ULTRASONIC GUIDED WAVE BONDLINE EVALUATION OF THICK METALLIC STRUCTURES ...

215 Pages·2013·13.15 MB·English

The Pennsylvania State University
The Graduate School
ULTRASONIC GUIDED WAVE BONDLINE EVALUATION OF
THICK METALLIC STRUCTURES WITH VISCOELASTIC
COATINGS AND THE DEMONSTRATION OF A NOVEL MODE
SWEEP TECHNIQUE
A Dissertation in
Acoustics
by
Jason Bostron
(cid:13)c 2013 Jason Bostron
Submitted in Partial Fulfillment
of the Requirements
for the Degree of
Doctor of Philosophy
December 2013
The dissertation of Jason Bostron was reviewed and approved∗ by the following:
Joseph L. Rose
Professor of Acoustics
Chair of Committee, Dissertation Advisor
Clifford J. Lissenden
Professor of Acoustics
Bernard R. Tittmann
Professor of Acoustics
Kevin L. Koudela
Professor of Engineering Science and Mechanics
Victor W. Sparrow
Professor of Acoustics
Interim Chair, Graduate Program in Acoustics
∗Signatures are on file in the Graduate School.
Abstract
Ultrasonic guided waves are becoming more widely used in nondestructive eval-
uation applications due to their efficiency in defect detection, ability to inspect
hidden areas, and other reasons. This dissertation addresses two main topics: ul-
trasonic guided wave bond evaluation of thin and thick coatings on thick metallic
structures, and the use of a novel phased array technique for optimal guided wave
mode and frequency selection.
Bondintegrityisofinteresttoresearchersinnon-destructiveevaluationbecause
it is used as an indicator when assessing the health of structures. We consider
both a thin and a thick viscoelastic layer bonded to a metallic plate and use a
guided wave ultrasonic signal to assess bond integrity in hidden regions. This
work applies to relatively low-curvature pressurized pipe and vessels. Analytical
and finite element models are developed to describe wave propagation at high
frequencies relative to the plate thickness, where the plate can be approximated
as a half space. Finite element models are used to visualize wave propagation.
Experiments are performed on a 25 mm thick steel plate with both relatively thin
(3 mm) and thick (25 mm) coatings of various stiffnesses bonded to the surface.
Physically based wave features, such as amplitude ratio, energy ratio, frequency
ratio, pulse width, and arrival time are identified which may be used to assess bond
integrity in hidden regions.
With a thorough understanding of guided wave mechanics, researchers can
predict which guided wave modes will have a high probability of success in a
particular nondestructive evaluation application. However, work continues to find
optimal mode and frequency selection for a given application. This “optimal”
modecouldgivethehighestsensitivitytodefectsorthegreatestpenetrationpower,
increasing inspection efficiency. Since material properties used for modeling work
may be estimates, in many cases guided wave mode and frequency selection can be
adjusted for increased inspection efficiency in the field. In this work, a novel mode
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sweep technique is described and used to identify optimal mode points based on
quantifiable wave characteristics. The technique uses an ultrasonic phased array
comb transducer to sweep in phase velocity–frequency space and is demonstrated
using interface waves to inspect thick bonded structures. After sweeping through
nearby mode points, an optimal mode and frequency can be selected which has
the highest sensitivity to a defect, or gives the greatest penetration power. The
optimal mode choice for a given application depends on the requirements of the
inspection.
