The influence of lubricant rheology and surface topography in modelling friction at concentrated contacts

1998 ◽  
Vol 212 (6) ◽  
pp. 391-400 ◽  
Author(s):  
K. A. Blencoe ◽  
G. W. Roper ◽  
J. A. Williams
Keyword(s):  
Coefficient Of Friction ◽  
Surface Engineering ◽  
Mechanical Response ◽  
Molecular Surface ◽  
Lubricant Layer ◽  
Load Parameter ◽  
Boundary Lubricant ◽  
Boundary Film ◽  
Surface Profiles ◽  
Conventional Picture

The conventional picture of a boundary lubricant layer is of a film which exhibits mechanical properties more like a solid than a liquid. In this paper the influence that the form of the dependence of shear strength on pressure has on the overall friction coefficient of contacts exhibiting both model and measured surface profiles is examined quantitatively. The analysis can provide plots of coefficient of friction versus a service or load parameter which also includes some aspects of contact topography. The results indicate that variations in the macroscopic coefficient of friction which may occur as the load is varied have their roots in both the statistical nature of the surface and the mechanical response of the lubricating boundary film. The effect of running-in on friction and safe working loads can also be observed. The value of this analysis is that it attempts to combine the behaviour of films at molecular dimensions with the topography of surfaces measured at an engineering scale and so gives an indication of the full-size effects that can be achieved by chemical or molecular surface engineering.

Effect of Carbon Nanotube-Phosphinate Ionic Liquid Thin Boundary Layer on the Tribological Behavior of Aluminum Alloy in Steel-on-Aluminum Contact

2018 ◽  
Author(s):  
Miguel A. Gutierrez ◽  
Michael Gydesen ◽  
Caitlin Marcellus ◽  
Ivan Puchades ◽  
Brian Landi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ionic Liquid ◽  
Aluminum Alloy ◽  
Optical Microscopy ◽  
Coefficient Of Friction ◽  
Tribological Behavior ◽  
Sliding Contact ◽  
Wear Volume ◽  
Thin Boundary Layer ◽  
Boundary Film

In this study, the tribological behavior of the Trihexyl tetradecylphosphonium-bis(2,4,4-trimethylpentyl)phosphinate [THTDP][Phos] ionic liquid with and without single-wall carbon nanotubes (SWCNT) dispersion as a thin boundary layer was intended for investigation. However, the surface heat treatment process was not sufficient to form a thin film on the sample surfaces. Thus, in each test condition, the lubricating agents were used as external (liquid) lubricants. Specifically, [THTDP][Phos] and ([THTDP][Phos]+0.1 wt.% SWCNT) boundary film layers were applied on 6061-T6 aluminum alloy disk samples and tested under sliding contact with 1.5 mm diameter 420C stainless steel balls using a ball-on-flat linearly reciprocating tribometer. A commercially available Mobil Super 10W-40 engine oil (MS10W40) was also tested and used as this investigation’s datum. The tribological behavior of [THTDP][Phos] and ([THTDP][Phos]+SWCNT) boundary film layers was analyzed via wear volume calculations from optical microscopy measurements, as well as by observation of the transient coefficient of friction (COF) obtained through strain gauge measurements made directly from the reciprocating member of the tribometer. Results indicate the potential for reduction of wear volume and coefficient of friction in the IL lubricated steel-on-aluminum sliding contact through (SWCNT) dispersion in the ionic liquid. Wear results are based on measurements obtained using optical microscopy (OM). Results discussed display improved tribological performance for both [THTDP][Phos] and ([THTDP][Phos]+SWCNT) over baseline MS10W40 oil lubricant for both roughness values tested for the steel-on-aluminum contact. No measurable improvements were observed between [THTDP][Phos] and ([THTDP][Phos]+SWCNT) tests.

Variation with load of the coefficient of friction and metallic transfer under conditions of boundary lubrication

1952 ◽  
Vol 212 (1111) ◽  
pp. 516-519 ◽  
Keyword(s):  
Coefficient Of Friction ◽  
Boundary Lubrication ◽  
General Pattern ◽  
Copper Plate ◽  
Experimental Conditions ◽  
Average Hardness ◽  
Boundary Lubricant ◽  
The Coefficient Of Friction ◽  
Fixed Load ◽  
Molecular Layers

Several papers have been published recently which show for a number of metals that, under certain experimental conditions, several molecular layers of boundary lubricant are necessary to give effective lubrication, i.e. a coefficient of friction of 0.1 or less. Recent experiments by the authors suggest that these results represent parts of a more general pattern. In the previous work, the experiments were carried out at a fixed load; in the present, the load has been varied. The apparatus used was a copy of that described by Bowden & Leben (1939) for studying friction at low speeds of sliding. A hemispherical copper slider of radius 0-45 cm was caused to slide upon a flat copper plate at a speed of approximately 1 cm/min. Several specimens were used; their average hardness was 100 v .p .h .

