Ultrasonics: Fundamentals and Applications

455 Pages·1991·26.977 MB·English

by  Heinrich Kuttruff (auth.)

ULTRASONICS
FUNDAMENTALS AND APPLICATIONS
UL TRASONICS
FUNDAMENTALS AND APPLICATIONS
HEINRICH KUTTRUFF
Professor of Technical Acoustics,
Technische Hochschule Aachen, Germany
ELSEVIER APPLIED SCIENCE
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© 1991 ELSEVIER SCIENCE PUBLISHERS LTD
British Ubrary cataloguing in Publication Data
Kuttruff, Heinrich.
Ultrasonics.
1. Ultrasonic waves
I. Title II. [Physik und Technik des Ultraschalls.
English)
534·55
ISBN 1-85166-553-6
Ubrary of Congress Cataloging-in-Publication Data
Kuttruff, Heinrich.
[Physik und Technik des Ultraschalls. English)
Ultrasonics fundamentals and applications/by Heinrich Kuttruff.
p. em.
Translation of: Physik und Technik des Ultraschalls.
Includes bibliographical references and index.
ISBN 1-85166-553-6
1. Ultrasonics. I. Title.
aC244.K8713 1991
534.5'5--dc20 90-1396
CIP
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Typeset and printed by The Universities Press (Belfast) Ltd.
PREFACE
This book is a translation of 'Physik und Technik des Ultraschalls',
originally published in 1988 by S. Hirzel Verlag, Stuttgart. As in the
German edition, it is based on lectures on ultrasound which the author
has given over the past fifteen years to students of electrical engineer
ing and physics at the Rheinisch-Westfiilische Technische Hochschule
Aachen, Germany. Its purpose is to explain and describe the
peculiarities of high frequency sound with general acoustics as a
foundation. It is these peculiarities which have led to the development
of specific methods of sound generation and sound detection on the
one hand and are relevant to the way ultrasound propagates in various
materials, and which are the origin of a wide range of technical
applications on the other.
The first part of the book is devoted to the fundamentals of
ultrasonics. Since the reader is not expected to have a knowledge of
general acoustics, introductory chapters survey the basic ideas and
laws of acoustics without systematically deriving the formulae pre
sented. Likewise, the third chapter, which deals with the radiation and
diffraction of sound, is still fairly general, although it is somewhat more
adapted to the specific requirements of ultrasound. In the three
subsequent chapters, the generation and detection or measurement of
ultrasound is dealt with. The seventh chapter is a digression on the
peculiarities of the hypersonic range. the following chapter is on the
most prominent causes of ultrasound absorption and also a description
of the basic methods of measuring sound velocities and attenuation in
the ultrasonic range.
In the second part of the book a series of typical and important
applications of ultrasound is covered. Firstly, mention is made of the
application of ultrasound in signal processing and measuring tech
niques which have gained particular importance in the use of Rayleigh
waves during the past decade. Then follow two chapters on diagnostic
v
PREFACE
methods employing ultrasound, namely in non-destructive material
testing and medical diagnostics. The subsequent Chapter XII can be
considered as still belonging under this heading since it deals with
special methods of ultrasonic imaging. A separate chapter is devoted
to cavitation, which plays a supporting-if not the decisive-role in
some of the applications of high intensity ultrasound as described in
Chapter XIV. The book concludes with a short chapter on possible
health hazards related to ultrasound.
For a complete understanding of the book the reader needs some
elementary knowledge of physics as well as relevant mathematical
techniques, in particular he should be familiar with the fundamentals
of differential and integral calculus and also with the most common
mathematical functions. But even if he does not meet these prerequis
ites totally, the major content of the book should be comprehensible.
The units employed are those of the International System of Units
(metre, kilogram, second, ampere, etc.). As far as the symbols in
mathematical expressions are concerned it is not possible to avoid the
situation where some symbols have several different meanings. In
general, however, it will become clear from the context which quantity
is referred to by a particular symbol and therefore there is little danger
of confusion. Furthermore, the list of symbols included at the end of
the book should prove helpful in this respect.
References to relevant literature are made only when the author has
adopted results from a particular publication, or to enable the reader
to obtain more detailed information on a new and particular topic.
