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Lubricants
Special Issues
Sustainable Elastohydrodynamic Lubrication
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Sustainable Elastohydrodynamic Lubrication

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

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 14165

Special Issue Editors

Dr. Thomas Lohner

E-Mail Website
Guest Editor
Gear Research Center (FZG), Technical University of Munich, Boltzmannstraße 15, D-85748 Garching near Munich, Germany
Interests: transmissions; gears; efficiency; heat balance; tribology; elastohydrodynamics; lubrication; friction
Prof. Dr. Roland Larsson

E-Mail Website
Guest Editor
Division of Machine Elements, Luleå University of Technology, 97187 Luleå, Sweden
Interests: roughness effects in EHL; green lubricants; running-in; friction; failure mechanisms in EHL; lubrication quality; condition monitoring

Special Issue Information

Dear Colleagues,

Making our living sustainable is a global challenge. It is addressed by the 17 Sustainable Development Goals of the United Nations. Tribology, as a multi-disciplinary science of interacting surfaces in relative motion, offers a variety of approaches for sustainable industrial applications with a great impact on energy saving and carbon footprint reduction.

Elastohydrodynamic lubrication (EHL) is characterized by the back-coupling between hydrodynamics and the elastic deformation of surfaces in motion. Many technical applications and machine elements such as gears and bearings include EHL contacts, from soft to hard and non-conformal to conformal. EHL contacts provide an important lever for significantly improving the sustainability of technical applications.

As approximately one-fifth of the world’s total energy consumption is used to overcome friction, reducing EHL friction has a large impact. Superlubricity with coefficients of friction smaller than 0.01 can be achieved by, for example, aqueous lubricants and glycerol. Tribological coatings can be an enabler for superlubricity. Reduced EHL friction lowers thermal energy dissipation and therefore the amount of lubricant required for heat removal. This makes it possible to further improve sustainability by on-demand oil supply, for example, addressed by minimum quantity, droplet-on-demand, and self-lubrication. Sustainable EHL technologies also includes appropriate tribosystem elements such as eco-friendly lubricants and bulk materials. Surface quality is a key aspect in EHL. The sustainable manufacturing of components and surfaces will provide the required surface finish qualities as quickly and simply as possible.

This Special Issue addresses all studies on EHL linked to sustainability. Contributions are welcome from all scientists working in tribology and related areas.

Dr. Thomas Lohner
Prof. Dr. Roland Larsson
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

  • elastohydrodynamic lubrication
  • sustainability
  • green lubrication
  • friction reduction
  • liquid superlubricity
  • ecofriendly lubricants
  • aqueous lubricants
  • on-demand oil supply
  • minimum quantity lubrication
  • self-lubrication
  • ecofriendly materials
  • coatings
  • surface finish

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Published Papers (6 papers)

