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Lubricants
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Selected Papers from the 8th Conference on Lubrication, Maintenance and...
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Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT)

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

Deadline for manuscript submissions: closed (31 October 2024) | Viewed by 9286

Special Issue Editors

Prof. Dr. Ian Sherrington

E-Mail Website
Guest Editor
Jost Institute for Tribotechnology, University of Central Lancashire, Preston, UK
Interests: piston ring seals; seal lubrication; coatings
Dr. Patricia Johns-Rahnejat

E-Mail Website
Guest Editor
The School of Engineering, University of Central Lancashire, Preston PR1 2HE, Lancashire, UK
Interests: tribology; elastohydrodynamics; contact mechanics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

LUBMAT 2023 was held on 17–19 July 2023 in the Engineering Innovation Centre (EIC) located in the Preston Campus of the University of Central Lancashire. The conference included plenary presentations from key experts, followed by parallel sessions, as well as an exhibition. It provided an academic/industry interface to discuss lubrication, maintenance and tribotechnology. There was a strong international presence with many contributions in tribology/lubrication of a host of engineering applications. Additionally, the exhibition space was filled with industrial/scientific companies, demonstrating the latest state-of-the-art technologies. MDPI sponsored this event, as well as having an exhibition stand with some selective publications, particularly Lubricants. 

The Organising Committee selected a number of presented papers from this event which form the basis of this Special Issue. 

Prof. Dr. Ian Sherrington
Dr. Patricia Johns-Rahnejat
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

  • tribology
  • lubrication
  • wear
  • contact mechanics
  • maintenance

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Published Papers (6 papers)

