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Ultrasonic TestingUltrasonic TestingDay 3Day 3
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The Phenomenon of Sound
REFLECTIONREFRACTION
DIFFRACTION
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The Phenomenon of Sound
REFLECTIONREFRACTION
DIFFRACTION
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Sound at an Interface
• Sound will e either tran!mitted acro!!or reflected ac"
#eflected
Tran!mitted
Interface
$ow much i! reflected and
tran!mitted depend! upon the
relati%e acou!tic impedance ofthe 2 material!
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Inclined incidence)not at *0o +
Incident
Tran!mitted
The !ound i! refracted due to difference! in
!ound %elocity in the 2 ,I--.#./T material!
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#.-#&CTI/• nly occur! when1
The incident angle is other than 0°
Water
Steel
Steel
Steel
Water
Steel
03
#efracted
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#.-#&CTI/• nly occur! when1The incident angle is other than
0°
Steel
Steel
Water
Steel
03
#efracted
The Two Materials has different
VELOCITIE
No Refraction
03
03
(3
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Snell5! Law
I
R
Material 1
Material 2
2Materialin
1Material
Vel
inVel
RSine
I Sine=
Incident
Refracted
/ormal
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Snell5! Law
C
Perspex
Steel
C
20
48.3
2Materialin
1Material
Vel
inVel
RSine
I Sine=
5960
2730
48.3
20=
Sine
Sine
4580.04580.0 =
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Snell5! Law
C
Perspex
Steel
C
15
34.4
2Materialin
1Material
Vel
inVel
RSine
I Sine=
5960
2730
R
15=
Sine
Sine
2730
596015SinSinR =
565.0=SinR
4.34=
R
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Snell5! LawC
Perspex
Steel
C
20
S
48.3
24
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Snell5! Law
Perspex
Steel
S
C
C
CC
S
When an incident eam of !ound
approache! an interface of twodifferent material!1
#.-#&CTI/ occur!
There may e more than one wa%eform
tran!mitted into the !econd material6
e7ample1 Compre!!ion and Shear
When a wa%eform change!
into another wa%eform1
8,. C$&/9.
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Snell5! Law
Perspex
Steel
C
CS
CS
C
S
If the angle of Incident i!
increa!ed the angle ofrefraction al!o increa!e!
:p to a point where the
Compre!!ion Wa%e i! at
*03 from the /ormal
!0° Thi! happen! at the
FIRT CRITICAL AN"LE
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;!t Critical &ngle
C
27.4
S
33
C Compre!!ion wa%e refractedat *0 degree!
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2nd Critical &ngle
C
S (Surface Wave
!0
C
Shear wa%e refracted at *0 degree!
57
Shear wa%e ecome! a !urface wa%e
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;!t Critical &ngle Calculation
C
Perspex
Steel C
5960
2730
90
I=
Sine
Sine
5960
2730=SinI
458.0=SinI
26.27= I
S
190 =Sin
27.2
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2nd Critical &ngle Calculation
C
Perspex
Steel
C
3240
2730
90
I=
Sine
Sine
3240
2730=SinI
8425.0=SinI
4.57= I
S190 =Sin
57.4
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#st$
%nd
$
&&°
!0°
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Summary
• Standard angle proe! etween ;!t and
2nd critical angle! )46(06>0+
• Stated angle i! refracted angle in !teel
• /o angle proe under 6 and more
than ?01 to a%oid eing 2 wa%e! in the
!ame material=
C
C S
ne ,efect Two .choe!
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Snell5! Law e7ample• Calculate the ;!t critical angle for a
per!pe7@copper interface
• A Comp per!pe7 1 2>0m@!ec
• A Comp copper 1 4>00m@!ec
5.355808.0
4700
2730===SinI
