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Lubricants
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  This is an Open Access Journal Open Access journal
     ISSN (Online) 2075-4442
     Published by MDPI Homepage  [124 journals]
  • Lubricants, Vol. 2, Pages 113-123: Tribofilm Formation As a Result of
           Complex Interaction at the Tool/Chip Interface during Cutting

    • Authors: German Fox-Rabinovich, Iosif Gershman, Mohamed Hakim, Mohamed Shalaby, James Krzanowski, Stephen Veldhuis
      Pages: 113 - 123
      Abstract: Tribofilms are dynamic structures that form at the interface during frictional sliding. These films play a significant role in friction control, particularly under heavy loaded/high temperature conditions, such as those found at the cutting tool/chip interface. The thermodynamic aspects of tribofilm formation are discussed here. Thermodynamic analysis of entropy production during friction shows that there are two types of tribofilms that affect the wear behavior of a cutting tool: (1) tribofilms forming as a result of the surface modification of the cutting tools with further tribo-oxidation; and (2) tribofilms that form as a result of material transfer from the contacting frictional body (the workpiece) during the tool/chip interaction. Experimental examples are presented, outlining the beneficial role of both types of tribofilms.
      PubDate: 2014-07-21
      DOI: 10.3390/lubricants2030113
      Issue No: Vol. 2, No. 3 (2014)
       
  • Lubricants, Vol. 2, Pages 124-136: Growth Control of Microbial in Miscible
           Cutting Fluids Using Ultraviolet Radiation

    • Authors: Eduardo Bianchi, Paulo Aguiar, Olavo de Arruda, Francine Piubeli
      Pages: 124 - 136
      Abstract: Considering the issues involved in industrial cutting and machining systems, and, in particular, the problems arising from the use of cutting fluids in these systems, this study presents the results of an analysis that points to a safe and efficient way to reduce contaminated microbial cutting fluids using ultraviolet radiation. The study proposes a transmitter system of simple ultraviolet radiation, safe and easy to obtain. The results of this study showed that the action of ultraviolet radiation on microorganisms in metalworking fluids is very effective and leads to a significant reduction of the load of microorganisms. In addition, no changes were observed during the experimental period that would lead to impairments in the performance of the activities of the cutting fluid used. Given the results, we can conclude that the use of ultraviolet radiation in the prevention and control of contamination is an important contribution to the durability of cutting fluids in machining and grinding operations.
      PubDate: 2014-09-02
      DOI: 10.3390/lubricants2030124
      Issue No: Vol. 2, No. 3 (2014)
       
  • Lubricants, Vol. 2, Pages 44-65: Graphite and Hybrid Nanomaterials as
           Lubricant Additives

    • Authors: Zhenyu Zhang, Dorin Simionesie, Carl Schaschke
      Pages: 44 - 65
      Abstract: Lubricant additives, based on inorganic nanoparticles coated with organic outer layer, can reduce wear and increase load-carrying capacity of base oil remarkably, indicating the great potential of hybrid nanoparticles as anti-wear and extreme-pressure additives with excellent levels of performance. The organic part in the hybrid materials improves their flexibility and stability, while the inorganic part is responsible for hardness. The relationship between the design parameters of the organic coatings, such as molecular architecture and the lubrication performance, however, remains to be fully elucidated. A survey of current understanding of hybrid nanoparticles as lubricant additives is presented in this review.
      PubDate: 2014-04-24
      DOI: 10.3390/lubricants2020044
      Issue No: Vol. 2, No. 2 (2014)
       
  • Lubricants, Vol. 2, Pages 66-89: Abrasive Resistant Coatings—A
           Review

    • Authors: Linmin Wu, Xingye Guo, Jing Zhang
      Pages: 66 - 89
      Abstract: Abrasive resistant coatings have been widely used to reduce or eliminate wear, extending the lifetime of products. Abrasive resistant coatings can also be used in certain environments unsuitable for lubrications. Moreover, abrasive resistant coatings have been employed to strengthen mechanical properties, such as hardness and toughness. Given recently rapid development in abrasive resistant coatings, this paper provides a review of major types of abrasive coatings, their wearing mechanisms, preparation methods, and properties.
      PubDate: 2014-05-21
      DOI: 10.3390/lubricants2020066
      Issue No: Vol. 2, No. 2 (2014)
       
  • Lubricants, Vol. 2, Pages 90-112: Reducing Friction and Wear of
           Tribological Systems through Hybrid Tribofilm Consisting of Coating and
           Lubricants

