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Lubricants
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Tribology of Machine Elements--Smart Lubricants
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Tribology of Machine Elements--Smart Lubricants

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

Deadline for manuscript submissions: closed (28 February 2018) | Viewed by 22561

Special Issue Editor

Prof. Dr. Pantelis G. Nikolakopoulos

E-Mail Website
Guest Editor
Machine Design Laboratory, Department of Mechanical Engineering and Aeronautics, University of Patras, 265 04 Patras, Greece
Interests: tribology of machine elements; journal bearings; thrust bearing; artificial texturing; piston ring tribology; magnetorheological; electrorheological fluids; active magnetic bearings
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The term tribology emerged in the 1960s, and is defined as “the science of rubbing” from the Greek translation; tribology is the engineering science of moving interacting surfaces. The science covers friction, wear, and lubrication for interacting machine elements. It has been related to human invention since ancient history, from the creation of wheels to inclusion of liquids while building pyramids or moving ships to avoid friction.

Machine elements, such as journal bearings, rolling bearings, piston rings, gears, crankshaft bearings, cams, brakes, clutches and floating ring bearings, etc., are crucial components in the operation of a machine.

Tribological design analysis and optimization, including friction wear and lubrication, will affect the performance of machine elements and further in machine operation, its efficiency, emitted gases, its lifetime, and at the end in the world economy.

Checking the properties of materials has attracted appreciable attention over the last few decades. Magneto/nanomagneto rheological and electrorheological fluids, etc., are smart lubricants in which rheological properties can be changed by applying a magnetic or an electric field, respectively. Smart lubricants are, commonly, a suspension of solid magnetized or dielectric particles, respectively diffused in non-conducting liquid. By applying a magnetic or electric field, their resistances to flow can be altered very quickly. Smart fluids can change their behavior, from a Newtonian type to Bingham type, in which particles form chain-like structures. Due to this behavior, smart fluids can endure external pressures or forces with advantages such as simple design, continuous control, and fast response time.

The combination of tribological design analysis and the optimization of machine elements with smart fluids, can offer controllable tribological properties and/or controllable dynamic behaviors.

Papers dealing with the tribological design of machine elements and/or combined with smart fluid lubrication are welcome in this Special Issue.

Prof. Dr. Pantelis G. Nikolakopoulos
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

  • tribology of machine elements
  • journal bearings; thrust bearing
  • artificial texturing
  • piston ring tribology
  • magnetorheological
  • electrorheological fluids
  • active magnetic bearings

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Published Papers (3 papers)

