Principles of Friction and Wear

Bely, V. A., A. I. Sviridenok, M. I. Petrokovets and V. G. Savkin, Friction and Wear in Polymer-Based Materials , Pergamon Press, New York, 1982. The basic principles of friction and wear, the function of structure and the application of these materials in friction assemblies is shown. 

The American Society of Lubrication Engineers has issued a compilation of friction and wear devices [2] which describes 234 different pieces of apparatus. However, the measurement of friction is governed by only a few basic principles, and consequently an appreciation of the practical techniques employed is not difficult to acquire. To quote Bowden and Tabor [3] Any method which will give at the same time a measure of the normal load between surfaces and of the tangential force necessary to cause sliding can be used to determine the coefficient of friction."... 

Suh, N.P. (1986) Tribophysics., Prentice-Hall, Inc. Englewood Cliffs, NJ. Engineering analysis of friction and wear of materials. Gathers and presents an overview of the author s own work and others on basic engineering principles that should be included in tribological study design and analysis. 

Friction and wear do not necessarily go together. This is an extremely important principle which applies to nonlubricated (dry) as well as lubricated systems. It is particularly true under conditions of boundary lubrication, to be discussed later. An additive may reduce friction and increase wear, reduce wear and increase friction, reduce both or increase both. Although the reasons are not fully understood, this is an experimental observation. Thus, friction and wear should be thought of as separate phenomena — an important point when we discuss theories of synovial joint lubrication. 

The term tribology is derived from the Greek XQipo) ( tribo ) meaning I mb . Tribology is the science and technology of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication, and wear... 

This Session presents five papers dealing with mechanisms of polymer friction and wear. The Plenary Lecture will be delivered by Professor David Tabor of the Cambridge University. Dr. Tabor has spent over twenty years in studying various aspects of polymer tribology. His school has been the focal point to all those interested in this subject. His paper should bring all of us up-to-date on basic principles in the mechanistic study. 

This paper will discuss the relevance and the irrelevance of surface energetics to polymer friction and wear. This survey covers most of the important works published in the past and during this recent Symposium. Since basic principles related to polymer friction have been reviewed by Tabor, and by Savkoor, the scope of this discussion will be limited to pertinent friction mechanisms with emphasis on surface interactions. First will be a brief discussion of the following friction processes polymer sliding, elastomer sliding, lubricated polymer sliding, polymer rolling. 

Perhaps also friction and wear are related in some distinct manner to the increase of entropy principle of the Second Law of Thermodynamics. While such a relationship may yield no further physical insight into the nature of wear itself, it would surely provide a worthwhile unifying influence hy now including wear and surface deterioration as part of the natural progression from order to randomness in the universe. 

Typical friction force data obtained at a constant load are shown in Fig. 4.17 (left). In these experiments, the applied load should be limited to <1 nN to ensure that the surface of the film to a depth of <2 nm is probed and that wear of the glassy PMMA film can be excluded. A clear maximum is observed that shifts to higher velocities with increasing temperature, in accordance with the time—temperature superposition principle [36]. From the master curve of friction force vs. velocity data for PMMA (shifted by aT to the reference temperature of 25°C) an activation energy of 35 kJ/mol can be estimated. 

Chapters 2 through 5 are focused on tribological principles and their applications in CMP. Chapter 2 discusses the surfaces of contacts, involving basic concepts such as surface roughness, conformity, real contact area, and wear-contact mechanism. At the end of this chapter, common defects in CMP are discussed. Chapter 3 focuses on the basics of friction as well as flash temperature and friction in CMP. Chapter 4 discusses lubrication fundamentals and their roles in CMP. 

---