Surface molecular engineering in the confined space of templated porous silica

2016 ◽  
Vol 40 (5) ◽  
pp. 4115-4131 ◽  
Author(s):  
Belén Albela ◽  
Laurent Bonneviot
Keyword(s):  
Porous Materials ◽  
Surface Engineering ◽  
Porous Silica ◽  
Molecular Engineering ◽  
Molecular Surface ◽  
Confined Space ◽  
Recent Developments

Recent developments in molecular surface engineering inside the confined space of porous materials are surveyed including a new nomenclature proposal.

Part III. Boundary and extreme pressure lubrication - Mechanism of boundary lubrication

1952 ◽  
Vol 212 (1111) ◽  
pp. 498-505 ◽  
Keyword(s):  
Frictional Resistance ◽  
Surface Damage ◽  
Lubricant Film ◽  
Effect Of Temperature ◽  
Solid Boundary ◽  
Chemical Attack ◽  
Boundary Lubricant ◽  
Boundary Film ◽  
The Difference ◽  
Boundary Films

This paper shows how the theory of metallic friction, discussed in earlier papers, is modified in the presence of boundary films. Over the regions of contact the load is mainly supported by the boundary film, but some metallic interaction occurs through it with the formation of minute metallic junctions. These junctions contribute to the frictional resistance and play a major part in the wear of lubricated surfaces. The effect of temperature shows that the most effective lubrication is provided by a solid boundary film which possesses a close-packed strongly oriented structure. When the film melts, a marked increase in friction and metallic interaction occurs. For this reason fatty acids are generally more effective than hydrocarbons or alcohols, since they can react with the surface to form metallic soaps of relatively high melting-points. This chemical attack generally occurs via the metal oxide film which is present on the surface. The soap formation and the difference between a physically adsorbed and a chemically formed layer have been investigated by radioactive methods. A recent study has been made of the metal transference from one surface to the other as sliding takes place, using radioactive metals. The results again show that at the melting-point of the lubricant film a marked increase in pick-up and friction occurs. A new observation is that at still higher temperatures a second deterioration in lubricating properties occurs, corresponding to the desorption of the lubricant film. Although the surface is flooded with a lubricant the friction and surface damage are comparable with that observed with unlubricated surfaces. These effects are reversible on cooling and correspond to changes in state of the lubricant film. Similar changes are observed in electron diffraction studies of the structure and orientation of boundary films. The paper concludes with a discussion, based on these results, of the properties which a good boundary lubricant should possess.

ADAPTIVE COATINGS a-C/MoS2

Tribologia ◽  
2018 ◽  
Vol 278 (2) ◽  
pp. 51-56
Author(s):  
Marcin KOT ◽  
Jurgen LACKNER ◽  
Łukasz MAJOR ◽  
Roman MAJOR ◽  
Grzegorz WIĄZANIA ◽  
...  
Keyword(s):  
Coefficient Of Friction ◽  
Room Temperature ◽  
Surface Engineering ◽  
Elevated Temperatures ◽  
Elasticity Modulus ◽  
Composite Coatings ◽  
High Wear Resistance ◽  
Scratch Testing ◽  
Indentation Tests ◽  
Steel Substrates

One of the latest ideas in surface engineering is the deposition of new kinds of coatings, called adaptive or chameleon. Based on literature review, the different mechanisms of the adaption of such coatings depend on the applied ranges of temperature and loads were compared. Moreover, the main directions of development of adaptive coatings were also presented. The paper includes results of single coatings, a-C and MoS2, as well composite coatings, a-C/MoS2, in which the mechanism of adaptation was expected. Indentation tests were carried out to determine nanohardness and elasticity modulus. The adhesion of coatings to steel substrates was studied by scratch testing, and tribological properties were studied using a high-temperature ball-ondisc tribometer and tests results conducted at room temperature and at elevated temperatures up to 300°C. Results showed that composite coating, a-C/MoS2, can work over the entire range of temperatures with a low coefficient of friction 0.02–0.1 and wear index of 0.07–0.47·10–6 mm3/Nm . Whereas, a-C and MoS2 coatings exhibited a low coefficient of friction and a high wear resistance at low and high temperatures, respectively.

Metallic transfer between sliding metals: an autoradiographic study

1951 ◽  
Vol 208 (1095) ◽  
pp. 455-475 ◽  
Keyword(s):  
Coefficient Of Friction ◽  
Photographic Plate ◽  
Frictional Resistance ◽  
Autoradiographic Study ◽  
Lubricant Film ◽  
Small Range ◽  
Main Function ◽  
Boundary Lubricant ◽  
The Coefficient Of Friction ◽  
Higher Temperature

