Table Of ContentMechanics of
Nondestructive Testing
Mechanics of
Nondestructive Testing
Edited by
W. W. Stinchcomb
Virginia Polytechnic Institute and State University
Blacksburg, Virginia
Associate Editors:
J. C. Duke, Jr.
E. G. Henneke, II
K. L. Reifsnider
Virginia Polytechnic Institute and State University
Blacksburg, Virginia
Plenum Press . New York and London
Library of Congress Cataloging in Publication Data
Conference on the Mechanics of Nondestructive Testing, Virginia Tech, 1980.
Mechanics of nondestructive testing.
Papers from a conference held Sept. 10-12, 1980, sponsored by the Materials
Response Group, Engineering Science and Mechanics Dept., Virginia Polytechnic
Institute and State University.
Includes index.
1. Non-destructive testing-Congresses. I. Stinchcomb, W. W. II. Virginia Poly
technic Institute and State University. Engineering Science and Mechanics Dept.
Materials Response Group. III. Title.
TA417.2.C661980 620.1'127 80-23808
ISBN-13 978-1-4684-3859-8 e-ISBN-13: 978-1-4684-3857-4
001: 10.1007/978-1-4684-3857-4
Proceedings of the Conference on the Mechanics of Nondestructive Testing,
held at Virginia Polytechnic Institute and State University, Blacksburg, Virginia,
September 10-12, 1980.
© 1980 Plenum Press, New York
Softcover reprint of the hardcover 15t edition 1980
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N. Y. 10011
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the publisher
PREFACE
The synergism of the mechanics of nondestructive testing and the
mechanics of materials response has great potential value in an era
of rapid development of new materials and new applications for con
ventional materials. The two areas are closely related and an
advance in one area often leads to an advance in the other. As our
understanding of basic principles increases, nondestructive testing
is outgrowing the image of "black box techniques" and is rapidly
becoming a legitimate technical area of science and engineering. At
the present time, however, an understanding of the mechanics of
nondestructive testing is lagging behind other advances in the field.
The key to further development in the mechanics of nondestructive
testing lies in the mechanics of the phenomena or response being
investigated - a better understanding of materials response suggests
better nondestructive test methods to investigate the response
which, in turn, advances our understanding of materials response, and
so on.
With this approach in mind, the Materials Response Group of the
Engineering Science and Mechanics Department at Virginia Polytechnic
Institute and State University hosted a Conference on the Mechanics
of Nondestructive Testing on September 10 through 12, 1980. Sponsors
of the conference were the Army Research Office, the National Science
Foundation, and the Engineering Science and Mechanics Department.
The objective of the conference was to promote an understanding of
the mechanics of nondestructive testing as related to the evaluation
of materials response. The papers in this volume cover many of the
frequently used NDT methods and introduce several new and innovative
ideas in the field. Five overview papers present the general phi
losophy of optical techniques, analysis of acoustic emission, electro
magnetic methods, stiffness measurements, and ultrasonic techniques.
Collectively, the papers seek to develop relationships between non
destructive methods of investigation and the response of materials.
Our sincere appreciation is extended to all who worked so hard
and contributed to the success of the conference: the authors and
participants, Dr. Daniel Frederick, Head of the Engineering Science
v
PREFACE
and Mechanics Department, Dean Paul Torgersen, Dean of the College of
Engineering, Dr. Clifford Astill, the National Science Foundation,
Dr. Fred Schmiedeshoff, the Army Research Office, Dr. Ralph Siu, and
Dr. Richard Harshberger and the staff of the Donaldson Brown Con
tinuing Education Center at Virginia Tech. A very special recog
nition and note of gratitude is expressed to Mrs. Phyllis Schmidt and
Mrs. Betty Eaton who worked with patience and dedication in preparing
the manuscripts for publication.
Wayne W. Stinchcomb, Editor
and
John C. Duke,
Edmund G. Henneke, II,
Kenneth L. Reifsnider,
Associate Editors
September, 1980
Virginia Polytechnic Institute
and State University
Blacksburg, Virginia
CONTENTS
SESSION I
Mechanics of Nondestructive Testing: Overview
1. Optical Interference for Deformation Measurements--
Classical, Holographic and Moire Interferometry. . . 1
Daniel Post
2. Basic Wave Analysis of Acoustic Emission. . • . • . . .• 55
Robert E. Green, Jr.
3. A Survey of Electromagnetic Methods of Nondestructive
Testing. • . . . . . . . . . . . . . . . . . . . 77
W. Lord
4. Stiffness Change as a Nondestructive Damage Measurement.. 101
T. Kevin O'Brien
5. Concepts and Techniques for Ultrasonic Evaluation of
Material Mechanical Properties . . . . . . . . . • . 123
Alex Vary
SESSION II
Material Property Determination
Harold Burger, Chairman
1. Neutron Diffraction and Small-Angle Scattering as
Nondestructive Probes of the Microstructure of
Ma terials . . . . . . . • . . . . . . . . . . . 143
C. J. Glinka, H. J. Prask and C. S. Choi
2. Determination of Fundamental Acoustic Emission
Signal Characteristics . 165
Richard Weisinger
vii
viii CONTENTS
3. A Simple Determination of Von Karman Critical
Velocities • • . . . . • • . . . . • • . . . 187
R. B. Pond, Sr. and J. M. Winter, Jr.
4. Fracture Prediction by Rayleigh Wave Scattering
Measuremen t • . • • . . . • . • . . . • . • • • 197
M. T. Resch, J. Tien, B. T. Khuri-Yakub,
G. S. Kino, and J. C. Shyne
5. Anisotropic Elastic Constants of a Fiber
Reinforced Boron-Aluminum Composite. • 215
S. K. Datta and H. M. Ledbetter
6. Nondestructive Evaluation of the Effects of
Dynamic Stress Produced by High-Power
Ultrasound in Materials ...... . 231
Richard B. Mignogna and Robert E. Green, Jr.