Thus, no attempt has been made to present in total all representative
publications. The same holds for the list of books and journals
compiled at the end of the book. Its only purpose is to facilitate access
to more special studies or to enable the reader to follow current
developments in the field of ultrasonics.
The author is indebted to many people who have assisted him in one
way or another. Thus, Professor Dr W. Eisenmenger has checked
through Chapters VII and VIII, whereas Professor Dr G. Rau has
critically read Chapter IX. To both of them lowe many valuable
comments. Diagrams and photographic material have been given to
the author by Professor Dr-Ing H. Ermert, Bochum; Dr-Ing H.
Giilhan, Aachen; Professor Dr W. Lauterborn, Darmstadt; Professor
Dr-Ing A. Troost and his co-workers, Aachen; and also by the
companies Ernst Leitz in Wetzlar, Scientific Medical Systems GmbH
in Wuppertal and VG Microscopes Inc. in East Grinstead (UK).
vi
PREFACE
Furthermore, the author is grateful to the firms KLN Ultraschall
GmbH in Heppenheim, Schoellerschall-Ultraschallanlagen GmbH in
Morfelden-Walldorf and Krautkramer GmbH in Cologne for giving
him the chance to collect information on modem ultrasonic methods
employed in their factories. Finally, he would like to thank Dipl.
Phys. M. Vorlander and Mr Pietzonka for preparing the drawings,
either by hand or computer.
The author wishes to express his most sincere thanks to his
colleague, Professor Peter Lord for his careful and sensitive translation
of the German text, and also to the publishers for complying with the
author's wishes and for the excellent production of the book.
vii
CONTENTS
Preface. . . . . . v
I Introduction. . . . 1
1.1 What is ultrasound? 1
1.2 A few historical remarks 3
1.3 Ultrasound in the living world . 5
1.4 Upper frequency limit of sound 7
n Basic Concepts of Acoustics. . 11
11.1 Sound fields and the physical quantities describing them 11
11.2 Sound propagation in gases and liquids. . . . . . .. 15
11.2.1 Basic relations between acoustical quantities,
the wave equation. . . . . . . . 15
11.2.2 Plane waves and spherical waves . 17
11.2.3 Energy density and intensity level. 22
11.2.4 Nonlinear effects 24
11.3 Sound waves in solids . 30
11.4 Reflection and refraction 38
11.5 Doppler effect. . . . . 46
m
Sound Radiation and Sound Diffraction 49
111.1 Signals in time and frequency representation, linear
systems. . . . . . . . . . . . . . . . 50
111.2 The principle of point source synthesis, the moving
piston . . . . . . . . . . . . 53
111.3 Radiation from a circular piston 58
111.3.1 Transient radiation. . . 58
III.3.2 Steady-state radiation. . 63
111.3.3 Total power radiated, radiation resistance. 69
111.4 Piston with non-uniform surface velocity 71
111.5 Diffraction and scattering. . . . . . . . . . . . 72
ix
CONTENTS
IV Generation of Ultrasound-Part I 79
IV.1 The piezoelectric effect. . . . . 80
IV.2 Piezoelectric materials . . . . . 86
IV.3 Basic piezoelectric equations, electro-mechanical cou
pling factor . . . . . . . . . . . . . . . . . . .. 89
IVA Dynamic characteristics of piezoelectric transducers
operated in their thickness mode. . . . . . . . . .. 94
IVA.1 Transducer loaded on both sides with media of
equal characteristic impedance, Z2 = Z1. .. 97
IVA.2 Transducer unloaded at its rear side, Z2 = 0 . 105
IVA.3 Transducer kept rigid on its rear side, Z2 = 106
00
IVAA Transducer matched at its rear side, Z2 = Zo. 106
IV.S Mechanical and electrical equivalent circuit of a piezo-
electric transducer near its resonance. . . . . . .. 109
IV.6 Practical design of piezoelectric ultrasound generators 112
V Generation of Ultrasound-Part II . 119
V.1 Composite piezoelectric transducers 119
V.2 Piezoelectric bending transducers . 122
V.3 Generation of high frequency ultrasound 124
VA Concentration of ultrasound by focusing 126