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Research

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17 pages, 3996 KiB  
Article
Elastic and Elastoplastic Contact Mechanics of Concentrated Coated Contacts
by Patricia M. Johns-Rahnejat, Nader Dolatabadi and Homer Rahnejat
Lubricants 2024, 12(5), 162; https://doi.org/10.3390/lubricants12050162 - 7 May 2024
Cited by 2 | Viewed by 1526
Abstract
Machines operate under increasingly harsher contact conditions, causing significant wear and contact fatigue. Sub-surface stresses are responsible for the premature contact fatigue of rolling element bearings, meshing gears, and cam–follower pairs. Surface protection measures include hard, wear-resistant coatings. Traditionally, contact integrity has been [...] Read more.
Machines operate under increasingly harsher contact conditions, causing significant wear and contact fatigue. Sub-surface stresses are responsible for the premature contact fatigue of rolling element bearings, meshing gears, and cam–follower pairs. Surface protection measures include hard, wear-resistant coatings. Traditionally, contact integrity has been predicted using classical Hertzian contact mechanics. However, the theory is only applicable when the contact between a pair of ellipsoidal solids of revolution may be considered as a rigid indenter penetrating a semi-infinite elastic half-space. Many coatings act as thin bonded elastic layers that undergo considerably higher pressures than those predicted by the classical theory. Furthermore, inelastic deformation of bonded solids can cause plastic flow, work-hardening, and elastoplastic behaviour. This paper presents a comprehensive, integrated contact mechanics analysis that includes induced sub-surface stresses in concentrated counterformal finite line contacts for all the aforementioned cases. Generated pressures and deformation are predicted for hard coated surfaces, for which there is a dearth of relevant analysis. The contact characteristics, which are of particular practical significance, of many hard, wear-resistant advanced coatings are also studied. The paper clearly demonstrates the importance of using efficient semi-analytical, detailed holistic contact mechanics rather than the classical idealised methods or empirical numerical ones such as FEA. The novel approach presented for the finite line contact of thin-layered bonded solids has not hitherto been reported in the open literature. Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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15 pages, 1658 KiB  
Article
The Environmental and Economic Importance of Mixed and Boundary Friction
by Robert Ian Taylor and Ian Sherrington
Lubricants 2024, 12(5), 152; https://doi.org/10.3390/lubricants12050152 - 28 Apr 2024
Cited by 1 | Viewed by 1208
Abstract
One route to reducing global CO2 emissions is to improve the energy efficiency of machines. Even small improvements in efficiency can be valuable, especially in cases where an efficiency improvement can be realized over many millions of newly produced machines. For example, [...] Read more.
One route to reducing global CO2 emissions is to improve the energy efficiency of machines. Even small improvements in efficiency can be valuable, especially in cases where an efficiency improvement can be realized over many millions of newly produced machines. For example, conventional passenger car combustion engines are being downsized (and also downspeeded). Increasingly, they are running on lower-viscosity engine lubricants (such as SAE 0W-20 or lower viscosity grades) and often also have stop–start systems fitted (to prevent engine idling when the vehicle is stopped). Some of these changes result in higher levels of mixed and boundary friction, and so accurate estimation of mixed/boundary friction losses is becoming of increased importance, for both estimating friction losses and wear volumes. Traditional approaches to estimating mixed/boundary friction, which employ real area of contact modelling, and assumptions such as the elastic deformation of asperities, are widely used, but recent experimental data suggest that some of these approaches underestimate mixed/boundary friction losses. In this paper, a discussion of the issues involved in reliably estimating mixed/boundary friction losses in machine elements is undertaken, highlighting where the key uncertainties lie. Mixed/boundary lubrication losses in passenger car and heavy-duty internal combustion engines are then estimated and compared with published data, and a detailed description of how friction is related to fuel consumption in these vehicles, on standard fuel economy driving cycles, is given. Knowing the amount of fuel needed to overcome mixed/boundary friction in these vehicles enables reliable estimates to be made of both the financial costs of mixed/boundary lubrication for today’s vehicles and their associated CO2 emissions, and annual estimates are reported to be approximately USD 290 billion with CO2 emissions of 480 million tonnes. Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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13 pages, 2009 KiB  
Article
The Effect of Ethanol Fuel-Diluted Lubricants on the Friction of Oil Control Ring Conjunction: A Combined Analytical and Experimental Investigation
by Nicholas Morris, Sean Byrne, Michael Forder, Nader Dolatabadi, Paul King, Ramin Rahmani, Homer Rahnejat and Sebastian Howell-Smith
Lubricants 2024, 12(5), 150; https://doi.org/10.3390/lubricants12050150 - 27 Apr 2024
Viewed by 1015
Abstract
This paper presents an investigation of the frictional behaviour of three-piece piston oil control rings. A bespoke tribometer replicates the kinematics of the contact between a full oil control ring and the cylinder liner. The three-piece oil control ring is composed of two [...] Read more.
This paper presents an investigation of the frictional behaviour of three-piece piston oil control rings. A bespoke tribometer replicates the kinematics of the contact between a full oil control ring and the cylinder liner. The three-piece oil control ring is composed of two segments, separated by a waveform-type expander. The experimental results indicate the dominance of a mixed regime of lubrication throughout the stroke. This is particularly the case when the experiments are conducted at 80 °C, a typical engine sump temperature, when compared with those at 20 °C (a typical engine start-up temperature in the UK in the summer). A mixed hydrodynamic analytical model of the oil control ring–cylinder liner tribological interface is employed to apportion frictional contributions with their physical underlying mechanisms. Therefore, combined numerical and experimental investigations are extended to lubricant contamination/dilution by ethanol-based fuels. This study shows that the transition from E10 to E85 would have an insignificant effect on the friction generated in the oil control ring conjunction. This holistic approach, using a detailed predictive l mixed regime of lubrication model and a representative bespoke tribometry, has not hitherto been reported in the open literature. Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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14 pages, 5646 KiB  
Article
The Effects of the Lubricant Properties and Surface Finish Characteristics on the Tribology of High-Speed Gears for EV Transmissions
by Boris Zhmud, Morteza Najjari and Boris Brodmann
Lubricants 2024, 12(4), 112; https://doi.org/10.3390/lubricants12040112 - 29 Mar 2024
Cited by 2 | Viewed by 1538
Abstract
Electric vehicle (EV) transmissions operate at high speeds. High-speed operation puts higher demands on bearings, seals, and gears. Bearings in EV transmissions are prone to electrically induced bearing damage and may exhibit signs of pitting and fluting. Surface-initiated rolling contact fatigue is another [...] Read more.
Electric vehicle (EV) transmissions operate at high speeds. High-speed operation puts higher demands on bearings, seals, and gears. Bearings in EV transmissions are prone to electrically induced bearing damage and may exhibit signs of pitting and fluting. Surface-initiated rolling contact fatigue is another common problem gaining increased attention lately. Most EV transmissions require a coupling between an oil-lubricated gearbox to an electrical motor that runs with minimal lubrication at very high rpm. The high mechanical and thermal stresses the seals are exposed to under starved lubrication conditions have a detrimental impact on their service life. Hence, proper lubrication is critical. In general, EV transmission fluids call for a somewhat different spectrum of properties compared to conventional ATFs. Gear tribology simulations open new ways to the design and optimization of lubrication for EV transmissions. Additionally, such simulations can also provide valuable insights into the effects of different oil properties on cooling and lubrication efficiencies, thereby helping in matching the lubricant and hardware characteristics for optimal performance. In the present communication, we demonstrate the effects of different lubricants and surface finishing technologies on the tribology of high-speed gears using tribological tests and advanced thermal elastohydrodynamic (TEHD) simulations. The important roles of lubricity additives and surface finish optimization are highlighted in conjunction with a move towards ultralow viscosity EV transmission fluids. Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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20 pages, 9505 KiB  
Article
Dynamic Effect Analysis of Cryogenic Solid-Lubricated Ball Bearings with Geometrical-Frictional Defects
by Yuhao Zhao, Zhenyi Chen, Yanyang Zi, Mingquan Zhang and Tao Tang
Lubricants 2024, 12(3), 84; https://doi.org/10.3390/lubricants12030084 - 6 Mar 2024
Viewed by 1449
Abstract
The traction behavior in cryogenic solid-lubricated ball bearings (CSLBBs) of liquid rocket engines (LREs) has a significant effect on the dynamic response of the bearing–rotor system. To reveal the fault mechanism of CSLBBs, a tribo-dynamic model is proposed in this paper that considers [...] Read more.
The traction behavior in cryogenic solid-lubricated ball bearings (CSLBBs) of liquid rocket engines (LREs) has a significant effect on the dynamic response of the bearing–rotor system. To reveal the fault mechanism of CSLBBs, a tribo-dynamic model is proposed in this paper that considers the solid-lubricated traction, six-DOF motion of the ball and contact collisions between the ball and the cage. The modified traction model uses fan-shaped and arched sections to discretize the contact area to eliminate the meshing error. The newly developed fault model, called ‘geometrical-frictional defects’, can more realistically represent solid-lubrication coating defects. The results show that the frictional excitation can significantly increase bearing vibration by increasing the traction force on the raceway. The change in the amplitude of the bearing vibration and its derivative can be used as a reference to determine the depth of defects. The width of the defect can be diagnosed by monitoring the double-pulse time interval and spectrum of the bearing vibration signal. This research may provide some theoretical guidance for the design and condition monitoring of CSLBBs. Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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Review

