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Source: MECHANICAL DESIGN HANDBOOK CHAPTER 7 FRICTION, LUBRICATION, AND WEAR
David Tabor, Sc.D. Professor Emeritus Laboratory for the Physics and Chemistry of Solids Department of Physics Cambridge University Cambridge, England
7.1 INTRODUCTION 7.1 7.4.8 Shear Properties of Thin Polymer 7.2 DEFINITIONS AND LAWS OF FRICTION 7.2 Films 7.13 7.2.1 Definition 7.2 7.4.9 Kinetic Friction 7.14 7.2.2 Static and Kinetic Friction 7.2 7.4.10 New Tribological Materials: 7.2.3 Basic Laws of Friction 7.2 Composites, Ceramics 7.15 7.3 SURFACE TOPOGRAPHY AND AREA OF 7.5 LUBRICATION 7.16 REAL CONTACT 7.2 7.5.1 Hydrodynamic or Fluid Lubrication 7.3.1 Profilometry and Asperity Slopes 7.2 7.16 7.3.2 Elastic and Plastic Deformation of 7.5.2 Elastohydrodynamic Lubrication Conical Indenters 7.3 7.18 7.3.3 Elastic and Plastic Deformation of Real 7.5.3 Boundary Lubrication 7.18 Surfaces 7.4 7.6 WEAR 7.21 7.4 FRICTION OF CLEAN METALS 7.7 7.6.1 Laws of Wear 7.21 7.4.1 Theory of Metallic Friction 7.7 7.6.2 Mild and Severe Wear 7.21 7.4.2 Microdisplacements before Sliding 7.6.3 Effect of Environment 7.22 7.9 7.6.4 Effect of Speed 7.22 7.4.3 Breakdown of Oxide Films 7.10 7.6.5 Wear by Abrasives 7.23 7.4.4 Friction of Metals after Repeated 7.6.6 Wear Behavior of Specific Materials Sliding 7.11 7.23 7.4.5 Friction of Hard Solids 7.11 7.6.7 Identification of Wear Mechanisms 7.4.6 Friction of Thin Metallic Films 7.11 7.23 7.4.7 Friction of Polymers 7.12
7.1 INTRODUCTION
Sliding friction is primarily a surface phenomenon. Consequently it depends very markedly on surface conditions, such as roughness, degree of work hardening, type of oxide film, and surface cleanliness.4,6,11 In general, in unlubricated sliding the rough- ness has only a secondary effect, but surface contamination can have a profound influ- ence on friction (and wear), particularly with surfaces that are nominally clean. Because of this the account given here concentrates mainly on the mechanisms involved in friction.4,11,20a In this way the reader may be better able to assess the main factors involved in any particular situation. Tables of friction values are given, but they must be used with caution. Very wide differences in friction may be obtained under apparently similar conditions, especially with unlubricated surfaces.
7.1
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FRICTION, LUBRICATION, AND WEAR
7.2 MECHANICAL DESIGN FUNDAMENTALS
7.2 DEFINITIONS AND LAWS OF FRICTION
7.2.1 Definition
The friction between two bodies is generally defined as the force at their surface of contact which resists their sliding on one another. The friction force F is the force required to initiate or maintain motion. If W is the normal reaction of one body on the other, the coefficient of friction