structural health monitoring by based on piezoelectric ......spectral finite element method...
TRANSCRIPT
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Structural Health Monitoring by Basedon Piezoelectric Sensors
Wiesław Ostachowicz
Polish Academy of SciencesInstitute of Fluid Flow Machinery
Gdańsk, Poland
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OUTLINE FOR THE FIRST LECTURE
General Overview on SHM and NDT Methods
NDT methods
Extended NDT methods
SHM methods
General definitions
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NDT methods
Conventional ultrasounds with frequency
analysis
Nonlinear ultrasounds
Laser excited ultrasounds
Eddy current
Strain gauges
……………………………..
General Overview on SHM and NDT Methods
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Extended NDT methods
Active thermography using optical excitation
Active thermography using ultrasound
excitation
THz technology
Electro–mechanical impedance
..................................................................
General Overview on SHM and NDT Methods
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Extended NDT Methods
Guided waves monitoring by 3D laser scanning vibrometry
Active thermography
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Energy distribution
540
952.1
850
500
1
1 PZT
2
2
43
2
16.5 kHz
Damage detection
35 kHz 100 kHz
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PZL – WA Stabilizer
A0 Wave 35 kHz
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Thermal damagein GFRP
Additional masses detectionNotch detection
Damage detection
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Extended NDT Methods
Electro-mechanicalimpedance
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Otherapplications:
Pulse thermography
Vibrothermography
Ultrasonichead
IR camera
Extended NDT Methods
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SHM methods
Vibration based methods
Guided wave methods
Fiber Optics Techniques
Acoustic Emission
Comparative Vacuum Monitoring
Electromagnetic layer
.........................................................................
General Overview on SHM and NDT Methods
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There is a need for SHM methods capable of comprehensive, real-time
condition monitoring
SHM
methods
Fiber OpticsVibration Based
Methods
Lamb Waves
SHM METHODS
Acoustic Emission
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Guided waves propagation
SHM METHODS
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L – Shape
A0 Wave 75 kHz
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Wing Section
A0 Wave 75 kHz
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Experimental vs. numerical results
Laser vibrometry Spectral Finite Element Method (numerical calcilations)
Lateral Velocities
Glass fibers/epoxy, laminate [0/90/0/90]
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Spectral Finite Element Method
– Damage Detection and Localization
Numerical Simulations – Geometry
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IMV Maps for displacements u, for the following periods: 0,125 ms; 0,25 ms; 0,375 ms; 0.5 ms
Aluminium plate, detection and localization of additional mass–IMV (Integral Mean Value) Maps
Spectral Finite Element Method
– Damage Detection and Localization
IMV Maps for displacements w, for the following periods: 0,125 ms; 0,25 ms; 0,375 ms; 0.5 ms
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Spectral Finite Element Method
– Damage Detection and Localization
Aluminium plate, detection and localization of additional mass–RMS (Root Mean Square) Maps
RMS Maps for displacements u, for the following periods: 0,125 ms; 0,25 ms; 0,375 ms; 0.5 ms
IMV Maps for displacements w, for the following periods: 0,125 ms; 0,25 ms; 0,375 ms; 0.5 ms
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RMS maps for displacements w | time: 0,125 ms; 0,25 ms; 0,375 ms; 0,5 ms
RMS (Root Mean Square) maps
Sheathing of a small aircraft wing –
detection and location of a failure
Weighted RMS maps for displacements w | time: 0,125 ms; 0,25 ms; 0,375 ms;
0,5 ms
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Part of the fuselage shell, detection and localization of fatique cracks
RMS Maps for amplitudes of displacement a, for the following periods: 0,125 ms; 0,25 ms; 0,375 ms; 0,5 ms
Spectral Finite Element Method
– Damage Detection and Localization
RMS (z ang. Root Mean Square) Maps
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SHM METHODS
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Experimental stands located on ship yacht Dar Młodzieży
(Maritime University | Gdynia )
The ship's route
29 May – 6 June 2011
source: http://www.am.gdynia.pl/
Fokmast with FBG sensors
Day 9 Day 7Day 8
Day 2
Day 3Day 4
Day 5
Day 1
Day 6
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Problems:
Sensors cannot measure damage
Size of detectable damage versus sensor size
Size of detectable damage versus sensor power
Levels of health monitoring
GENERAL DEFINITIONS
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Sensors cannot measure damage.
Feature extraction though signal analysis andstatistical classification are necessary to convertsensor data into damage information.
The size of damage that can be detected fromchanges in system dynamics is inversely proportionalto the frequency range of excitation.
