Abstract

Fiber Bragg grating (FBG) sensors are often applied as Lamb wave detectors for structural health monitoring (SHM) systems. Analyzing the measured signal for the identification of structural damage requires a high signal-to-noise ratio (SNR) because of the low-amplitude Lamb waves. This paper applies a two-dimensional ultrasonic horn between the structure and a remotely bonded FBG sensor to increase the amplitudes of the measured signal. Experimentally we test a variety of ultrasonic geometries and demonstrate a 100% increase in the measured ultrasonic signal amplitude using a metallic ultrasonic horn with step-down geometry. A bonding procedure for the combined ultrasonic horn and optical fiber is also developed that produces repeatable signal measurements. For some horn geometries, an additional vibration signal at the Lamb wave excitation frequency is observed in the measurements. Laser Doppler vibrometry (LDV) measurements and finite element analysis demonstrate that the signal is due to the natural vibration of the horn. The experimental results demonstrate that using an aluminum ultrasonic horn to focus wave is an excellent method to increase the sensitivity of the FBG to the small amplitude Lamb wave, provided the horn vibration characteristics are taken account in the design of the measurement system.

References

1.
Betz
,
D. C.
,
Thursby
,
G.
,
Culshaw
,
B.
, and
Staszewski
,
W. J.
,
2003
, “
Acousto-Ultrasonic Sensing Using Fiber Bragg Gratings
,”
Smart Mater. Struct.
,
12
(
1
), pp.
122
128
.
2.
Fakih
,
M. A.
,
Mustapha
,
S.
, and
Abdul-Aziz
,
A.
,
2019
, “
Robust Localization and Classification of Barely Visible Indentations in Composite Structures by Fusion of Ultrasonic Damage Indices
,”
ASME J. Nondestr. Eval.
,
2
(
3
), p.
031004
.
3.
Betz
,
D. C.
,
Thursby
,
G.
,
Culshaw
,
B.
, and
Staszewski
,
W. J.
,
2007
, “
Structural Damage Location With Fiber Bragg Grating Rosettes and Lamb Waves
,”
Struct. Health Monit.
,
6
(
4
), pp.
299
308
.
4.
Sikdar
,
S.
, and
Ostachowicz
,
W.
,
2019
, “
Ultrasonic Lab Wave-Based Debonding Monitoring of Advanced Honeycomb Sandwich Composite Structures
,”
Strain
,
55
(
1
), p.
12302
.
5.
Yu
,
L.
, and
Tian
,
Z.
,
2013
, “
Lamb Wave Structural Health Monitoring Using a Hybrid PZT-Laser Vibrometer Approach
,”
Struct. Health Monit.
,
12
(
5–6
), pp.
469
483
.
6.
Thursby
,
G.
,
Sorazu
,
B.
,
Betz
,
D.
, and
Culshaw
,
B.
,
2005
, “
Novel Methods of Lamb Wave Detection for Material Damage Detection and Location
,”
Proc. SPIE
,
5768
, pp.
313
322
.
7.
Staszewski
,
W. J.
,
bin Jenal
,
R.
,
Klepka
,
A.
,
Szwedo
,
M.
, and
Uhl
,
T.
,
2012
, “
A Review of Laser Doppler Vibrometry for Structural Health Monitoring Applications
,”
Key Eng. Mater.
,
518
, pp.
1
15
.
8.
Ramdhas
,
A.
,
Pattanayak
,
R. K.
,
Balasubramaniam
,
K.
, and
Rajagopal
,
P.
,
2015
, “
Symmetric Low-Frequency Feature-Guided Ultrasonic Waves in Thin Plates With Transverse Bends
,”
Ultrasonics
,
56
, pp.
232
242
.
9.
Postnova
,
J.
, and
Craster
,
R. V.
,
2007
, “
Trapped Modes in Topographically Varying Elastic Waveguides
,”
Wave Motion
,
44
(
3
), pp.
205
221
.
10.
Postnova
,
J.
, and
Craster
,
R. V.
,
2008
, “
Trapped Modes in 3D Topographically Varying Plates
,”
IMA J. Appl. Math.
,
73
(
6
), pp.
950
963
.
11.
Yan
,
X.
,
Zhu
,
R.
,
Huang
,
G.
, and
Yuan
,
F. G.
,
2013
, “
Focusing Guided Waves Using Surface Bonded Elastic Metamaterials
,”
Appl. Phys. Lett.
,
103
(
12
), p.
121901
.
12.
Tol
,
S.
,
Degertekin
,
F. L.
, and
Erturk
,
A.
,
2019
, “
3D-printed Phononic Crystal Lens for Elastic Wave Focusing and Energy Harvesting
,”
Addit. Manuf.
,
29
, p.
100780
.
13.
Tian
,
Z.
, and
Yu
,
L.
,
2017
, “
Wavefront Modulation and Controlling for Lamb Waves Using Surface Bonded Slice Lenses
,”
J. Appl. Phys.
,
122
(
23
), p.
234902
.
14.
Kudela
,
P.
, and
Ostachowicz
,
W.
,
2018
, “
Comparison of Lamb Wave Focusing Performance Using Wave Dispersion-Compensated Actuation and Plano-Concave Lenses
,”
J. Appl. Phys.
,
124
(
9
), p.
094901
.
15.
Sakai
,
T.
,
Suzuki
,
S.
, and
Wakayama
,
S.
,
2016
, “
Sensitivity Enhancement of FBG Sensors for Acoustic Emission Using Waveguides
,”
Exp. Mech.
,
56
(
8
), pp.
1439
1447
.
16.
Giurgiutiu
,
V.
,
Roman
,
C.
,
Lin
,
B.
, and
Frankforter
,
E.
,
2014
, “
Omnidirectional Piezo-Optical Ring Sensor for Enhanced Guided Wave Structural Health Monitoring
,”
Smart Mater. Struct.
,
24
(
1
), p.
015008
.
17.
Wee
,
J.
,
Wells
,
B.
,
Hackney
,
D.
,
Bradford
,
P.
, and
Peters
,
K.
,
2016
, “
Increasing Signal Amplitude in Fiber Bragg Grating Detection of Lamb Waves Using Remote Bonding
,”
Appl. Opt.
,
55
(
21
), pp.
5564
5569
.
18.
Tsuda
,
H.
,
Kumakura
,
K.
, and
Ogihara
,
S.
,
2010
, “
Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain
,”
Sensors
,
10
(
12
), pp.
11248
11258
.
19.
Wee
,
J.
,
Hackney
,
D.
,
Bradford
,
P.
, and
Peters
,
K.
,
2017
, “
Simulating Increased Lamb Wave Detection Sensitivity of Surface Bonded Fiber Bragg Grating
,”
Smart Mater. Struct.
,
26
(
4
), pp.
11
20
.
20.
Huang
,
H.
, and
Balusu
,
K.
,
2021
, “
A Theoretical/Numerical Study on Ultrasound Wave Coupling Form Structure to Remotely Bonded Fiber Bragg Grating Ultrasound Sensor
,”
ASME J. Nondestr. Eval.
,
4
(
5
), p.
021007
.
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