Engineering Tribology — Second Edition

Engineering Tribology — Second Edition

Tribology International 34 (2001) 723–724 Book Review Engineering Tribology — Second Edition Gwidon W. Stachowiak an...

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Tribology International 34 (2001) 723–724

Book Review Engineering Tribology — Second Edition Gwidon W. Stachowiak and Andrew W. Batchelor; Butterworth-Heinemann, 2001, pp. 744, Price $79.95, ISBN 0750673044 “The strengths of this book are the comprehensive nature of its coverage and the excellent schematic diagrams of friction and wear mechanisms provided to clarify the text.” This statement was made in one of the reviews of the first edition of this book, published in the journal Industrial Lubrication and Tribology, and we share this opinion in regard to the new edition. In fact the second edition even exceeds this impression. The subject is split into 16 chapters covering the whole field of engineering tribology, including lubrication, hydrodynamic theory, and various types of wear mechanisms, and this not only for metals, but also for non-metallic materials, such as ceramics and polymers. More than 400 schematic diagrams and line-illustrations are spread throughout the various chapters, to assist the already easily understandable descriptions of complex friction and wear phenomena. Complicated tribological concepts and theories are introduced extremely clearly. This is one of the reasons why we believe that this book will be beneficial not only for beginners in this field, as it was the authors’ original intention of this textbook, but also for experienced specialists. Similar to other textbooks, this book starts in Chapter 1 with an introduction to the history of tribology, which is especially valuable for newcomers. Several phenomena in engineering tribology are defined, and the relationship between friction, wear and lubrication are discussed. A general selection guide for wear control is presented from the viewpoint of materials science, and the principle importance of lubricants in reducing the friction and wear of two solid surfaces in sliding contact is elucidated. Maintaining the same order of presentation, the authors used the first half of their book (Chapters 2–8), to describe the composition, properties and functional mechanisms of various types of lubricants. In Chapter 2 the physical properties of lubricants, including the viscosity of oils, their temperature characteristics, and the solubility of gases in oil lubricants are described. A thorough knowledge of lubricants’ fundamental physical properties is very helpful in understanding their performance described in the following chapters. In Chapter 3 “Lubricants and Their Composition”, PII: S 0 3 0 1 - 6 7 9 X ( 0 1 ) 0 0 0 4 1 - X

the manufacturing, characteristics and applications of various lubricants, i.e. mineral and synthetic oils, emulsions and greases, are introduced. Additives have to be blended into some lubricants for different practical cases. The limitations of additives are also indicated. The basic principles of the hydrodynamic lubrication theory are outlined in Chapter 4, based on fluid mechanics assumptions of viscosity. Derived from the onedimensional Reynolds equation, lubricating parameters, such as pressure distribution, load capacity, friction force and oil flow, can be found from analytical solutions for linear pad and journal bearings. This approach is widely applied in engineering analysis. Since the two-dimensional Reynolds equation could provide a more exact solution, numerical methods were employed in the following chapter. Chapter 5,entitled “Computational Hydrodynamics”, describes the finite difference numerical method, which allows obtaining solutions for different bearing geometries and operating conditions, leading to closer approximations towards the characteristics of real bearings. The numerical analysis of hydrodynamic lubrication in this chapter is supported by a number of MATLAB computer programs attached in the book’s Appendix. Chapter 6, entitled “Hydrostatic Lubrication”, deals mainly with hydrostatic or aerostatic lubrication, which has a unique practical importance (zero or negligible wear and very low friction) for the design and operation of precision control systems. It contains the analysis of hydrostatic bearings, optimization of hydrostatic bearing design, and relates to questions about the stability of hydrostatic and aerostatic bearings. In Chapter 7, “Elastohydrodynamic Lubrication”, a fundamental lubrication mechanism involved in highly loaded concentrated contacts is discussed, where the elastic deformation of the contacting bodies and the variations of viscosity with pressure play key roles. The mechanism of film generation and the calculation of the minimum film thickness in rolling bearings and gears are introduced. The analysis of contact stresses and the formation of elastohydrodynamic lubrication films are also presented in this chapter. Chapter 8 focuses on boundary and extreme pressure lubrication. It is made clear by the authors, that at present, benefits towards the reduction of friction and wear under various conditions are not achieved by a single lubrication mechanism. Each type of lubrication mechanism, e.g. hydrodynamic and elastohydrodynamic, has its own merits. In addition, the operating temperature


