Ultrasonic Spectral Analysis for Nondestructive Evaluation

359 Pages·1981·32.46 MB·English

by  Dale W. Fitting, Laszlo Adler

Ultrasonic
Spectral Analysis
for Nondestructive
Evaluation
Ultrasonic
Spectral Analysis
for Nondestructive
Evaluation
Dale W. Fitting
and
Laszlo Adler
Ohio State University
Columbus, Ohio
Springer Science+Business Media, LLC
Library of Congress Cataloging in Publication Data
Fitting, Dale.
Ultrasonic spectral analysis for nondestructive evaluation.
Bibliography: p.
Includes indexes.
1. Non-destructive testing. 2. Ultrasonic testing. 3. Spectrum analysis. 1. Adler,
Laszlo, 1932- . Title.
TA417.4. FS4 620.1'1274 80-14991
ISBN 978-1-4613-3128-5 ISBN 978-1-4613-3126-1 (eBook)
DOI 10.1007/978-1-4613-3126-1
© 1981 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1981.
Softcover reprint of the hardcover 1s t edition 1981
AlI rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electrical, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
Acknowledgments
The authors are grateful to Battelle Memorial Institute for financial support of this
work. Special thanks are extended to Mr. G. J. Posakony, Battelle Northwest
Laboratories Program Monitor, for his initiation and continuous interest in this
problem.
Appreciation is also extended to the following:
Nondestructive Testing Laboratory, Metals & Ceramics Division, Oak Ridge
National Laboratory-especially R. W. McClung, Hugh Whaley (now at Babcock &
Wilcox, Lynchburg, Virginia), K. V. Cook, and Bill Simpson-who initiated our
interest in ultrasonic spectroscopy;
Ultrasonics Group, The University of Tennessee-especially M. A. Breazeale
and T. K. Bolland-for their suggestions and cooperation;
Maxine Martin for her editorial assistance and excellent typing of the
manuscript.
Gale Slutski and Kerstin Kleber for transferring our ideas into the illustrations.
Last but not least, we would like to acknowledge the scientists, both here and
abroad, whose contributions to the field of ultrasonic spectral analysis made this
work possible.
The work contained in this book was performed while the authors were
associated with the University of Tennessee, Knoxville.
Ohio State University Dale W. Fitting
Laszlo Adler
v
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2. Ultrasonic Spectroscopic Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Continuous-Wave Sinusoid and Sinusoidal Burst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Ideal Broadband Pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Rectangular Pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Other Pulse Shapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Single Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Exponential Pulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Arbitrary Pulse Shapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Electrical Coupling Network, I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Coaxial Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Response Equalization Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Transmitting Transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Equivalent-Circuit Representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Derivation of Frequency Response from the
Equivalent Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Mechanical Pulse Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Broadband Transmitting Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Electrostatic Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Electromagnetic Acoustic Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Transmitting Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Matching Components to Optimize Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Producing an Ultrasonic Pulse Having an
Arbitrarily Chosen Spectrum................................................... 34
Laser Generation of Ultrasonic Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Radiation Coupling, I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Mechanical Coupling Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Intrinsic Energy Losses-Scattering and Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Geometrical Energy Loss-The Ultrasonic Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Material under Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Radiation Coupling, II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Transfer Function for Disk-to-Disk Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Receiving Transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Piezoelectric Receivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
vii
viii Contents
Acoustoelectric Transducer 52
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Capacitive Receiver 53
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Electrical Coupling Network, II 53
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Differentia tor 54
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Low-Pass Filter .. 54
0 0 ...... 0 .. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .... 0 0 0 0 0 0 0 0 0 .. 0 0 0 0 0 0 0 .. 0 0 .... 0 0 0 0 0 0 0 0 .. 0
Amplifier 55
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Analog Gate 57
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Sampling and Digitization 58
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Sampling 58
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Digitization 58
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Transient Recorders 62
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Charge-Transfer Devices 63
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Equivalent-Time Sampling 63
