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8/17/2019 Ut Presentation Small

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METHODNONDESTRUCTIVE TESTING

ULTRASONIC TESTING

Presented By

Eng. Mohamed El-Sayed


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Basic Principles of Sound

• Sound is produced by a vibrating body

and travels in the form of a wave.• We need two conditions to be satisfied:

1.Mass

2.Elasticityball on a spring pendulum


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The ball starts to oscillate as soon as it is pushed and theoscillation will decreases and decelerate until it has used all its

kinetic energy.

Oscillation


T

W


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Understanding wave propagation

Spring = elastic bonding forceBall = atom



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T

distance travelled


•Sound waves travel through materials by vibrating the particlesthat make up the material.


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gas liquid solid

Atomic structures

• low density• weak bonding

forces

• medium density• medium bonding

forces

• high density• strong bonding

forces



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Basic Principles of SoundMovement of the ball over time

► Cycle: The complete sequence of movements.

► Period: The time required for moving one completecycle.

► Wave length: The distance a wave travels during onecomplete cycle. ( )

► Frequency: The number of cycles in a given period of

time . ( f )

Time

displacement


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Typical velocities of propagation in different materials


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Spectrum of soundFrequency range Hz Description

0 - 20 Infrasound /subsound Earth quake

20 - 20.000 Audible sound Speech, music


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Basic Principles of SoundWhy we use Ultrasound waves?

displacement

discontinuity

• Minimum discontinuity can be

2detected should be loated at /

• for steel V=5920 m/s

• using Audible sound waves at f =20.000 cps /2= 150 mm

• using Ultrasound waves at f =5000.000 cps /2 = 0.5 mm


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1. Longitudinal wave (Compressional wave)

Sound propagation

Longitudinal waves propagate in all kind of materials.

Direction ofoscillation

Direction of propagation


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Direction of propagationDirection of oscillation

Sound propagation2. Shear wave (Transverse wave)

•Transverse waves only propagate in solid

bodies.


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Sound propagation3. Surface wave (Rayleigh wave)

- Surface waves only propagate in solidbodies.

- Penetrate only )1 ( so, its used to

detect surface cracks.

- Can follow the surface contour as long

as the contour does not sharply change.

- The wave travels with an ellipticparticle motion.


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Sound propagation 4. lamb wave (Plate wave)

We Can not propagate neither shear nor Surface waves in parts thinnerthan (3/2(


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Acoustic Impedance

Properties Of Sound Wave

We use sound waves in flaw detection because they willreflect when they encounter a sudden change in acousticimpedance in material.


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Medium 1 Medium 2

Interface

Incoming wave Transmitted wave

Reflected wave

Behaviour at an interface

As soon as a sound wave comes to a change in material characteristics ,

e.g. the surface of a workpiece wave propagation will change too:


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Reflection and mode conversion►Reflection occurs due to sudden change in

Acoustic Impedance.


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β β

βα

αα

LL

S S

Reflection and mode conversion cont.


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Couplant► We use substance to provide suitable sound path between the

transducer and the test surface.

There are some items should be found in the couplant:

1. It must exclude all air between the transducer and test surface.

2. Fills in and smoothes out irregularities on the surface of the test part.

3. Aids in the movement of the transducer over the surface in contact

testing.4. Must be easy to apply and easy to remove and not to be harmless to

the tested part.

Types of couplant used:

1. Oil.

2. Water mixed with glycerin with ratio 2:13. Heavy oil or grease for rough or vertical surfaces.

4. Thin rubber.


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Refraction and SNELL’s law:►Occurs due to the difference in sound velocity

between two mediums

Perspex - Water Perspex - Steel


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Refraction and SNELL’s law :

θr

θi

L

S

θ RS

S

θr

L

θ R L

S

L

Medium 1 - Perspex

Medium 2 - Steel

law:SNELL’s

Interface

We can summarise refraction and reflectionand mode conversion as following:


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► If we increase θi, θRL will increase until it reach 90° and still have ashear wave in medium 2.

