An Analysis of the Plastic Interaction of Surface Asperities and its Relevance to the Value of the Coefficient of Friction

1968 ◽  
Vol 10 (2) ◽  
pp. 101-110 ◽  
Author(s):  
C. M. Edwards ◽  
J. Halling
Keyword(s):  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Time Interval ◽  
Surface Films ◽  
Interfacial Forces ◽  
Molecular Adhesion ◽  
Coefficient Of Sliding Friction ◽  
The Coefficient Of Friction ◽  
History Of ◽  
Tangential Forces

Surface asperities are considered as wedge-shaped bodies which are plastically deformed wherever relative motion occurs between mating surfaces. This plastic interaction produces interfacial forces between the surface asperities which are considered, in the collective sense, to represent the total applied normal and tangential forces acting on the sliding surfaces. A solution is proposed which enables the values of the interfacial forces to be obtained at each time interval during the life history of a junction interaction. Furthermore, it is shown that the nature of these forces is markedly dependent on both the initial asperity geometry and on the nature of any surface films which may be present at the asperity interfaces. From such results it is possible to predict the macroscopic values of the coefficient of sliding friction. Such results suggest that an earlier solution due to Tabor should be considered as the special case for perfectly plane surfaces. The solution also indicates the nature of the plastic deformation of the asperities and displays the phenomena of junction growth. Furthermore, it is demonstrated that very large values of the macro-scopic coefficient of friction are associated with very strong molecular adhesion of the surface asperities particularly for materials having high ductility.

scholarly journals Influence of Heat Treatment and the Coefficient of Friction on the Volume of Metal Removed During Grinding Steel 35

2015 ◽  
Vol 2 ◽  
pp. 72
Author(s):  
Igor Nikiforov ◽  
Pavel Maltsev
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Physical And Mechanical Properties ◽  
Abrasive Grain ◽  
Coefficient Of Sliding Friction ◽  
The Coefficient Of Friction ◽  
Relative Change

The role of external friction and chip contraction during microcutting by abrasive grain is showed. The method for determining the relative change in the coefficient of friction during grinding is proposed. The hypothesis about the influence of physical and mechanical properties and microstructure of steel 35 on the volume removes metal through the change in the coefficient of sliding friction of the chip by face of the abrasive grain is experimentally proved.

scholarly journals Scaling theory of rubber sliding friction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Reinhard Hentschke ◽  
Jan Plagge
Keyword(s):  
Experimental Data ◽  
Dimensional Analysis ◽  
Coefficient Of Friction ◽  
Solid Surface ◽  
Viscoelastic Properties ◽  
Sliding Friction ◽  
Simple Expression ◽  
The Other ◽  
Coefficient Of Sliding Friction ◽  
The Coefficient Of Friction

AbstractCurrent theoretical descriptions of rubber or elastomer friction are complex—usually due to extensive mathematical detail describing the topography of the solid surface. In addition, the viscoelastic properties of the elastomer material itself, in particular if the rubber is highly filled, further increase the complexity. On the other hand, experimental coefficients of sliding friction plotted versus sliding speed, temperature or other parameters do not contain much structure, which suggests that a less detailed approach is possible. Here we investigate the coefficient of sliding friction on dry surfaces via scaling and dimensional analysis. We propose that adhesion promotes viscoelastic dissipation by increasing the deformation amplitude at relevant length scales. Finally, a comparatively simple expression for the coefficient of friction is obtained, which allows an intuitive understanding of the underlying physics and fits experimental data for various speeds, temperatures, and pressures.

The Efficiency of Involute Spur Gears

1981 ◽  
Vol 103 (1) ◽  
pp. 160-169 ◽  
Author(s):  
K. F. Martin
Keyword(s):  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Experimental Tests ◽  
Rolling Friction ◽  
Gear Train ◽  
Small Range ◽  
Load Effect ◽  
Coefficient Of Sliding Friction ◽  
The Coefficient Of Friction ◽  
Basic Characteristics

Approximate equations produced by Trachman |15| are used to predict the coefficient of sliding friction between the gear teeth. These equations apply when the lubrication regime is elastohydrodynamic; this is true during many gear contacts. The equations, which require only certain basic characteristics of the lubricant and the gears, are relatively simple and produce values for the coefficient of friction which are acceptable. The use of this coefficient of friction, together with a calculation for the rolling friction force allows the calculation of instantaneous and overall efficiency of the gear train. Contact ratios greater than one are accounted for and the load is assumed to be shared equally between the pairs of teeth. The computed values show that the load torque has a significant effect on both coefficient of friction and efficiency; as the load increases the coefficient of friction increases and the efficiency decreases. The effect of speed does not, over the small range of computations made, have as much significance as load, although it appears that efficiency will probably increase as the speed increases. Comparison of these predicted results with the few experimental tests which are relevant indicates some support, especially for the load effect.

