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Copyright © 2004 WI Ltd

Ultrasonic TestingUltrasonic Testing

Day 2Day 2

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Sound Waveforms

Sound travels in different waveforms indifferent conditions

•Compression waveCompression wave•Shear waveShear wave•Surface waveSurface wave•Lamb waveLamb wave

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Compression / Longitudinal

• Viration and propagation in the samedire!tion / parallel

• "ravel in solids# li$uids and gases

%ropagation

%arti!le viration

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Shear / "ransverse• Viration at right angles / perpendi!ular to

dire!tion of propagation

• "ravel in solids only

• Velo!ity ≈ &/2 !ompression 'same material(

%ropagation

%arti!le viration

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Surfa!e Wave

• )llipti!al viration• Velo!ity *+ less than shear

• %enetrate one ,avelength deep

)asily dampened y heavy grease or ,et finger

-ollo,s !urves ut refle!ted y sharp !orners or

surfa!e !ra!.s

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Lam / %late Wave• %rodu!ed y the manipulation of surfa!e

,aves and others

• sed mainly to test very thin materials /plates

• Velo!ity varies ,ith plate thi!.ness andfre$uen!ies

SYMETRIC ASSYMETRIC

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Compression v Shear

-re$uen!y

• 013

• & 3

• 23• 43

• 536

Compression

• &&*

• 17

• 271• &4*

• 07*

Shear

• 51

• 82

• &5• 0*

• 014

"he smaller the ,avelength the etter the

sensitivity

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Sound travelling through a material

• Velo!ity varies a!!ording to the material

Compression ,aves

• Steel 1750m/se!

• Water &490m/se!

• :ir 844m/se!

• Copper 4900m/se!

Shear ,aves

• Steel 8241m/se!

• Water ;:

• :ir ;:

• Copper 2880m/se!

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Sound at an Interfa!e

• Sound ,ill e either transmitted a!rossor refle!ted a!.

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:!ousti! Impedan!e

• =efinition

"he se!

• Steel 459 > &05

• Water &4* > &05

• :ir 0004& > &05

• %erspe> 82 > &05

= ensit! " # = #elocit!

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+ Sound

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3o, mu!h sound is refle!ted at a steel to ,ater

interfa!eB

• 6& 'Steel( @ 459 > &05 • 62 'Water( @&4* > &05

reflected %10048.17.46

48.17.46 2

=×

+

−

reflected %10018.48

22.45 2

=×

reflected %88.0910093856.02

=×

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$ow much sound transmitted%

&'' ( ) the reflected sound

E*ample + Steel to water

&'' ( ) ,, ( - RE.LECTE/ = &0 ( TRA1SMITTE

The 2I33ER the Acoustic Impedance Ratio

or ifference between the two materials+

More sound RE.LECTE than transmitted4

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Steel

Air Steel

Air

Steel

Steel Aluminum

Steel

Lar5e Acoustic Impedance

Ratio

Lar5e Acoustic Impedance

Ratio

1o Acoustic Impedance

ifference

Small Acoustic Impedance

ifference

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Loses intensity

due to

Sound travelling through a material

Attenuation

• Sound eam !omparale

to a tor!h eam

•

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S!atter

• "he igger the grainsie the ,orse the

prolem

• "he higher the

fre$uen!y of theproe the ,orse the

prolem

& 3 1 3

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eam Spread

"he sound eam

spread out and the

intensity de!reases

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eam spread and :ttenuation !omined

*0+-S3

40+

-S3

;o attenuation#only eam

spread 5d redu!tion

*0+

-S3

85+

-S3

:ttenuation and eam

spread 5d? redu!tion

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Sound Intensity

Comparing the intensity of 2 signals

1

0

1

0

P

P

I

I =

)le!tri!al po,er proportional to the

s$uare of the voltage produ!ed

2

1

2

0

1

0

)(

)(

V

V

P

P =

2

1

2

0

1

0

)(

)(

V

V

I

I =3en!e

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Sound Intensity

2

1

2

0

1

0

)()(

V V

I I = Will lead to large ratios

21

2

0

10..1

0

10.. )(

)(

V

V Log

I

I Log ="herefore

dB

V

V Log

I

I Log

1

0

10..

