NDE forInfrastructure
Krishnan BalasubramaniamProfessor in Mechanical Engineering and Head of Centre for Nondestructive EvaluationIndian Institute of Technology, [email protected]
Nondestructive EvaluationNon-destructive means of making diagnostic measurements to obtain relevant information on the state of a material, a structure, or a process, without in any way decreasing its performance capabilities.
The Centre for Nondestructive Evaluation at IITM will strive to be a world leader in NDE information, research, education, and training, through the development of the means to achieve and enhance important NDE engineering methodologies, measurement techniques and interpretive models for more reproducibility, reliability and life extension of materials, structures and processes.
Stepping StonesThrust Areas
• Inverse Modeling• Advanced Sensors
– (Micro & Nano Imaging)• Measurements
– (Process & Product)• Aging Infrastructure• Structural Health
Monitoring• Knowledge Base• Education and Training
Technologies & Facilities
• Ultrasonics and Acoustics
• Optical Methods• Thermal Imaging• Electro-magnetism• Digital Radiography• Hybrid
Industry Incubation
•Mahindra JDC
•Trotix Robotics
•OPTech Pct Ltd
•Escon Technologies (Singapore)
Multi-Disciplinary Teams•Mathematics•Physics•Aerospace Engineering•Civil and Ocean Engineering•Electrical and Computers•Materials and Mechanics•Mechanical Engineering
International Collaborations•Iowa State University, USA•Penn State University, USA•Michigan State University, USA•Auburn University, USA•Northwestern University, USA•Imperial College, UK•CEA, France•Izfp, Germany•BAM, Germany
Visible Outputs•Publications•Patents•Products•Training•Projects•Collaboration
Role of CNDE Manufacturing•Corning•TISCO•HLL ….
Aero & Defence•HAL/ADA •ISRO•DRDL•AFRL
Energy•DAE•BPCL
Human Resources•ISNT Level III•ASNT Level III
Infrastructure•Bridges•Rails•Pipes
CNDE@IITM
Structural Health Monitoring of LCA
Ultrasonic Image of LCA Wing
Sensor
Pipe
Support
Corrosion
NDT ofPipeSupportCorrosion
Cleanliness of Steel
Online Evaluation of Brake Pads
Eddy CurrentFor cracks inGas Pipes
Bridge Deck Evaluation
21
43
43
21
Indiagenous NDE
C-Scan Ultrasonic System at 30 % cost of imported system.
LCA NDE Data Analysis Software Saves Time by 70%
TOFD System for Crack Sizing of PSLV Rocket Casing at 20% of imported System Cost.
Eddy Current Tube Inspection Model for Nuclear and Pipeline Industries
CNDE Results
AEA Results
Key Technologies• Modeling : Forward and Inverse Methods• Nano & Micro Imaging• Sensor Development• Materials Characterization• Signal and Image Processing• Manufacturing Process Monitoring• Aging Infrastructure Inspection Techniques Development• Structural Health Monitoring• Damage Prognosis• Products Gallery
CNDEProducts
Comprehensive NDE Head of Egyptian Queen Teje
Goebbels, BAM-I.4
What & WHY?
• Flaws• Material Properties• Process Properties• Structural Properties
• Improve Safety• Increase Performance• Residual Life
Assessment• Enhance Productivity• Re-engineering • Security Information
NDE for Flaws
• Cracks• Voids• Corrosion• Delamination• Disbonds• Material Variations
• Detect• Locate• Characterize• Size• Evaluate Criticality.
Quantitative and Verifiable Information
NDE Methods
Visual and Surface MethodsRadiography TechniquesUltrasonic MethodsElectromagnetic MethodsOptical TechniquesThermal ImagingHybrid Methodology
Nondestructive Evaluation
ExcitationSource
TestSpecimen
SignalConditioning
InverseModel
Input Transducer
Output Transducer
Motivation
• There are a very large number of industries concerned about its health.