► θi at this time called First Critical Angle and equal 28° for Perspex toSteel and equal to 15° for Water to Steel.

θi

θ RS

θ R L

S

L

Medium 1 - Perspex

Medium 2 - Steel

Interface


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θi

θ RS

θr L

L

Medium 1 - Perspex

Medium 2 - Steel S

Interface

If we still increase θi, Longitudinal wave will Reflected and θRS increases untilreach 90° then we produces surface wave.

θi at this time called Second Critical Angle and equal 58° for Perspex to Steel .

Th G ti Of Ult i


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The Generation Of Ultrasonic waves

ff


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Transducer And Piezo Electric Effect

► The conversion of electrical pulses to mechanical vibrations and the

conversion of returned mechanical vibrations back into electrical energy.

Piezoelectric Effect

Piezoelectrical

Crystal (Quartz)Battery

+


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An alternating voltage generates crystal oscillations at the frequency f

U(f)

Sound wavewith

frequency f

Piezoelectric Effect


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Reception of ultrasonic waves

A sound wave hitting a piezoelectric crystal, induces

crystal vibration which then causes electrical voltages

at the crystal surfaces.

Electricalenergy

Piezoelectricalcrystal Ultrasonic wave

T Of C t l t i l


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Types Of Crystal materials:

Quartz

(SiO2)

Lithium

Sulphate(Li2 SO4)

Polarized Ceramics

Types 1.Lead Metaniobate2.Barium Titanate3.Lead Zirconate/Titanate

Generator 2.3 Х10 m/v 15 Х10 m/v 125 Х10 m/v

Receiver 4.9 Х10 v/m 8.2 Х10 v/m 1.5 Х10 v/m

Curie 576° C 130° C 120° C

Advantages Very stablefrequency c/c

Long life time The best generator

Disadvantages Poor generator Soluble in water Have a tendency to wear

items

Crystal

-12 -12 -12

99 9

C l C


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Crystal Cutting:Crystal cutting methods which have responsibility of generate either

Longitudinal or Shear waves.

1. Cutting Perpendicular to X-axis Produce longitudinal waves.

2. Cutting Perpendicular to Y-axis Produce shear waves.


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Crystal size is a contributing factor in itsPerformance

Input data Results

With decreasing diameter. D Spread of sound beam Θ With D and f Can detect small defects λ

With D and f Penetration


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Probe Design:1. case: consist of metal housing

That contains all the following parts.2. Backing Material:

Provide damping of the transducer

Oscillations (made of epoxy, rubber

or Plastics).

3.Electrodes: Are primarily silver

or gold deposited on the piezo-

Electric element.

4.Crystal (piezo Electric element)

5. Wear face: Thin layer made of

Lucite, Ceramic or Quartz wear plate..

Types of Probe according to the refracted


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Types of Probe according to the refracted

wave introduced

1. Normal ProbeIn normal beam testing, the sound beam isintroduced into the test article at 90 degree tothe surface.


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. Angle Probe2

► Angle beam transducersincorporate wedges tointroduce a refracted shearwave into a material.

►The incident wedge angle is

used with the material velocityto determine the desiredrefracted shear wave accordingto Snell’s Law)

►Transducers can use fixed or

variable wedge angles.►Common application is in weld

examination.

Types of Probe according to crystal which


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Types of Probe according to crystal whichhousing

►Single Element:1. Sender only

2. Receiver only

3. Sender and Receiver

► Double Element:Two single mounted side by side or stacked

(one sender and the other receiver)

Single crystal probe

The Capabilit Of T ansd ce


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The Capability Of Transducer:

1. Sensitivity: The ability to detect small discontinuities.

2. Resolution: The ability to separate the sound reflections from twodiscontinuities close together in depth or time.

3. Efficiency: Energy conversion effectiveness.

P ti f Ult d


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Attenuation► The decay rate of the wave as it propagates through material.