SESSION III
Defect and Flaw Characterization
Robert Crane, Chairman
1. The Mechanics of Vibrothermography . . 249
K. L. Reifsnider, E. G. Henneke,
and W. W. Stinchcomb
2. Dynamic Photoelasticity as an Aid to Sizing
Surface Cracks by Frequency Analysis . . • . 277
A. Singh, C. P. Burger, L. W. Schmerr
and L. W. Zachary
3. Ultrasonic and X-Ray Radiographic Inspection and
Characterization of Defects in Gr/Al Composites. 293
T. Romano, L. Raymond, and L. Davis
4. Evaluation of Sensitivity of Ultrasonic Detection
of Delaminations in Graphite/Epoxy Laminates . . . 309
S. W. Schramm, I. M. Daniel
and W. G. Hamilton
SESSION IV
Material Damage-Initiation and Growth: Life Prediction
Francis Chang, Chairman
1. Influence of Initial Defect Distribution on
the Life of the Cold Leg Piping System . . . 325
B. N. Leis, M. E. Mayfield, T. P. Forte,
and R. J. Eiber
CONTENTS ix
2. In-Flight Acoustic Emission Monitoring. . • . . • • . . .• 343
Gary G. Martin
3. On Interrelation of Fracture Mechanisms of
Metals and Acoustic Emission. . . . . . 367
G. S. Pisarenko, S. I. Likhatsky,
and Yu. V. Dobrovolsky
4. Fatigue Delamination in CFRP Composites:
Study with Acoustic Emission and Ultrasonic
Testing • . . . . • . . . . 391
F. X. De Charentenay, K. Kamimura
and A. Lemascon
Index . . . . . . . . . • 403
OPTICAL INTERFERENCE FOR DEFORMATION MEASUREMENTS-
CLASSICAL, HOLOGRAPHIC AND MOIRE INTERFEROMETRY
Daniel Post
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061
INTRODUCTION
Interferometry is a powerful tool. It enables measurements
of surface topography, dimensional changes and deformations of
solid bodies, all in the sub-wavelength sensitivity range. This
article is a tutorial treatment of the subject. Its purpose is
to introduce modern interferometric techniques of engineering
measurements; and to explain them in sufficient detail to gener
ate a comfortable association with the subject. Ultimately,
the mission is to foster understanding and appreciation in order
to inspire increased utilization and further development.
The fundamentals of interferometry are easy to understand.
The rather diverse implementations, including holographic and
moire interferometry, fit under a common umbrella. Only a few
basic concepts and a few equations are involved and these will be
reviewed in sufficient depth for practical usefulness. Inter
ferometry is easy to apply to many important measurements problems.
The name has long been associated with delicate instrumentation
and masterful laboratory technique. These images no longer
represent many applications, and they are grossly relaxed in most
others. More than anything else, the substitution of lasers in
place of classical light sources has simplified the technology.
The fundamental ideas and relationships will be reviewed
first. Classical interferometry will be described, but with the
admission of lasers to the classical technology. Then, holography
and holographic interferometry will be explained. These techni
ques are especially useful for out-of-plane measurements, e.g.,
surface topography, change of specimen length, and displacements
2 DANIEL POST
normal to the specimen surface.
Moire interferometry will be presented last. This is an emerging
technology to measure in-plane displacements, i.e., displacements
in the plane of the specimen surface, with high sensitivity and
accuracy. While placed last by historical chronology, it holds
the promise of a powerful NDT technique for observation and
measurement of material integrity and structural performance.
Familiar codes will be used in the diagrams. It is es
pecially important to remember that a sketch of an eye (as in
Fig. 9) represents any observing system, such as a human eye, a
camera or a video receiver. In addition, a ray of light in a
diagram (as in Fig. 2) represents the beam of light that contains
the ray; when a reader sees a simple ray, he/she should always
picture the full beam and the wave trains and wavefronts traveling
in the beam. Always.
FUNDAMENTALS
Our Model of Light
The wave theory of light is sufficient to explain all the
characteristics we use. A parallel beam of light emitted in the
z-direction is depicted (at a given instant) as a train of re
gularly spaced disturbances that vary with z as
A a cos 2n ~ (1)
A
Symbol A describes the amplitude or strength of the disturbance,
which is usually viewed as the strength of an electro-magnetic
field at a point in space. Coefficient a is a constant. The
field strength varies harmonically along z, where the distance
between neighboring maxima is A, called the wavelength. Length
z is not endless--for that would represent an eternal light-
but it is very long compared to A; in the case of laser light,
length z of the wave train may be a million wavelengths or more.
Many such wave trains exist simultaneously in a beam of light.
However, the wave train is not stationary. It travels or
propagates through space with a very high constant velocity C.
At any fixed point along the path of the wave train, the disturb
ance is a periodic variation of field strength. Field strength
varies through one full cycle in the brief time interval A/C
(seconds/cycle); its frequency w is CiA (cycles/second). During
the passage of the wave train through any fixed point z = zo' the
light disturbance varies with time t as