• These include bridges, Dams, power plants, transportation pipes used in chemical, petro-chemical, fertilizer, power, oil, ga, water, ......,
• Catastropic failures often harmful to humans and the environment.
• The concerns are serious.
Sept 2002
Infrastructure
• Sectors– Transportation– Energy– Manufacturing– Environment– Real Estate– ……….
• Applications– Pavement– Rails– Bridges– Dams– Loaded Structures– Pipes– Storage Containers
Materials used include concrete, metals, composites, ….
Capabilities of various NDE techniques for assessment of concrete structures
Strength
Elastic modulus
Thickness
Crack depth
Crack width
Crack distribution
Crack development
Honeycombing & voids
Laminations
Bar location
Bar size
Bar corrosion
Rebound hammer ♦
Penetration resistance
♦
Pull out ♦
Ultrasonic ♦ ♦ ♦ ♦ ♦ ♦ ♦
Radar ♦ ♦ ♦ ♦
Thermography ♦ ♦ ♦
Radiography ♦ ♦ ♦ ♦ ♦
Acoustic emission ♦
Magnetic or eddy current
♦ ♦ ♦
Half-cell potential ♦
Photography ♦ ♦
Difficulties• Heterogeneous nature• Infinite combination of mixers• Efficiency of consolidation and effectiveness of
curing • Thick sections and Heavy reinforcements• Surfaces are not accessible without digging.• Universal failure criteria do not exist :
– What to look for?– How to see it?– Absence of codes and guidelines for NDT
Procedures and acceptance standards– Fitness - For – Purpose Criterion !
NDE in Concrete Structures
• Strength• Elastic modulus • Mixing composition• Homogeneity• Ageing effects• Presence of delaminations• Cracks• Voids• Depth of damage due to fire
Impact Echo Principle
ASTM Standard C 1383-98a"Standard Test Method for Measuring the P-Wave Speed and the Thickness of Concrete Plates Using the Impact-Echo Method", AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM).
• The Impact-Echo (IE) method is a highly developed acoustic technique for detecting the presence of flaws and estimating their location in solid material.
• The equipment is also used to estimate the thickness of e.g. pavements and slabs.
• The IE tests rely on reflection of compression waves from the bottom of the structural member or from any hidden discontinuity. An instrumented hammer or an impactor is used as a source to generate compression waves which are sensed by a receiver after being reflected.
•How Impact-echo works??
Impact-echo principle
Where
d = depth in mmv = velocity in concrete in m/sf = frequency in kHz
Impact-echo Acoustical Spectral Imaging
Compressional Wave
Raleigh WaveSpectral Analysis of Surface Waves
(SASW) is the name given to an elegant non-destructive method for in-situ determination of shear wave velocity. It is based on the dispersion of surface (Rayleigh) waves. SASW measurements require one surface to be accessible for testing. The depth that can be tested by SASW measurements is controlled by the accessible surface extent.
SASW measurements are accurate to within 5% for the determination of the thickness and stiffness of the top layer in a pavement system or of the concrete liner of a tunnel.
Theory of Impact-echo
The force-time function for the elastic impact.
Distribution of frequenciescorresponding to force-time
function
The frequency coverage and maximum useful frequencies for 6 and 16mmdiameter of impactors
The relationship between the maximum frequency and diameter of the impactor is given by
Df 291
max = , kHz
Applications• Measurement of thickness of concrete elements• Location of voids• Location of cracks and crack depth measurement• Detection of delamination caused by reinforcement
corrosion• Comparative surveys of concrete quality• Qualitative surveys of bond strength between concrete
layers.
Commercial Equipment
http://www.impact-echo.com/
Data Visualisation
Impact Echo System Development
• Single Impactor– Prototype Completed– 2nd Prototype under fabrication
• Array based IE Technique Development– Prototype Completed– Prototype under Construction.