    • Authors: Shuichiro Yazawa, Ichiro Minami, Braham Prakash
      Pages: 90 - 112
      Abstract: The role of surface protective additives becomes vital when operating conditions become severe and moving components operate in a boundary lubrication regime. After protecting film is slowly removed by rubbing, it can regenerate through the tribochemical reaction of the additives at the contact. However, there are limitations about the regeneration of the protecting film when additives are totally consumed. On the other hand, there are a lot of hard coatings to protect the steel surface from wear. These can enable the functioning of tribological systems, even in adverse lubrication conditions. However, hard coatings usually make the friction coefficient higher, because of their high interfacial shear strength. Amongst hard coatings, diamond-like carbon (DLC) is widely used, because of its relatively low friction and superior wear resistance. In practice, conventional lubricants that are essentially formulated for a steel/steel surface are still used for lubricating machine component surfaces provided with protective coatings, such as DLCs, despite the fact that the surface properties of coatings are quite different from those of steel. It is therefore important that the design of additive molecules and their interaction with coatings should be re-considered. The main aim of this paper is to discuss the DLC and the additive combination that enable tribofilm formation and effective lubrication of tribological systems.
      PubDate: 2014-06-23
      DOI: 10.3390/lubricants2020090
      Issue No: Vol. 2, No. 2 (2014)
       
  • Lubricants, Vol. 2, Pages 1-10: The Application of Molecular Dynamics in
           Fullerene-Based Journal Bearing Simulation

    • Authors: Alexey Kornaev, Leonid Savin, Mikhail Nozdrichkin
      Pages: 1 - 10
      Abstract: The article is devoted to modeling of the molecular microscopic journal bearing. The walls and the lubricant of the bearing are fullerene-like molecules. On the basis of similarity theory and analysis of the dimensions, the similarity criterion is proposed. This criterion characterizes the convergence of a numerical solution. The test calculation is also made to evaluate the quality of the proposed criterion.
      PubDate: 2014-02-24
      DOI: 10.3390/lubricants2010001
      Issue No: Vol. 2, No. 1 (2014)
       
  • Lubricants, Vol. 2, Pages 11-20: Lubricants for Metal Belt Continuously
           Variable Transmissions

    • Authors: Keiichi Narita
      Pages: 11 - 20
      Abstract: This paper reviews the effects of lubricant additives and base stock used in metal belt continuously variable transmissions (CVT) fluids on the CVT transmission torque capacity. Additive formulation composed of phosphorus anti-wear agent, calcium detergent, and dispersant improved the friction coefficient between the metals. The analysis on the post-test surface suggests that the friction behavior strongly depends on the local morphology of the tribofilms derived from lubricant additives. Examining the effect of base stock on the torque capacity in actual belt CVTs revealed that SN (synthetic naphthene) exhibited 10% higher torque capacity than that of PAO (polyalphaolefin). It is believed that the difference in the torque capacity is due to the difference in the oil-film shearing force generated by the relative sliding between the belt and pulley.
      PubDate: 2014-02-25
      DOI: 10.3390/lubricants2010011
      Issue No: Vol. 2, No. 1 (2014)
       
  • Lubricants, Vol. 2, Pages 21-43: Lubricants in Pharmaceutical Solid Dosage
           Forms

    • Authors: Jinjiang Li, Yongmei Wu
      Pages: 21 - 43
      Abstract: Lubrication plays a key role in successful manufacturing of pharmaceutical solid dosage forms; lubricants are essential ingredients in robust formulations to achieve this. Although many failures in pharmaceutical manufacturing operations are caused by issues related to lubrication, in general, lubricants do not gain adequate attention in the development of pharmaceutical formulations. In this paper, the fundamental background on lubrication is introduced, in which the relationships between lubrication and friction/adhesion forces are discussed. Then, the application of lubrication in the development of pharmaceutical products and manufacturing processes is discussed with an emphasis on magnesium stearate. In particular, the effect of its hydration state (anhydrate, monohydrate, dihydrate, and trihydrate) and its powder characteristics on lubrication efficiency, as well as product and process performance is summarized. In addition, the impact of lubrication on the dynamics of compaction/compression processes and on the mechanical properties of compacts/tablets is presented. Furthermore, the online monitoring of magnesium stearate in a blending process is briefly mentioned. Finally, the chemical compatibility of active pharmaceutical ingredient (API) with magnesium stearate and its reactive impurities is reviewed with examples from the literature illustrating the various reaction mechanisms involved.
      PubDate: 2014-02-25
      DOI: 10.3390/lubricants2010021
      Issue No: Vol. 2, No. 1 (2014)
       
  • Lubricants, Vol. 1, Pages 75-94: On the Interactions of Additives in
           Metalworking Fluids with Metal Surfaces

