Ultra sonic test

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Copyright © 2004 WI Ltd

Ultrasonic TestingUltrasonic Testing

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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




Compression / Longitudinal

• Viration and propagation in the samedire!tion / parallel

• "ravel in solids# li$uids and gases

%ropagation

%arti!le viration




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




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




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



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!



Sound at an Interfa!e

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

<efle!ted

"ransmitted

Interfa!e

3o, mu!h is refle!ted and

transmitted depends upon the

relative a!ousti! impedan!e ofthe 2 materials



:!ousti! Impedan!e

• =efinition

"he <esistan!e to the

passage of sound

,ithin a material

• -ormula

V Z ×= ρ

• easured in

.g / m2 > se!

• Steel 459 > &05

• Water &4* > &05

• :ir 0004& > &05

• %erspe> 82 > &05

= ensit! " # = #elocit!



+ Sound <efle!ted at an

Interfa!e

reflected

Z Z

Z Z %100

2

21

21 =×

+

−

+ Sound <efle!ted ? + Sound "ransmitted @ &00+

"herefore

+ Sound "ransmitted @ &00+ A + Sound <efle!ted



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 %100

18.48

22.45 2

=×

reflected %88.0910093856.02

=×




$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




Steel

Air Steel

Air

Steel

Steel Aluminum

Steel

Lar5e Acoustic Impedance

Ratio

Lar5e Acoustic Impedance

Ratio

1o Acoustic Impedance

ifference

Small Acoustic Impedance

ifference




Loses intensity

due to

Sound travelling through a material

Attenuation

• Sound eam !omparale

to a tor!h eam

•<edu!tion differs for small

and large refle!tors

• )nergy losses due to

material

•ade up of asorption

and s!atter

2eam Spread




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




eam Spread

"he sound eam

spread out and the

intensity de!reases




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




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




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=




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=




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=




:mplitude ratios in de!iels

• 2 E & @ 5

• 4 E & @ &2d

• 1 E & @ &4d• &0 E & @ 20d

• &00 E & @ 40d




Sound Feneration

• 3ammers 'Wheel tapers(

• agnetostri!tive

• Lasers• %ieoAele!tri!

magnetostri!tive




%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 ?




%ieoA)le!tri! aterials

G:<"6

• <esistant to ,ear

• Insolule in ,ater

• <esists ageing

• Ineffi!ient !onverter ofenergy

• ;eeds a relatively high

voltage

Very rarely used nowadays

LI"3I SL%3:")

• )ffi!ient re!eiver

• Lo, ele!tri!al

impedan!e

• Hperates on lo, voltage• Water solule

• Lo, me!hani!al

strength

• seale only up to 80CUsed mainly in medical




%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




%roes




%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




%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.




%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




%roe =esign

• Compression %roe

K ;ormal proe

K 0M

=amping

"ransdu!er

)le!tri!al!onne!tors

3ousing




%roe =esign

• Shear %roe

K :ngle proe

=amping"ransdu!er

%erspe> ,edge

2ac<in5

medium

6robeShoe




%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 <e!eiver

-o!using

lens

Separator /

Insulator




:utomated Inspe!tions

• %ulse )!ho

• "hrough "ransmission

• "ransmission ,ith <efle!tion

• Conta!t s!anning

• Fap s!anning

• Immersion testing




Fap S!anning

• %roe held a fi>ed

distan!e aove the

surfa!e '& or 2mm(

• Couplant is fed intothe gap




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



Immersion "esting

Water

path

distan!e

W t th di t

-ront surfa!e a!. surfa!e

efect

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Ultra sonic test