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Table of Contents
List of Figures x
List of Tables xv
List of Symbols xvi
Acknowledgments xix
Chapter 1
Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 Guided waves for bond evaluation . . . . . . . . . . . . . . . 2
1.1.2 A novel technique to optimize mode selection . . . . . . . . 3
1.2 Literature review . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 Overview of guided wave ultrasound . . . . . . . . . . . . . 4
1.2.2 Foundational theory . . . . . . . . . . . . . . . . . . . . . . 6
1.2.3 Solutions by matrix methods . . . . . . . . . . . . . . . . . . 6
1.2.4 Numerical methods . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.5 Modeling viscoelastic materials . . . . . . . . . . . . . . . . 10
1.2.6 Bond quality assessment . . . . . . . . . . . . . . . . . . . . 12
1.3 Dissertation scope, layout, and objectives . . . . . . . . . . . . . . . 14
Chapter 2
Description and development of useful tools 19
2.1 Global Matrix Method (GMM) . . . . . . . . . . . . . . . . . . . . 20
2.1.1 About the GMM . . . . . . . . . . . . . . . . . . . . . . . . 20
2.1.2 Rayleigh waves . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1.3 Stoneley waves . . . . . . . . . . . . . . . . . . . . . . . . . 22
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2.1.4 Guided waves in a layer on a half space . . . . . . . . . . . . 24
2.2 Semi-Analytical Finite Element Method (SAFEM) . . . . . . . . . . 26
2.2.1 About the SAFEM . . . . . . . . . . . . . . . . . . . . . . . 26
2.2.2 Inclusion of absorbing regions . . . . . . . . . . . . . . . . . 26
2.2.3 Validation of the SAFEMAR . . . . . . . . . . . . . . . . . 29
2.3 Abaqus FEA software . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.3.1 Using Abaqus to simulate guided wave propagation . . . . . 38
2.3.2 Python scripting in Abaqus . . . . . . . . . . . . . . . . . . 40
2.3.3 Implementation of important concepts . . . . . . . . . . . . 40
2.4 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Chapter 3
Thin elastic layer on an elastic half space - Theory/models 46
3.1 Problem definition . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.2 Mode solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.3 Mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4 Wave propagation simulation . . . . . . . . . . . . . . . . . . . . . 52
3.4.1 Finite element model design . . . . . . . . . . . . . . . . . . 52
3.4.2 Wave visualization . . . . . . . . . . . . . . . . . . . . . . . 53
3.4.3 Node displacement waveforms . . . . . . . . . . . . . . . . . 54
3.5 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Chapter 4
Thin viscoelastic layer on an elastic half space - Experiment 60
4.1 Considerations for viscoelastic materials . . . . . . . . . . . . . . . 61
4.2 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.2.1 Materials and sample fabrication . . . . . . . . . . . . . . . 65
4.2.2 Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.3 Experimental results . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.3.1 Waveform envelope and energy feature . . . . . . . . . . . . 68
4.3.2 Frequency-related features . . . . . . . . . . . . . . . . . . . 69
4.3.3 Arrival time feature and group velocity . . . . . . . . . . . . 72
4.4 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 5
Thick viscoelastic layer on an elastic half space - Theory/models 76
5.1 Guided interface wave mode solutions . . . . . . . . . . . . . . . . . 77
5.1.1 Stoneley wave solution . . . . . . . . . . . . . . . . . . . . . 77
5.1.2 Leaky Rayleigh-like wave solution . . . . . . . . . . . . . . . 80
5.1.3 SAFE method with absorbing regions . . . . . . . . . . . . . 81
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5.2 Wave propagation simulation . . . . . . . . . . . . . . . . . . . . . 84
5.2.1 Finite element model details and wave visualization . . . . . 84
5.2.2 Node displacement waveforms and features . . . . . . . . . . 88
5.2.3 Parametric model studies of attenuation feature . . . . . . . 89
5.3 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Chapter 6
Thick viscoelastic layer on an elastic half space - Experiment 93
6.1 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
6.1.1 Materials and sample fabrication . . . . . . . . . . . . . . . 94
6.1.2 Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
6.2 Experimental results . . . . . . . . . . . . . . . . . . . . . . . . . . 96
6.2.1 Example data: polycarbonate sample . . . . . . . . . . . . . 96
6.2.2 Attenuation feature . . . . . . . . . . . . . . . . . . . . . . . 97
6.2.3 Hidden defects . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.2.4 Mapping the defect edge . . . . . . . . . . . . . . . . . . . . 99
6.2.5 Frequency effect . . . . . . . . . . . . . . . . . . . . . . . . . 101
6.2.6 Cure cycle monitoring . . . . . . . . . . . . . . . . . . . . . 102
6.2.7 Cast coatings . . . . . . . . . . . . . . . . . . . . . . . . . . 104
6.3 Summary of experimental results . . . . . . . . . . . . . . . . . . . 109
6.4 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Chapter 7
Mode sweep technique for optimal mode selection 111
7.1 Precursors to the mode sweep technique . . . . . . . . . . . . . . . 112
7.2 Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
7.3 PAL Software development . . . . . . . . . . . . . . . . . . . . . . . 120
7.4 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
7.5 Experimental results . . . . . . . . . . . . . . . . . . . . . . . . . . 123