scholarly journals Scaling Theory of Rubber Sliding Friction

2021 ◽  
Author(s):  
Reinhard Hentschke ◽  
Jan Plagge
Keyword(s):  
Experimental Data ◽  
Dimensional Analysis ◽  
Coefficient Of Friction ◽  
Solid Surface ◽  
Viscoelastic Properties ◽  
Sliding Friction ◽  
Simple Expression ◽  
The Other ◽  
Coefficient Of Sliding Friction ◽  
The Coefficient Of Friction

Abstract Current theoretical descriptions of rubber or elastomer friction are complex-usually due to extensive mathematical detail describing the topography of the solid surface. In addition, the viscoelastic properties of the elastomer material itself, in particular if the rubber is highly filled, further increase the complexity. On the other hand, experimental coefficients of sliding friction plotted versus sliding speed, temperature or other parameters do not contain much structure, which suggests that a less detailed approach is possible. Here we investigate the coefficient of sliding friction on dry surfaces via scaling and dimensional analysis. We propose that adhesion promotes viscoelastic dissipation by increasing deformation amplitude at relevant length scales. Finally, a comparatively simple expression for the coefficient of friction is obtained, which allows an intuitive understanding of the underlying physics and fits experimental data for various speeds, temperatures and pressures.

scholarly journals Solid Lubrication by Multiwalled Carbon Nanotubes in Air and in Vacuum for Space and Aeronautics Applications

2005 ◽  
Author(s):  
K. Miyoshi ◽  
K. W. Street ◽  
R. L. Vander Wal ◽  
R. Andrews ◽  
David Jacques ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Multiwalled Carbon Nanotubes ◽  
Coefficient Of Friction ◽  
Sliding Friction ◽  
Solid Lubrication ◽  
Multiwalled Carbon ◽  
Solid Lubrication Friction ◽  
The Coefficient Of Friction ◽  
Dry Conditions ◽  
Steel Balls

To evaluate recently developed aligned multiwalled carbon nanotubes (MWNTs) and dispersed MWNTs for solid lubrication applications, unidirectional sliding friction experiments were conducted with 440C stainless steel balls and hemispherical alumina-yttria stabilized zirconia pins in sliding contact with the MWNTs deposited on quartz disks in air and in vacuum. The results indicate that MWNTs have superior solid lubrication friction properties and endurance lives in air and vacuum under dry conditions. The coefficient of friction of the dispersed MWNTs is close to 0.05 and 0.009 in air and in vacuum, respectively, showing good dry lubricating ability. The wear life of MWNTs exceeds 1 million passes in both air and vacuum showing good durability. In general, the low coefficient of friction can be attributed to the combination of the transferred, agglomerated patches of MWNTs on the counterpart ball or pin surfaces and the presence of tubular MWNTs at interfaces.

scholarly journals Anisotropic Vibration Tactile Model and Human Factor Analysis for a Piezoelectric Tactile Feedback Device

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 448 ◽  
Author(s):  
Jichun Xing ◽  
Huajun Li ◽  
Dechun Liu
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Ciliary Body ◽  
Human Factor ◽  
Sliding Friction ◽  
Excitation Frequency ◽  
Tactile Feedback ◽  
Body Structure ◽  
Full Coverage ◽  
The Coefficient Of Friction

Tactile feedback technology has important development prospects in interactive technology. In order to enrich the tactile sense of haptic devices under simple control, a piezoelectric haptic feedback device is proposed. The piezoelectric tactile feedback device can realize tactile changes in different excitation voltage amplitudes, different excitation frequencies, and different directions through the ciliary body structure. The principle of the anisotropic vibration of the ciliary body structure was analyzed here, and a tactile model was established. The equivalent friction coefficient under full-coverage and local-coverage of the skin of the touch beam was deduced and solved. The effect of system parameters on the friction coefficient was analyzed. The results showed that in the full-coverage, the tactile effect is mainly affected by the proportion of the same directional ciliary bodies and the excitation frequency. The larger the proportion of the same direction ciliary body is, the smaller the coefficient of friction is. The larger the excitation frequency is, the greater the coefficient of friction is. In the local-coverage, the tactile effect is mainly affected by the touch position and voltage amplitude. When changing the touch pressure, it has a certain effect on the change of touch, but it is relatively weak. The experiment on the sliding friction of a cantilever touch beam and the experiment of human factor were conducted. The experimental results of the sliding friction experiment are basically consistent with the theoretical calculations. In the human factor experiment, the effects of haptic regulation are mainly affected by voltage or structure of the ciliary bodies.

