Structural Dynamics and Vibration in Practice An Engineering Handbook by Douglas Thorby
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Structural Dynamics and Vibration in Practice An Engineering Handbook by Douglas Thorby


This book is primarily intended as an introductory text for newly qualified graduates, and experienced engineers from other disciplines, entering the field of structural dynamics and vibration, in industry. It should also be found useful by test engineers and technicians working in this area, and by those studying the subject in universities, although it is not designed to meet the requirements of any particular course of study.

No previous knowledge of structural dynamics is assumed, but the reader should be familiar with the elements of mechanical or structural engineering, and a basic knowledge of mathematics is also required. This should include calculus, complex numbers and matrices. Topics such as the solution of linear second-order differential equations, and eigenvalues and eigenvectors, are explained in the text. Each concept is explained in the simplest possible way, and the aim has been to give the reader a basic understanding of each topic, so that more specialized texts can be tackled with confidence.

The book is largely based on the author’s experience in the aerospace industry, and this will inevitably show. However, most of the material presented is of completely general application, and it is hoped that the book will be found useful as an introduction to structural dynamics and vibration in all branches of engineering. Although the principles behind current computer software are explained, actual programs are not provided, or discussed in any detail, since this area is more than adequately covered elsewhere. It is assumed that the reader has access to a software package such as MATLAB .

A feature of the book is the relatively high proportion of space devoted to worked examples. These have been chosen to represent tasks that might be encountered in industry. It will be noticed that both SI and traditional ‘British’ units have been used in the examples.

This is quite deliberate, and is intended to highlight the fact that in industry, at least, the changeover to the SI system is far from complete, and it is not unknown for young graduates, having used only the SI system, to have to learn the obsolete British system when starting out in industry.

The author’s view is that, far from ignoring systems other than the SI, which is sometimes advocated, engineers must understand, and be comfortable with, all systems of units. It is hoped that the discussion of the subject presented in Chapter 1 will be useful in this respect.

The book is organized as follows. After reviewing the basic concepts used in structural dynamics in Chapter 1, Chapters 2, 3 and 4 are all devoted to the response of the single degree of freedom system. Chapter 5 then looks at damping, including non-linear damping, in single degree of freedom systems.

Multi-degree of freedom systems are introduced in Chapter 6, with a simple introduction to matrix methods, based on Lagrange’s equations, and the important concepts of modal coordinates and the normal mode summation method. Having briefly introduced eigenvalues and eigenvectors in Chapter 6, some of the simpler procedures for their extraction are described in Chapter 7. Methods for dealing with larger structures, from the original Ritz method of 1909, to today’s finite element method, are believed to be explained most clearly by considering them from a historical viewpoint, and this approach is used in Chapter 8.

Chapter 9 then introduces the classical Fourier series, and its digital development, the Discrete Fourier Transform (DFT), still the mainstay of practical digital vibration analysis. Chapter 10 is a simple introduction to random vibration, and vibration isolation and absorption are discussed in Chapter 11. In Chapter 12, some of the more commonly encountered self-excited phenomena are introduced, including vibration induced by friction, a brief introduction to the important subject of aircraft flutter, and the phenomenon of shimmy in aircraft landing gear.

Finally, Chapter 13 gives an overview of vibration testing, introducing modal testing, environmental testing and vibration fatigue testing in real time.

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