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Receiving Subsystems 66
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Response Equalization Networks .. 67
0 0 0 .... 0 0 0 0 .... 0 0 0 0 .... 0 0 0 0 0 0 0 0 0 0 .... 0 0 0 0 0 .... 0 0 0
Spectrum Analysis 69
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Fourier Analysis 70
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Analog Spectrum Analyzers 73
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Digital Spectrum Analyzer 78
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Additional Analysis Techniques 82
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Complete Ultrasonic Spectroscopic Systems 85
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
3. Applications of Ultrasonic Spectroscopy to
Materials Evaluation 93
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 • 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 • 0 0 0 0 0
Defect Characterization 93
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
General Considerations 94
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Theoretical Considerations 94
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Experimental Work .. 98
0 0 .... 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .... 0 ...... 0 0 0 0 .. 0 0 .. 0 0 .... 0 0 0 0 0 0 0 0 0 0 .. 0
Defect Characterization Utilizing Contact Measurements 101
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Characterization of Defects in Flat Immersed Samples I 02
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Phase Spectroscopy ...... 106
0 .. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ........ 0 0 0 0 0 .. 0 .. 0 0 0 .... 0 0 0 0 0 0 0 0 0 0 .. 0
Inversion Techniques 109
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Adhesive Bonds I 10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Models and Theoretical Developments I 10
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Experimental Investigations 113
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Surface Properties 116
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Surface Roughness 116
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Periodic Structure 118
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Corrosion, Deformation, and Fatigue 119
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Surface-Breaking Cracks 120
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Subsurface Gradients 122
0 0 0 0 0 0 0 ................ 0 0 0 0 0 0 0 .. 0 0 ...... 0 0 0 .. 0 0 0 0 0 .......... 0 0
Strength-Related Properties 124
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Fracture Mechanics Parameters .... 125
0 0 .... 0 0 0 0 .... 0 0 0 .. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .... 0 .... 0 0 ..
Fracture Toughness 126
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Microstructure 128
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Grain Size Distribution 129
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Quantitative Scattering Formulae 129
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Experimental Determination of Microstructure 130
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Ultrasonic Backscattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Frequency-Dependent Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Intrinsic Energy Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Measurement Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Velocity Dispersion.................................................................. 136
Mechanisms Causing Dispersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
4. Questionnaire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
5. Abstracted Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
1
Introduction
Ultrasonic spectroscopy is the study of ultrasonic waves resolved into their Fourier
frequency components. Since many material properties manifest themselves as
amplitude or phase changes in ultrasonic waves used to interrogate a specimen,
ultrasonic spectroscopy has proven to be quite valuable.
Initially, investigations were carried out using narrowband ultrasonic instru
mentation. Later, the value of a broadband ultrasonic pulse was recognized. Analysis
of the pulse was found to give information simultaneously over a wide range of
frequencies. The first system to utilize multifrequency (broadband) ultrasonic pulses
was built by Gericke (1960-059)* at the Army Research Laboratory. His system used
a contact transducer operated in the pulse-echo mode. Gericke also appears to have
been the first to use the term ultrasonic spectroscopy. In analogy with visual
inspection by white light, he postulated that additional information could be
obtained corresponding to the "color" of the waves after interaction with the
material. Gericke attempted to obtain "white ultrasound" by shock-exciting a
damped ceramic transducer. His results indicated qualitatively that the ultrasonic
spectrum of an echo contains information related to the configuration of a void in a
solid and to the microstructure (grain size) of a material.
A few years later, Whaley and Cook (005) at Oak Ridge National Laboratory
built the first immersion system for spectrum analysis. Whaley and Adler (036)
extended spectrum analysis to a multitransducer system, thus introducing pitch-catch
and through-transmission ultrasonic spectroscopy. In a number of model experi
ments (012, 036, 037, 038, 039) Whaley and Adler demonstrated that quantitative
information could be obtained from the spectrum of the received ultrasonic signal.
Their interference model was the first analytical approach for relating size and
orientation of simple discontinuities to the frequency spectrum.