7.5.1 Penetration power . . . . . . . . . . . . . . . . . . . . . . . 123
7.5.2 Energy ratio feature . . . . . . . . . . . . . . . . . . . . . . 128
7.5.3 Frequency shift feature . . . . . . . . . . . . . . . . . . . . . 133
7.6 Suggestions for use of the new technique . . . . . . . . . . . . . . . 136
7.7 Chapter summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Chapter 8
Concluding remarks 138
8.1 Dissertation summary . . . . . . . . . . . . . . . . . . . . . . . . . 138
8.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
8.3 Future directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
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Appendix A
SAFEM formulation 143
Appendix B
PAL Program User’s Manual 149
B.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
B.2 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
B.3 Running the program . . . . . . . . . . . . . . . . . . . . . . . . . . 150
B.4 Settings tab container . . . . . . . . . . . . . . . . . . . . . . . . . 152
B.4.1 A/D and pulser settings . . . . . . . . . . . . . . . . . . . . 152
B.4.2 Individual channel pulser settings (ICPS) . . . . . . . . . . . 155
B.4.3 Digital Filtering . . . . . . . . . . . . . . . . . . . . . . . . . 156
B.4.4 Advanced Features . . . . . . . . . . . . . . . . . . . . . . . 157
B.4.5 Graph Settings . . . . . . . . . . . . . . . . . . . . . . . . . 159
B.4.6 Sweep Options . . . . . . . . . . . . . . . . . . . . . . . . . 160
B.4.7 Save Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
B.5 Display tab container . . . . . . . . . . . . . . . . . . . . . . . . . . 163
B.5.1 Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
B.5.2 FFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
B.5.3 Summation . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
B.6 Saving data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
B.7 Software structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Appendix C
Basic guided wave tutorial in Abaqus 169
C.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
C.2 Tutorial part 1: Guided waves in a 2D plate . . . . . . . . . . . . . 169
C.2.1 General notes . . . . . . . . . . . . . . . . . . . . . . . . . . 169
C.2.2 Part Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
C.2.3 Property Module . . . . . . . . . . . . . . . . . . . . . . . . 172
C.2.4 Assembly Module . . . . . . . . . . . . . . . . . . . . . . . . 172
C.2.5 Step Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
C.2.6 Interaction Module . . . . . . . . . . . . . . . . . . . . . . . 173
C.2.7 Load Module . . . . . . . . . . . . . . . . . . . . . . . . . . 173
C.2.8 Mesh Module . . . . . . . . . . . . . . . . . . . . . . . . . . 174
C.2.9 Job Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
C.2.10 Visualization Module . . . . . . . . . . . . . . . . . . . . . . 175
C.3 Tutorial part 2: Further exploration . . . . . . . . . . . . . . . . . . 176
C.4 Supporting code and other tips . . . . . . . . . . . . . . . . . . . . 178
C.4.1 Creating amplitudes . . . . . . . . . . . . . . . . . . . . . . 178
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C.4.2 Example batch files . . . . . . . . . . . . . . . . . . . . . . . 180
C.4.3 Example data extraction file . . . . . . . . . . . . . . . . . . 181
C.4.4 Tips for parametric studies . . . . . . . . . . . . . . . . . . . 183
C.4.5 Dispersion curves for 1 mm Al plate. . . . . . . . . . . . . . 186
Bibliography 188
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List of Figures
1.1 Normal beam and guided wave ultrasound inspection areas . . . . . 5
1.2 Flow chart for choosing guided wave type for bond inspection based
on coating and structure geometry . . . . . . . . . . . . . . . . . . 15
1.3 Flow chart describing the Hybrid Analytical FEM approach for
solving guided wave problems . . . . . . . . . . . . . . . . . . . . . 17
2.1 Rayleigh wave structure showing both the in-plane and out of plane
displacement relative to depth . . . . . . . . . . . . . . . . . . . . . 22
2.2 Stoneley wave structure for an aluminum-tungsten interface show-
ing both the in-plane and out of plane displacement relative to depth 24
2.3 Phase velocity dispersion curves for a soft layer on a hard half space 25
2.4 Normalized stiffness coefficient in the absorbing region (AR) calcu-
lated from Equation 2.7 for (a) continuous and (b) discrete ARs. . . 28
2.5 Phase velocity and attenuation calculated with SAFEMAR for a
Rayleigh wave in aluminum at 0.5 to 2 MHz . . . . . . . . . . . . . 31
2.6 Phase velocity and attenuation calculated with SAFEMAR for a
Rayleigh wave in aluminum at 0.167 to 2 MHz . . . . . . . . . . . . 32
2.7 Rayleigh wave structure calculated with SAFEMAR showing both
the in-plane and out of plane displacement . . . . . . . . . . . . . . 32
2.8 Rayleigh wave structure calculated with SAFEMAR showing the
displacement relative to normalized depth with the same mesh for
several different frequencies . . . . . . . . . . . . . . . . . . . . . . 33
2.9 Phase velocity and attenuation calculated with SAFEMAR for a
Stoneley wave at an aluminum-tungsten interface at 0.5 to 2 MHz . 34
2.10 StoneleywavestructurecalculatedwithSAFEMARforanaluminum-
tungsten interface showing both the in-plane and out of plane dis-
placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.11 Phase velocity dispersion curves calculated with SAFEMAR for a
soft layer on a hard half space . . . . . . . . . . . . . . . . . . . . . 35
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