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Managing Civil Infrastructure on the Basis of Structural Health Monitoring
Christian Boller, Jochen Kurz and Gerd DobmannFraunhofer Institute of Non-Destructive Testing Methodology (IZFP)
Universität des Saarlandes, Saarbrücken/Germany
© C. Boller, Fraunhofer IZFP
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51st Brazilian Concrete CongressCuritiba/Brazil, October 6-10, 2009
Built forever!?
© C. Boller, Fraunhofer IZFP
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B52 – Built to fly 100 years?
© C. Boller, Fraunhofer IZFP
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Design Principles for Structures100%
50%0%Stress Without inspection of the component
(no corrosion effects considered)
Safe Life
SafeLife
Log cycles
StressInspectable
crack possible
Damage tolerance
Fracture With inspection of the component(no corrosion effects considered)
© C. Boller, Fraunhofer IZFP
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Log cycles
Short cracks Slow crack propagation
Fail safe
Endurance limit SafeLife
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Estimation of damage accumulation
Time
ltage
A
B D
I. Load signal
Time
ain
A
B Dmax
II. Countingload cycles
IV. Fatigueevaluation
Vol
C
Stra
C
min
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III. Rainflow matrix
)Strength Residual( fN =Δ
Res
idua
l stre
ngth
Critical crack length
Detectable crack length
Cra
ck le
ngth
ΔN
Δa
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Crack lengthNumber of cycles or time
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Steps to be considered for crack propagation calculation
1. Initial crack length a02 Y factor
For example:2. Y factor3. Load (stress)4. K value5. Crack propagation
equation (i.e. Forman)6. Crack extension ∆a
waY πsec=
aYKI πσ=
© C. Boller, Fraunhofer IZFP
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7. a = a0+∆a & back to step 1 with a0 = a ( ) KKR
KCdNda
c
m
F
F
Δ−−Δ
=1
Influence of Stringers on Fracture
© C. Boller, Fraunhofer IZFP
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Source: A. Grant: Fundamentals of Structural Integrity
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Fatigue Design
Airframe Fatigue Design Principles
Safe Life Design Damage Tolerant Design
Fail SafeSlow Crack Propagation
How muchpotential left?
© C. Boller, Fraunhofer IZFP
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Crack StopperMultiple Load Path
Ageing bridge infrastructure in Germany
Autobahn
National
Ageing bridge infrastructure in Germany over the last centuryBridges and highways
Age of structure relative to the number of constructions [%] (Date: 31.12.2005, source BASt)
15.8BABB Str World
changed:
• More traffic
• Environment
• etc.
National Highways
5.4
2.5
5.9
11.912.3
8.4
7.17.5
11.8
9.7
2.3 2.52.6
4.8
7.3
9.6 9.6
13.5
9.6
8.88.4 8.5 8.4
B-Str
© C. Boller, Fraunhofer IZFP
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BUT
2008 Civil infrastructure remained
0.0 0.0 0.0 0.1 0.20.5
0.1 0.40.70.8
0.40.7 0.8
0.3 0.6 0.6
bis1899
1900 -1909
1910 -1919
1920 -1929
1930 -1934
1935 -1939
1940 -1944
1945 -1949
1950 -1954
1955 -1959
1960 -1964
1965 -1969
1970 -1974
1975 -1979
1980 -1984
1985 -1989
1990 -1994
1995 -1999
2000 -2004
2005 -2009
year of establishment
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Civil infrastructure - An issue for monitoring• Bridges
• Pipelines and processing industry
• Power supply (e. g. supply lines, wind energy
Example: bridge area in 106 m2 in Germany sorted by type of construction:
plants)
• Dams
• Buildings of the early ages of reinforced concrete
• Tunnels
• Waste refilling
• Cultural heritage0,16
5,14
1,381,840,02SteelComposite
© C. Boller, Fraunhofer IZFP
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Date 31.12.2005, source BASt
g
• Others19,39
StoneConcretePrestressed ConcreteWood
Options and challenges for life cycle management
Options: Challenges:
• Sensors and miniaturisation• Robotics
• Enhanced computation power
• Internet
• Wireless data communication