Low Cost Impactor Development
SENSOR COST
INR 10-10,000
PC SOUND CARD A/D
LABVIEW GUI
Solenoid Impactor
Sensor
Bandwidth 0-20kHz
Initial ResultsColumn Wall
Array Based IE Development
• Use Multiple Impacts and Multiple receivers
• Use Phase Reconstruction Techniques similar to Kirchhoff Migration Algorithms for B-Scan imaging.
• Use Simulation for optimisation of the Array parameters.
• How to device it for practical applications ?
Experimental Setup
IMPACTORS
SENSORS
PC with DAQ and DSP
and Imaging SoftwareNI 9201 USB Interface
IITM
Driver
PCB
Sample
IMPACT ARRAY SYSTEM
Prototype in Action
Simulation Results for all receptors
PML
Defect1
FDTD Domain
Defect3
Defect2
Exciting
Receiving
Signal at all receivers
Image Reconstruction : Phased Addition similar to SAFT or Migration Algorithms
DrpDtp
Transmitter Receiver
( )( , )T R
I x y S t= ∑∑
2+
= +tp rp widthofsignaltD Dt
v
P(x,y)
Reconstructed Image for 8 and 20 transmitters and receivers
FDTD DomainPML PML
Delaminations on a 1mx1m sample
Delaminations
Reconstructed Image for delamination
FDTD Domain
PML PML
Delaminations
1.4m 1m
0.2
0.2
Reconstructed Image
Large Concrete Specimen-Honeycomb Defects
100 cm
50 c
m
50 c
m
50 cm
Collaborative effort between IITM and BAM
• With the momentum obtained fom the previous results, tests are conducted on LCS for the detection of honeycombs using Impact-echo.
• Not able to detect any of the honeycombs.
C and B-scans of areacontaining K1 and K2
Experiments on LCS
Honeycombing
Shear Wave Ultrasonics for LCS
• Thought of using Ultrasonic shear wave-array transducer.• Normal shear wave transducer.• Array of 24 point contact probes.• No need of any couplant.• Variation of polarisation direction• Centre frequency of the transducer is 55kHz.
S R
Polarizationdirection
Experimental setup for ultrasonic pulse-echo
Function generator and pulser/receiver
A laptop and an oscilloscope
Shear wave array transducer
C and B- scans of k1 and k2 from ultrasonic time signals
C and B- scans of k1 and k2 from SAFT(IZFP, Saarbruchen) of ultrasonic time signals
First Experimental Results from K1 and K2Polarisation direction
Wavelet Transforms for LCS data
•Wavelet Transforms: WT decompose the signal in to different frequency bands and analyse the signal with a resolution matched to its scale.
Level 1 DWT coeff reconstrucion Level 2 DWT coeff reconstruction
Level 3 DWT coeff reconstruction Level 4 DWT coeff reconstruction
normal ultrasonictime domain signals
wavelet transformedultrasonic time signals
Comparative Clear indication ofDirect reflection
•The ratio of intensities of the defective to non defective region showed a 22.20 % increase after performing wavelet transforms
C and B- scans from SAFT C and B- scans from wavelet transformd ultrasonic time signals
Clear identification of k2 compared to SAFT
Automated Chain Drag (NDE) for Bridge Deck Inspection
• Pros– Quickly scans large areas– Detects voids similar to
pulse echo• Cons
– Difficult to hear due to weak signals
– Distance between source and human allow other sounds to swamp out signals of interest
A Collaborative project between Mississippi State University and Department of Transportation
Currently Used NDE Technology for Bridge Decks
• Field personnel still use “old” techniques.– Chain Drag– Hammer-tap– Visual Inspection
• Newer technologies are expensive and/or time consuming.– Pulse-Echo– Ground Penetrating Radar
Experimental Device
Odometer
Anechoic Chamber
Baby Carriage
Microphone Pre-amp
Acquisition Break-out Box
Computer
Automatic Marking System(not shown)
Effects of Traffic Noise
After Filter
Passing Vehicle
Defect Signature
Automated Inspection
Automated System Results
Expa
nsio
n Jo
int
Expa
nsio
n Jo
int
Manual Results
Expa
nsio
n Jo
int
Expa
nsio
n Jo
int
Comparision of Results
Verification of Results
Benefits
• Fast Inspection• Unaffected by traffic noise• Archival of raw data• Immediate Feedback• “Bad” locations objectively identified• “Bad” spots marked immediately• A archival map file is created for reference
PIPES: What are we looking for ?
