribo-oxidation). It is important to [...] Read more.
Rolling bearings operated at small oscillation angles or exposed to vibrations during standstill show typical damage after only a short period of operation. This can be false brinelling damage, so-called standstill marks or classic fretting damage (fretting corrosion, tribo-oxidation). It is important to differentiate here according to the amplitude-ratio x/2b, which indicates the ratio between the rolling element Motion (x) and the Hertzian contact half-axis (b). Depending on this ratio, suitable laboratory test methods must be used to test the lubricating grease practically for the particular application. For this purpose, the Fafnir wear test, according to the standard of the American Society for Testing and Materials ASTM D4170, is also listed in the current high-performance multi-use specification of the National Lubricating Grease Institute (NLGI) as a release test for lubricating greases. In Europe, the SNR-FEB2 test is frequently used, which is also required to release greases in the blade bearings of wind turbines, among other things. In the case of standstill marks due to very small oscillation angles or vibrations, the Mannheim Tribology Competence Center (KTM) has developed a special test now established in the industry. The oscillating angles vary in these three different standard tests in the range from ±6° in the Fafnir test to ±3° in the SNR-FEB2 test to ±0.5° in the KTM standstill marking test; the x-to-2b ratios range from 5.5 (Fafnir) to 3.4 (SNR) to 0.5 (KTM). This paper will explain the scientific basis for these special operating and test conditions and compare test results of specially prepared model greases in these three standard rolling bearing tests, two test variations and a classical fretting test under oscillating sliding friction (ASTM D7594). The paper’s main objective is to show that the suitability of grease for such an application depends strongly on the prevailing operating conditions. Different tests in this field are, therefore, not interchangeable. Good results in one test do not automatically mean good results in a similar test at first glance. Therefore, selecting the right test for the application is important. Full article
(This article belongs to the Special Issue Tribological Studies of Roller Bearings)
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22 pages, 8457 KiB  
Article
Study of the Plastic Behavior of Rough Bearing Surfaces Using a Half-Space Contact Model and the Fatigue Life Estimation According to the Fatemi–Socie Model
by Flavien Foko Foko, Lukas Rüth, Oliver Koch and Bernd Sauer
Lubricants 2023, 11(3), 133; https://doi.org/10.3390/lubricants11030133 - 13 Mar 2023
Cited by 2 | Viewed by 1445
Abstract
A multiscale approach for the fatigue life estimation of rolling bearings is presented in this paper and applied to inner rings of cylindrical roller bearings of the type NU208. The forces acting in the rolling contact are determined from system-oriented modeling at the [...] Read more.
A multiscale approach for the fatigue life estimation of rolling bearings is presented in this paper and applied to inner rings of cylindrical roller bearings of the type NU208. The forces acting in the rolling contact are determined from system-oriented modeling at the macro level. The microscale contact simulations are carried out in a half-space contact model. The stresses on the inner ring are determined and used in the local fatigue approach, according to Fatemi–Socie, for fatigue life estimation. Four surface variants were investigated, one ideally smooth surface and three real (rough) surfaces. The three rough surface variants used different finishing processes: fine ground, hard turned, and rough ground were produced. A load case with a maximum pressure of 2.4 GPa in the roller-inner ring contact was investigated. In addition to the fatigue life estimation, the plasticity behavior (surface topography, resulting contact pressure, and residual stress) of the three manufactured surfaces stood in the focus of the work. As the comparison between experimental and simulated results confirms, good predictions can be made with the simulation model. Full article
(This article belongs to the Special Issue Tribological Studies of Roller Bearings)
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Graphical abstract

18 pages, 4906 KiB  
Article
Influence of Tribolayer on Rolling Bearing Fatigue Performed on an FE8 Test Rig—A Follow-up
by Joerg W. H. Franke, Janine Fritz, Thomas Koenig and Daniel Merk
Lubricants 2023, 11(3), 123; https://doi.org/10.3390/lubricants11030123 - 09 Mar 2023
Cited by 1 | Viewed by 2085
Abstract
The tribological contact between raceways and rolling elements is essential for rolling bearing performance and lifetime. The geometrical description of these contacts is well known and can be used in several mechanical simulation tools. The material description, especially of the near-surface volume after [...] Read more.
