Frictional Properties of a Surface Covered With a Soft Metal Film—Part 2: Analysis of Friction Between a Single Protuberance and a Surface

1982 ◽  
Vol 104 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Shinobu Kato ◽  
Katsumi Yamaguchi ◽  
Etsuo Marui ◽  
Kiyoo Tachi
Keyword(s):  
Pressure Distribution ◽  
Coefficient Of Friction ◽  
Metal Film ◽  
Surface Film ◽  
Analytical Investigation ◽  
Friction Characteristic ◽  
Frictional Properties ◽  
The Coefficient Of Friction ◽  
Soft Metal ◽  
Side Flow

Analytical investigation of the evaluation of the coefficient of friction is made to clarify the mechanism of the load dependency of friction, which was obtained in Part 1 of this research, and also to ascertain the effects of the surface film on the friction characteristic. The plastic flow of the soft metal film between a protuberance and the subsurface is presumed, and the pressure distribution originating from the side flow is calculated on the basis of the plasticity theory. The effects of the coefficient of friction of the load, the thickness and hardness of the film, and the radius of the protuberance, are examined. As a result, it is clarified that the load dependency of friction arises from the extremely high pressure distribution generated in the film.

Frictional Properties of a Surface Covered With a Soft Metal Film—Part 1: Experiments on Friction Between a Single Protuberance and a Surface

1981 ◽  
Vol 103 (2) ◽  
pp. 236-242 ◽  
Author(s):  
S. Kato ◽  
K. Yamaguchi ◽  
E. Marui ◽  
K. Tachi
Keyword(s):  
Coefficient Of Friction ◽  
Deformation Mechanism ◽  
Metal Film ◽  
Surface Film ◽  
Thin Metal Film ◽  
Film Properties ◽  
Empirical Expression ◽  
Frictional Properties ◽  
The Coefficient Of Friction ◽  
Soft Metal

Frictional properties in the contact between a hard protuberance and a metal surface covered by a soft thin metal film are examined experimentally. The protuberance used in the experiment is a hard steel ball which simulates asperities on many engineering surfaces. The load dependency of the coefficient of friction and the effects of thickness and hardness of the film on the friction are clarified. The simple empirical expression of friction, which represents the effect of the film properties, is presented, considering the deformation mechanism of the surface film.

Frictional Properties of a Surface Covered With Soft Metal Film (Interference Effect of Soft Metal Film Deformation Between Two Protuberances)

1985 ◽  
Vol 107 (4) ◽  
pp. 444-451 ◽  
Author(s):  
Shinobu Kato ◽  
Etsuo Marui ◽  
Kiyoo Tachi
Keyword(s):  
Plastic Flow ◽  
Interference Effect ◽  
Metal Film ◽  
Flow Line ◽  
Contact Pressure Distribution ◽  
Frictional Properties ◽  
Frictional Characteristic ◽  
The Coefficient Of Friction ◽  
Soft Metal ◽  
Flow Deformation

The frictional characteristic is examined with reference to a model considering the interference effect of plastic flow (deformation) in soft metal film, when a two-protuberance indentor is slid on a surface covered by electroplated soft metal film. The result is compared with that of a single-protuberance indentor. The coefficient of friction in a two-protuberance indentor, where the interference effect exists, is lower than in a single-protuberance indentor, where the interference effect does not. This fact can well be explained with the configuration of plastic flow line on protuberances described by deforming soft metal film, and the corresponding contact pressure distribution between protuberances and a surface.

Frictional Properties of a Surface Covered With Soft Metal Surface Film (Surface Topography and Frictional Properties)

1987 ◽  
Vol 109 (3) ◽  
pp. 545-551 ◽  
Author(s):  
Shinobu Kato ◽  
Etsuo Marui ◽  
Kiyoo Tachi
Keyword(s):  
Surface Topography ◽  
Metal Surface ◽  
Metal Film ◽  
Surface Film ◽  
Frictional Coefficient ◽  
Film Surface ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Frictional Properties ◽  
Soft Metal

The friction between a real engineering surface composed of many micro-asperities and a surface covered with soft metal film is discussed. First, the frictional coefficient shows a remarkable load dependency, when a hard single protuberance with a small radius of curvature is slid on a soft metal surface. This load dependence originates from the ploughing effect induced by the cooperation of contact pressure and shearing resistance of the soft metal film deforming on the protuberance surface. Based on this result, the effect of the real engineering surface topography on the frictional properties is studied.