• During Manufacturing– Cracks– Porosity– Inclusions
• During Deployment– Weld Flaws– Cracks
• In-service– IGSCC– Weld Flaws– Corrosion– Erosion (FAC/Gouges)– Fretting Damage– Insulation
Missing/Disbonds
Candidate Pipes
• Cross country Pipelines • Industrial piping • Down-hole casing for drilling• Reformer pipes• Boiler tubes• ……
Conventional Methods• Calipers• Cameras• Surface Methods using
– LPT and – MPT
• Weld Inspection using – X-rays and – Ultrasound.
• Electromagnetic Inspection using– MFL– ECT
Newer Methods
• Ultrasound– Phased Array– TOFD– Long Range Guided Waves– Circumferential Waves– EMATS– GMS
• Radiography– Digital Tomosynthesis/
Laminography
• Electromagnetic Methods– LFET Arrays– PIGS
• Thermal Imaging• Structural Health
Monitoring– GMS or PZT based.
Challenges for NDT of Pipes
• Variety in diameters, schedules, standards, materials.
• Long lengths• Curvatures and Joints• Corrosion Protection Coatings• Insulation Coatings• Valves, etc…
Guided Leaky Lamb Waves
Specular reflection
Null zone
Symmetric .vs. Anti-Symmetric
Energy: Pipe InspectorNeed:Refineries, Chemical, Fertilizer, and Power Plants have in accessible pipe support regions in pipelines that are most prone to corrosion.
Solution:Guided Ultrasonic Waves are generated in the accessible regions and propagate circumferentially to inaccessible regions to detect and quantify corrosion.
Unique•Capable of detecting and imaging 1 mm pitting corrosion.•The Shell capability is 15 mm or higher.•Commercialisation underway.
Energy Response
Circumferential Guided wave Simulation in pipes
Need for crawler and its design
Crawler
Switch
Wedge
Defect free A-scan
Reverberations within the wedge
360 degree travelled signal
A-scan for 3mm radial holes for different depth
20%
80%
60%
40%
100%
0%
Reverberations within the wedge 360 degree traveled waveGates
Real time imaging of defects
Defect Detection-Time domain B scan
20%
40%
80%
60%
100%
Imaging of real corroded sample8inch 40 Schedule Service Pipe with Internal Corrosion and
Radial pin type hole
Internal localised corrosion (i.e.:pitting) with 3mm dia through hole
3mm dia through hole
Detection of circumferentially located holes
8 inch 80 schedule pipe with 3 weld defects along the length
Mapping of defect image to the pipe geometry
Internal Corrosion
Pin hole type corrosion
Energy plots of holes from 1.5 mm to 9 mm diameter
20% 40% 60% 80%
Calculation of size of the defects
Pipe Support Inspector
Crude Lines Pipe SupportsP1
T1
S1
Long Range Guided Waves in Pipes
• Guided waves travel along the pipe and are reflected from changes in the cross-section
• Amplitude of the reflection depends on the total change in the pipe wall cross-section
structure
transducer
guided wave
defect
Long Range Guided Waves
• Long lengths of pipe• Restricted access• Un-pigable• Under water• Buried
• Regular UT and RT techniques are not cost effective
• Typical coverage 0.1%
Long Range GW Benefits
Guided Wave screening offers:• High productivity – kms per day• Access required only at remote locations• Carried out with pipe on-line• Sub-Sea equipment available• 100% coverage except for Flanges, Tees
and other large features
Long Range Guided WavesDispersion Curves for pipes
Guided Mode Types
F(1,1)
L(0,1)
T(0,1)
Test achieving 80m one direction range
0 20 40 60 800.0
0.2
0.4
0.6
0.8
Distance (m)
Am
p (m
V)
Corrosion at entrance to sleeved road crossing
-30.0 -20.0 -10.0 0.0 10.00.0
0.2
0.4
0.6
0.8
1.0
Distance (m)
Am
p (m
V)
+F1 +F2 +F3+F4-F1-F2-F3-F4
corrosion
Guided Waves in PipesThe percentage cross-section loss is given by the
reflection amplitude, but it could be…
… concentrated in a narrow portion of the pipe (e.g. a critical deep defect)
Non-symmetric Case
… equally distributed around the circumference (e.g. a shallow wall loss)
Symmetric Case
Structural Health Monitoring?
