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TRANSCRIPT
Experimental Vibration-based Damage
Detection in Aluminum Plates and Blocks
Using the Acoustic Emission Signals
NDTiC 2015
Edmonton, AB
M. Mirsadeghi, M. Sanati, R. Hugo, S. Park
Department of Mechanical & Manufacturing EngineeringSchulich School of Engineering at the University of Calgary
ND
T in C
anada 2015 Conference, June 15-17, 2015, E
dmonton, A
B (C
anada) - ww
w.ndt.net/app.N
DT
Canada2015
Outline
• Introduction
• Objective
• Experimental Setup
• Results
• Discussion
• Summary
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Introduction:
NDE Motivation
3
Why NDE? Preventing:
� Crack propagation in pipelines� Fatigue and fracture in aircraft
structures and engine blades
� Explosions in boilers and nuclear
facilities
� Crack initiation in bridges
Applications� Pipelines and Corrosion monitoring
� Aerospace structures� Civil infrastructures: Ship hulls,
bridges and buildings
� Composite Damage Detection
AcellentTechnologies Inc
Demands� Safe and stable operation of
structures � Enhancing Maintenance Strategies
� Cost effective and reliable NDT
Introduction
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Challenges:
• Limitation in applying high frequency excitation
• Mostly suitable for rotating
machinery
• Noise and signal spikes
• Defect classification uncertainty
Vibration-based Damage Detection
Advantages:
• Independent to the structural complexity
• Calculation weight
• Global method (compared to
radiography and conventional ultrasonic methods)
• Can be applied in working
conditions
NDT Methods X-ray
Ultrasonic
Eddy Current
Magnetic Particle Testing
Introduction:
Literature Review
5
Vibration-based Damage Detection by GA
(Hao et al 2002)
Effect of Delamination Axial Position on Natural Frequencies
(Zou et al 2000)
Development of Vibration-based Structural damage Detection (Composite Airfoil Model and Given
Damage Status)(Yan et al 2007)
Note:Using AE sensors instead of accelerometers to provide more sensitivity to higher frequency components.
Introduction:
Literature Review
6
Steel pipeline on air-bed and placement of accelerometer
(He and Zhu 2011)
Cantilever steel beam damage detection
(Golubovic 2014)
Application of CWT in Vibration-based Damage Detection
(Rucka et al. 2006)
Locating Damage Using CWT in Beams(Qiu et al. 2014)
Objectives
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Vibration based damage detection using AE sensors, and investigating the effect of sensor position
A. Implementation of the experimental procedure and computing FRFs
� Instrumentation and data acquisition
� Processing the signal and plotting FRFs
� Repeating experiments
B. Modal parameters extraction and analysis
� Analyzing variation of the modal parameters
� Mode sensitivity discussion
Experimental Setup
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Target Structure Properties
Material Aluminum 6061
Dimensions
Plate 152x76x6.3 mm
Block 1 (B1) 152x50.8x25.4 mm
Block 2 (B2) 152x50.8x38.1mm
Boundary ConditionsFree (Using Foam 15cm
thickness)
a. Plate (152x76x6.3 mm) b. Block 1 (152x50.8x25.4mm) c. Block 2 (152x50.8x38.1 mm)
Test Steps
1 Healthy Structure
2 Damage 1 through hole 8mm diameter
3 Damage 2 through hole 12.5mm diameter
Experimental Setup
Sensors
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Acoustic Emission Sensors (MISTRAS Nano 30)Purpose of AE sensors is to detect the motion of stress waves that cause a local dynamic material displacement and convert this displacement to an electrical signal.
Dynamic Specifications
Peak Sensitivity, Ref V/(m/s) 62 dB
Operating Frequency Range 125-750 KHz
Resonant Frequency, RefV/(m/s) 140 KHz
Weight 2 grams
Note: the measured physical quantity of the AE sensors is
proportional to velocity, contrary to displacement or acceleration
Results
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The figures have been prepared based on following considerations:
1. Analyzed frequency range: 1-12500 Hz
FRFs windowed to the most sensitive modes.