1

0

10.. 20=

BELS

V

V Log

I

I Log

1

0

10..

1

0

10.. 2=

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1

0

10..20

H

H Log dB =

2 signals at 20+ and 40+ -S3

What is the differen!e et,een them in dDsB

2..2020

4020

1010.. Log Log dB ==

3010.020×=dB

dBdB 6=

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1

0

10..20

H

H Log dB =

2 signals at &0+ and &00+ -S3

What is the differen!e et,een them in dDsB

10..2010

10020

1010.. Log Log dB ==

120×=dB

dBdB 20=

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:mplitude ratios in de!iels

• 2 E & @ 5d 10+

• 4 E & @ &2d 21+

• 1 E & @ &4d 20+• &0 E & @ 20d &0+

• &00 E & @ 40d &+

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Sound Feneration

• 3ammers 'Wheel tapers(

• agnetostri!tive

• Lasers• %ieoAele!tri!

magnetostri!tive

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%ieoA)le!tri! )ffe!t

• When e>posed to an alternating !urrent a!rystal e>pands and !ontra!ts

• Converting ele!tri!al energy into me!hani!al

A ? ? A A ?

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%ieoA)le!tri! aterials

G:

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%olaried Crystals

• %o,ders heated to

high temperatures

• %ressed into shape• Cooled in very

strong ele!tri!al

fields

)>amples

• arium titanate 'a "i H8(

• Lead metanioate '% ; H5(

• Lead ir!onate titanate

'% "i H8 or % 6r H8(

Most of the probes for conventional usa5e use

67T + Lead 7irconate Titanate

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%roes

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%roes• "he most important part of the

proe is the !rystal• "he !rystal are !ut to a

parti!ular ,ay and thi!.ness to

give the intended properties

• ost of the !onventional !rystal

are J K !ut to produ!e

Compression ,ave

7

8

8 8

Y

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%roes

• "he fre$uen!y of the proe depends on

the "3IC;)SS of the !rystal

• -ormula for fre$uen!yE

.f = # 9 0t

Where Ff = the Fundamental frequency

V = the velocity in the crystal

t = the thickness of the crystal

Fundamental frequency is the frequency of the material ( crystal )

where at that frequency the material will vibrate.

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%roes

• "he "hinner the !rystal the 3igher the fre$uen!y

• Whi!h of the follo,ings has the "hinnest !rystal B

& 3 Compression proe

1 3 Compression proe

&0 3 Shear proe

21 3 Shear proe

0: M$; Shear6robe

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%roe =esign

• Compression %roe

K ;ormal proe

K 0M

=amping

"ransdu!er or!rystal

)le!tri!al!onne!tors

3ousing

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%roe =esign

• Shear %roe

K :ngle proe

=amping"ransdu!er or

!rystal

%erspe> ,edge

2ac

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%roe =esign

Twin Cr!stal

:dvantages

• Can e fo!used

• easure thin plate

• ;ear surfa!e

resolution

=isadvantages

• =iffi!ult to use on

!urved surfa!es• Siing small defe!ts

• Signal amplitude /

fo!al spot length

"ransmitter

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:utomated Inspe!tions

• %ulse )!ho

• "hrough "ransmission

• "ransmission ,ith

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Fap S!anning

• %roe held a fi>ed

distan!e aove the

surfa!e '& or 2mm(

• Couplant is fed intothe gap

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Immersion "esting

• Component is pla!ed in a ,ater filled tan.

• Item is s!anned ,ith a proe at a fi>ed

distan!e aove the surfa!e

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Immersion "esting

Water

path

distan!e

W t th di t

-ront surfa!e a!. surfa!e

efect

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