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Research

21 pages, 8638 KiB  
Article
Coated Piston Ring Pack and Cylinder Liner Elastodynamics in Correlation to Piston Subsystem Elastohydrodynamic: Through FEA Modelling
by Prakash Chandra Mishra, Arka Roychoudhury, Ayan Banerjee, Nutan Saha, Sudhansu Ranjan Das and Anshuman Das
Lubricants 2023, 11(5), 192; https://doi.org/10.3390/lubricants11050192 - 27 Apr 2023
Cited by 4 | Viewed by 2552
Abstract
A finite element model is developed to assess the effects of the TiSiCN thin film coating of the piston ring on the structural strength of the piston subsystem. The complex, cyclically variable forces are considered in load and boundary conditions. The model included [...] Read more.
A finite element model is developed to assess the effects of the TiSiCN thin film coating of the piston ring on the structural strength of the piston subsystem. The complex, cyclically variable forces are considered in load and boundary conditions. The model included combustion dynamics, contact kinetics, piston subsystem primary and secondary motions, and lubricated contact conditions to evaluate the applied forces. A comparative analysis is performed for coated and uncoated cases. Four different crown geometries are tried for selecting the best case of crown design for coated piston subsystem components. The analysis predicts better strength in coated cases compared to uncoated ones. The type-A crown design develops less stress, while the compression ring suffers the most due to elastic deformation and is more prone to fatigue failure. Full article
(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)
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13 pages, 2032 KiB  
Article
A Computational Study on the Role of Lubricants under Boundary Lubrication
by Walter Holweger, Luigi Bobbio, Zhuoqiong Mo, Jörg Fliege, Bernd Goerlach and Barbara Simon
Lubricants 2023, 11(2), 80; https://doi.org/10.3390/lubricants11020080 - 13 Feb 2023
Cited by 4 | Viewed by 1619
Abstract
The knowledge of how lubricants contribute to the operational life of a drive train is unclear until now, despite the fact that plenty of literature is available. A novel concept is presented in order to estimate the wear appearing in bearings addressed to [...] Read more.
The knowledge of how lubricants contribute to the operational life of a drive train is unclear until now, despite the fact that plenty of literature is available. A novel concept is presented in order to estimate the wear appearing in bearings addressed to the regime of mixed friction with respect to the composition and the so-called “inner” structure of the lubricant. In doing so, the composition is turned into a set of predictors describing the dipolar and inducible dipolar properties of all components as an activity amongst them and toward the surface. The results show that the activity of the solvated specie apparent, stated as the “inner” structure of the lubricant, is closely related to the surface activity and the expected wear. The technique presented here allows a fast computational procedure such that a given lubricant, once known by its constituents, could be explored with respect to the expected wear. Reducing time-consuming tests is desirable by the fact that new materials are forthcoming as a consequence of regulations and evolving green technology. Full article
(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)
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28 pages, 6659 KiB  
Article
Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part I: The Full-Film Condition
by Yuechang Wang, Changlin Li, Jianjun Du and Ardian Morina
Lubricants 2022, 10(12), 368; https://doi.org/10.3390/lubricants10120368 - 18 Dec 2022
Cited by 3 | Viewed by 1985
Abstract
Understanding the responses of tribosystems to multiscale roughness is fundamental for the identification of the relevant roughness scales. This work used a point-contact elastohydrodynamic lubrication (EHL) problem as a representative tribosystem and artificially generated waviness with different amplitudes, frequencies, and directions to mimic [...] Read more.
Understanding the responses of tribosystems to multiscale roughness is fundamental for the identification of the relevant roughness scales. This work used a point-contact elastohydrodynamic lubrication (EHL) problem as a representative tribosystem and artificially generated waviness with different amplitudes, frequencies, and directions to mimic the multiscale roughness. The amplitudes and frequencies are related to the feature geometry of smooth EHL problems. This work consists of Part I (this paper), focusing on the full-film condition, and Part II, focusing on the partial-film condition. Generated waviness is input to a transient thermal EHL model. The simulation is conducted 1600 times for different waviness parameters, loads, and speeds. Seven performance parameters are extracted: the minimum film thickness, maximum pressure, central film thickness, central pressure, mean film thickness, coefficient of friction (COF), and maximum temperature rise. The ratios of these parameters with and without waviness are plotted on the frequency–amplitude coordinate plane as contour maps. The influences of the amplitude, frequency, wave direction, load, and speed on the seven performance parameters are analyzed and summarized. The simulated data and plotted contour maps are provided to the readers in the Supplementary Material. Full article
(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)
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22 pages, 4834 KiB  
Article
Piston Compression Ring Elastodynamics and Ring–Liner Elastohydrodynamic Lubrication Correlation Analysis
by Swagatika Biswal and Prakash Chandra Mishra