V.5 Generation of high vibrational amplitudes 130
V.5.1 Stepped transformer. . . 131
V.S.2 Conical transformer. . . . . . . 132
V.5.3 Exponential transformer. . . . . 134
V.6 Generation of shear waves and Rayleigh waves 135
V.7 Magnetostrictive generation of ultrasound. 139
V.8 Electrostatic ultrasound generators. 145
V.9 Mechanical methods . . . . . . . . . . 148
VI Detection and Measurement of Ultrasound 153
VI. 1 Detection of ultrasound with extended piezo trans-
ducers, reciprocity . . . . . . . . . 154
VI.2 Electrostatic receivers . . . . . . . 160
VI. 3 Ultrasound microphones, calibration 161
VIA Mechanical detection. . . . . . . . 167
VI.S Thermal ultrasound detectors . . . . 170
VI. 6 Diffraction of light by ultrasound waves 171
x
CONTENTS
VI.6.1 Debye-Sears effect. . . .... 171
V1.6.2 Diffraction of light by shear waves 177
V1.6.3 Bragg diffraction. 178
VI.7 Visualization of ultrasound . . . . . . . 180
VII Generation and Detection of Sound with Frequencies
above 1 GHz (Hypersound). . . . . . . . . . . . . 187
VII. 1 Coherent methods for the generation and detection of
hypersound . . . . . . . . . . . . . . . . . . . . 188
VII.2 Phonons (sound quanta) in solids . . . . . . . . . . 191
VII.3 Quantum acoustical interpretation of some effects of
ultrasound . . . . . . . . . . . . . . . 193
VII.4 Generation of hypersound with heat pulses . 195
VII.5 Detection of hypersound with superconducting bolo-
meters . . . . . . . . . . . . . . . . . . . 197
VII.6 Generation and detection of incoherent hypersound with
superconducting tunnel contacts . 199
VII.7 Detection of 'natural' hypersound 203
VIII Absorption of Ultrasound. . . . 207
VIII. 1 Classical sound absorption in gases and liquids 208
VIII.2 Molecular sound absorption in gases 210
VIII.3 Sound absorption in liquids . . . . 217
VIII.4 Sound absorption in solids . . . . 221
VIII.4.1 Polycrystalline materials . 223
VII1.4.2 Sound absorption due to dislocations 226
VIII.4.3 High polymers . . . . . . 229
VIII.4.4 Sound absorption due to interaction with
thermal phonons . . . . . . . . . 231
VII1.4.5 Sound absorption due to interaction with
electrons . . . . . . . . . . . . 232
VIII. 5 Experimental methods for the determination of sound
velocity and attenuation in the ultrasonic range . . . . 233
IX Applications in Signal Processing and Measuring Techn-
iques . ................ . 241
IX.l Ultrasonic delay lines. . . . . . . . . . . 242
IX.l.l Lines with monomode propagation . 245
IX.1.2 Lines with multimode propagation . 247
xi
CONTENTS
IX.2 Rayleigh wave filters . 250
IX.2.1 The interdigital transducer as a transversal filter 251
IX.2.2 Real Rayleigh wave filters. 254
IX.2.3 Delay lines 256
IX.2.4 Further SAW devices . 259
IX.2.5 Fabrication of SAW devices . 260
IX.3 Light modulation and light deflection. 262
IX.4 Other small-signal applications 264
X Non-destructive Testing of Materials . 269
X.l Survey of various testing methods 270
X.2 Impulse echo method. 273
X.3 Frequencies and wave types . 277
X.4 Transducers for flaw detection. 279
X.5 Types of display . 284
X.6 Suitability of materials for testing 287
X.7 Practical examples of ultrasonic flaw detection. 290
XI Application of Ultrasound in Medical Diagnostics 297
XLI Acoustic properties of biological tissue 298
XI.2 Impulse echo method. 300
XI.2.1 Time gain control 301
XI.2.2 Transducers . 302
XI.2.3 Modes of display . 306
XL2.4 Scanning 308
XI.3 Typical applications of the impulse echo method in
sonography . 312
XI.3.1 Internal medicine 312
XI.3.2 Gynaecology and obstetrics 315
XI.3.3 Cardiography 317
XI.3.4 Encephalography. 318
XI.3.5 Opthalmology . 320
XI.3.6 Ultrasound-guided aspiration 321
XL4 Doppler sonography . 322
XII Special Methods of Ultrasonic Imaging . 325
XII. 1 Ultrasonic microscopy 326
XII. 1.1 Microscopes with extended sensors 327
xii