    • Authors: Joachim Schulz, Ekkard Brinksmeier, Daniel Meyer
      Pages: 75 - 94
      Abstract: Metalworking fluids (MWF) play a significant role in manufacturing processes, such as machining or forming. Consequently, a high number of MWF with varying chemical composition are commercially available. However, the working mechanisms of the MWF are still object of discussion in science and application. This paper addresses the possible interactions of additives with metal surfaces taking the characteristic conditions in machining and forming processes as well as the chemical properties of the surface and the additives into account. The new model for possible interaction of additives with the metal surface is considered and supported by experimental data. This new model does not imply reaction layers as tribological active layer anymore.
      PubDate: 2013-11-15
      DOI: 10.3390/lubricants1040075
      Issue No: Vol. 1, No. 4 (2013)
       
  • Lubricants, Vol. 1, Pages 95-101: Nanomaterials in Lubricants: An
           Industrial Perspective on Current Research

    • Authors: Boris Zhmud, Bogdan Pasalskiy
      Pages: 95 - 101
      Abstract: This paper presents an overview on the use of various classes of nanomaterials in lubricant formulations. The following classes of nanomaterials are considered: fullerenes, nanodiamonds, ultradispersed boric acid and polytetrafluoroethylene (PTFE). Current advances in using nanomaterials in engine oils, industrial lubricants and greases are discussed. Results of numerous studies combined with formulation experience of the authors strongly suggest that nanomaterials do indeed have potential for enhancing certain lubricant properties, yet there is a long way to go before balanced formulations are developed.
      PubDate: 2013-11-20
      DOI: 10.3390/lubricants1040095
      Issue No: Vol. 1, No. 4 (2013)
       
  • Lubricants, Vol. 1, Pages 102-131: Experimental Investigations of
           Biological Lubrication at the Nanoscale: The Cases of Synovial Joints and
           the Oral Cavity

    • Authors: Javier Sotres, Thomas Arnebrant
      Pages: 102 - 131
      Abstract: Interactions between surfaces are ubiquitous phenomena in living organisms. Nature has developed sophisticated strategies for lubricating these systems, increasing their efficiency and life span. This includes the use of water-based lubricants, such as saliva and synovial fluid. These fluids overcome the limitations of water as a lubricant by the presence of molecules such as proteins, lipids, and polysaccharides. Such molecules may alter surface interactions through different mechanisms. They can increase viscosity enabling fluid-film lubrication. Moreover, molecules adsorb on the surfaces providing mechanisms for boundary lubrication and preventing wear. The mentioned molecules have typical sizes in the nanometer range. Their interaction, as well as the interaction with the entrapping surfaces, takes place through forces in the range of nanonewtons. It is therefore not surprising that the investigation of these systems have been boosted by development of techniques such as scanning probe microscopies and the surface force apparatus which allow studying tribological processes at the nanoscale. Indeed, these approaches have generated an enormous amount of studies over the last years. The aim of this review is to perform a critical analysis of the current stage of this research, with a main focus on studies on synovial joints and the oral cavity.
      PubDate: 2013-11-25
      DOI: 10.3390/lubricants1040102
      Issue No: Vol. 1, No. 4 (2013)
       
  • Lubricants, Vol. 1, Pages 132-148: Phosphate Esters, Thiophosphate Esters
           and Metal Thiophosphates as Lubricant Additives

    • Authors: David Johnson, John Hils
      Pages: 132 - 148
      Abstract: Phosphate esters, thiophosphate esters and metal thiophosphates have been used as lubricant additives for over 50 years. While their use has been extensive, a detailed knowledge of how they work has been a much more recent development. In this paper, the use of phosphate esters and thiophosphate esters as anti-wear or extreme pressure additives is reviewed with an emphasis on their mechanism of action. The review includes the use of alkyl phosphates, triaryl phosphates and metal containing thiophosphate esters. The mechanisms of these materials interacting with a range of iron and steel based bearing material are examined.
      PubDate: 2013-12-18
      DOI: 10.3390/lubricants1040132
      Issue No: Vol. 1, No. 4 (2013)
       
  • Lubricants, Vol. 1, Pages 61-74: Employing Acoustic Emission for
           Monitoring Oil Film Regimes

    • Authors: Mhmod Hamel, Abdulmajid Addali, David Mba
      Pages: 61 - 74
      Abstract: The major purpose of a gear lubricant is to provide adequate oil film thickness to reduce and prevent gear tooth surface failures. Real time monitoring for gear failures is important in order to predict and prevent unexpected failures which would have a negative impact on the efficiency, performance and safety of the gearbox. This paper presents experimental results on the influence of specific oil film thickness on Acoustic Emission (AE) activity for operational helical gears. Variation in film thickness during operations was achieved by spraying liquid nitrogen onto the rotating gear wheel. The experimental results demonstrated a clear relationship between the root mean square (r.m.s) value of the AE signal and the specific film thickness. The findings demonstrate the potential of Acoustic Emission technology to quantify lubrication regimes on operational gears.
      PubDate: 2013-07-03
      DOI: 10.3390/lubricants1030061
      Issue No: Vol. 1, No. 3 (2013)
       