• CAE simulation
P ti
• New materials• Higher loads
• Global warming
• Criminal threats and security policies
• Regulations
• Possibly others
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• Prognostics
• Risk assessment
• Life cycle cost analysis
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BetoScan: self navigating mobile robot
Batteries
BetoScan
Sensors
Robot with 2 computer systems
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Air temperature and humidity
Concrete humidity (surface)
Concrete humidity (volume)
Concrete coverage Geometry information
Reinforcement information Corrosion risk
Hytelog Hf MOIST RP, microwaveHf MOIST PP,
microwaveProfometer, eddy
currentAcsys A1220,
ultrasound Mala ProEx, radarCanin, potential
(resistivity)
BetoScan: multi-sensor data acquisition
BetoScan
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OOnnSSite ite SCASCAnnenneRR
OSSCAR
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www.vdivde-it.de/innonet
OOnnSSite ite SCASCAnnenneRR
OSSCAR
Reinforcement
Data cube also called OLAP (Online Analytical Processing) cube data format
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information Geometry information Concrete coverage
Mala ProEx, radar Acsys A1220, ultrasound Profometer, eddy current Generalized data concept
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OOnnSSite ite SCASCAnnenneRR
OSSCAR
Data acquisition and
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Data acquisition and motion control
Data analysis: comparison, fusion, joint-inversion
Data fusion:
Outlook data analysis
Test specimen before placing of concrete
Fused image of NDT data measured at specimen on the left
Source: BAM Berlin
combination of multiple source data to achieve inferences
Joint inversion or multi-
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objective optimization: finding model that explains several data sets at once Data cube Function container
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Visualisation of inner parts of constructionsUltrasound measurements on a concrete deck
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Source: Alexander Taffe, BAM Berlin
Diagnosis of prestressed tendons
Magnetic rotating head scanner
Rotating speed: 2HzLinear speed: 720m/hRotor diameter: 3.5m
electromagnet
magnetic sensors
sensor traces
Application: prestressed steel rupturedetection in concrete plates rotating head
scanner
measurement results of a concrete bridge
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prestressing tendons
ruptures
……
Source: Klaus Szielasko and Albert Kloster, IZFP Saarbrücken
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Crack and flaw detection in pipelines
Inspection of pipelines using pigs
LDefect contour Simplification
Crack and flaw detection by ultrasound pigs
Correlation of data from mearuemnts and geometry models of cracks for assessment
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dt
L• Up to 300 km of pipelines have to be inspected in one run
• Signals from up to 1000 sensors have to analysed for each segment
Source: W. Bähr IZFP & O.A. Barbian NDT Systems & Services
Barkhausen noise and Eddy current MIcroscope (BEMI)
3D Manipulator Control PCMiniaturised inductive sensor(modified video recorder head)
Stationary Electromagnet(for Barkhausen Mode)
3D Manipulator Control PC (modified video recorder head)
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Resolution: ~ 10 μm• Manipulator control• Eddy current hardware• Barkhausen noise hardware
Records Barkhausen noise
Source: M. Rabung, U. Rabe, S. Hirsekorn, I. Altpeter, Fraunhofer IZFP
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HCM ~ HC HCµ ~ HC
Monitoring Technique
Flux Density B
Barkhausen Noise
CM C Cµ C
Higher Mode AnalysisMulti Frequency Eddy
Current Impedance
Superimposed Permeability
Magnetisation Force H
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Source: K. Szielasko, R. Tschuncky, I. Altpeter, Fraunhofer IZFP
Quantitative NDT / Calibration
Data Base(NDT Recorded Data + Reference Data)
Computation