Lubricants 2022, 10(12), 356; https://doi.org/10.3390/lubricants10120356 - 9 Dec 2022
Cited by 1 | Viewed by 2000
Abstract
Friction loss in an internal combustion engine largely depends on elastohydrodynamic lubrication. The piston compression ring is a contributor to such parasitic losses in the piston subsystem. The complex elastodynamics of the ring are responsible for the transient and regime-altering film that affects [...] Read more.
Friction loss in an internal combustion engine largely depends on elastohydrodynamic lubrication. The piston compression ring is a contributor to such parasitic losses in the piston subsystem. The complex elastodynamics of the ring are responsible for the transient and regime-altering film that affects the elastohydrodynamic lubrication of the ring liner contact conjunction. The current paper will discuss the ring radial, lateral deformation, and axial twist, and its effect on the film profile of the compression ring and its subsequent effect on tribological characteristics like elastohydrodynamic pressure, friction, and lubricant. A finite difference technique is used to solve the elastohydrodynamic issue of elastodynamic piston compression by introducing the elastodynamically influenced film thickness into the lubrication model. The results show that consideration of the elastodynamics predicts a 23.53% reduction in friction power loss in the power stroke due to the elastodynamic ring compared to the rigid ring. The elastodynamic effect improves the lubricant oil flow into the conjunction. A finite element simulation predicts a von-Mises stress of 0.414 N/mm2, and a maximum deformation of 0.513 µm at the core and coating interface is observed at the ring–ring groove contact. The sustainability of EHL in this case largely depends on the ring–liner elastodynamics. Full article
(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)
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10 pages, 1954 KiB  
Article
A Traction (Friction) Curve Is Not a Flow Curve
by Scott Bair
Lubricants 2022, 10(9), 221; https://doi.org/10.3390/lubricants10090221 - 12 Sep 2022
Cited by 9 | Viewed by 2432
Abstract
With the uncertainty regarding the global energy future, the ability to lubricate concentrated contacts with sufficiently thick liquid films while minimizing friction is of extreme importance. The assumptions of classical elastohydrodynamic lubrication have remained unchanged since the early days. It has not been [...] Read more.
With the uncertainty regarding the global energy future, the ability to lubricate concentrated contacts with sufficiently thick liquid films while minimizing friction is of extreme importance. The assumptions of classical elastohydrodynamic lubrication have remained unchanged since the early days. It has not been possible to test many of these assumptions without the measurement of the viscosity at elastohydrodynamic lubrication (EHL) pressures, and viscometer measurements have been ignored. One of these assumptions has been the equivalence of a traction curve to a rheological flow curve for the lubricant. This notion should have been discarded forty years ago, simply because it required the pressure–viscosity behavior to be unlike the behavior observed in viscometers. At the heart of the problem is the fact that the pressure within the EHL contact is not homogeneous and the liquid properties are highly dependent on pressure, making the contact a very poor rheology laboratory. These past failures must be avoided in the future. Full article
(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)
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21 pages, 9626 KiB  
Article
CFD Investigation of Reynolds Flow around a Solid Obstacle
by Ruchita Patel, Zulfiqar Ahmad Khan, Adil Saeed and Vasilios Bakolas
Lubricants 2022, 10(7), 150; https://doi.org/10.3390/lubricants10070150 - 11 Jul 2022
Cited by 1 | Viewed by 2706
Abstract
The Reynolds equation defines the lubrication flow between the smooth contacting parts. However, it is questionable that the equation can accurately anticipate pressure behavior involving undeformed solid asperity interactions that can occur under severe operating conditions. Perhaps, the mathematical model is inaccurate and [...] Read more.
The Reynolds equation defines the lubrication flow between the smooth contacting parts. However, it is questionable that the equation can accurately anticipate pressure behavior involving undeformed solid asperity interactions that can occur under severe operating conditions. Perhaps, the mathematical model is inaccurate and incomplete, or some HL (hydrodynamic lubrication) and EHL (elastohydrodynamic lubrication) assumptions are invalid in the mixed lubrication region. In addition, the asperity contact boundary conditions may not have been properly defined to address the issue. Such a situation motivated the recent study of a 3D CFD investigation of Reynolds flow around the solid obstacle modelled in between the converging wedge. The produced results have been compared to analytical and numerical results obtained by employing the Reynolds equation. The validated CFD simulation is compared with the identical wedge, with cylindrical asperity at the center. A significant increase in pressure has been predicted because of asperity contact. The current study shows that the mathematical formulation of the ML problem has shortcomings. This necessitates the development of a new model that can also include fluid flow around asperity contacts for the accurate prediction of generated pressure. Consequently, sustainable tribological solutions for extreme loading conditions can be devised to improve efficiency and component performance. Full article
(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)
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