About the same time as work in the United States was going on, several groups
of investigators in England began developing ultrasonic spectroscopic systems.
Brown and Lloyd at City University in London (026, 030, 180, 192, 245) began to
utilize spectroscopy for the study of laminated structures and for defect characteriza
tion. In addition, they began development of broadband transducers. Note should
be made of the two symposia dealing with ultrasonic spectroscopy which were held
at City University-one in 1970 (268-272), the next in 1976 (241-250).
During the last few years, additional groups of investigators in the United
States have become involved with ultrasonic spectroscopy. Much of this research has
been stimulated by a program on quantitative nondestructive testing supported by
*See Chapter 5, Abstracted Bibliography, for an explanation of the referencing system.
1
2 Chspter1
the Advanced Research Projects Agency (ARPA), the Air Force Materials Labora
tory (AFML), and operated through the Rockwell Science Center. Theoretical
investigations were funded, as well as basic experimental research and applications
oriented studies.
At the Rockwell Science Center, Tittmann and Elsley (004, 133, 379, 409) have
studied scattering of ultrasonic waves from voids. Their unique experimental system
permits accumulation of data on the angular as well as the frequency dependence of
scattering. Additional work by Tittmann and others at Rockwell (181) has been
directed toward the development of improved ultrasonic standards. Studies of waves
diffracted by fluid-filled cavities were carried out at Cornell by Pao and Sachse (087,
091, 149, 176).
Ultrasonic spectroscopy has been applied to the evaluation of adhesive bonds
by Alers (200, 432, 459, 466) at Rockwell, Rose and Meyer (020, 034, 118) at Drexel,
and Chang, Couchman, and Yee (177, 218, 256) at General Dynamics.
Not all investigations have centered on experimental work. Several theoreticians
have recently developed theories for elastic wave diffraction by voids. These theories
provide the basis for relating the frequency dependence of the scattered signal to
defect characteristics. In the long-wavelength limit Gubernatis, Domany, and
Krumhansl (304, 314, 318) used the Born approximation, Datta (325, 333) employed
a matched asymptotic method, and Pao and Varaden (327, 329, 330) as well as
Waterman (326, 328) used a scattering matrix technique to investigate the frequency
dependent nature of ultrasonic scattering. Achenbach, Gautesen, and McMaken
(323, 324) used elastodynamics and ray theory to obtain analytically the diffraction
field in the short-wavelength limit. For this same regime, Adler and Lewis (14, 145)
applied Keller's theory to study scattering from planar cracks. Inversion techniques
developed by Bleistein and Cohen (427, 455) and Mucciardi et a/. (119, 126, 447,
454) provide a means for relating spectral features to flaw characteristics.
Adler, Cook, and Simpson at Oak Ridge N a tiona) Laboratory have introduced
several applications of ultrasonic spectroscopy, which include wall thickness, phase,
and attenuation measurements (005, 044). Investigations are being made of phase
spectroscopy by Nabel (073, 232) in Germany, and by Simpson, Adler, and Elsley in
the United States. An important contribution to the understanding of ultrasonic
spectroscopy was provided by Simpson (002, 013), who used a Fourier-transform
model to explain features in the diffracted wave spectra.
Correlations of the ultrasonic spectrum with strength-related properties have
been made theoretically by Rice and Budiansky (234), and experimentally by Vary
(334, 488, 489) and Elsley, Richardson, and Thompson (004).
Ultrasonic studies of surface roughness and periodicity by Quentin, Jungman,
deBilly, and Cohen-Tenoudji (138, 139, 140) have shown the value of information
contained in the spectra. Szabo (211) and Richardson and Tittmann (321, 403) have
developed inversion techniques for deducing subsurface gradients from surface wave
dispersion measurements.
Papadakis at Ford Motor Company has performed thorough investigations of
the application of ultrasonic spectroscopy to attenuation measurements (016, 023,
212) and microstructure (021, 031, 186).