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9 pages, 674 KiB  
Review
The Invention of Tribology: Peter Jost’s Contribution
by John Williams
Lubricants 2024, 12(3), 65; https://doi.org/10.3390/lubricants12030065 - 21 Feb 2024
Viewed by 1997
Abstract
Peter Jost is known to the international tribology community as the father of the subject—‘the man who made the world spin a little easier’. He was the author of the eponymous ‘Jost Report’, the report of the Working Group set up [...] Read more.
Peter Jost is known to the international tribology community as the father of the subject—‘the man who made the world spin a little easier’. He was the author of the eponymous ‘Jost Report’, the report of the Working Group set up in 1964 to investigate the state of lubrication education and research in the UK. Over the following five decades, up to his death in 2016, he was tireless in extolling the importance of tribology to manufacturing efficiency, energy conversion and environmental sustainability. He was instrumental in establishing the International Tribology Council and its prestigious gold, silver and bronze medals. Jost was himself the recipient of numerous national and international awards. In 1976, he was the President of the Institution of Production Engineers, and in 2013, he received the Sustained Achievement Award from the Royal Academy of Engineering. What is less well known is the story behind the Jost report—what was it that led the recently elected Labour government and its newly established Ministry of Technology to investigate lubrication and to choose Jost to lead the investigating panel? The story illustrates the combination of serendipity and determination on which success can so often depend. Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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