► This further weakening results from :

1. Absorption-of energy due to moving the vibrating molecules.

2. Scatter-of sound waves reflecting from the grain boundaries.

3. Interference effects- close to the transducer

4. Beam spread

Propagation of Ultrasound



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Beam spread

•Since the ultrasound originatesfrom a number of points along thetransducer face, the ultrasoundintensity along the beam isaffected by constructive and

destructive wave interference .

•This wave interference leadsto extensive fluctuations inthe sound intensity near thesource and is known as thenear field. Because of acousticvariations within a near field,it can be extremely difficult toaccurately evaluate flaws inmaterials when they are

positioned within this area.


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Propagation of UltrasoundBeam spread

N

Near Zone(Fresnel)

Far Zone (Fraunhofer)

Focus Angle of divergenceCrystal

Accoustical axis

D

θ

Secondary lobes

Ult i B i T ti M th d


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►To get useful levels of sound energy into a material, the air between thetransducer and the test article must be removed. This is referred to ascoupling.

►In contact testing a couplant such as oil, grease or a gel is appliedbetween the transducer and the part.

Ultrasonic Basic Testing Methods

A) Contact Testing Method

•Using Transducers With Frequency between (1 to 5 MHZ)

The Basic Test Techniques


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The Basic Test Techniques

1. Pulse – Echo Technique

• A transducer sends out a pulse of energy and the same or a secondtransducer listens for reflected energy (an echo).

• Reflections occur due to the presence of discontinuities and the surfacesof the test article.

• The amount of reflected sound energy is displayed versus time, whichprovides the inspector information about the size and the location offeatures that reflect the sound.

Straight beam probe


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1. Pulse-Echo Testing (cont.)

•Digital display showingsignal generated fromsound reflecting off backsurface.

•Digital display showing thepresence of a reflectormidway through material, withlower amplitude back surfacereflector.

•The pulse-echo technique allows testing when access to onlyone side of the material is possible, and it allows the location ofreflectors to be precisely determined.

2 D l C t l T h i


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2. Duel Crystal Technique

•There are two crystals One act as a Transmitter

and the other as a receiver.•There are may be side by side or may be stacked.

3 Pi h C h T h i


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3. Pitch-Catch Technique► Its acts as duel crystal technique but with separate two

transducers.

Transmitter Transducer Receiver Transducer

Transmission-Through4


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Transmission-. Through4

0 2 4 6 8 10

2

11

• Two transducers located on opposing sides ofthe test specimen are used. One transduceracts as a transmitter, the other as a receiver.

• Discontinuities in the sound path will result in apartial or total loss of sound being transmittedand be indicated by a decrease in the receivedsignal amplitude.

• Through transmission is useful in detectingdiscontinuities that are not good reflectors, and

when signal strength is weak. It does notprovide depth information.

T R

T R

11

2

Transmission (cont )-Through4


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Digital display showing

received sound through

material thickness.

Digital display showing

loss of received signaldue to presence of a

discontinuity in the

sound field.

Transmission (cont.)-. Through4

5 Tandem Technique


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Receiver Transducer

5. Tandem Technique

Acts as Through Transmission but with angle transducers

Transmitter Transducer

B) Immersion Testing Method


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B) Immersion Testing Method►Using Transducers With Frequency between (10 to 25 MHZ)

► In immersion testing, the part and the transducer are place in a

water bath. This arrangement allows better movement of thetransducer while maintaining consistent coupling.

►With immersion testing, an echo from the front surface of the partis seen in the signal.

Immersion testing

B) Immersion Testing Method cont


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B) Immersion Testing Method cont.


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Immersion test with propagate

Longitudinal wave

Immersion test with propagate

shear wave

0 2 4 6 8 10

FWE

BWEDE

2IP

0 2 4 6 8 10

FWE

BWE

1IP

1 2

Defect

I i T d


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Immersion Transducers►Immersion transducers are

designed to transmit sound

whereby the transducer andtest specimen are immersed ina liquid coupling medium(usually water).

►Immersion transducers doesn’tneed protective layer.

►Immersion transducersare manufactured with

planar, cylindrical or sphericalacoustic lenses (focusing lens).


