Friction Reduction at Interfaces

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

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 16790

Special Issue Editor

Prof. Tomoko Hirayama
E-Mail
Guest Editor
Department of Mechanical Science and Engineering, Kyoto UniversityAddress: Katsura, Nishikyo-ku, Kyoto 615-8540, Japan
Interests: hydrodynamic lubrication; elastohydrodynamic lubrication; dynamic characteristics/instability/rotor dynamics; mixed lubrication/transition of lubrication regimes; boundary lubrication mechanism; tribochemistry; adsorption/adsorbed film; surface texturing; hydrostatic bearings, gas/air bearings

Special Issue Information

Dear Colleagues,

“Interface” is where friction originates, so it greatly affects the tribological properties of the target surface, especially under boundary lubricated conditions. In order to optimize the interfacial structure to achieve excellent tribological properties, many analytical approaches have been used to clarify the physical and chemical phenomena that occur at the interface. The condensation of oil molecules, additive adsorption, tribofilm formation, and atomic structuration of materials are typical phenomena—"Interface” is quite complex, and many researchers have become fascinated with investigating it.

This Special Issue focuses on the latest advances and future trends in the study of interface friction reduction. Paper submissions are highly welcome, regardless of whether you are an academic researcher or an industrial engineer. Our aim is to produce a Special Issue that promotes an open-minded discussion of the new approaches and challenges that reveal valuable clues that all tribologists can utilize in order to further reduce friction.

Prof. Tomoko Hirayama
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.

Keywords

  • Interfacial structure
  • Friction reduction
  • Sliding surface
  • Additive adsorption
  • Tribofilm formation
  • Atomic structuration of materials

Published Papers (5 papers)

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Research

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15 pages, 4655 KiB  
Article
Friction and Temperature Behavior of Lubricated Thermoplastic Polymer Contacts
Lubricants 2020, 8(6), 67; https://doi.org/10.3390/lubricants8060067 - 24 Jun 2020
Cited by 10 | Viewed by 3971
Abstract
This work focuses on the friction and temperature behavior of thermo-elastohydrodynamically lubricated (TEHL) contacts under rolling-sliding conditions. For this purpose, a twin-disk test rig is used with a hybrid setup of plain and fiber-reinforced polyamide (PA) 66 and polyetheretherketone (PEEK) disks paired with [...] Read more.
This work focuses on the friction and temperature behavior of thermo-elastohydrodynamically lubricated (TEHL) contacts under rolling-sliding conditions. For this purpose, a twin-disk test rig is used with a hybrid setup of plain and fiber-reinforced polyamide (PA) 66 and polyetheretherketone (PEEK) disks paired with case-hardened steel disks and three different lubricants. Experimental investigations include various lubrication regimes by varying sum velocity and oil temperature as well as load and slip ratio. The measured friction in thermoplastic TEHL contacts is particularly very low in the area of high fluid load portion, which refers to the large deformation of the compliant polymer surface. Newtonian flow behavior mainly determines fluid friction. The low thermal effusivity of polymers insulates the contact and can further reduce the effective lubricant viscosity, and thus the fluid friction. For low sum velocities, solid friction influences the tribological behavior depending on the solid load portion. Although the interfacial contact friction is comparably small, material damping strongly contributes to power losses and increases bulk temperature, which in turn affects the TEHL contact. Thus, loading frequency and the resulting bulk temperature are identified as one of the main drivers of power losses and tribological behavior of lubricated thermoplastic polymer contacts. Full article
(This article belongs to the Special Issue Friction Reduction at Interfaces)
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18 pages, 6235 KiB  
Article
Study on the Quantitative Evaluation of the Surface Force Using a Scanning Probe Microscope
Lubricants 2020, 8(6), 66; https://doi.org/10.3390/lubricants8060066 - 17 Jun 2020
Viewed by 2359
Abstract
There are two types of friction modifiers (FMs) used as lubricant additives: Reaction film FMs (RF-FMs) and adsorption film FMs (AF-FMs). While RF-FMs provide good performance in severe conditions, AF-FMs excel in mild conditions. This empirical evidence leads us to combine these two [...] Read more.
There are two types of friction modifiers (FMs) used as lubricant additives: Reaction film FMs (RF-FMs) and adsorption film FMs (AF-FMs). While RF-FMs provide good performance in severe conditions, AF-FMs excel in mild conditions. This empirical evidence leads us to combine these two FMs to cover broader conditions. However, the effects of their combination are highly complicated due to the interaction between these FMs. If the interaction force of AF-FMs with various materials can be evaluated, it would help us to improve tribological performances of lubricants. Although atomic force microscopy seems suitable for this application, we found some obstacles, such as fluid resistance, electrostatic force, and laser positioning of the cantilever, to achieve proper measurements of the adsorption force. In this study, the adsorption force between the polar group and the surface was directly measured in oil with a 1 µm silica probe modified with CH3 or COOH. This paper proposed how to eliminate errors included in the adsorption force measurement using AFM and a calibration method for obtaining an accurate adsorption force of the polar group, and a test of normality of the measured data was conducted by 400 measurements. As a result, it was shown that approximately 100 tests were needed to obtain an accurate adsorption force in this study. Full article
(This article belongs to the Special Issue Friction Reduction at Interfaces)
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15 pages, 4506 KiB  
Article
“Green” Synthesis of Nanocarbons for Reduced Friction and Wear
Lubricants 2020, 8(2), 13; https://doi.org/10.3390/lubricants8020013 - 02 Feb 2020
Cited by 4 | Viewed by 2358
Abstract
In the following study, green carbon nanotubes and green few-layer reduced graphene oxide (rGO) were synthesized through simple, sustainable, and scalable processes starting from recycled plastic and charcoal, respectively, and with the highest number of steps involving non-harmful substances. After an extensive physicochemical [...] Read more.
In the following study, green carbon nanotubes and green few-layer reduced graphene oxide (rGO) were synthesized through simple, sustainable, and scalable processes starting from recycled plastic and charcoal, respectively, and with the highest number of steps involving non-harmful substances. After an extensive physicochemical characterization, which evidenced that both nano-carbons exhibit structures comparable with that of materials produced through more traditional methods and from pure sources, the samples were dispersed in two types of conventional base oils, in particular group I and group III, in order to carry out, for the first time on these green nanomaterials, an accurate study on their tribological performance. Tribological tests evidenced a remarkable reduction of coefficient of friction and wear scar diameter, especially for the green rGO dispersed at 0.1 wt% in the group III oil along with SDBS-Tween 80 surfactants mixture: 18% and 15% at ambient temperature, 12% and 13% at 80 °C, respectively. Furthermore, the tribological performance of the synthesized samples in both oils remained high for 160 min of investigation. A comparison with the same material obtained with a traditional synthesis revealed the absence of fouling phenomena in the lubrication chambers in our case, confirming the higher tribological performances of the green rGO sample, probably, as a consequence of its less ordered nature. Full article
(This article belongs to the Special Issue Friction Reduction at Interfaces)
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Review

