- Email: [email protected]
Introduction to electromagnetic nondestructive test methods
BOOK REVIEW Introduction to electromagnetic nondestructive test methods H. L. Libby John Wiley & Sons Ltd, Chichester, 1971. £8.50. pp 365 This book approaches the complex field of electromagnetic test methods in a new way, giving a number of views on the "tree of insight' from different perspectives. The first three chapters illuminate the trunk and the main branches of this tree; the origin, general principles, techniques and applications will provide a general view of electromagnetic ndt to the inexperienced, but interested reader; the experienced reader, however, will find it useful as a basis for the following chapters, The final chapters illustrate the young twigs of new knowledge and complicated developments such as multiparameter testing and special applications of eddy-current techniques other than that for ndt. In this way the book serves as an introduction to students, physicists and engineers and as an aid to those who are engaged in development and application. We have to judge whether this book achieves its purpose.
The properties of the different coil designs and arrangements of coils are treated in Chapter 6 semi-intuitively. All the usual coil arrangements are mentioned and discussed using the same approximation: the coil is assumed to be built up of many short winding parts which individually contribute to the resulting signal. Such a treatment results, however, in generalisations about coil choice and coil design. Chapter 7 deals with the new multi-frequency eddy-current system which allow the separation of the many different parameters each playing a role in eddy-current testing. Ii~ this chapter the author presents new mathematical approches to help in the understanding of the method and the practical instrumentation. Pulse methods related to the multi-frequency method are developed in Chapter 8 Some special aspects of eddy-current testing such as low and high temperature applications, temperature measurement, eddy-current exciting and receiving of ultrasonic waves and research interests in eddy-current testing are collected in Chapter 9. Under the title 'Development Aids' the final chapter conrains miscellaneous items such as a discussion of the advantages of vector presentation of signals, the use of models for research in eddy-current testing and some remarks o11 test standards. The final comparison of the most important impedance diagrams using different systems of units helps in the understanding of both the early and the newer publications in the field of eddy-current testing.
The book starts with the definition of electromagnetic testing and with a not so easy limitation of this topic. The historical background leading to the principles is given, Chapter 2 focuses more technically, but always in an intuitive manner, on the basic principles, techniques and applications and combines basic physical quantities such as magnetic field, magnetisation, frequency etc with the quantities guiding ndt such as signals, penetration depth etc. Handy formulae in the MKSA Unit System (rationalised units) which is used consistently in the whole book (praiseworthy!) are conducive to the practical application of electromagnetic test methods, Chapter 3 embodies typical block diagrams and functional
Some details of the mathematical treatment used in the book are found in the appendix. The author succeeded in bringing together in a new and very impressive way a great deal of the information that has up to now been scattered over a large number of publications.
descriptions of selected circuits. In Chapter 4 the test is viewed and analysed as a communication system, and communication system theory is then applied to explain the operation of the test and to analyse the test signals. This chapter is introducing the complex relations and quantities of a signal theory, which are used later in the book when multiparameter methods are
The whole presentation of this book is extraordinarily clear, this is partly due to the short abstracts preceding each chapter. The reader will also find excellent references which are not simply numbered and collected; short comments on each cited publication are given in the right place in the text, thus helping the reader to find the best way of informing himself more precisely on special topics.
described. Electromagnetic field theory and eddy-current flow prmciples are presented in Chapter 5. It should be noted that this very clear presentation approaches the problems from different view-points. This is not only a simple solution of Maxwell's equations under abstract boundary and initial conditions. It moreover relates the theoretical solutions and the final formulae to different physical facts. The different treatment of conceptions, such as plain electromagnetic wave, steady state oscillation, impedance, specialized transformer and a transmission line model, help to give a better understanding of the complicated phenomena,
Some practical examples of real instrumentation and some more details on results are missed a little in this book. These details have been purposely omitted by the author. but it may be possible that the advantages of a book being up-to-date for a longer time are outweighed by the need for more illustrative examples. On the other hand. this book does not set out to be a simple collection of recipes for daily practical problems of non-destructive testing. This book produces the right premises to understand new problems and questions and it encourages the reader to look for new solutions. He is forced to proceed into new fields in this special research and development, and this book is able to show him how to do so and where he has to start and perhaps this is the main value of this book which, after all, can be warmly recommended.