• Provides a simple means of repeating guided wave inspection of a pipeline over an extended period of time.
• Sealed in a polyurethane mould to give lifetime protection.
PIMS is a transducer ring permanently attached to the pipe under interrogation.
Motivation for SHM
• The time and cost incurred in the inspection of many pipelines is dominated by the access costs.
• The installation needs to be done once.
• Repeat testing is then a simple matter of attaching transducer cables at a conveniently placed location and retesting.
Features
• Standard weather proof box is uniquely serial numbered
• Programmed with all test parameters during installation
• Custom connectors can be used such as for sub sea use
• Re-testing is a simple plug in and collect
PIMS Example Application
• 24” buried line in tank farm• PIMS installed on buried
section beneath instrument• Connection box on yellow post
PIMS For Monitoring
Monitoring - Sensitivity study on a 12 inch pipe.
PIMS Example ApplicationResult
-18d
B
-5.0 0.0 5.0 10.0 15.00
90
180
270
360
Angl
e (d
eg)
0 0
0.2
0.4
0.6
0.8
1.0
1.2
Amp
(mV)
+F1 +F2 +F3 +F4-F2-F1-F3
Smart Pipes
Pipe
Permanent Magnet
Coil
FluxConcentrator
Ms StripTape
Pipe
Drilled Hole Sensitivity
00.010.020.030.040.050.060.07
0.00 1.25 1.57 2.27
% Defect Crosssection
Ref
lect
ion
Coe
ff
A B
Typical Signal At 165 kHz
-1.50E-02
-7.50E-03
0.00E+00
7.50E-03
1.50E-02
0 0.001 0.002 0.003 0.004 0.005
Time (Seconds)
Am
plitu
de ( Arb
. Uni
ts)
Initial Bang
Direct Signal
A
B
AB & BA
ABA
BAB
ABAB & BABA
Saw Cut Sensitivity (approx)
0
0.05
0.1
0.15
0.2
0.25
0.3
0 13 17 19 20 25 29
% Crosssecton Area
Ref
lect
ion
Coe
ff
Tank Floor InspectionNeed:Refineries, Chemical, Fertilizer, and Power Plants have tank floor annular plate regions that are most prone to corrosion/wall thinning.
50mm
Liquid side of tank
Ring wall foundation
Corrosion
Outside inspection accessible region
GRP Liner
ANNULAR PLATE
Vertical shell with decreasing thickness
Solution:Higher order Modes Ultrasonic Guided Waves are generated in the accessible regions and propagated to detect and quantify corrosion in the annular plate region of tank floor . This could be done as an in-service inspection without empting the tank.
ANNULAR PLATE
Higher Order Modes Cluster
ROBOTIC SCANNER
1 m/min
Field Trials
Live Tank Results3 4 5 6 7 81 2
6
1
8
7542,3
Summary• NDE has a potential role in every aspect of civil
infrastructure.• NDE issues must be considered early and at every
stage to reduce costs and ensure component quality and performance.
• Several emerging NDE methods address each of these aspects.
• Non-contact, Wide-area, in-situ Health-Monitoring, …… are the new paradigms in NDE of the future. They will provide enhanced information at reduced overheads.