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20 pages, 3260 KiB  
Review
Tribochemistry as an Alternative Synthesis Pathway
Lubricants 2020, 8(9), 87; https://doi.org/10.3390/lubricants8090087 - 29 Aug 2020
Cited by 19 | Viewed by 4242
Abstract
While reactions driven by mechanical force or stress can be labeled mechanochemical, those specifically occurring at a sliding interface inherit the name tribochemical, which stems from the study of friction and wear: tribology. Increased perception of tribochemical reactions has been gained through technological [...] Read more.
While reactions driven by mechanical force or stress can be labeled mechanochemical, those specifically occurring at a sliding interface inherit the name tribochemical, which stems from the study of friction and wear: tribology. Increased perception of tribochemical reactions has been gained through technological advancement, and the development of new applications remains on-going. This surprising physico-kinetic process offers great potential in novel reaction pathways for synthesis techniques and nanoparticle interactions, and it could prove to be a powerful cross-disciplinary research area among chemists, engineers, and physicists. In this review article, a survey of the history and recent usage of tribochemical reaction pathways is presented, with a focus on forging new compounds and materials with this sustainable synthesis methodology. In addition, an overview of tribochemistry’s current utility as a synthesis pathway is given and compared to that of traditional mechanochemistry. Full article
(This article belongs to the Special Issue Friction Reduction at Interfaces)
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14 pages, 2702 KiB  
Review
Tribochemistry and Lubrication of Alkaline Glass Lubricants in Hot Steel Manufacturing
Lubricants 2020, 8(7), 70; https://doi.org/10.3390/lubricants8070070 - 30 Jun 2020
Cited by 7 | Viewed by 3440
Abstract
Nowadays, the increasing demand to reduce energy consumption and improve process reliability requires an alternative lubricant with an effective tribological performance and environmentally friendly properties to replace traditional lubricants in hot steel manufacturing. The current work reviews recent comprehensive experimental and theoretical investigations [...] Read more.
Nowadays, the increasing demand to reduce energy consumption and improve process reliability requires an alternative lubricant with an effective tribological performance and environmentally friendly properties to replace traditional lubricants in hot steel manufacturing. The current work reviews recent comprehensive experimental and theoretical investigations in a new generation of alkaline-based glass lubricants, with phosphate, borate, and silicate being intensively researched. This class of lubricants showed an outstanding friction reduction, anti-wear, and anti-oxidation performance on coupled steel pairs over a wide range of temperatures (from 650 °C to 1000 °C). Each type had different tribochemical reactions within itself and with oxidized steel surfaces, which were largely determined by their chemical nature. In addition, the critical role of each structural component was also determined and corroborated by computational simulation. The theoretical studies at quantum and atomic levels reinforced our experimental findings by providing insights into the reaction mechanism using the static and dynamic simulations of the adsorption of lubricant molecules onto iron oxide surfaces. Additionally, the new reactive molecular dynamics (MD) model developed for alkali phosphate will need to be extended further to consider the realistic operating conditions of these lubricants at the atomic scale. Full article
(This article belongs to the Special Issue Friction Reduction at Interfaces)
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