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8/20/2019 UT Day2
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Copyright © 2004 WI Ltd
Ultrasonic TestingUltrasonic Testing
Day 2Day 2
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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
Compression / Longitudinal
• Viration and propagation in the samedire!tion / parallel
• "ravel in solids# li$uids and gases
%ropagation
%arti!le viration
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Copyright © 2004 WI Ltd
Shear / "ransverse• Viration at right angles / perpendi!ular to
dire!tion of propagation
• "ravel in solids only
• Velo!ity ≈ &/2 !ompression 'same material(
%ropagation
%arti!le viration
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Copyright © 2004 WI Ltd
Surfa!e Wave
• )llipti!al viration• Velo!ity *+ less than shear
• %enetrate one ,avelength deep
)asily dampened y heavy grease or ,et finger
-ollo,s !urves ut refle!ted y sharp !orners or
surfa!e !ra!.s
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Copyright © 2004 WI Ltd
Lam / %late Wave• %rodu!ed y the manipulation of surfa!e
,aves and others
• sed mainly to test very thin materials /plates
• Velo!ity varies ,ith plate thi!.ness andfre$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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Copyright © 2004 WI Ltd
$ow much sound transmitted%
&'' ( ) the reflected sound
E*ample + Steel to water
&'' ( ) ,, ( - RE.LECTE/ = &0 ( TRA1SMITTE
The 2I33ER the Acoustic Impedance Ratio
or ifference between the two materials+
More sound RE.LECTE than transmitted4
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Copyright © 2004 WI Ltd
Steel
Air Steel
Air
Steel
Steel Aluminum
Steel
Lar5e Acoustic Impedance
Ratio
Lar5e Acoustic Impedance
Ratio
1o Acoustic Impedance
ifference
Small Acoustic Impedance
ifference
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Copyright © 2004 WI Ltd
Loses intensity
due to
Sound travelling through a material
Attenuation
• Sound eam !omparale
to a tor!h eam
•
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Copyright © 2004 WI Ltd
S!atter
• "he igger the grainsie the ,orse the
prolem
• "he higher the
fre$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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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
: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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Copyright © 2004 WI Ltd
Sound Feneration
• 3ammers 'Wheel tapers(
• agnetostri!tive
• Lasers• %ieoAele!tri!
magnetostri!tive
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Copyright © 2004 WI Ltd
%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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Copyright © 2004 WI Ltd
%ieoA)le!tri! aterials
G:
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Copyright © 2004 WI Ltd
%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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Copyright © 2004 WI Ltd
%roes
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Copyright © 2004 WI Ltd
%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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Copyright © 2004 WI Ltd
%roes
• "he fre$uen!y of the proe depends on
the "3IC;)SS of the !rystal
• -ormula for fre$uen!yE
.f = # 9 0t
Where Ff = the Fundamental frequency
V = the velocity in the crystal
t = the thickness of the crystal
Fundamental frequency is the frequency of the material ( crystal )
where at that frequency the material will vibrate.
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Copyright © 2004 WI Ltd
%roes
• "he "hinner the !rystal the 3igher the fre$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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Copyright © 2004 WI Ltd
%roe =esign
• Compression %roe
K ;ormal proe
K 0M
=amping
"ransdu!er or!rystal
)le!tri!al!onne!tors
3ousing
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Copyright © 2004 WI Ltd
%roe =esign
• Shear %roe
K :ngle proe
=amping"ransdu!er or
!rystal
%erspe> ,edge
2ac
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Copyright © 2004 WI Ltd
%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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Copyright © 2004 WI Ltd
:utomated Inspe!tions
• %ulse )!ho
• "hrough "ransmission
• "ransmission ,ith
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Copyright © 2004 WI Ltd
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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Copyright © 2004 WI Ltd
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