(Approximation Function, Similarities, …)
Residual Austenite
(Approximation Function, Similarities, …)Hardness
(Approximation Function, Similarities, …)
Residual Stresses
p(Regression Analysis, Pattern Recognition, …)
QNDT
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QNDTHardness
QNDTResidualAustenite
QNDTStress
Source: K. Szielasko, R. Tschuncky, I. Altpeter, Fraunhofer IZFP
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3MA Test System
Control Unit:- Notebook- Industrial PC- Server
3MA-Frontend- TCP/IP interface- Network link- ExtendableExtendable
Modular Hardware
- Components linked via aTCP/IP interface
- Expandable throughadditional components(i.e. magnetostriction, US)
- Easily upgradable withnew components
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3MA-Sensor- Available in different sizes and shapes
new components
Source: K. Szielasko, R. Tschuncky, I. Altpeter, Fraunhofer IZFP
MikroMach Test System
Mikromagnetic Materials charakterisationMaterials charakterisation in its most compact form
Sensor = Test Equipment
Link control PC via
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Standardised USB link
Source: K. Szielasko, I. Altpeter, Fraunhofer IZFP
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Quantitative Determination of Residual Stresses
∆α = 14.04°
∆α = 22.26°∆α =
0.95°
Stamp Edge
0
300
400
500
600M
Pa] (
3MA
) A001A003A002A004B001B002
A001 A003 ∆α = 14.04°
A002 A004
∆α = 22 26°
-300
-200
-100
0
100
200
0 1 2 3 4 5 6 7 8
Res
idua
l Str
ess σ
[M
B002X-Ray Ref. A001X-Ray Ref. A002X-Ray Ref. B001
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04
8
22.26°
B001 B002
Position [cm]
Source: B. Wolter, K. Szielasko, I. Altpeter, Fraunhofer IZFP
17 CrNiMo 6 residual stress maeasurement in 400
600
800
Oberfläche
QNDT of Residual Stresses due to Machining
maeasurement in gear wheels
-400
-200
0
200
3MA
-Wer
t
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-600-600 -400 -200 0 200 400 600 800
Eigenspannung [M Pa] (X-ray)
Source: B. Wolter, K. Szielasko, I. Altpeter, Fraunhofer IZFP
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Results:
Calibaration Probes:
Residual Austenite Determination on Anchor Bolts using 3MA
44 Anchor bolts with a RA of 2,6% 43 Anchor bolts with a RA of 2,6%44 Anchor bolts with a RA of 4,6% 43 Anchor bolts with a RA of 11,3%15 Anchor bolts with a RA of 5,8%
Validation Probes:
Charge 1 with a RA of 3,4%
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Charge 1 with a RA of 3,4% Charge 2 with a RA of 4,8% Charge 3 with a RA of 4,9% Charge 4 with a RA of 4,5% 25 anchor bolts each from different hardening charges
Source: K. Szielasko, R. Tschuncky, I. Altpeter, Fraunhofer IZFP
400
600
800
1000
1200
1400
1600
m [M
Pa] (
3MA
)
Ultimate Strength
Inspection of Sheet Steel using the 3MA System
600
800
1000
1200
1400
1600
.2 [M
Pa] (
3MA
)
0
200
400
0 200 400 600 800 1000 1200 1400 1600
Rm [MPa] (zerstörend)
R m
Yield Strength
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0
200
400
0 200 400 600 800 1000 1200 1400 1600
Rp0.2 bzw. REH [MPa] (zerst.)
R p0.
Trolley with integrated 3MA Systemfor inspection of milled sheets during rolling
Unit for remote control of trolley with 3MA system
Source: B. Wolter, K. Szielasko, I. Altpeter, Fraunhofer IZFP
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The Central Question
Without compromising safety, could we make our structures:– Better available?– Lighter weight?– More cost efficient?– More reliable?
by making sensors (and possibly also actuators) t b i t l t f th t t ?
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to become an integral part of the structure?
What about …• Looking at advanced cheap sensors, which are
continuously becoming– Smaller,
Li ht– Lighter,– Cheaper?
• Making the sensors an integral part of the structural component?
• Combining the sensors through advanced microelectronics and possibly– Wireless technology with
Advanced microprocessors and
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– Advanced microprocessors and – Advanced signal processing?