See K. Worden, C. R. Farrar, G. Manson and G. Park “The Fundamental Axioms ofStructural Health Monitoring,” Proceedings of the Royal Society A: Mathematical,Physical and Engineering Sciences Issue 463 (2082) June, 2007.
GENERAL DEFINITIONS
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Levels of Health Monitoring
Level 5: Self diagnostics. Level 6: Self healing.
Level 1: Detect the existence of damage. Level 2: Detect and locate damage. Level 3: Detect, locate and quantify damage. Level 4: Estimate remaining service life (prognosis).
INCREASING DEGREE OF COMPLEXITY.GREATER NEED FORANALYTICAL MODELS
GENERAL DEFINITIONS
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ON MODELLING OF STRUCTURAL STIFFNESS LOSS DUE TO DAMAGE
Continuous models
Discrete - continuous models
Discrete models
Boundary Element Method
Transition Matrix Method
Graph Method
Analogue Method
Finite Element Method
Ostachowicz W., Krawczuk M. (2009). Modelling for Detection of Degraded Zones in Metallic andComposite Structures, in Encyclopedia of Structural Health Monitoring, Boller, C., Chang, F. andFujino, Y. (eds). John Wiley & Sons Ltd, Chichester, UK, pp. 851–866. (ISBN 978–0–470–05822–0)
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Continuous models
Zou et al. (2000)
Tracy & Pardoen (1989)
Chai et al. (1981)
Botega & Maewal (1983)
Whitcomb (1986)
Yin et al. (1986)
Chen (1992)
Ramkumar et al. (1979)
Wang et al. (1982)
Ostachowicz W., Krawczuk M. (2009). Modelling for Detection of Degraded Zones in Metallic andComposite Structures, in Encyclopedia of Structural Health Monitoring, Boller, C., Chang, F. andFujino, Y. (eds). John Wiley & Sons Ltd, Chichester, UK, pp. 851–866. (ISBN 978–0–470–05822–0)
ON MODELLING OF STRUCTURAL STIFFNESS LOSS DUE TO DAMAGE
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Discrete - Continuous models
Adams et al. (1978)
Ju et al. (1982)
Springer et al. (1987)
Liang et al. (1988)
Ostachowicz & Krawczuk (1991)
Rajab & Al-Sabeeh (1991)
Rytter et al. (1991)
Cuntze & Hajek (1985)
Papaeconomu & Dimarogonas (1989)
Kikidis & Papadopoulos (1992)
Krawczuk & Ostachowicz (1992)
A fatigue crack is represented by additional spring -
like elements, compliance of which is calculated
according to the laws of fracture.
This method can successfully be used for modelling fatigue
cracks in one-dimensional constructional elements (rods,
beams, shafts, columns and pipes) or in constructions made of
such elements (frames and trusses).
Papadopoulos & Dimarogonas (1987)
Liebowitz et al. (1967)
Okamura et al. (1969)
Rice & Levy (1972)
Dimarogonas & Massouros (1980)
Anifantis & Dimarogonas (1983)
Dimarogonas & Papadopoulos (1983)
Krawczuk (1992)
Nikpour & Dimarogonas (1988)
Nikpour (1990)
Gudmudson (1982)
Ostachowicz W., Krawczuk M. (2009). Modelling for Detection of Degraded Zones in Metallic and Composite Structures, in Encyclopedia of Structural Health Monitoring, Boller, C., Chang, F. and Fujino, Y. (eds). John Wiley & Sons Ltd, Chichester, UK, pp. 851–866. (ISBN 978–0–470–05822–0)
ON MODELLING OF STRUCTURAL STIFFNESS LOSS DUE TO DAMAGE
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ON MODELLING OF STRUCTURAL STIFFNESS LOSS DUE TO DAMAGE
Finite Element Method
Markstrom & Storakers, (1980)
Zastrau, (1985)
Shen & Pierre, (1990)
Krawczuk & Ostachowicz, (1990s)
Ostachowicz W., Krawczuk M. (2009). Modelling for Detection of Degraded Zones in Metallic andComposite Structures, in Encyclopedia of Structural Health Monitoring, Boller, C., Chang, F. andFujino, Y. (eds). John Wiley & Sons Ltd, Chichester, UK, pp. 851–866. (ISBN 978–0–470–05822–0)
Discrete models
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Composite beam finite element with a crack
Shaft beam finite element with a crack
Composite beam finite element
with a delamination
US Army Grant
No N68171-94-C-9108
Duration: 1994 – 1996
Title: Dynamics of cracked Composite
Material Structures
ON MODELLING OF STRUCTURAL STIFFNESS LOSS DUE TO DAMAGE
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Solid finite element with a crack
Composite plate finite element with a delamination
Plate finite elements with a crack
US Army Grant
No N68171-94-C-9108
Duration: 1994 – 1996
Title: Dynamics of cracked Composite
Material Structures
ON MODELLING OF STRUCTURAL STIFFNESS LOSS DUE TO DAMAGE
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Ostachowicz W., Krawczuk M.