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Advantages Of Focussing Lens

1. Increasing The intensity.

2. Greater width of length (for spherical lens) greatersensitivity.

3. Used with rough surfaces.


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Display Ultrasonic IndicationsTypes of Scanning

►Information from ultrasonic testing can be presentedin a number of differing formats.

►Three of the more common formats include:

A-scan

B-scan

C-scan

Types of Scanning


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scan- A

► A-scan presentationdisplays the amount ofreceived ultrasonic energyas a function of time.

► Relative discontinuity sizecan be estimated bycomparing the signalamplitude to that from aknown reflector.

► Reflector depth can bedetermined by the positionof the signal on thehorizontal sweep.

Time

S i g n a l A m p l i t u d e

S i g n a l A m p

l i t u d e

Time

Types of Scanning

Types of Scanning


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B-scan

►B-scan presentations display aprofile view (cross-sectional) of atest specimen.

►Only the reflector depth in thecross-section and the lineardimensions can be determined.

► A limitation to this display techniqueis that reflectors may be masked bylarger reflectors near the surface.

Types of Scanning

Types of Scanning


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C-scan►The C-scan presentation displays a plan type view of

the test specimen and discontinuities.

►C-scan presentations are produced with an automateddata acquisition system, such as in immersionscanning.

►Use of A-scan in conjunction with C-scan is necessarywhen depth determination is desired.

Photo of a CompositeCom onent

C-Scan Image ofInternal Features

yp g

Calibration Methods


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•The user must "calibrate" the system, which includes the equipment settings,

the transducer, and the test setup, to validate that the desired level of precisionand accuracy are achieved.

Calibration Methods

•standards also help the inspector to estimate the size of flaws. In a pulse-echotype setup, signal strength depends on both the size of the flaw and thedistance between the flaw and the transducer.

•By comparing the signal from the reference standard to that received from theactual flaw, the inspector can estimate the flaw size.

•The type of standard used is dependent on the application and the form and shapeof the object being evaluated.

Th IIW T C lib ti Bl k


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The IIW Type Calibration Block

►IIW "type" blocks can be commercially

obtained in a selection of materials.

►IIW "type" blocks usually have English units.

►IIW "type" blocks include additional

calibration and references features such asnotches, circular groves, and scales .

►There are two full-sized and a mini versions

of the IIW type blocks.

Block)-1(V 1-IIW Type US


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)(yp

Block)-1(V 2-IIW Type US

The IIW type US-2 block was developed for US Air Force applications.

IIW Type Mini


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IIW Type Mini

Used for setting metal-distance and sensitivitysettings, determining the sound exit point andrefracted angle of angle beam transducers, and

evaluating depth resolution of normal beaminspection setups.

Block)-2Beam or ROMPAS Calibration Block (V -The Miniature Angle•block is much smaller and lighter than the IIWblock but performs many of the same functions.

•The miniature angle-beam block can be used to

check the beam angle and exit point of thetransducer. The block can also be used to makemetal-distance and sensitivity calibrations for bothangle and normal-beam inspection setups.

wave Distance/Sensitivity Calibration (DSC) Block AWS Shear


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This block is used to determine the beam exit point andrefracted angle of angle-beam transducers and to calibratedistance and set the sensitivity for both normal and anglebeam inspection setups.

wave Distance Calibration (DC) Block AWS Shear

The DC AWS Block is a metal path distance and beamexit point calibration standard that conforms to therequirements of the American Welding Society (AWS)and the American Association of State Highway andTransportation Officials (AASHTO).

AWS Resolution Calibration (RC) Block


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The RC Block is used to determine the resolutionof angle beam transducers per the requirementsof AWS and AASHTO. Engraved Index markers are

provided for 45, 60, and 70 degree refracted anglebeams.

FBH Resolution Reference Block30

The 30 FBH resolution reference block is used toevaluate the near-surface resolution and flawsize/depth sensitivity of a normal-beam setup. Theblock contains number 3 (3/64"), 5 (5/64"), and 8

(8/64") ASTM flat bottom holes at ten metal-distances ranging from 0.050 inch (1.27 mm) to1.250 inch (31.75 mm).

