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Ultrasonic Guided Waves for NDE OF

WELDED STRUCTURESan overview by

Krishnan Balasubramaniam

Professor of Mechanical Engineering and

Head of Centre for Nondestructive Evaluation

Indian Institute of Technology, Madras

Chennai 600 036 INDIA

Tele: 044-445-8588

Email: balas@iitm.ac.inWWW.CNDE-IITM.ORG

mailto:balas@iitm.ac.inhttp://www.cnde-iitm.org/http://www.cnde-iitm.org/http://www.cnde-iitm.org/http://www.cnde-iitm.org/mailto:balas@iitm.ac.in

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Guided Wave Types

Based on GeometrySurface Waves

Plate Waves

Cylindrical Waves

Rod Waves

Based on ModeTorsional

CircumferentialLongitudinal

Shear Horizontal

Shear Vertical

Flexural

Based on Symmetry

Symmetric

Anti-symmetricAxi-symmetric

Non-axisymmetric

http://www.cnde-iitm.org/http://www.cnde-iitm.org/http://www.cnde-iitm.org/http://www.cnde-iitm.org/

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Plate Wave Basics

Three basic wave mode

types :

Shear HorizontalShear Vertical

Symmetric

anti-symmetric

Longitudinal Symmetric

anti-symmetric

Anti - Symmetric Mode

Symmetric Mode

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Guided Waves Characteristics

Dispersive (group .vs. phase)

Contour Following

Long Range Propagation

Leaky Phenomena

Multi-Mode Behavior

Mode Specific Displacement

and Stress Profiles.

Null Zone

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Plate Wave SimulationANSYS FEM Model.

Input impulse at 200

kHz. (2 cycles) at the top

left corner. 4 cases displayed.

Total Plate Length 12

inchs Total Plate Thickness 0.5

inchs.

Defect Height 0.25

T R

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Plate Wave Simulation ResultsDefect Free

Corrosion Crack

Rectangular Defect

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partial differential equation for particle motion in a continuous

medium is given by

(+) u j,ij + u i,jj + i = i

Since in a plate the domain is not infinite we require boundary conditionsto solve these equations.

The solution of these two independent equations along with boundary

condition, in this case

31 = 33 = 0 x = +- d/2

Rayleighs equations

2

2 2 2tan( ) 4tan( ) ( )qh k qpph k q

for symmetric modes

for anti-symmetric modes2 2 2

2

tan( ) ( )

tan( ) 4

qh k q

ph k qp

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Lamb Waves in a steel plate

0

10

10

a0

s0

a1

s1

s2

a2

Top surface

Bottom surface

Frequency (MHz)

Phasevelocity(km/sec)

Mode Shapes

Propagation direction

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Dispersion of Pulses

Time (usecs)

1 23

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Phase Velocity Dispersion Curves

for Steel Plate

0 2 40

2

4

6

Frequency-Thickness (MHz-mm)

Phasevelocity(km

/s)

S0

S1

A0

A1

6

10

8S2

A2

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Group Velocity Dispersion Curves

for Steel Plate

0 2 40

2

4

6

Frequency-Thickness (MHz-mm)

Groupvelocity(k

m/s)

S0

S1

A0

A1SH0

SH1SH2

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Attenuation Dispersion Curves for

Steel Plate Immersed in Water

S0

S1

A0

A1S2

A2

Scholte

0.0 2.0 4.0 6.00

500

1000

1500

2000

Frequency-Thickness (MHz-mm)

Att(dB-mm/m

)

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Types of Guided Wave Inspection

Short range (

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Guided Wave Applications

Process Monitoring

Viscosity, Density, Level, Temperature

Material Characterization

Stiffness, Density, Visco-elastic, Ply-lay-up

Non-destructive Evaluation

Corrosion, Bond quality, Cracks, .

Data Communication

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Symmetric and Antisymmetric

Mode Shapes

L(0,2) F(1,3)

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Guided Wave in Pipes

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Test achieving 80m one direction range

0 20 40 60 800.0

0.2

0.4

0.6

0.8

Distance (m)

Amp(mV)

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Corrosion at entrance to sleeved

road crossing

-30.0 -20.0 -10.0 0.0 10.0

0.0

0.2

0.4

0.6

0.8

1.0

Distance (m)

Amp(m

V)

+F1 +F2 +F3+F4-F1-F2-F3-F4

corrosion

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Guided Wave Systems

http://www.guided-ultrasonics.com/photos/se16andr2b10_on_pipe_full_size.jpg

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Commercial Transducer System

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Reflection coefficient for notch over 11% of pipe

circumference as function of notch depth

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Reflection coefficient from notch 50% of wall

thickness deep as function of circumferential extent

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Guided Waves in Pipes and

Tubes

*Rose et al, Proc of WCNDT 1996

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Energy Distributions for Selected

Modes Energy in the

head

Energy in theweb

Energy in thefoot

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Prototype System

Rail under test

clamping mechanism

User interface

System electronics

transducer

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Comparison predicted and

experimental sensitivity

0 10 20 30 40

0

0.2

0.4

0.6

0.8

1

Cross sectional area loss (%)

Reflectioncoeff

icient

Experiment

Finite element prediction

50

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Probe

Weld

Direction of Probe Motion

Probe-SoundfieldWeld Defects

Ultrasonic wave

Inspection of Laser Welds of Tailored Blanks by SH-mode SS0

NDT by guided waves

Salzburger

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Blank is stationary - Probe is moved by a robot

Probe

Inspection of Laser Welds of Tailored Blanks

NDT by guided waves

Salzburger

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Weld

End face

Laser Weld InspectionScanning direction

Pos. 3 on X-ray film

Ultrasonic B-imageMicrofocus X-ray

Inspection of Laser Welds of Tailored Blanks by SH-mode SS0

Inspection result

NDT by guided waves

Salzburger

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Guided Circumferential Waves

AEA Technology

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Crack

Ultrasonic Surface Wave

RT

Amplitude

Time of flight

RT RT

Time of flight

EE E

E E

Amplitude

Ultrasonic A-ScanTread in good condition

Tread with defects

Time of flight

RTRT

RT

Ultrasonic surface wave inthe tread of the wheel

Probe Probe

Wheelbody

In-motion Inspection of the running surface of Railway

Wheels by Rayleigh waves

Inspection Principle

NDT by guided waves

Salzburger

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ENSURING THE OPERATIONAL RELIABILITY

OF RAIL VEHICLES BY NONDESTRUCTIVE TESTING OF WHEEL SETS

Wheel set being tested

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Transducer Array Flexi-Patch

PZT crystal array or GMS film array

Mylar based PCB construction with

Adhesive sticker like installation

50-200 kHz Freq

8-16 crystals/transducer

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Guided Wave Smart Pipe

Non-dispersive Wave mode

Low attenuation wave mode

Low Leakage wave mode for embedded portions

Controlling Parameters:

Input Frequency and Signal BW

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Summary

Guided Waves offer a new and effective

technique for evaluation of welded structures.

Cost savings due to the long range nature of thetechnique

Increased sensitivity due to multi-mode nature

Ability to inspect in-accessible regions

Ability to online monitor the welding process.

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Inaccessible

Pipelineinspection

tools (PIGS)

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MFL Inspection of gaspipelinesDefect

Differential

Probe

Tube

D f Ch i i

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Defect Characterization

MFL signal

Defect profile

Prediction with 1 resolution

Prediction with 2 resolutions