Author

# E. Fred Macks

Bio: E. Fred Macks is an academic researcher. The author has contributed to research in topics: Lubrication & Breed. The author has an hindex of 1, co-authored 1 publications receiving 119 citations.

Topics: Lubrication, Breed

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TL;DR: In this paper, the genesis of friction is explained in terms of a new theory, which postulates that the frictional force (and thus the friction coefficient μ) is affected by the sliding distance and the environment because of the changing contributions of three components of friction, i.e., deformation of surface asperities, plowing by wear particles and hard as perities, and adhesion of the flat portions of the sliding surface.

Abstract: The genesis of friction is explained in terms of a new theory. Contrary to the postulates of the adhesion theory of friction, this theory postulates that the frictional force (and thus the friction coefficient μ) is affected by the sliding distance and the environment because of the changing contributions of three components of friction, i.e. that due to the deformation of surface asperities (denoted μd), that due to plowing by wear particles and hard asperities (denoted μp) and that due to the adhesion of the flat portions of the sliding surface (denoted μa). Therefore the coefficient of friction is not a simple material property. There are four or six stages of the friction regime depending on the sliding conditions. The initial friction coefficient μi can range from 0.1 to 0.2 for most machined surfaces. μi is largely independent of environmental conditions (including lubricants), materials and surface topography. μp varies from 0 to 1.0 and μa from 0 to 0.4. Only μa depends on the quality of surface adhesion. The history-dependent frictional behavior of materials is represented in the “friction space” diagram. According to this theory, the compatibility of sliding surfaces is dictated more by the mechanical properties of materials such as hardness than by their relative solubility at low temperatures.

374 citations

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TL;DR: In this article, the effect of roughness of surfaces of a slider bearing on the load-carrying capacity and friction force was studied, and the distinction between waviness and roughness was made between random quantities which may be characterized by a probability density function, determined experimentally.

Abstract: The effect of roughness of surfaces of a slider bearing on the load-carrying capacity and friction force, is studied. The distinction is made between waviness and roughness, the latter being treated as a random quantity which may be characterized by a probability density function, determined experimentally. Results can be obtained in closed form suitable for calculation if a Beta distribution is assumed. Actually, this can approximate quite closely a Gaussian distribution, yielding quite accurate results. However, the procedure developed can be carried out for any desired distribution.

251 citations

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TL;DR: In this paper, a general solution is deduced of the differential equations which describe the propagation of elastic waves in a nondissipative liquid-filled porous solid, and the solution is then used to examine some of the phenomena which arise when each of the three body waves predicted by the field equations is, in turn, incident on a plane traction-free boundary.

Abstract: A general solution is deduced of the differential equations which describe the propagation of elastic waves in a nondissipative liquid-filled porous solid. The solution is then used to examine some of the phenomena which arise when each of the three body waves predicted by the field equations is, in turn, incident on a plane traction-free boundary. It is found, for example, that an obliquely incident wave of each type in general gives rise to reflected waves of all three types.

220 citations

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TL;DR: In this paper, a study of the friction and surface damage produced when a hard steel sphere rolls between flat parallel surfaces of a softer metal is presented, where the deformation produced during rolling is very heavily sheared in the direction of rolling, and with repeated traversals this may lead to rapid fatigue of the metal.

Abstract: This paper describes a study of the friction and surface damage produced when a hard steel sphere rolls between flat parallel surfaces of a softer metal. When rolling first starts, even at small loads there is marked plastic flow of the surfaces and a grooved track is formed. The resistance to rolling is primarily due to the plastic displacement of metal ahead of the ball and may be calculated in terms of the area of the grooved track and the yield pressure of the metal. In the first traversal the ball is supported on the front half of the circle of contact. On rolling back along this track there is no such support for the ball unless it sinks further into the surfaces. This leads to an increase in the width of the groove and further displacement of metal. With successive traversals there is a slow increase in groove width and a gradual decrease in rolling resistance. For metals such as tin which do not work-harden appreciably these changes may be explained quantitatively on the assumption that the area supporting the load remains substantially the same throughout the series of traversals. The rolling resistance throughout this stage is due primarily to plastic displacement and depends little on lubrication. A study of the deformation produced during rolling shows that the centre of the grooved track is very heavily sheared in the direction of rolling, and with repeated traversals this may lead to rapid fatigue of the metal. Here again lubricants have little effect on the rate of fatiguing. As rolling proceeds there is an increase in track width, a slight change in track curvature and, in general, appreciable work-hardening of material within and around the track. As a result of these factors an equilibrium stage is gradually reached (if fatigue failure does not occur first) at which the whole of the load is borne by the ellipse of contact formed by elastic deformation within the width of the existing track. No further appreciable increase in track width occurs, and the rolling friction remains substantially constant for repeated traversals of the track. The rolling friction at this stage is again scarcely affected by lubricants.

155 citations

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TL;DR: In this paper, the stable and unstable vibrational characteristics of rigid shafts symmetrically supported on short journal bearings are obtained directly from Reynolds equation and conveniently represented in terms of two important parameters.

Abstract: The stable and unstable vibrational characteristics of rigid shafts symmetrically supported on short journal bearings are obtained directly from Reynolds equation and conveniently represented in terms of two important parameters.

101 citations