Date post: | 23-Jan-2018 |
Category: |
Documents |
Upload: | robert-mitchell-mbindt-eng-tech-lep-aindt |
View: | 540 times |
Download: | 4 times |
Mitchells NDT Inspection Services
Introduction toUltrasonic Testing
Research by Robert Mitchell. Engineering Technician: L.E.P. Registered welding Consultant
M.InstNDT: AINDT.Ex Owner- Director of Mitchells NDT Ltd.
2008
Mitchells NDT Inspection Services
Co-axial cable socket
Matching-element
Damping-medium
Crystal Probe shoe(probe delay)
Housing
workpieceSound pulse
Straight beam probe
Back wall
Mitchells NDT Inspection Services
CrystalPerspex Wedge(probe delay)
Damping mediums
Socket
Probe Housing
workpieceSound pulse
Angle beam probe
Back wall
Probe shoe
10 20 30 40
Mitchells NDT Inspection Services
Near field
Far field
Acoustical axis (central beam)
N = near field length
γ = angle of divergence
3
Sound field
Mitchells NDT Inspection Services
Defect
Flaw detection
Scatter
Mitchells NDT Inspection Services
Defect
10 20 30 40
Flaw detection
Scatter
Scatter
Mitchells NDT Inspection Services
10 20 30 40
Flaw detection
Shear wave
Compressional
Defect
Compressional
Mitchells NDT Inspection Services
Poor flaw orientation
Poor defect orientation
Mitchells NDT Inspection Services
Crack
Improper flaw location
Mitchells NDT Inspection Services
10 20 30 40
crack
Angle reflection
Mitchells NDT Inspection Services
Angle reflection 10 20 30 40
crack
Mitchells NDT Inspection Services
10 20 30 40
Vertical, near surface flaw
Mitchells NDT Inspection Services
10 155 10 155T R
a1
Tandem technique (top)
Mitchells NDT Inspection Services
10 155 10 155T R
a 2Tandem technique (middle)
Mitchells NDT Inspection Services
10 155 10 155T R
a 3
Tandem technique (bottom)
Mitchells NDT Inspection Services
10 20 30 40
Improper flaw orientation
Mitchells NDT Inspection Services
10 20 30 40
Perfect flaw orientation
Mitchells NDT Inspection Services
Sound beam
Flat defect
15105
Reflected sound waves
Flaw detectability with improper flaw orientation
Mitchells NDT Inspection Services
Depth.
Flaw Distance
Defect
Return Echo
Compressional Probe.
Mitchells NDT Inspection Services
Start signal(pulse)
Finish signal(echo)
Transmitter
Transit timemeasurement
Probe
Work piece
Sound transitpath
Stop-watch
Principle of transit time measurement
Return echopath
Mitchells NDT Inspection Services
0 2 4 6 8 10
CRT / A-scan display
Un calibrated time base
Mitchells NDT Inspection Services
0 2 4 6 8 10
Work piece
Probe
Sound wave starts at crystal
Light point or Initial pulse
transmittertransmitterTransmission
pulse
Priciple, transmission pulse
Mitchells NDT Inspection Services
0 2 4 6 8 10
Work piece
Probe
Sound wave
TransmitterTransmitter
Priciple, sound wave in the workpiece
Light point or Initial pulse
Mitchells NDT Inspection Services
0 2 4 6 8 10
Work piece
Probe
TransmitterTransmitter
Priciple, sound pulse at the back wall
Light point or Initial pulse
Mitchells NDT Inspection Services
0 2 4 6 8 10
work piece
probe
transmittertransmitter
Priciple, sound pulse at the coupling surface
Mitchells NDT Inspection Services
0 2 4 6 8 10
Work piece
ProbeBack wall
echo
TransmitterTransmitter
Priciple, echo display and 2nd run
Light point or Initial pulse
Mitchells NDT Inspection Services
2 4 6 8 10
Protecting face or probe shoe
CrystalCompressional
Probe
Electricalzero
(initial pulse)
Mechanicalzero
(surface)
Probe delay
Mitchells NDT Inspection Services
Electicalzero
(initial pulse)
Mechanicalzero
(surface)Sound wave
Work piece
Delay(wedge)
Shear wave probe 0 2 4 6 8 10
Probe delay
Mitchells NDT Inspection Services
0 2 4 6 8 10
Work piece
ProbeBack wall
echo
Flaw
Flawecho
Flaw location and echo display
Mitchells NDT Inspection Services
0 2 4 6 8 10
work piece
Probe
Back wallecho
Flaw
Defectecho
Flaw location and echo display
Initial pulse
Mitchells NDT Inspection Services
0 2 4 6 8 10
Work piece
Probe
Back wallecho
Flaw
Flawecho
Flaw location and echo display
Initial pulse
Mitchells NDT Inspection Services
0 2 4 6 8 10
flaw echocoveredby initialpulse
Work piece
Probe
back wallecho
Flaw
Flaw location and echo display
Mitchells NDT Inspection Services
0 2 4 6 8 10
back wallecho:
without
with flaw
Work piece
Probe
Flaw
Flaw location and echo display
Mitchells NDT Inspection Services
0 2 4 6 8 10
Flaw echosequence
Work piece
Probe
Flaw
Flaw location and echo display
Mitchells NDT Inspection Services
0 2 4 6 8 10
Dead zone (can be measured)
Dead zone
Work piece
Mitchells NDT Inspection Services
Direction ofosscillation
Direction of propagation
Wave length (can be measured)
Longitudinal wave
Mitchells NDT Inspection Services
Direction ofosscillation