Book Review / Tribology International 34 (2001) 723–724

should also be considered and is discussed in this chapter. At the beginning of the second half of this book, Chapter 9 introduces characteristic features of solid lubricants and basic surface treatments. This is a rapidly developing topic with the attractive advantage of superior cleanliness. Extensive research and the development of new surface treatment technologies are proposed by the authors. They also stated, that for a better understanding of the tribological behaviour of solids, contact problems between solids must be studied more fundamentally. As a consequence, Chapter 10 deals with this topic in more detail. The topography of the contacting surfaces was considered from an atomic to a macroscopic level, and the problem of determining the real contact area has been indicated. After a general introduction to wear and friction of materials within this chapter, the following 5 chapters concentrate more specifically on various types of wear loading. The chapter “Abrasive, Erosive and Cavitation Wear” (Chapter 11) deals with these three basic forms of particle-surface interaction and their related wear mechanisms. The authors emphasize that materials optimization for a specific application is essential because a material, which is resistant to one form of wear, may fail under other wear loading conditions. Chapter 12 focuses on adhesion and adhesive wear, which is the fundamental cause of failure of most metal sliding contacts. Mechanisms of adhesion and the control of adhesive wear are discussed. Corrosive and oxidative wear are the main topics of the Chapter 13. Chemical reactions between the worn material and a reactive medium, such as a chemical reagent, a reactive lubricant or air, are the primary reasons for these two forms of wear. Understanding the underlying wear mechanism and ways of its control is important since these two forms of wear occur in a wide variety of situations. In the following two chapters, fatigue wear and fretting wear are of special concern. Fatigue wear is caused by high local contact stresses, which are reversed for a large number of cycles. It is very difficult to avoid, even for perfectly lubricated contacts. Thus, the mechanisms relating to the structure and properties of the materials in contact seem to be more

important for controlling fatigue wear. Minor wear mechanisms, fretting wear, melting wear, wear due to electrical discharges, diffusive wear and impact wear are also introduced in Chapter 15. These wear mechanisms are of importance when defining the limits of wear under extreme conditions, often dominated by extremes of energy. The final chapter on “Wear of Non-metallic Materials”, deals mainly with the wear properties of polymers and ceramics. The fundamental wear mechanisms operating in non-metallic materials are described together with some predictions concerning the future developments of these materials. The benefits and limitations in using non-metallic materials as bearing or wear resistant materials are discussed, and the potential of composites in tribological application is also shown. Besides the main topic, each chapter contains an introduction, where usually several fundamental but interesting questions of practical importance to engineers are asked. One is always encouraged to find the answer for each question whilst reading the chapter. This is recommended especially for beginners, as through this process the main content of the chapter is learnt. Additionally, more than 1000 references, placed, according to their relevance, directly at the end of each chapter, are provided to give the reader access to more specialized information if required. To conclude, the authors have very competently integrated fundamental theories and physical phenomena with some recent developments in tribological engineering in this new edition. This well-illustrated textbook is a valuable source of information for anyone working and/or studying in the field of tribological and mechanical engineering, i.e. researchers, lecturers, engineers and students. Due to the excellent content of this book, it would even justify a price twice as high as demanded, particularly if the binding and paper quality chosen by the new publisher was of the same standard as the first edition. K. Friedrich and Z. Zhang Institute for Composite Materials Ltd., University of Kaiserslautern, D-67663 Kaiserslautern Germany