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Research

19 pages, 4027 KiB  
Article
Lubrication Performance of Engine Commercial Oils with Different Performance Levels: The Effect of Engine Synthetic Oil Aging on Piston Ring Tribology under Real Engine Conditions
by Pantelis G. Nikolakopoulos, Stamatis Mavroudis and Anastasios Zavos
Lubricants 2018, 6(4), 90; https://doi.org/10.3390/lubricants6040090 - 9 Oct 2018
Cited by 27 | Viewed by 10150
Abstract
To further improve efficiency in automotive engine systems, it is important to understand the generation of friction in its components. Accurate simulation and modeling of friction in machine components is, amongst other things, dependent on realistic lubricant rheology and lubricant properties, where especially [...] Read more.
To further improve efficiency in automotive engine systems, it is important to understand the generation of friction in its components. Accurate simulation and modeling of friction in machine components is, amongst other things, dependent on realistic lubricant rheology and lubricant properties, where especially the latter may change as the machine ages. Some results of research under laboratory conditions on the aging of engine commercial oils with different performance levels (mineral SAE 30, synthetic SAE10W-40, and bio-based) are presented in this paper. The key role of the action of pressure and temperature in engine oils’ aging is described. The paper includes the results of experiments over time in laboratory testing of a single cylinder motorbike. The aging of engine oil causes changes to its dynamic viscosity value. The aim of this work is to evaluate changes due to temperature and pressure in viscosity of engine oil over its lifetime and to perform uncertainty analysis of the measured values. The results are presented as the characteristics of viscosity and time in various temperatures and the shear rates/pressures. This paper also includes a Computational Fluid Dynamics (CFD) model, applying the experimental results in the piston ring tribology problem. Full article
(This article belongs to the Special Issue Tribology of Machine Elements--Smart Lubricants)
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29 pages, 97712 KiB  
Article
Dynamical Simulations of a Flexible Rotor in Cylindrical Uncavitated and Cavitated Lubricated Journal Bearings
by Alessandro Ruggiero, Roberto D’Amato, Emanuele Magliano and Drazan Kozak
Lubricants 2018, 6(2), 40; https://doi.org/10.3390/lubricants6020040 - 25 Apr 2018
Cited by 12 | Viewed by 6611
Abstract
Due to requirements of their operating conditions, such as high speed, high flexibility and high efficiency, rotating machines are designed to obtain larger operating ranges. These operating conditions can increase the risk of fluid-induced instability. In fact, the presence of non-linear fluid forces [...] Read more.
Due to requirements of their operating conditions, such as high speed, high flexibility and high efficiency, rotating machines are designed to obtain larger operating ranges. These operating conditions can increase the risk of fluid-induced instability. In fact, the presence of non-linear fluid forces when the threshold speed is overcome by the rotational speed, can generate rotor lateral self-excited vibrations known as “oil whirl” or “oil whip”. These instabilities derive from the interaction between the rotor and the sliding bearing and they are typically sub-synchronous and they contribute to eventual rubbing between rotor and stator with consequent damage to the rotating machines. For these reasons, the aim of this paper is to numerically investigate the differences in the dynamic behaviour of a flexible rotor supported by cylindrical lubricated journal bearings. The study considers two different cases, uncavitated and cavitated lubricated films, in order to develop an original Matlab-Simulink algorithm for the numerical solution of the differential non-linear equations of motion of the unbalanced flexible rotor supported on hydrodynamic journal bearings. The bearings were modelled as uncavitated and cavitated (π-Film) short bearings derived from classical Reynolds’ theory. Dynamic simulation allowed prediction of the shape and size of the orbit performed by the system and evaluation of the vibrating phenomena exerted by the rotor during the motion. The results show that cavitation completely modifies the behaviour of the system in every aspect. The analysis of the diagrams obtained showed that the proposed algorithm provides consistent results and represents a valuable instrument for dynamic analysis of rotating systems. Full article
(This article belongs to the Special Issue Tribology of Machine Elements--Smart Lubricants)
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Graphical abstract

8 pages, 2693 KiB  
Communication
Influence of Slip and Lubrication Regime on the Formation of White Etching Cracks on a Two-Disc Test Rig
by Francisco Gutiérrez Guzmán, Mehmet Ozan Oezel, Georg Jacobs, Gero Burghardt, Christoph Broeckmann and Thomas Janitzky
Lubricants 2018, 6(1), 8; https://doi.org/10.3390/lubricants6010008 - 12 Jan 2018
Cited by 12 | Viewed by 4502
Abstract
A common cause for maintenance and downtime in multiple fields of the mechanical transmission industries are premature rolling bearing failures due to white etching cracks (WEC). Within this work, WEC have been successfully recreated on a two-disc test rig under rolling contact loading [...] Read more.
A common cause for maintenance and downtime in multiple fields of the mechanical transmission industries are premature rolling bearing failures due to white etching cracks (WEC). Within this work, WEC have been successfully recreated on a two-disc test rig under rolling contact loading without additional loading such as hydrogen pre-charging. This paper summarizes the state of the investigations regarding the influence of the slip type and the lubrication regime on the WEC formation on the two-disc test rig. Full article
(This article belongs to the Special Issue Tribology of Machine Elements--Smart Lubricants)
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