  • Lubricants, Vol. 1, Pages 22-47: Nanotribological Behavior of Carbon Based
           Thin Films: Friction and Lubricity Mechanisms at the Nanoscale

    • Authors: Costas Charitidis, Elias Koumoulos, Dimitrios Dragatogiannis
      Pages: 22 - 47
      Abstract: The use of materials with very attractive friction and wear properties has raised much attention in research and industrial sectors. A wide range of tribological applications, including rolling and sliding bearings, machining, mechanical seals, biomedical implants and microelectromechanical systems (MEMS), require thin films with high mechanical strength, chemical inertness, broad optical transparency, high refractive index, wide bandgap excellent thermal conductivity and extremely low thermal expansion. Carbon based thin films like diamond, diamond-like carbon, carbon nitride and cubic boron nitride known as “super-hard” material have been studied thoroughly as the ideal candidate for tribological applications. In this study, the results of experimental and simulation works on the nanotribological behavior of carbon films and fundamental mechanisms of friction and lubricity at the nano-scale are reviewed. The study is focused on the nanomechanical properties and analysis of the nanoscratching processes at low loads to obtain quantitative analysis, the comparison obtain quantitative analysis, the comparison of their elastic/plastic deformation response, and nanotribological behavior of the a-C, ta-C, a-C:H, CNx, and a-C:M films. For ta-C and a-C:M films new data are presented and discussed.
      PubDate: 2013-04-02
      DOI: 10.3390/lubricants1020022
      Issue No: Vol. 1, No. 2 (2013)
       
  • Lubricants, Vol. 1, Pages 48-60: Interaction between Lubricants Containing
           Phosphate Ester Additives and Stainless Steels

    • Authors: David Johnson, Matthew Bachus, John Hils
      Pages: 48 - 60
      Abstract: One way to improve fuel efficiency in today’s jet aircraft engines is to create an environment for higher operating temperatures and speeds. New and improved lubricants and bearing materials must be developed to remain stable in these elevated operating temperatures. Three lubricants, with varying amounts of tricresyl phosphate added as an anti-wear/extreme pressure additive were tested on two different stainless steels at varying temperatures ranging from 300 °C to 350 °C in vacuum. Significant decomposition of the lubricant base-stocks and the phosphate ester additive did occur in most of the trials resulting in the formation of carboxylic acids and phenols. In these cases a film containing phosphorus was deposited onto the stainless steel substrate.
      PubDate: 2013-05-17
      DOI: 10.3390/lubricants1020048
      Issue No: Vol. 1, No. 2 (2013)
       
  • Lubricants, Vol. 1, Pages 3-21: A Review of Ionic Liquid Lubricants

    • Authors: Anthony Somers, Patrick Howlett, Douglas MacFarlane, Maria Forsyth
      Pages: 3 - 21
      Abstract: Due to ever increasing demands on lubricants, such as increased service intervals, reduced volumes and reduced emissions, there is a need to develop new lubricants and improved wear additives. Ionic liquids (ILs) are room temperature molten salts that have recently been shown to offer many advantages in this area. The application of ILs as lubricants in a diverse range of systems has found that these materials can show remarkable protection against wear and significantly reduce friction in the neat state. Recently, some researchers have shown that a small family of ILs can also be incorporated into non-polar base oils, replacing traditional anti-wear additives, with excellent performance of the neat IL being maintained. ILs consist of large asymmetrical ions that may readily adsorb onto a metal surface and produce a thin, protective film under boundary lubrication conditions. Under extreme pressure conditions, certain IL compounds can also react to form a protective tribofilm, in particular when fluorine, phosphorus or boron atoms are present in the constituent ions.
      PubDate: 2013-01-21
      DOI: 10.3390/lubricants1010003
      Issue No: Vol. 1, No. 1 (2013)
       
  • Lubricants, Vol. 1, Pages 1-2: Welcome to Lubricants, a New Open Access
           Journal for Interdisciplinary Research in the Field of Tribology

    • Authors: James E. Krzanowski
      Pages: 1 - 2
      Abstract: Welcome to Lubricants, a new open access journal for researchers and practitioners working in the field of tribology. The journal will publish peer-reviewed research papers, reviews, letters and communications, as well as papers on research ideas and proposals. The concept of open access is exciting because it allows free access of all publications to anyone, resulting in the widest dissemination possible for the authors publishing in the journal. In addition, publication is rapid, and full use can be made of color figures which are published at no additional cost to the authors. The contents of the journal will nonetheless be archival and articles can therefore have a long-term impact. [...]
      PubDate: 2012-07-02
      DOI: 10.3390/lubricants1010001
      Issue No: Vol. 1, No. 1 (2012)
       
 
 
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