scholarly journals Boundary lubrication of heterogeneous surfaces and the onset of cavitation in frictional contacts

2016 ◽  
Vol 2 (3) ◽  
pp. e1501585 ◽  
Author(s):  
Daniele Savio ◽  
Lars Pastewka ◽  
Peter Gumbsch
Keyword(s):  
Boundary Lubrication ◽  
Wall Slip ◽  
Atomistic Simulations ◽  
Heterogeneous Surfaces ◽  
Load Bearing Capacity ◽  
Frictional Contacts ◽  
Lubricated Contact ◽  
Pressure Changes ◽  
Lubrication Conditions ◽  
Onset Of Cavitation

Surfaces can be slippery or sticky depending on surface chemistry and roughness. We demonstrate in atomistic simulations that regular and random slip patterns on a surface lead to pressure excursions within a lubricated contact that increase quadratically with decreasing contact separation. This is captured well by a simple hydrodynamic model including wall slip. We predict with this model that pressure changes for larger length scales and realistic frictional conditions can easily reach cavitation thresholds and significantly change the load-bearing capacity of a contact. Cavitation may therefore be the norm, not the exception, under boundary lubrication conditions.

scholarly journals Comparison Between the Action of Nano-Oxides and Conventional EP Additives in Boundary Lubrication

Lubricants ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 54
Author(s):  
Valdicleide Silva Mello ◽  
Marinalva Ferreira Trajano ◽  
Ana Emilia Diniz Silva Guedes ◽  
Salete Martins Alves
Keyword(s):  
Friction Coefficient ◽  
Boundary Lubrication ◽  
Friction And Wear ◽  
Film Formation ◽  
Environmental Issues ◽  
Protective Film ◽  
Extreme Pressure ◽  
Extreme Pressure Additives ◽  
Environmental Requirements ◽  
Lubrication Conditions

Additives are essential in lubricant development, improving their performance by the formation of a protective film, thus reducing friction and wear. Some such additives are extreme pressure additives. However, due to environmental issues, their use has been questioned because their composition includes sulfur, chlorine, and phosphorus. Nanoparticles have been demonstrated to be a suitable substitute for those additives. This paper aims to make a comparison of the tribological performance of conventional EP additives and oxides nanoparticles (copper and zinc) under boundary lubrication conditions. The additives (nanoparticles, ZDDP, and sulfur) were added to mineral and synthetic oils. The lubricant tribological properties were analyzed in the tribometer HFRR (high frequency reciprocating rig), and during the test, the friction coefficient and percentual of film formation were measured. The wear was analyzed by scanning electron microscopy. The results showed that the conventional EP additives have a good performance owing to their anti-wear and small friction coefficient in both lubricant bases. The oxides nanoparticles, when used as additives, can reduce the friction more effectively than conventional additives, and displayed similar behavior to the extreme pressure additives. Thus, the oxide nanoparticles are more environmentally suitable, and they can replace EP additives adapting the lubricant to current environmental requirements.

Wear Behavior and Chemical Friction Modification in Binary-Additives System under Boundary-Lubrication Conditions

1981 ◽  
Vol 24 (4) ◽  
pp. 517-525 ◽  
Author(s):  
Masayuki Kagami ◽  
Masataro Yagi ◽  
Seiichiro Hironaka ◽  
Toshio Sakurai
Keyword(s):  
Boundary Lubrication ◽  
Wear Behavior ◽  
Lubrication Conditions

Thin coatings with tetrahedral amorphous carbon structure and their behavior in boundary lubrication conditions

2020 ◽  
pp. 506-511
Author(s):  
V.D. Samusenko ◽  
I.A. Zavidovskii ◽  
O.A. Streletskii ◽  
I.A. Buyanovskii ◽  
M.M. Khrushchov ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Boundary Lubrication ◽  
Carbon Structure ◽  
Thin Coatings ◽  
Tribological Tests ◽  
Tetrahedral Amorphous Carbon ◽  
Structural Peculiarities ◽  
Lubrication Conditions

The results of an investigation of the structural peculiarities of the thin ta-C coatings obtained by the method of impulse arc sputtering of graphite and of their tribological tests in boundary lubrication conditions are presented.