The development of wear-protective oxides and their influence on sliding friction

1980 ◽  
Vol 369 (1739) ◽  
pp. 557-574 ◽  
Keyword(s):  
Metal Oxide ◽  
Coefficient Of Friction ◽  
Metal Surfaces ◽  
Sliding Friction ◽  
Constant Thickness ◽  
Partial Pressures ◽  
Metal Wear ◽  
The Coefficient Of Friction ◽  
Metal Wear Particles ◽  
Clean Metal

The friction behaviour of iron and Fe-Cr alloys in unidirectional and reciprocating sliding motions at 293 K has been examined in oxygen of controlled partial pressure. During sliding, a progressive decrease in coefficient of friction accompanies the development of compacted oxide films on the metal surfaces, eventually resulting in a steady value of about 0.6 when almost complete oxide coverage is attained. This is achieved more rapidly at higher oxygen partial pressures. A model to account for the experimental observations is proposed, based on the growth of oxide on the clean metal surfaces and metal wear particles between each wear traversal and the removal of that oxide during the subsequent traversal. The oxidized debris is fragmented further and compacted on to the metal surfaces to form a layer of nominally constant thickness, the area of which increases progressively with the number of sliding traversals. The model relates the coefficient of friction to the area of compacted oxide in terms of several interfacial metal, oxide and metal-oxide parameters. The importance of some of these parameters on the frictional behaviour is discussed in light of the experimental observations.

The friction of clean crystal surfaces

1966 ◽  
Vol 295 (1442) ◽  
pp. 233-243 ◽  
Keyword(s):  
Coefficient Of Friction ◽  
High Surface ◽  
High Vacuum ◽  
Surface Films ◽  
Surface Adhesion ◽  
Crystal Surfaces ◽  
Deformation And Fracture ◽  
The Coefficient Of Friction ◽  
Molecular Layers ◽  
Frictional Behaviour

A study is made of the frictional behaviour of crystals (diamond, magnesium oxide, sapphire) sliding on themselves in high vacuum (10 -10 torr). The surface films normally present on these crystals are very tenacious but they may be worn away by repeated sliding in the same track. Under these conditions the friction of the clean crystals may increase by a factor of ten so that the coefficient of friction may rise to μ ≈ 1. The frictional rise is limited because of the elastic and brittle behaviour of the contact regions. Under these conditions subsurface deformation and fracture of the crystal occurs and this, combined with the high surface adhesion, causes pronounced wear. Adsorption of a few molecular layers of gas can again reduce the friction to a low value. The results are relevant to the operation of bearings and to the wear of surfaces in space.

The Influence of Surface Roughness on the Mechanism of Friction

1970 ◽  
Vol 92 (2) ◽  
pp. 264-272 ◽  
Author(s):  
T. Tsukizoe ◽  
T. Hisakado
Keyword(s):  
Surface Roughness ◽  
Metal Surface ◽  
Coefficient Of Friction ◽  
Dry Friction ◽  
Metal Surfaces ◽  
Roughness Effects ◽  
Real Area Of Contact ◽  
The Coefficient Of Friction ◽  
Tangential Forces ◽  
Soft Metal

A study was made of surface roughness effects on dry friction between two metals, assuming that the asperities are cones of the slopes which depend on the surface roughness. The theoretical explanations were offered for coefficients of friction of the hard cones and spheres ploughing along the soft metal surface. A comparison of calculated values based on these with experimental data shows good agreement. Moreover, theoretical discussion was carried out of surface roughness effects on dry friction between two metal surfaces on the basis of the analyses of the frictional mechanism for a hard slider on the metal surface. The theoretical estimation of the coefficient of friction between two metal surfaces can be carried out by using the relations between the surface roughness and the slopes of the asperities, and the coefficient of friction due to the adhesion at the interface. The experiments also showed that when two metal surfaces are first loaded normally and then subjected to gradually increasing tangential forces, real area of contact between them increases and the maximum tangential microslip of them increases with the increase of the surface roughness.

A Theory of Dynamic Rubber Friction

1966 ◽  
Vol 39 (2) ◽  
pp. 320-327 ◽  
Author(s):  
A. Schallamach
Keyword(s):  
Coefficient Of Friction ◽  
Time Lag ◽  
Quantitative Agreement ◽  
Dynamic Friction ◽  
Average Life ◽  
Thermally Activated ◽  
Molecular Adhesion ◽  
Rubber Friction ◽  
The Coefficient Of Friction ◽  
Rate Processes

Abstract Assuming dynamic friction to arise from the shearing and subsequent breaking of distinct bonds between the rubbing members, a general equation is derived for the frictional force which involves the number and average life of the bonds as well as the average time lag between breaking and re-making of a bond at a given site. In the case of friction between rubber and smooth, hard surfaces, the bonds are attributed to local molecular adhesion between rubber and track, both formation and breaking of the bonds being thermally activated rate processes. A theory developed on this basis reproduces the experimental results obtained by Grosch in that the coefficient of friction as function of the velocity has a pronounced maximum. The height of the maximum and the velocity at which it occurs are in semi-quantitative agreement with Grosch's findings.

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