Robust speckle metrology techniques for stress analysis and NDT

202 Pages·2014·24.918 MB·English

by  Albertazzi, Armando, Viotti, Matias R

Library of Congress Cataloging-in-Publication Data
Viotti, Matias R., author.
RobustspecklemetrologytechniquesforstressanalysisandNDT/MatiasR.Viotti
and Armando Albertazzi, Jr.
pages cm.
Includes bibliographical references and index.
1.Specklemetrology.2.Strainsandstresses.3.Nondestructivetesting.I.Albertazzi,
Armando, Jr., author. II. Title.
TA418.7.V56 2014
620.1'1230287–dc23
2014021899
Published by
SPIE
P.O. Box 10
Bellingham, Washington 98227-0010 USA
Phone: [phone]
Fax: [phone]
Email: [email protected]
www.spie.org
Copyright © 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
All rights reserved. No part of this publication may be reproduced or distributed in
any form or by any means without written permission of the publisher.
The content of this book reflects the thought of the author(s). Every effort has been
made to publish reliable and accurate information herein, but the publisher is not
responsible for the validity of the information or for any outcomes resulting from
reliance thereon.
Printed in the United States of America.
First printing.
Table of Contents
Preface ix
List of Symbols and Notation xiii
1 NDT Applications in Engineering 1
1.1 Mechanical Design of Structures and Mechanical Parts 1
1.1.1 Mechanical-design procedure 1
1.1.2 The influence of working conditions on the mechanical
performance of the structure 3
1.2 The Importance of Inspection: Avoiding Accidents 5
1.3 Application of Nondestructive Techniques 6
1.4 TheImportanceofOpticalTechniquesasNondestructiveEvaluationTools 8
1.5 Requirements for Field Applications of Optical Techniques 9
References 11
2 Principles of Digital Speckle Pattern Interferometry 13
2.1 Introduction 13
2.2 Speckle Principle 14
2.3 Objective and Subjective Speckle 17
2.3.1 Objective speckle 17
2.3.2 Subjective speckle 18
2.4 Speckle Interferometry 19
2.5 Phase Shifting as a Quantitative Tool 27
2.6 Phase-Unwrapping Processing 32
References 36
3 Optical Configurations for Measurements Using DSPI 41
3.1 Displacement Measurements 41
3.1.1 Out-of-plane sensitivity 41
3.1.2 In-plane sensitivity 44
3.1.2.1 Measuring with only one sensitivity direction 44
3.1.2.2 Measuring along two sensitivity directions 45
3.1.2.3 Measuring along radial sensitivity directions 46
3.2 Derivative Measurements 52
v
vi TableofContents
3.3 Concluding Remarks 57
References 58
4 Robust Optical Systems 61
4.1 Introduction 61
4.2 Negative Environmental Agents for Optical Methods 62
4.2.1 Temperature 63
4.2.2 Humidity 64
4.2.3 Atmospheric conditions 64
4.2.4 Shock and vibration 65
4.2.5 Radiation and background illumination 65
4.3 Requirements for Robust Measurements 66
4.3.1 Robust 67
4.3.2 Flexible 67
4.3.3 Compact 67
4.3.4 Stable 67
4.3.5 User-friendly 67
4.3.6 Organized 68
4.4 Possible Solutions to Improve Robustness 68
4.4.1 Isolation 68
4.4.1.1 Environmental isolation 68
4.4.1.2 Temperature isolation 68
4.4.1.3 Radiation isolation 69
4.4.1.4 Vibration isolation 69
4.4.2 Robustness 70
References 72
5 Quantitative Evaluation of Stresses and Strains 75
5.1 Mechanical Stress and Strain Fields 75
5.2 Experimental Measurement of Stress and Strain Fields 79
5.3 Interferometric Solutions to Measure Mechanical
Stress and Strains 81
5.4 In-Field Applications 92
5.5 Final Remarks 96
References 96
6 Quantitative Evaluation of Residual Stresses 99
6.1 Residual Stress Fields 99
6.2 Experimental Measurement of Residual Stresses 101
6.3 Interferometric Solutions to Measure Residual Stresses 104
6.4 Qualitative Evaluation of Residual Stresses by Indentation 112
6.5 In-Field Applications 114
6.5.1 Determining the external loading of a pipeline 115
6.5.2 Measurement of combined stresses in a gas pipeline in
service 119
TableofContents vii
6.6 Final Remarks 120
References 121
7 Qualitative Fault Detection and Evaluation 125
7.1 Traditional Nondestructive Methods to Detect Defects 125
7.1.1 Visual inspection 125
7.1.2 Radiographic techniques 125
7.1.3 Magnetic techniques 126
7.1.4 Ultrasonic techniques 126
7.1.5 Liquid-penetrant inspection 126
7.1.6 Eddy-current methods 126
7.1.7 Thermography 127
7.2 Shearography as a NDT Inspection Tool 127
7.2.1 Optical configurations suitable for field applications 127
7.2.2 The importance of shearography as a NDT inspection tool 131
7.3 Excitation Methods Used for Flaw Detection 131
7.4 Requirements for in situ Applications 135
7.4.1 Uncooperative surfaces 135
7.4.2 Large inspection areas 135
7.4.3 Quality control for in-line production 135
7.4.4 Loading adjustment 136
7.5 Optical Setups for Inspection 136
7.5.1 Pipeline inspection 136
7.5.2 Tank inspection 140
7.5.3 Aeronautical inspection 141
7.6 Image Processing Tools for Fast Defect Identification 143
7.7 Commercial Systems 146
References 147
8 Digital Image Correlation for Structural Monitoring 151
8.1 Noninterferometric Methods for Monitoring 151
8.2 Fundamentals of Image-Matching Methods 152
8.3 Subset Shape Functions 153
8.4 Optimization Criteria for Pattern Merging 154
8.5 Optical Configurations Used in DIC 155
8.5.1 In-plane measurements using 2D DIC 155
8.5.2 Three-dimensional measurements using DIC 156
8.6 Application Examples 160
References 168
9 Closing Remarks 173
Index 177

