Courses in tribology

Courses in tribology

BOOK REVIEWS Teeting of Polymers Vol 3 J. V. Schnzilz and W. E. Brow11 (Edilors) Wiley Interscience (1967) 379 pp, f 9 5s This is the third volume...

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REVIEWS

Teeting of Polymers Vol 3 J. V. Schnzilz and W. E. Brow11 (Edilors) Wiley Interscience

(1967) 379 pp, f 9 5s

This is the third volume of a series intended to make readily available authoritative discussions of all aspects of the testing of polymers for testing experts, polymer chemists, physicists, materials scientists, engineers, manufacturers and all who need to control and apply test data. According to the editors, as much emphasis as possible is placed on the application of test evaluating service performance without presuming to establish standard procedures. To allow flexibility the preface states that each volume of the series will include contributions on a variety of testing topics with no formalised organization. However, to comply with the suggestions of readers of the two previous volumes, a thematic treatment has been attempted in the present volume by the grouping of related articles; seven chapters are concerned with the measurement of surface properties. These supplement two chapters in volume 1 and three chapters in volume 2 in the same area of testing. To avoid repetition, content of earlier volumes is omitted from some of the articles. Although referred to, the ommissions further defeat any aim of complete coverage of a part of the subject in one volume. Similar to volumes 1 and 2, the book is really a collection of articles of varying quality. Chapter 1 is a general guide to setting up, organizing and running a polymer testing laboratory. It emphasises the simple, intelligent approach which any responsible person would be expected to pursue. Chapter 2, ‘Influence on properties of specimen shape and preparation’, presents a comprehensive survey of the problems associated with specimen preparation. It provides a useful guide to factors which influence test results from the various types of standard test specimens and reviews the literature on the subject; discussion is adequately illustrated by relevant test data. A list of commercially available equipment for the moulding and manufacture of specimens is given but is of use only to readers in the USA. Thermal testing is dealt with in chapter 3. Special teste to assess the effect of temperature on mechanical and physical properties and dimensional stability of polymers are discussed but the descriptions of some test methods included in previous volumes have been omitted. Relevant ASTM test methods are listed and many references are included. The introduction to the section on surface property testing consists essentially of a list of references supplementing those given in the other six chapters. Many of the references are of a very general nature and some do not appear to be particularly relevant to polymer testing. Four of the chapters cover tribological aspects of surfaces. Under ‘Wear testing’ the complex mechanisms of wear are discussed and many of the now numerous abrasive wear testing machines are described together with the underlying basic principles of their operation. The development of a specific machine, the Armstrong abrader, is covered and significant conclusions derived from its use are summarized as a guide to standardizing wear testing procedure and the correlation of test results with service experience. The chapter on rubbing contact evaluation of polymers stresses the importance of presenting clear, accurate and complete test results; the significance of the ‘PV’ limit is emphasised. Test equipment and techniques for the determination of this parameter are described. The BpeCid application of plastics as ship’s hearings is reviewed with a short history of their application, the conditions of service and the failure mechanisms encountered by the US Fleet. The development of laboratory tests for bearing wear is discussed. An introduction to the mechanism of cavitation erosion of viscoelastic materials and the value and limitations of equipment used for its investigation are given. Indentation hardness testing, a most convenient and practical method of characterizing and assessing polymetric materials is covered

comprehensively. The shortcomings of standard hardness testing methods developed for metal when applied to polymers and rubbers are discussed. Modifications of test procedures and methods of presenting test data are dealt with in detail. The final chapter of the section explains the principles of sound recording and describes the manufacture of phonographic records in some twenty-five pages. Two pages are devoted to the testing procedure for surface quality, wear, noise and response concluding that the ear must be relied upon as the final judge. The final chapter of the book consists of forty-three pages of references on the source of standards and tests for polymers. It is a review of chapter 14 of volume 1, containing the same references with a few additions. Ten pages are devoted to the addresses of publishers or services. It is difficult to see why the articles with no real continuity are presented in expensive book form rather than contributions to a journal of similar title. D. Scott

Friction Ferodo

Materials

for Engineers

(2nd edition)

Ltd (1966) 79 pp

This book has been produced by the technical staff of Ferodo Ltd as a reference for transmission designers and users of friction materials. It is written in a readable style. Although it is intended primarily for general industrial applications, automotive as well as industrial transmission engineers will find it an extremely useful reference book. This second edition is a considerably revised and enlarged version of the first edition, which was published in 1961. It contains more recent information about thermal effects in brakes and clutches. Further improvement could have been made by the inclusion of an index instead of a rather elaborate and somewhat confusing contents page. The book gives a comprehensive guide to designing clutches and brakes with many worked examples. Numerous references are given for the reader who wishes to make a deeper study of the subject. The advantages and limitations of different friction materials are discussed. The chapter dealing with methods of attaching friction materials could be very valuable to maintenance engineers. The importance of the correct combination of friction material and ferrous mating surfaces to prevent excessive wear is explained. The composition and micro-structure for a suitable cast iron for brake drums is given and the effect upon brake drum performance of adding nickel, chromium and silicon is also discussed. A notable absence in the second edition is the chapter on ceramic friction materials. There must still be several applications for these materials other than in automotive and aviation practices, such as off-highway vehicles. The chapter on ‘Sintered metal clutch and brake linings’ contains the statement that oil has no adverse effect upon sintered metal plate clutches.in oil immersed applications. This would be a very questionable statement if an active extreme pressure oil was present under frequent clutch engagement conditions. The section on oil immersed clutches could be expanded to give more positive guidance on choosing the correct oil 60 avoiding clutch and brake band failures experienced by General Motors’ engineers in developing the first automobile automatic transmission in 1937. The inclusion of metric equivalents in tables has improved the value of this book but they have been omitted from some tables. In Table 2 a decimal figure has crept into the midst of fractions1 These are only small criticisms compared with the high technical value of the book which is enhanced by the excellent quality of the printing and illustrations. E. V. Evans TRIBOLOGY

May 1969

135

Psychologie | Schinkenmesser | Vedi Prodotto