Many clear diagrams illustrate the text. The effects of ferromagnetic material are only briefly discussed. This can be forgiven as there is little information about this complex field.
414
I¥. Stumm
NON-DESTRUCTIVE
TESTING
. DECEMBER
t97t
The properties of the different coil designs and arrangements of coils are treated in Chapter 6 semi-intuitively. All the usual coil arrangements are mentioned and discussed using the same approximation: the coil is assumed to be built up of many short winding parts which individually contribute to the resulting signal. Such a treatment results, however, in generalisations about coil choice and coil design. Chapter 7 deals with the new multi-frequency eddy-current system which allow the separation of the many different parameters each playing a role in eddy-current testing. Ii~ this chapter the author presents new mathematical approches to help in the understanding of the method and the practical instrumentation. Pulse methods related to the multi-frequency method are developed in Chapter 8 Some special aspects of eddy-current testing such as low and high temperature applications, temperature measurement, eddy-current exciting and receiving of ultrasonic waves and research interests in eddy-current testing are collected in Chapter 9. Under the title 'Development Aids' the final chapter conrains miscellaneous items such as a discussion of the advantages of vector presentation of signals, the use of models for research in eddy-current testing and some remarks o11 test standards. The final comparison of the most important impedance diagrams using different systems of units helps in the understanding of both the early and the newer publications in the field of eddy-current testing.
The book starts with the definition of electromagnetic testing and with a not so easy limitation of this topic. The historical background leading to the principles is given, Chapter 2 focuses more technically, but always in an intuitive manner, on the basic principles, techniques and applications and combines basic physical quantities such as magnetic field, magnetisation, frequency etc with the quantities guiding ndt such as signals, penetration depth etc. Handy formulae in the MKSA Unit System (rationalised units) which is used consistently in the whole book (praiseworthy!) are conducive to the practical application of electromagnetic test methods, Chapter 3 embodies typical block diagrams and functional
Some details of the mathematical treatment used in the book are found in the appendix. The author succeeded in bringing together in a new and very impressive way a great deal of the information that has up to now been scattered over a large number of publications.
descriptions of selected circuits. In Chapter 4 the test is viewed and analysed as a communication system, and communication system theory is then applied to explain the operation of the test and to analyse the test signals. This chapter is introducing the complex relations and quantities of a signal theory, which are used later in the book when multiparameter methods are
The whole presentation of this book is extraordinarily clear, this is partly due to the short abstracts preceding each chapter. The reader will also find excellent references which are not simply numbered and collected; short comments on each cited publication are given in the right place in the text, thus helping the reader to find the best way of informing himself more precisely on special topics.
described. Electromagnetic field theory and eddy-current flow prmciples are presented in Chapter 5. It should be noted that this very clear presentation approaches the problems from different view-points. This is not only a simple solution of Maxwell's equations under abstract boundary and initial conditions. It moreover relates the theoretical solutions and the final formulae to different physical facts. The different treatment of conceptions, such as plain electromagnetic wave, steady state oscillation, impedance, specialized transformer and a transmission line model, help to give a better understanding of the complicated phenomena,
Some practical examples of real instrumentation and some more details on results are missed a little in this book. These details have been purposely omitted by the author. but it may be possible that the advantages of a book being up-to-date for a longer time are outweighed by the need for more illustrative examples. On the other hand. this book does not set out to be a simple collection of recipes for daily practical problems of non-destructive testing. This book produces the right premises to understand new problems and questions and it encourages the reader to look for new solutions. He is forced to proceed into new fields in this special research and development, and this book is able to show him how to do so and where he has to start and perhaps this is the main value of this book which, after all, can be warmly recommended.
Many clear diagrams illustrate the text. The effects of ferromagnetic material are only briefly discussed. This can be forgiven as there is little information about this complex field.
414
I¥. Stumm
NON-DESTRUCTIVE
TESTING
. DECEMBER
t97t