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Structural Health Monitoring (SHM)
… is the integration of sensing and possibly also actuation devices to allow the loading and damaging conditions of a structure to be g grecorded, analysed, localised and predicted in a way that non-destructive testing becomes an integral part of the structure. SHM is not an additional NDT application, nor QNDT, a fatigue analysis, vibration analysis, signal processing, material science or any other single technological area but rather lateral integration
© C. Boller, Fraunhofer IZFP
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technological area but rather lateral integration of all those in terms of a structure’s life cycle management.
What We Need to Know
• Structural Behaviour and Performance• Loads• Design Principles• Maintenance• Systems for Structural Assessment• Emerging Technologies
© C. Boller, Fraunhofer IZFP
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e g g ec o og es
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Enhancing Damage Tolerance through SHM
Stress
Gain in weight
Stress
Gain in weight
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Life
withmonitoring
withoutmonitoring
Gain in life
Life
withmonitoring
withoutmonitoring
Gain in life
Source: H.-J. Schmidt, Airbus
Technologies Beyond State-of-the-Art in Aircraft NDT
WavelengthWavelength
Inte
nsity
Inte
nsity Incident Light Transmission
Index Modulation WavelengthWavelength
Inte
nsity
Inte
nsity Incident Light Transmission
Index Modulation
Smart Layer:Acousto-Ultrasonics
Optical Fibre Bragg Grating Sensor:• Strain• Pressure
Period Λ
Inte
nsity
λ Bragg
Wavelength
Reflection
Period Λ
Inte
nsity
λ Bragg
Wavelength
Reflection
• Pressure• Temperature
Acoustic Emission
Phased Array
Electro
MEMS
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ComparativeVacuumMonitoring:• Crack
Electro MagneticLayer
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What is a Sensor?
Amplifier DataA i iti
Switch Box
p Acquisition
Processor
Amplifier WaveformGenerator
Smart Suitcase™Smart Layer®
with 12 transducers
© C. Boller, Fraunhofer IZFP
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Smart Suitcasewith 12 transducers
Smart Sensing System with 1 input and output
Stress measurements of a suspension bridge
• Six strands on center-east and anchorage chamber measured
Fibre optic sensors for loads monitoringCable opened for tests
• SOFO Dynamic fiber optic sensing system used• Two 12-wheels trucks, ~30 tons each• Quasi-static test: 7 km/h; dynamic test: 72 km/h
Anchor block tested
© C. Boller, Fraunhofer IZFP
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Source: Smartec SA, Lugano Switzerland
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Remote dynamic loads monitoring
SSI implemented in Labview VI operates in real-time and confirms operation of TMD during strong winds via eight-times increase in damping
25
30
10-2
100
© C. Boller, Fraunhofer IZFP
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Source: James Brownjohn, The University of Sheffield0 0.5 1 1.5 2 2.5 3 3.5 40
5
10
15
20
Frequency (Hz)
Ord
er
0 0.5 1 1.5 2 2.5 3 3.5 410-10
10-8
10-6
10-4
Structural health monitoring using wireless sensor networks
sensors- robust - low power consumption- high bandwidth - cheap
wireless data transmission( i l
self configuring netzwork
embedded networkingautomatic data
MEMS / MotesMEMS / Motes
Insitu-Processing
wireless RF data
transmission Daten
transmitter and receiver (internet)
© C. Boller, Fraunhofer IZFP
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Source: Christian Grosse MPA University of Stuttgart
(wireless communication)
netzwork extractionself calibrating
transmission of a few but meaningful data
extrahierten Daten
transmittermobile data collector
server
Analysis / AlarmAnalysis / Alarm
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Acoustic emission sensors
