The understanding of vibration signals from turbo-machinery is an important feature of many industries. It forms the basis of condition monitoring and is of crucial importance in the rapid diagnosis and rectifcation of faults. The feld calls for a variety of skills ranging from instrumentation expertise to mathematical manipulation and signal processing. The focus is on gaining a physical understanding of the processes giving rise to vibration signals. This may be viewed as a process of seeking to infer internal conditions from (sometimes limited) external measured data.
This often requires some form of mathematical model, and the approach taken is to use some basic fnite element analysis to study system behaviour. These methods were frst applied to rotating machinery several decades ago, but with progress in computing and the advent of packages such as MATLAB®, the ease with which the concepts may be applied has dramatically improved. It is now a relatively straightforward matter to examine proposed design changes – in effect, to perform numerical experiments.
The material in this book stems both from my experiences in the industry and, in more recent years, of teaching and research in academia. Inevitably, my own experiences have, to some degree, inﬂuenced my choice of examples. In my various posts, I have had fruitful interactions with many people who have signifcantly enhanced my perception of problems in machinery.
There are too many people involved to thank individually, but I must mention three. Professor Mike Friswell and I have worked together closely for 20 years, and I acknowledge innumerable helpful and illuminating discussions. I also thank Professor John Penny for his help with proofreading and a number of helpful suggestions on the structure of the text. Both of these people were my co-authors, together with Professor Seamus Garvey, of the book I refer to in many places which gives a more complete discussion of rotor dynamics. My deepest thanks go to my wife, Rita: Not only has she given me grammatical advice, but has also helped maintain my sanity throughout the final months of preparing this text.