Miniature Resolution Block


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The miniature resolution block is used toevaluate the near-surface resolution andsensitivity of a normal-beam setup It can be

used to calibrate high-resolution thicknessgages over the range of 0.015 inches (0.381mm) to 0.125 inches (3.175 mm).

Step and Tapered Calibration Wedges

Step wedges are typically manufactured withfour or five steps but custom wedge can be

obtained with any number of steps.

Distance/Sensitivity (DS) Block


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The DS test block is a calibration standard used tocheck the horizontal linearity and the dB accuracyper requirements of AWS and ) AASHTO ( American

Association of State Highway and TransportationOfficials.

Amplitude Blocks-Distance/Area

Distance/area amplitude correction blocks typically arepurchased as a ten-block set.

Sets can be purchased in Aluminum or titanium.

Each block contains a single flat-bottomed, plugged hole.The hole sizes and metal path distances are as follows:

•3/64" at 3"•5/64" at 1/8", 1/4", 1/2", 3/4", 11/2", 3", and 6"•8/64" at 3" and 6"

Normal Beam Inspection


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p)Compression wave Technique)

Calibration To ensure proper positioning of zero and time base linearity

A) Distance Calibration

Normal Beam Inspection Cont.


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B) Resolution

Normal Beam Inspection cont.


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p

Normal Beam Inspection Cont.


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p

Normal Beam Inspection Applications


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Plate testing

laminationPlate 0 2 4 6 8 10

IP

F

BE

IP = Initial pulse

F = Flaw

BE = Backwall echo




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Flaw Detection - Delaminations

Signal showing multiple back

surface echoes in an unflawed area.

Additional echoes indicatedelaminations in the member.

Contact, pulse-echo inspection for delaminations on 36” rolled

beam.



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0 2 4 6 8 10

s

s

Wall thickness measurement

Corrosion



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Thickness Gauging

Ultrasonic thickness gauging is

routinely utilized in thepetrochemical and utilityindustries to determine variousdegrees of corrosion/erosion.

• Applications include

piping systems, storageand containmentfacilities, and pressurevessels.

Angle Beam Inspection


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(A) IIW Determination of the beam exit point.

(B) IIW Determination of refracted angle of angle-beam.



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(C) Distance Calibration Using (V2-Block)



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Angle Beams I

Angle Beam Inspection Cont.


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Angle Beams II



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Angle Beam Inspection Applications


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Flaw Detection in Welds

►One of the most widelyused methods ofinspecting weldments isultrasonic inspection.

►Full penetration groovewelds lend themselvesreadily to angle beamshear wave examination.

Movements of Transducer to scan


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Longitudinal or Transverse discontinuities

Rotational movement

•For Longitudinal discontinuities

• For Transverse discontinuities

Lateral movement

Transverse movement

Interpretation And Evaluation Of Defects According ToAWS D1 1 C d


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AWS D1.1 Code

►D=A-B-C► D: Discontinuity Severity► A: Indication Level

► B: Reference Level

► C: Attenuation Factor

C=(S-1)Х2

Where S in inch

Interpretation And Evaluation Of Defects According ToAWS D1 1 C d C t


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AWS D1.1 Code Cont.

► Using V1-Block to get the

reference level.► From the reference hole

indication and Rising The Amplitude To 80% Of CRT.

► Get (B) in dB.

Interpretation And Evaluation Of Defects According ToAWS D1 1 C d C t


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AWS D1.1 Code Cont.

During scanning any indication appearsshould be evaluated by rising the maxamplitude to 80% of the CRT.From this indication we get (A) in dBand (C) in inch.

where, C=(S-1)Х2

Interpretation And Evaluation Of Defects According ToAWS D1 1 Code Cont


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AWS D1.1 Code Cont. Using all previous data we get (D) Which is the discontinuity severity.From AWS D1.1 acceptance criteria.



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AWS D1.1 Code Cont.



