This paper presents the results on the utilization of a wavelet transform to study the dispersion of laser-generated surface waves in an epoxy-bonded copper-aluminum layered specimen with and without unbond areas. Laser ultrasonic experiments based on the point-source/point-receiver (PS/PR) technique were undertaken to measure surface wave signals in a layered specimen. The wavelet transform with a Morlet wavelet function was adopted to analyze the group velocity dispersion of the surface wave signals. A novel hybrid formula for group velocity dispersion is proposed for measurements across unbond regions. Results and data obtained are in good agreement with calculated and experimental dispersion curves. The general behavior of the group velocity dispersion for different measurement, configurations can be utilized to differentiate the unbond regions in a layered structure.

1.
Braga
MB
,
1990
,
Wave Propagation in Anisotropic Layered Composites
,
Ph.D. dissertation
Stanford University
Stanford, CA
2.
Castagnede
B
Kim
KY
Sachse
W
Thompson
MO
,
1991
,
Determination of the Elastic Constants of Anisotropic Materials Using Laser-Generated Ultrasonic Signals
,
J. Appl. Phys
, vol.
66
2
(pg.
150
-
157
)
3.
Chai
J-F
Wu
TT
,
1994
,
Determinations of Anisotropic Elastic Constants Using Laser Generated Surface Waves
,
J. Acoustic Soc. Am
, vol.
66
2
(pg.
3232
-
3241
)
4.
Chen
Y-C
,
1994
,
Dispersion of Surface Waves in an Anisotropic Layered Medium
,
M.S. thesis
National Taiwan University
5.
Cho
H
Ogawa
S
Takarnoto
M
,
1996
,
Noncontact Laser Ultrasonics for Detecting Subsurface Lateral Defects
,
NDT&E International
, vol.
66
2
(pg.
301
-
306
)
6.
Dewhurst
R. J
Edwards
C
McKie
A. D. W
Palmer
S. B
,
1987
,
Estimation of the Thickness of Thin Metal Sheet Using Laser Generated Ultrasound
,
Appl. Phys. Lett
, vol.
66
2
(pg.
1066
-
1068
)
7.
Doyle
P. A
Scala
C. M
,
1991
,
Ultrasonic Measurement of Elastic Constants for Composite Overlays
,
Rev. Prog. in QNDE
, vol.
66
2
(pg.
1453
-
1459
)
8.
Ewing
WM
Jardetzky
WS
Press
F
,
1957
,
Elastic Waves in Layered Media
McGraw-Hill
New York
9.
Hlawatsch
F
Boudreaus-Bartels
GF
,
1992
,
Linear and Quadratic Time-Frequency Signal Representations
,
IEEE Signal Process Mag.
, vol.
66
2
(pg.
21
-
67
)
10.
Hurley
DA
Spicer
JB
Conant
RJ
Telschow
KL
,
1997
,
Determination of the Optical Absorption Coefficient via Analysis of Laser Generated Plate Waves
,
IEEE Ultrasonics, Ferro. Freq. Control
, vol.
66
2
(pg.
902
-
908
)
11.
Hutchins
DA
Lundgren
K
Palmer
SB
,
1989
,
A Laser Study of the Transient Lamb Waves in Thin Materials
,
J. Acoust. Soc. Am
, vol.
66
2
(pg.
1441
-
1448
)
12.
Johnson
MA
Berthelot
YH
Brodeur
PH
Jacobs
LA
,
1996
,
Investigation of Laser Generation of Lamb Waves in Copy Paper
,
Ultrasonics
, vol.
66
2
(pg.
703
-
710
)
13.
Kishimoto
K
Inoue
H
Hamada
M
Shibuya
T
,
1995
,
Time-Frequency Analysis of a Dispersive Waves by Means of Wavelet Transform
,
ASME JOURNAL OF APPLIED MECHANICS
, vol.
66
2
(pg.
841
-
846
)
14.
Nakano
H
Nagai
S
,
1991
,
Laser Generation of Anti-symmetric Lamb Waves in Thin Plates
,
Ultrasonics
, vol.
66
2
(pg.
230
-
234
)
15.
Onsay
T
Haddow
AG
,
1994
,
Wavelet Transform Analysis of Transient Wave Propagation in a Dispersive Medium
,
J. Acoustic Soc. Am.
, vol.
66
2
2
(pg.
1441
-
1449
)
16.
Proctor
TM
,
1982
,
An Improved Piezoelectric Acoustic Emission Transducer
,
J. Acoustic Soc. Am
, vol.
66
2
(pg.
1163
-
1168
)
17.
Rioul
O
Vetterli
M
,
1991
,
Wavelet and Signal Processing
,
IEEE Sp. Magazine
Oct
(pg.
14
-
38
)
18.
Ruskai
MB
Belykin
G
Daubechies
I
Meyer
Y
Coifman
R
Mallat
S
Ralphel
L
,
1992
,
Wavelets and Their Applications
Jones and Bartlett
Boston
19.
Scruby
CB
Drain
LE
,
1990
,
Laser Ultrasonics: Techniques and Applications
IOP Publishing Ltd
Bristol, UK
20.
Scudder
LP
Hutchin
DA
Guo
N
,
1996
,
Laser-Generated Ultrasonic Guided Waves in Fiber-Reinforced Plates: Theory and Experiment
,
IEEE Trans. Ultra. Ferro. and Freq. Control
, vol.
66
2
(pg.
870
-
880
)
21.
Spicer
JB
McKie
ADW
Wagner
JW
,
1990
,
Quantitative Theory for Laser Ultrasonic Waves in a Thin Plate
,
Appl. Phys. Lett
, vol.
66
2
(pg.
1882
-
1884
)
22.
Stroh
AN
,
1962
,
Steady-State Problems in Anisotropic Elasticity
,
J. Math. and Phys
, vol.
66
2
(pg.
77
-
103
)
23.
Veidt
M
Sachse
W
,
1994
,
Ultrasonic Point-Source/Point-Receiver Measurements in Thin Specimens
,
J. Acoust, Soc. Am
, vol.
66
2
(pg.
2318
-
2326
)
24.
Wu
TT
Chai
J-F
,
1994
,
Propagation of Surface Waves in Anisotropic Solids: Theoretical Calculation and Experiment
,
Ultrasonics
, vol.
66
2
(pg.
21
-
29
)
25.
Wu
T-T
Chen
YC
,
1996
,
Dispersion of Laser Generated Surface Waves in an Epoxy-Bonded Layered Medium
,
Ultrasonics
, vol.
66
2
(pg.
793
-
799
)
26.
Wu
T-T
Liu
Y-H
,
1999
,
Inverse Determinations of Thickness and Elastic Properties of a Bonding Layer Using Laser-Generated Surface Waves
,
Ultrasonics
, vol.
66
2
(pg.
23
-
30
)
This content is only available via PDF.
You do not currently have access to this content.