Preface
The invention of the laser in the early 1960s allowed for light sources with a
high coherence degree, which generated many novel research lines in order
to make use of them. People working with these light sources noticed that a
high-contrast and fine-scale granular pattern was produced when a rough
surface was illuminated with laser light. This effect was called a “speckle
effect,” characterized by a random distribution of scattered light. After
recognizing that each speckle has a definite phase, several techniques were
developed to measure deformations, displacements, stresses, vibrations, and
inner defects.
Several multiauthor books have been published beyond the first one
published in 1978 (Speckle Metrology, edited by R. K. Erf)—including Digital
SpecklePatternInterferometryandRelatedTechniques,editedbyP.K.Rastogi,
and Advances in Speckle Metrology and Related Techniques, edited by
G. H. Kaufmann—show new branches in speckle metrology, new proposed
schemesandimprovementsinprocessingtechniques,andopticalapproachesthat
haveoccurredoverthelast20years.
The main goal of nondestructive testing (NDT) is to detect and
characterize anomalies that can adversely affect the performance of the
component under test without impairing its intended service.
Opticaltechniquescanbeconsideredasalternativeapproachestotraditional
NDT methods. They are very attractive for NDT due to their noncontacting
nature and their high relative speed of inspection. The application of digital
techniques allows for automatic processing. Consequently, a fast inspection
procedure enables the evaluation of large areas (e.g., aircraft wings and ship
structures) or a large number of parts (e.g., automotive components). Speckle
techniqueshavetheadvantagescitedforopticalmethods.Additionally,theyare
appropriatefortheevaluationofrealcomponentswithoutfurtherpreparationof
thesurfaceortime-intensiveanalysis.
Thisbookprovidestips,ideas,andexamplesforthesuccessfulapplication
of optical techniques (more specifically based on the speckle phenomenon)
outside the laboratory room. Readers can see that the topics presented in the
following nine chapters have been selected to benefit graduate students,
engineers, and scientists who are interested in the in-field application of
ix