Direction of propagation
wave length (can be measured)
Transverse wave
Mitchells NDT Inspection Services
L
LL
L
L
Medium 1
Medium 2
Reflectedwave
Refractedwave
Incidentwave
Reflection and Refraction
Mitchells NDT Inspection Services
0 2 4 6 8 10
10 20 30 40
L
TPossible flawlocations
Angle beam probe with both wave types
Mitchells NDT Inspection Services
T
L
L
T
L
Perspex
Steel
Reflectedwave
Refractedwaves
Incidentwave
α = α1 = 27.5°βT = 33.3°βL = 90°
Longitudinal surface wave
Mitchells NDT Inspection Services T
L
T
Perspex
Steel
Reflectedwave
Refractedtransverse wave
Incidentwave
α = 36.4°βT = 45°
45° transverse wave in steel
Mitchells NDT Inspection Services
L
T O
surfacewaveperspex
steel
reflectedwave
incidentwave
α = α2 = 57°βT = 90°
Transverse surface wave
Mitchells NDT Inspection Services
L
total reflection
perspex
steel
reflectedwave
incidentwave
α > 57°
Total reflection
Mitchells NDT Inspection Services
27,5°
57°
33,3°
90°perspex
steel
L
T
Ranges for incident waves
Mitchells NDT Inspection Services
10 20
Near surface detectability with angle beam pobes
Mitchells NDT Inspection Services
Receiversocket
Transmittersocket
Damping blocks
Crystal
Delay
Acoustical corkbarrier
TR-probe / dual crystal probe
Probe Shoe
Mitchells NDT Inspection Services
0 2 4 6 8 10
IP
BE
Work piece
TR-probe
Probe delay with TR-probes
Mitchells NDT Inspection Services
0 2 4 6 8 10
IP
BE
Flaw
Cross talkecho
flawecho
TR-probe
Cross talk at high gain
Mitchells NDT Inspection Services
0 2 4 6 8 10
0 100 mm50
steel, L
div.
Range calibration
Mitchells NDT Inspection Services
5 10 15
70°
45°
100
mm
Rad
ious
60°
Calibration block 1 with angle beam probes
100mm85mm90mm
10mm
45mm
15mm
5mmIndex point
300mm
Mitchells NDT Inspection Services
5 10 15
0 2 4 6 8 10
100 mm
1st echo from circular section
Mitchells NDT Inspection Services
5 10 15
0 2 4 6 8 10
100 mm 200 mm 300 mm
Echo sequence from 100 mm radius
Mitchells NDT Inspection Services
s = 25 mms = 100 mms = 175 mmetc.
1
2
3
this wave will be absorbed !
25 mm radius of calibration block 2
Mitchells NDT Inspection Services
s = 50 mms = 125 mms = 200 mmetc.
1
2
3
50 mm radius of calibration block 2
Mitchells NDT Inspection Services
5 10 15
0 2 4 6 8 10
0 100 mmsteel
100 mm range calibration on K2
Mitchells NDT Inspection Services
51015
Test piece Discontinuity
Sound path
0 2 4 6 8 10
s = k•Rs = sound pathk = scale factorR = screen reading
Flaw loaction
Mitchells NDT Inspection Services
flaw location
a
s d
Sound entry point projectionpoint
a = s•sin ßd = s•cos ß
ß
ßa = surface distance
ß = probe angled = depth
S = sound path
Flaw triangle
Snells law
Flaw location with angle beam probes
Mitchells NDT Inspection Services
51015
work piece reflector
aa'
s d
x
Index point -Front edge of probe
a = surface distance from index pointa' = reduced surface distancex = x-value = distance:
Flaw location with angle beam probes
Mitchells NDT Inspection Services
51015
apparent flaw location
a
sd = apparent depth
T
Flaw location with an angle beam probe on a plate
Mitchells NDT Inspection Services
51015
apparent flaw location
real flaw location
a
s d
d'
d' = apparent depthd = real depthT = work piece thickness
T
a = s • sinβd‘ = s • cosβd = 2T - d
Flaw location with an angle beam probe on a plate
Mitchells NDT Inspection Services
Large defects parallel to the scanning surface
Mitchells NDT Inspection Services
Scanning the edge of the defect 6 db drop
Flaw echo drops to 50% of its maximum value
Mitchells NDT Inspection Services
"half value" positions
delaminationprobe positionwith echo amplitudereduced to 50 % = 6db drop
Determination of the defect area
Mitchells NDT Inspection Services
0 2 4 6 8 100 2 4 6 8 10 0 2 4 6 8 10
IP BER IP BER IP BER
Flaw sizes and echo amplitudes
Mitchells NDT Inspection Services
0 2 4 6 8 10
0 2 4 6 8 10
0 2 4 6 8 10
IP BER
IP BER
IP BER
Flaw distances and echo amplitudes
Mitchells NDT Inspection Services
0 500100 200 300 400
B 4 S
6 mm
4 mm3 mm
BE
F
Distance amplitude curves on the CRT screen
Mitchells NDT Inspection Services
0 2 4 6 8 10
IP BEF
F
instrument gain: G = 34 dB
80 %
Defect evaluation by comparison - 1
Mitchells NDT Inspection Services
0 2 4 6 8 10
IP BER
instrument gain: 34 dB
Defect evaluation by comparison - 2
Mitchells NDT Inspection Services
0 2 4 6 8 10
IP BERE
+ 8 dB
instrument gain: 42 dB
Defect evaluation by comparison - 3
Mitchells NDT Inspection Services
0 2 4 6 8 10
10 20 30 40 10 20 30 40 10 20 30 40 10 20 30 40
1
1
2
2
3
3
4
4
Echo
Position
Distance amplitude curve (DAC)
Mitchells NDT Inspection Services
0 2 4 6 8 10 0 2 4 6 8 10
time corrected gainDAC
DAC and TCG