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AWS D1.1 Code Cont.



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AWS D1.1 Code Cont.

Note the relation D=A-B-C

Interpretation And Evaluation Of Defects According To


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ASME Code

Distance Amplitude Correction (DAC)

Acoustic signals from the same reflecting surface will have different amplitudes atdifferent distances from the transducer. Distance amplitude correction (DAC)provides a means of establishing a graphic reference level sensitivity as a function ofsweep distance on the A-scan display.



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ASME Code Cont.



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ASME Code Cont.



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ASME Code Cont.

Interpretation And Evaluation Of Defects According ToASME Code Cont


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From ASME Code acceptance criteria

ASME Code Cont.

All indications which produce aresponse Smaller than 20% of thereference level , they are acceptable

regardless of the length of discontinuity

Where indications are interpreted to be

cracks, lack of fusion, or incompletepenetration, they are unacceptable regardless of discontinuity or signal

amplitude.



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ASME Code Cont.

All indications which produce a responsegreater than 80% of the reference level ,they are acceptableregardless of the length of discontinuity



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ASME Code Cont.

DefectLength

WeldThickness

Acceptance

6 mm Up to19 mm

Reject

t/3 From 19 mmTo 57 mm

Reject

19 mm For t over

57 mm

Reject

Instrumentation


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► Ultrasonic equipment is usually purchased to satisfyspecific inspection needs, some users may purchasegeneral purpose equipment to fulfill a number ofinspection applications.

►

Test equipment can be classified in a number ofdifferent ways, this may include portable orstationary, contact or immersion, manual orautomated.

► Further classification of instruments commonly

divides them into four general categories: D-meters,Flaw detectors, Industrial and special application.

Instrumentation (cont.)


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►D-meters or digital thicknessgauge instruments providethe user with a digital(numeric) readout.

►They are designed primarilyfor corrosion/erosioninspection applications.

• Some instruments provide the user with both a digital readout and adisplay of the signal. A distinct advantage of these units is that theyallow the user to evaluate the signal to ensure that the digitalmeasurements are of the desired features.



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( )

►Flaw detectors areinstruments designedprimarily for the inspectionof components for defects.

►However, the signal can be

evaluated to obtain otherinformation such as materialthickness values.

►Both analog and digitaldisplay.

►Offer the user options ofgating horizontal sweep andamplitude threshold.



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►Industrial flaw detection

instruments, provide userswith more options thanstandard flaw detectors.

►May be modulated unitsallowing users to tailor the

instrument for their specificneeds.

►Generally not as portableas standard flaw detectors.



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►Immersion ultrasonic scanning

systems are used for automateddata acquisition and imaging.

►They integrate an immersiontank, ultrasonic instrumentation,a scanning bridge, and computercontrols.

►The signal strength and/or thetime-of-flight of the signal ismeasured for every point in thescan plan.

►The value of the data is plottedusing colors or shades of gray to

produce detailed images of thesurface or internal features of acomponent.

Advantage of Ultrasonic Testing


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►Sensitive to both surface and subsurface discontinuities.

►Depth of penetration for flaw detection or measurement issuperior to other methods.

►Only single-sided access is needed when pulse-echotechnique is used.

►High accuracy in determining reflector position andestimating size and shape.

►Minimal part preparation required.

►Electronic equipment provides instantaneous results.

►Detailed images can be produced with automated systems.►Has other uses such as thickness measurements, in addition

to flaw detection.

Limitations of Ultrasonic Testing


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g

►Surface must be accessible to transmit ultrasound.►Skill and training is more extensive than with some other

methods.

►Normally requires a coupling medium to promote transfer ofsound energy into test specimen.

►Materials that are rough, irregular in shape, very small,exceptionally thin or not homogeneous are difficult to inspect.

►Cast iron and other coarse grained materials are difficult toinspect due to low sound transmission and high signal noise.

►Linear defects oriented parallel to the sound beam may goundetected.

►Reference standards are required for both equipmentcalibration, and characterization of flaws.


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Thank you

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