This paper describes a study of the friction and metallic transfer between sliding metal surfaces in the absence and in the presence of boundary lubricant films. One surface is made radioactive and is slid over the surface of a second, non-radioactive metal, the amount of metal transferred being detected by the blackening of a photographic plate placed in contact with the second surface. The results show that, in general, the metallic transfer or ‘pick-u p ’, consists of a relatively small number of discrete particles. For unlubricated surfaces the pick-up is about 40 times larger for similar than for dissimilar metals, although the coefficient of friction covers a relatively small range (μ ≈ 0.4 to μ ≈ 1). With well-lubricated surfaces the friction is reduced by a factor of not more than 20 (μ ≈0.05), whilst the ‘pick-u p ’ may be diminished by a factor of 20,000 or more. A simple analysis suggests that under these conditions the welded metallic junctions formed through the lubricant film play a very small part in determining the frictional resistance to motion. Consequently two lubricants possessing widely differing abilities to protect the surfaces may give essentially the same coefficient of friction. The lowest friction and ‘pick-up ’ are observed when the lubricant film is solid. As the temperature is raised a marked increase in friction and ‘pick -u p ’ occurs a t a temperature close to the melting-point of the film. A new observation is that at a somewhat higher temperature a further deterioration in lubricating properties occurs; although the surfaces are visibly covered with lubricant, the frictional behaviour and the metallic transfer are similar to those observed with unlubricated surfaces. These changes are reversible on cooling, and it is suggested that they correspond to changes in state of the lubricant film. The results provide direct support for the view that the friction between metals is due largely to the formation and shearing of metallic junctions, and that the main function of a boundary lubricant is to reduce the amount of metallic interaction. The investigation also shows that the metallic transfer is immensely more sensitive to changes in surface conditions than is the coefficient of friction.

Analysis of Porous Layered Journal Bearing Lubricated with Ferrofluid

2016 ◽  
Vol 819 ◽  
pp. 474-478 ◽  
Author(s):  
T.V.V.L.N. Rao ◽  
A.M.A. Rani ◽  
T. Nagarajan ◽  
F.M. Hashim
Keyword(s):  
Magnetic Field ◽  
Layer Thickness ◽  
Coefficient Of Friction ◽  
Journal Bearing ◽  
Load Capacity ◽  
Lubricant Layer ◽  
Distance Ratio ◽  
Load Carrying ◽  
Magnetic Field Model ◽  
The Coefficient Of Friction

This paper presents an analysis of porous layered long journal bearing lubricated with ferrofluid using displaced infinitely long wire magnetic field model. The ferrofluid flow in the porous region is analyzed using modified Brinkman model. Nondimensional pressure and shear stress expressions are derived using Reynolds boundary conditions. Nondimensional load capacity and coefficient of friction are evaluated under the influence of permeability of porous media, porous layer thickness, lubricant layer thickness, magnetic field intensity and distance ratio parameter. A porous layered journal bearing lubricated with ferrofluid increases the load carrying capacity and reduces the coefficient of friction.

Contributions to the Influence of Retained Austenite Content in Steels on the Temperature Stability of Boundary Lubricant Layers in Friction

1975 ◽  
Vol 97 (3) ◽  
pp. 512-515 ◽  
Author(s):  
R. M. Matveevsky ◽  
V. M. Sinaisky ◽  
I. A. Buyanovsky
Keyword(s):  
Surface Layer ◽  
Critical Temperature ◽  
Boundary Lubrication ◽  
Retained Austenite ◽  
Temperature Stability ◽  
Mineral Oil ◽  
Lubricant Layer ◽  
Austenite Content ◽  
Boundary Lubricant

The results of investigations by various authors on the influence of retained austenite on seizure are briefly considered. Using as an example the investigation of the critical temperature of mineral oil in the friction of alloyed steels, it is shown that the temperature of destruction of the lubricant layer appreciably depends on the nature and content of the alloying elements and doe not strictly depend on the retained austenite content in the surface layer of steel specimens. Certain questions are considered—the influence of the contact geometry on the determination of the critical temperature in conditions of boundary lubrication, and the expediency of using austenite steel for investigating the temperature stability of lubricant layers.

scholarly journals Chitosan biopolymer‐derived self‐powered triboelectric sensor with optimized performance through molecular surface engineering and data‐driven learning

InfoMat ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 116-125 ◽  
Author(s):  
Chenxiang Ma ◽  
Shengjie Gao ◽  
Xinqi Gao ◽  
Min Wu ◽  
Ruoxing Wang ◽  
...  
Keyword(s):  
Surface Engineering ◽  
Molecular Surface ◽  
Data Driven ◽  
Self Powered ◽  
Chitosan Biopolymer

The Conflicting Roles of Carbontetrachloride as a Boundary Lubricant

1978 ◽  
Vol 100 (2) ◽  
pp. 244-248 ◽  
Author(s):  
T. Shirakashi ◽  
R. Komanduri ◽  
M. C. Shaw
Keyword(s):  
Beneficial Effect ◽  
Plastic Flow ◽  
Coefficient Of Friction ◽  
Shear Stresses ◽  
Low Speed ◽  
Sliding Surfaces ◽  
Boundary Lubricant ◽  
Normal And Shear Stresses

Under certain conditions, carbontetrachloride is found to be a negative boundary lubricant (gives a higher coefficient of friction than that of dry surfaces in air), while under other conditions, it lowers friction and gives a beneficial effect. Both of these situations are illustrated for heavily loaded sliding surfaces where the subsurface is undergoing gross plastic flow and an explanation is presented which appears to be consistent with all experimental facts. Carbontetrachloride is found to be more reactive chemically when the sliding surfaces are heavily strained or galled under high normal and shear stresses and containing microcracks, a situation that arises when cutting at low speed.

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