(2009).
Modelling for Detection of Degraded
Zones in Metallic and Composite
Structures,
in: Encyclopedia of Structural
Health Monitoring,
Boller, C., Chang, F. and Fujino,
Y. (eds).
John Wiley & Sons Ltd,
Chichester, UK, pp. 851–866.
(ISBN 978–0–470–05822–0)
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Changes of dynamic properties i.e.:
mode shapes,
natural frequencies,
amplitudes of forced vibrations,
damping
...................
Low frequency method
VIBRATION BASED METHODS
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Changes:
first (a)
second (b)
third (c)
natural frequencies of the cantilever
composite beam as a function of damage
location (delamination):
beam axis
Rel
ativ
e ch
anges
of
nat
ura
l fr
equ
ency
3/
03
Relative location of delamination L1/L
Rel
ativ
e ch
ang
es o
f n
atu
ral
freq
uen
cy
2/
02
Relative location of delamination L1/L
Rel
ativ
e ch
anges
of
nat
ura
l fr
equ
ency
1/
01
Relative location of delamination L1/L
b)a)
c)
VIBRATION BASED METHODS
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Changes:
first (a)
second (b)
third (c)
natural frequencies of the simple supported
composite beam as a function of damage
location (delamination):
beam axis
Rel
ativ
e ch
anges
of
nat
ura
l fr
equ
ency
2/
02
Relative location of delamination L1/L
Rel
ativ
e ch
anges
of
nat
ura
l fr
equ
ency
3/
03
Relative location of delamination L1/L
a)
c)
b)
Rel
ativ
e ch
anges
of
nat
ura
l fr
equen
cy
1/
01
Relative location of delamination L1/L
VIBRATION BASED METHODS
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Summary of Detection Methods
Method Strengths Limitations SHM Potential
Optical fibres
Embeddable
Simple results
Very comfortable
Expensive
High data rate
Accuracy??
Requires laser
localised results
Eddy currentSurface mountable
Most sensitive
Expensive
Complex results
Safety hazard
High power
Localised results
Damage differentiation
Acoustic
emission
Inexpensive
Surface mountable
Good coverage
Complex results
High data rates
Event driven
No power
Impact detection
Modal analysis
Inexpensive
Surface mountable
Simple procedure
Complex results
High data rates
Global results
Low power
Complex structures
Multiple sensor types
Lamb waves
Inexpensive
Surface mountable
Good coverage
Complex results
High data rates
Linear scans
High power
Damage differentiation
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Arrays of distributed piezotransducers:
applicable to most structures
can monitor structural condition throughout the life
of the structure
can detect changes in:
can focus on damage
stiffness
inertial and damping characteristics
stress levels
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Motivation
Signal
processing
sensors
TOF
Damage identification methods:
Deterministic (based on Time of Flight,
amplitude changes)
Non-deterministic:
Neural Networks
Evolutionary Algorithms
Genetic Algorithms
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Use theoretical, classical finite element
and spectral finite element methods
d
rf
y
Produce
data to
train the
expert
system
Model of the structure
Neural Networks
Genetic Algorithms
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Elastic Waves
Longitudinal waves – particle motion is in the direction of travel
Longitudinal (P) Wave
Shear waves – particle displacement at each point in the
material is perpendicular to the direction of wave propagation
Shear (S) Wave
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Lamb waves are waves of plane strain that occurs in a free plate.
Complex wave mechanism –shear vertical (SV) waves form modes in
connections with the longitudinal P wave; these P+SV waves are known
as Lamb waves.
Infinite number of dispersive modes which can propagate
in structures.
222
2
)kq(
pqk4
)phtan(
)qhtan(
pqk
kq
ph
qh2
222
4
)(
)tan(
)tan(
LAMB WAVES
X X
Symmetric Antisymmetric
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J. L. Rose. Ultrasonic waves in solid media. Cambridge University Press, 1999.
LAMB WAVES
Dispersion equations are given by Rayleigh-Lamb frequency relations.
Lamb wave velocity is a function of the frequency- thickness (f*d) product.
Fundamental modes – S0 and A0 modes.
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DISPERSION AND WAVE MODES
Mod 2
Mod 1
3 kHz
100 kHz12 kHz
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Wave propagation modelling
• Finite element Method
• Finite Difference Method (LISA)
• Semi-analytical methods
• FFT-based Spectral Element Method (Doyle)
• Hybrid methods
• Spectral Element Method (Patera 1984)