2. Eight natural frequency for plate
Analysis for the first two natural frequencies due to higher amplitudesin actuation signal power spectrum
3. Two natural frequencies for blocks based on the sensor location.
Results
Specimen: Plate
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Healthy Damage 1 Damage 2
fn (Hz)Damping
Ratio (%)κ fn (Hz)
Damping
Ratio (%)κ fn (Hz)
Damping
Ratio (%)κ
Plate
Sensor 1Mode 1 3778 2.85E-01 -4.33E+08 3777 2.46E-01 -3.92E+08 3771 1.88E-01 -2.29E+08
Mode 2 5754 5.29E-01 -4.01E+09 5726 4.17E-01 -4.71E+09 5644 5.00E-01 1.40E+09
Sensor 2Mode 1 3786 2.29E-02 -2.25E+09 3782 1.60E-01 -3.57E+08 3773 1.39E-01 -3.60E+08
Mode 2 5760 5.97E-01 6.65E+08 5699 4.78E-01 7.52E+08 5658 1.86E-01 8.42E+08
Natural frequency sensitivity for plate specimen
ResultsPlate – Sensor in Position 1 – Mode 2
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Results
Specimen: Block 1
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Healthy Damage 1 Damage 2
fn (Hz)Damping
Ratio (%)κ fn (Hz)
Damping
Ratio (%)κ fn (Hz)
Damping
Ratio (%)κ
Block 1
Sensor 1Mode 1 8554 4.67E-02 1.83E+09 8557 3.86E-02 6.15E+09 8533 3.83E-02 8.33E+09
Mode 2 NA NA NA NA NA NA NA NA NA
Sensor 2Mode 1 7810 7.49E-01 9.65E+09 7666 1.09E+00 7.25E+09 7467 7.20E-01 2.55E+10
Mode 2 8592 1.71E-01 -2.68E+10 8599 3.51E-01 1.13E+10 8568 1.78E-01 2.29E+10
Natural frequency sensitivity for block 1 specimen
ResultsBlock 1 – Sensor in Position 2 – Mode 1
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Results
Specimen: Block 2
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Healthy Damage 1 Damage 2
fn (Hz)Damping
Ratio (%)κ fn (Hz)
Damping
Ratio (%)κ fn (Hz)
Damping
Ratio (%)κ
Block 2
Sensor 1Mode 1 8674 4.17E-02 4.63E+09 8687 4.47E-02 4.33E+09 8680 3.77E-02 2.76E+10
Mode 2 NA NA NA NA NA NA 8723 4.72E-02 4.67E+10
Sensor 2Mode 1 8702 1.86E-01 -2.55E+10 8710 1.04E-01 1.60E+10 8748 3.55E-01 8.70E+09
Mode 2 9125 2.46E-01 -7.84E+10 8972 1.67E-01 2.70E+10 8748 3.55E-01 8.70E+09
Natural frequency sensitivity for block 2 specimen
ResultsBlock 2– Sensor in Position 2- Mode 1 and 2
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Discussion
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• The AE sensors can successfully be utilised for detection of material
discontinuity in the structure by monitoring modal parameters of the specimen
• Mode sensitivity in plate specimen
• The significance of sensor positioning for the block specimen
• Different trend for natural frequencies variation in experiments for block 2.
• As the acoustic emission sensors have been used we can not provide exact units for the FRFs, however the measured quantity is proportional to the velocity.
Discussion
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Assumptions
• Free-free boundary condition using the 15cm thickness foam.
• Same hammer impact point
• Negligible effect for the adhesive material used for mounting the AE sensors to the structure
Limitations
• Low frequency analysis, Excitation signal frequency limitation (Max 12500 Hz)
• Unable to compare mode shapes unless many sensors are used
• Insensitive modes to specific damages
• Units in FRFs
Summary
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• Extracted modal parameters using the acoustic emission data. This method
which is global and independent of geometrical complexities can be used to detect crack initiation/propagation in pipelines.
• It was shown that certain modes of vibration for the different specimens provides more sensitivity to the damage and is preferred to be used for damage
detection.
• Sensor location effect in terms of observability of different modes of the
structure.
Future Work• Parametric FE study using a verified numerical model• Extending studies to high frequency excitation signal
• Investigation of various kinds of defects (corrosion, fatigue crack, etc.)
Thank You
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