Tribochemical Interactions of Friction Modifier and Antiwear Additives With CrN Coating Under Boundary Lubrication Conditions

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
T. Haque ◽  
A. Morina ◽  
A. Neville ◽  
S. Arrowsmith
Keyword(s):  
Boundary Lubrication ◽  
Photoelectron Spectroscopy ◽  
Antiwear Additives ◽  
Low Friction ◽  
Friction Modifier ◽  
Crn Coating ◽  
Atomic Force ◽  
Surface Analysis Techniques ◽  
Positive Effect ◽  
Lubrication Conditions

In recent years, the optimized use of low friction nonferrous coatings under boundary lubrication conditions has become a challenge to meet the demands of improved fuel economy in automotive applications. This study presents the tribological performance of chromium nitride (CrN) coating using conventional friction modifier (moly dimer) and/or antiwear additive (zinc dialkyl dithiophosphate (ZDDP)) containing lubricants in a pin-on-plate tribometer. Using surface analysis techniques such as the atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), both topographical and chemical analyses of tribofilms were performed. This paper shows that ZDDP and moly dimer both give a positive effect for both low friction and antiwear performance in CrN/cast iron system. Both AFM and XPS analyses give evidence of the formation of ZDDP and moly dimer derived tribofilms on the CrN coating and thus support friction and wear results.

A Theory of Mixed Lubrication

1972 ◽  
Vol 186 (1) ◽  
pp. 421-430 ◽  
Author(s):  
H. Christensen
Keyword(s):  
Hydrodynamic Lubrication ◽  
Dynamic Properties ◽  
Mixed Lubrication ◽  
Rapid Rise ◽  
Operating Characteristics ◽  
Lubrication Regime ◽  
Lubricated Contact ◽  
Mixed Lubrication Regime ◽  
Lubrication Conditions ◽  
Lubrication Properties

The phenomena observed when a lubricated contact or bearing is operating under mixed lubrication conditions are assumed to arise from an interaction of the surface asperities or roughness as well as from hydro-dynamic action of the sliding surfaces. It is shown how one of the previously published stochastic models of hydrodynamic lubrication can be extended or generalized to deal with mixed lubricating conditions. As an illustration of the application of the theory to a concrete example the influence on the operating characteristics of a plane pad, no side-leakage bearing is analysed. It is found that in the mixed lubrication regime friction is mainly controlled by the boundary lubrication properties of the liquid–solid interface. Load, on the other hand, is almost entirely controlled by the hydro-dynamic properties of the bearing. It is demonstrated how transition to mixed lubrication conditions will cause a rapid rise in friction thereby producing a minimum point in the Stribeck type diagram.

Tribological evaluation of piston skirt/cylinder liner contact interfaces under boundary lubrication conditions

2010 ◽  
Vol 22 (3) ◽  
pp. 73-87 ◽  
Author(s):  
Nicholaos G. Demas ◽  
Robert A. Erck ◽  
George R. Fenske
Keyword(s):  
Boundary Lubrication ◽  
Cylinder Liner ◽  
Piston Skirt ◽  
Lubrication Conditions

Thermal Influence on Torque Transfer of Wet Clutches in Limited Slip Differential Applications

2005 ◽  
Author(s):  
Pa¨r Marklund ◽  
Rikard Ma¨ki ◽  
Roland Larsson ◽  
Erik Ho¨glund ◽  
Michael M. Khonsari ◽  
...  
Keyword(s):  
Boundary Lubrication ◽  
High Load ◽  
Low Velocity ◽  
Thermal Influence ◽  
Lubrication Conditions

Wet clutches operating under low velocity and high load are studied with the aim of obtaining reliable models for the torque transfer during boundary lubrication conditions.

Antiwear tribofilm growth in rolling bearings under boundary lubrication conditions

2017 ◽  
Vol 113 ◽  
pp. 43-49 ◽  
Author(s):  
Andreas Stratmann ◽  
Georg Jacobs ◽  
Chia-Jui Hsu ◽  
Carsten Gachot ◽  
Gero Burghardt
Keyword(s):  
Boundary Lubrication ◽  
Rolling Bearings ◽  
Lubrication Conditions
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