Frictional Vibrations

1955 ◽  
Vol 22 (2) ◽  
pp. 207-214
Author(s):  
David Sinclair
Keyword(s):  
Coefficient Of Friction ◽  
Equations Of Motion ◽  
Static Friction ◽  
Uniform Motion ◽  
Friction Characteristic ◽  
Stick Slip ◽  
The Coefficient Of Friction ◽  
Brake Lining ◽  
Solid Bodies ◽  
Frictional Vibrations

Abstract Frictional vibrations, such as stick-slip motion and automobile-brake squeal, which occur when two solid bodies are rubbed together, are analyzed mathematically and observed experimentally. The conditions studied are slow uniform motion and relatively rapid simple harmonic motion of brake lining over a cast-iron base. The equations of motion show and the observations confirm that frictional vibrations are caused primarily by an inverse variation of coefficient of friction with sliding velocity, but their form and occurrence are greatly dependent upon the dynamical constants of the mechanical system. With a constant coefficient of friction, the vibration initiated whenever sliding begins is rapidly damped out, not by the friction but by the “natural” damping of all mechanical systems. The coefficient of friction of most brake linings and other organic materials was essentially invariant with velocity, except that the static coefficient was usually greater than the sliding coefficient. Most such materials usually showed a small decrease in coefficient with increasing temperature. The persistent vibrations resulting from the excess static friction were reduced or eliminated by treating the rubbing surfaces with polar organic compounds which produced a rising friction characteristic.

Paper 21: Variations in Friction and Wear between Unlubricated Steel Surfaces

1966 ◽  
Vol 181 (15) ◽  
pp. 16-24
Author(s):  
S. W. E. Earles ◽  
D. G. Powell
Keyword(s):  
Wear Rate ◽  
Mild Steel ◽  
Oxide Layer ◽  
Coefficient Of Friction ◽  
Surface Film ◽  
Frictional Heating ◽  
Subsequent Increase ◽  
Track Condition ◽  
The Coefficient Of Friction ◽  
Steel Disc

Experiments have been conducted in a normal atmosphere using a 0·25-in diameter mild-steel pin specimen sliding on a 10-in diameter mild-steel disc. The ranges of normal force and speed are 0·5–10·4 lbf and 20–190 ft/s respectively. Initially the coefficient of friction is comparatively large, and the wear is of the severe metallic form. However, frictional heating causes rapid oxidation of the surfaces and, if the sliding distance is sufficient, the eventual retention of an oxide layer causes a rapid decrease in the coefficient of friction and the wear rate decreases by 3–4 orders of magnitude. At speeds above about 75 ft/s and loads below about 5 lbf the formation, after several hours' sliding, of a continuous oxide layer on the track causes a further reduction in the pin wear rate. At higher loads and/or lower speeds this track condition is not attained. At speeds of 75 ft/s and above there exists a critical load (the magnitude of which depends on speed) above which periodic removals of the surface film(s) occur producing metallic wear and high friction. However, the subsequent increase in oxidation allows conditions of mild wear to be re-established generally within a few seconds. The steady-state coefficient of friction has been observed to be a function of load1/2 × speed, and periodic surface breakdowns found to occur when load1/2 × speed exceeds 170 lbf1/2 ft/s, the frequency decreasing with increasing load or speed.

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.

The Calculation of Roll Pressure in Hot and Cold Flat Rolling

1943 ◽  
Vol 150 (1) ◽  
pp. 140-167 ◽  
Author(s):  
E. Orowan
Keyword(s):  
Pressure Distribution ◽  
Yield Stress ◽  
Coefficient Of Friction ◽  
Static Friction ◽  
Rolled Stock ◽  
Theoretical Treatment ◽  
Frictional Drag ◽  
Roll Pressure ◽  
Plate Rolling ◽  
The Coefficient Of Friction

A numerical or graphical method is given for computing, in strip or plate rolling, the distribution of roll pressure over the arc of contact and the quantities derived from this (e.g. the vertical roll force, the torque, and the power consumption). The method avoids all mathematical approximations previously used in the theoretical treatment of rolling, and permits any given variation of the yield stress and of the coefficient of friction along the arc of contact to be taken into account. It can be used, therefore, in both hot and cold rolling, provided that the basic physical quantities (yield stress and coefficient of friction) are known. The usual assumption that the deformation could be regarded as a locally homogeneous compression has not been made, and the inhomogeneity of stress distribution has been taken into account approximately by using results derived by Prandtl and Nádai from the Hencky treatment of two-dimensional plastic deformation. It is found that the discrepancy between the roll pressure distribution curves calculated from the Kármán theory and those measured by Siebel and Lueg is due to the assumption in the theory that the frictional drag between the rolls and the rolled stock is equal to the product of the roll pressure and the coefficient of friction. If frictional effects are dominant, as in hot rolling, this product may easily exceed the yield stress in shear which is the natural upper limit to the frictional drag, and then static friction, instead of slipping, occurs. This has been taken into account in the present method, and the calculated curves of roll pressure distribution show good agreement with the curves measured by Siebel and Lueg.

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