The tribological contact between raceways and rolling elements is essential for rolling bearing performance and lifetime. The geometrical description of these contacts is well known and can be used in several mechanical simulation tools. The material description, especially of the near-surface volume after interaction with lubricants, is not as simple. In particular, the Schaeffler FE8-25 test with cylindrical roller thrust bearings exhibits different failure modes depending on the lubricant chemistry. The main failure mechanisms of this test are sub-surface fatigue damage due to WECs (White Etching Cracks) and/or surface-induced fatigue damage (SIF). The harsh test conditions with mixed friction at high speeds and multiple slip conditions over the raceway width additionally provides different tribological conditions on a small area. This leads finally to the formation of certain tribological layers on the raceway because of the interaction of the surface with the lubricant chemistry under local frictional energies, which are worth investigating. The characterization of the layers was performed by the two less time-consuming, spatially resolved analysis methods of µXRF and ATR FTIR microscopy adapted by Schaeffler. This paper shows the results of this research and offers new approaches to optimizing rolling bearing testing and predicting the risk of early failures. Full article
(This article belongs to the Special Issue Tribological Studies of Roller Bearings)
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27 pages, 37363 KiB  
Article
Experimental Investigations on Wear in Oscillating Grease-Lubricated Rolling Element Bearings of Different Size and Type
by Gernot Bayer, Arne Bartschat, Sebastian Wandel, Sebastian Baust and Gerhard Poll
Lubricants 2023, 11(3), 120; https://doi.org/10.3390/lubricants11030120 - 08 Mar 2023
Cited by 5 | Viewed by 1457
Abstract
Grease-lubricated rolling element bearings can suffer from wear due to lubricant starvation under certain oscillating operating conditions. Especially for large-scale slewing bearings, such as blade bearings in wind turbines, experimental investigations are complex compared to small-scale reference testing. For an easier manner of [...] Read more.
Grease-lubricated rolling element bearings can suffer from wear due to lubricant starvation under certain oscillating operating conditions. Especially for large-scale slewing bearings, such as blade bearings in wind turbines, experimental investigations are complex compared to small-scale reference testing. For an easier manner of testing, it is desirable to know whether the results of small-scale testing are applicable to larger-sized bearings. In this work, three different bearing types were tested and compared to already published results from a small-scale ACBB with a pitch diameter of 60 mm. The newly tested bearing types comprise a downscaled blade bearing (4-point contact double row ball bearing) with a pitch diameter of 673 mm, a small-scale CRTB with a pitch diameter of 77.5 mm and another ACBB with a pitch diameter of 95 mm. Qualitatively, all tested bearings show similar wear behaviour in terms of friction energy when operation parameters are varied. With higher oscillation frequency, damage becomes more severe. The oscillation amplitude shows three distinctive regimes. Within the range of small amplitudes, an increase in amplitude leads to more pronounced damage. We observe a threshold amplitude where this is no longer the case; a further increase in amplitude counteracts wear initiation until a final threshold is reached, beyond which no more wear is observed. These findings are in accordance with the reference results of the small-scale ACBB. Direct comparison between point and line contact shows that the latter is more prone to wear initiation under grease-lubricated, oscillating operating conditions. Furthermore, a previously introduced empirical number shows good performance in assessing critical operating parameters of the different bearing types. Specifically, harmful operating conditions can be classified for all studied bearing types with an accuracy of 78%. This method can be useful to assess operating conditions of greased, oscillating, rolling element bearings, e.g., to assess different pitch controllers or designs of slewing bearings. Full article
(This article belongs to the Special Issue Tribological Studies of Roller Bearings)
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21 pages, 64954 KiB  
Article
Wear Development in Oscillating Rolling Element Bearings
by Sebastian Wandel, Arne Bartschat, Jakob Glodowski, Norbert Bader and Gerhard Poll
Lubricants 2023, 11(3), 117; https://doi.org/10.3390/lubricants11030117 - 07 Mar 2023
Cited by 4 | Viewed by 2053
Abstract
Rotor blade bearings enable rotor blades to pivot about their longitudinal axis and thus control the power output and reduce the loads acting on the wind turbine. Over a design period of 20 years, rolling bearings are exposed to frequent oscillation movements with [...] Read more.
Rotor blade bearings enable rotor blades to pivot about their longitudinal axis and thus control the power output and reduce the loads acting on the wind turbine. Over a design period of 20 years, rolling bearings are exposed to frequent oscillation movements with amplitude ratios of x/2b > 1, especially due to new control concepts such as Individual Pitch Control, which can lead to wear and a reduction in service life. The objective of this paper was to identify the dominant wear mechanisms and their consequences for the operation of oscillating bearings. Oscillating experiments with an increasing number of cycles on the angular contact ball bearings of two different sizes (types 7208 and 7220) show that the damage initiation starts with adhesive and corrosive wear mechanisms, which result in a sharp increase in the torque as well as the wear volume on the bearing raceway. As the number of cycles increases, an abrasive mechanism occurs, resulting in a lower slope of the wear curve and a smoothing of the resulting wear depressions. The wear and torque curves were evaluated and classified using an energy-wear approach according to Fouvry. Full article
(This article belongs to the Special Issue Tribological Studies of Roller Bearings)
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