Specimen Sensor Attachment
sensorsPhased arraytransducers
Smart Layer transducers
© C. Boller, Fraunhofer IZFP
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Acoustic emission sensors
3
4
1to22 (Path 1) 3to23 (Path 2) 2to24 (Path 3) 4to25 (Path 4) 5to26 (Path 5) 6to27 (Path 6) 7to28 (Path 7) 10to17 (Path 8)
Damage Index of the 1st wave packet in parallel wave path
Normalized Damage Index = Measured Damage Index / 1st Damage Index
Channel numberChannel numberThreshold
Data Processing Results
1
2
3
Dam
age
Inde
x
9to16 (Path 9) 12to19 (Path 10) 11to18 (Path 11) 14to21 (Path 12) 13to20 (Path 13)
132456710912111413
20 21 18 19 16 17 28 27 26 25 24 23 22
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3000
040
000
5000
060
000
7000
080
000
9000
0
1000
00
1100
00
1200
00
1300
00
1400
00
1500
00
1600
00
1700
00
1800
00
0
No. of cycle
AU sensor - SMART Layer
Cracked area
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Argumentation of Threshold Setting
Damage Index against the estimation of the crack length from the parallel paths at 183kcycle
1 0
1.5
2.0
2.5
3.0
3.5
4.0
Dam
age
Inde
x
Damage Index against Crack length
© C. Boller, Fraunhofer IZFP
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0.0
0.5
1.0
0 2 4 6 8 10 12 14 16crack length [in mm]
Constraints:
Transducer Locations
Crack Location
Crack Initiation at Countersunk Rivet Holes
Constraints:• Transducers only to be
placed inside the fuselage• Acoustic signals passing a
lap can reduce up to a factor of 4
• Area around riveted lap allows for a multitude of
© C. Boller, Fraunhofer IZFP
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acoustic wave reflections
OuterFuselage
InnerFuselage
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Wave Modulation at Tapered Surfaces
Crack
Crack
Cra ck Initia tion
© C. Boller, Fraunhofer IZFP
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Am
plitu
de (a
rbitr
ary)
I: Incident Wae, R: Reflected Wave
UX,topUX,bottomUY,topUYb tt
(S0)I (S0)Rθ=90o
Am
plitu
de
I:Incident Wave, R: Reflected Wave, C: Converted Wave
UX,topUX,bottomUY,topUY bottom
(S0)R(S0)I (A0)CTRθ=45o
Mode Conversion at Tapered Surfaces
0 20 40 60 80 100 120Time (μsec)
UY,bottom
0 20 40 60 80 100 120-0 4
-0.2
0
0.2
0.4
0.6
Am
plitu
de,
ε xx
S0(Incidend)
S0(Reflected)
0 20 40 60 80 100 120
Am
plitu
de,
ε xx
S0(Incident)
TR A0(Converted)S0
(Reflected)
0 20 40 60 80 100 120Time (μsec)
Y,bottom
© C. Boller, Fraunhofer IZFP
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0 20 40 60 80 100 1200.4Time (μsec)
0 20 40 60 80 100 120Time (μsec)
Time (μsec)
frequ
ency
(MH
z)
0 20 40 60 80 100 1200
0.4
1 IncidentS0
ReflectedS0
Transient C/RConverted
A0
Time (μsec)
frequ
ency
(MH
z)
0 20 40 60 80 100 1200
0.4
1 IncidentS0
ReflectedS0
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X
Y (mm)
015
0 15 30 45 60
X
Y (mm)
015
0 15 30 45 60
Effect of Holes on Scattered Wave Distribution
X
Y (mm)
015
0 15 30 45 60
X
Y (mm)
015
0 15 30 45 60
(mm
)5
30(m
m)
530
0.9
1
1.1
0.9
1
1.1
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(mm
)30
45(m
m)
3045
0.5
0.6
0.7
0.8
0.5
0.6
0.7
0.8
Meshing for Cracks around Holes
Without Crack With Crack
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Without Crack With Crack
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25
400
450
0.9
1
++++++
+++++++
+ 400
450
0.6
0.7
0.8
400
450
0.6
0.7
0.8
400
450
0 6
0.7
0.8
0.9
Effect of Cracks on Scattered Wave Differentials
X (mm)
Y (m
m)
0 50 100250
300
350
0.3
0.4
0.5
0.6
0.7
0.8
++ + + + +
++ + + + ++
+
X (mm)
Y (m
m)
0 50 100250
300
350
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
X (mm)
Y (m
m)
0 50 100250
300
350
-0.1
0
0.1
0.2
0.3
0.4
0.5
X (mm)
Y (m
m)
0 50 100250
300
350
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Reference 10 mm Crack 15 mm Crack 20 mm Crack
© C. Boller, Fraunhofer IZFP
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Crack length 2.5 x rivet diameter needs to be monitored no further away than 12.5 x rivet diameter
Crack 10.91
0.9
1
Multiple Path Monitoring for Confidence Enhancement
1
3
24
5A
6
8
79
10
B
20 10 20 15 15 20
PZT Transducer
Through Hole
30 3020 10 20 15 15 20
PZT Transducer
Through Hole
30 30
C ac
92
1 64
7
0 2
0.3
0.4
0.5
0.6
0.7
0.8
Nor
mal
ised
Am
plitu
de
9 46 27 10 2
0.3
0.4
0.5
0.6
0.7
0.8
Nor
mal
ised
Am
plitu
de
9 46 27 1
© C. Boller, Fraunhofer IZFP
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0 5 10 150.1
0.2
Crack 1 Length
7 1
0 5 10 150.1
0.2
Crack 1 Length
7 1
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26
500
Loading Condition Influence on Damage Monitoring
InitialFatigue + Under static Load Fatigue + Unload
Ampl
itude
(mV)
100
200
300
400 Fatigue + Under static Load Fatigue + Unload
1
3
24
5A
6
8
79
10
B
300 30020 10 20 15 15 20
PZT Transducer
Through Hole
30 3020 10 20 15 15 20
PZT Transducer
Through Hole
30 30
Cracks
A 2
1
3
4
5
© C. Boller, Fraunhofer IZFP
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2 3 4 50Path Number
A 12 3 4 50Path Number
A
high frequency
• Acoustic Emission (passive)
A t Ult i ( ti )
Monitoring of Windmill Rotor Blades
• Acousto Ultrasonic (active)
Sensor/actor elements
• piezo fibre patches (HF) as sensors
(and low range actors)
36 HF piezo fibre transducer
© C. Boller, Fraunhofer IZFP
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( g )
• pzt stacks for lamb wave generation
(large range actuators)
6 HF pzt stacksSource: B. Frankenstein et al., Fraunhofer IZFP
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• structure independent application for SHM
SHM Systems
• online reconfiguration
• online and offline analysis, documentation of structural damage
• realization of structure dependent data base
• development and test of online SHM algorithms
© C. Boller, Fraunhofer IZFP
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Source: B. Frankenstein et al., Fraunhofer IZFP
SHM in Publication• Internat., European and Asia-Pacific
Workshop on SHM• Encyclopedia of SHM; John Wiley &
Sons, 5. Vols., ca. 3,000 pages, 01/2009
• Structural Health Monitoring – An International Journal; SAGE Publ.
• Int. Journal on Structural Control and Monitoring; John Wiley & Sons
• Smart Materials and Structures; Inst. of Physics Publ.
• Intelligent Material Systems and Structures; SAGE Publ.
• Staszewski W.J., C. Boller and G.R. Tomlinson (Ed.s), 2003: Health Monitoring of Aircraft Structures; J
• Introduction and Definitions • Physical Monitoring Principles • Signal Processing • Simulation
© C. Boller, Fraunhofer IZFP
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Monitoring of Aircraft Structures; J. Wiley & Sons
• Balageas D., C.-P. Fritzen and A. Güemes, 2005: Structural Health Monitoring; ISTE Ltd.
• …
• Simulation • Sensors• Systems and System Design• Principles of SHM-Based Structural
Monitoring, Design and Maintenance• Aerospace Applications• Civil Engineering Applications • Other Applications• Standardization and Specification• Glossary
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• Ageing structures must have a damage tolerance if they should be managed
• Structural design principles and geometry must be understood• Operational loads need to be known
Di it l d l f th t t i h l f l f d l ti
Conclusions
• Digital model of the structure is helpful for damage accumulation evaluation
• NDT methods available for in situ structural and materials characterisation
• Different sensing system principles to be ready for structural integration
• NDT phenomena around the areas to be monitored have to be known• SHM technologies considered provide sufficient maturity and
reliability
© C. Boller, Fraunhofer IZFP
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reliability• A lot of technology around for SHM based ageing infrastructure
management