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Ultrasonic test.
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Copyright © 2004 WI Ltd
Ultrasonic TestingUltrasonic TestingPart 1Part 1
Copyright © 2004 WI Ltd
Ultrasonic Testing
NDT Training & Certification
Copyright © 2004 WI Ltd
Course Layout
• Duration : 9.5 Days (Mon – Fri)• Start : 8:30 am• Coffee Break : 10:00 – 10:30 am• Lunch : 12:30 – 1:30 pm• Tea Break : 3:00 – 3:30 pm• Day End : 5:00 pm• Course Objective: To train and prepare
participants to obtain required skill and knowledge in Ultrasonic Testing and to meet the examination schemes requirements.
Copyright © 2004 WI Ltd
NDTMost common NDT methods:
Penetrant Testing (PT)
Magnetic Particle Testing (MT)
Eddy Current Testing (ET)
Radiographic Testing (RT)
Ultrasonic Testing (UT)
Mainly used for surface testing
Mainly used for Internal Testing
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NDT
• Which method is the best ?
Depends on many factors and conditions
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Basic Principles of Ultrasonic Testing
• To understand and appreciate the capability and limitation of UT
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Basic Principles of Ultrasonic Testing
Sound is transmitted in the material to be tested
The sound reflected back to the probe is displayed on
the Flaw Detector
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Basic Principles of Ultrasonic TestingThe distance the sound traveled can be displayed on the Flaw DetectorThe screen can be calibrated to give accurate readings of the distance
Bottom / Backwall
Signal from the backwall
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Copyright © 2004 WI Ltd
Basic Principles of Ultrasonic TestingThe presence of a Defect in the material shows up on the screen of
the flaw detector with a less distance than the bottom of the material
The BWE signal
Defect signal
Defect
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The depth of the defect can be read with reference to the marker on the screen
0 10 20 30 40 50 60
60 mm
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Thickness / depth measurement
A
A
B
B
C
C
The THINNER the material the less distance the sound
travel
The closer the reflector to the surface, the signal will be more to the left of
the screen
The thickness is read from the screen
684630
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Ultrasonic Testing
Principles of Sound
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Sound• Wavelength :
The distance required to complete a cycle– Measured in Meter or mm
• Frequency :
The number of cycles per unit time– Measured in Hertz (Hz) or Cycles per second (cps)
• Velocity :
How quick the sound travels
Distance per unit time– Measured in meter / second (m / sec)
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Properties of a sound wave• Sound cannot travel
in vacuum• Sound energy to be
transmitted / transferred from one particle to another
SOLID LIQUID GAS
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Velocity• The velocity of sound in a particular material is CONSTANT• It is the product of DENSITY and ELASTICITY of the
material• It will NOT change if frequency changes• Only the wavelength changes• Examples:
V Compression in steel : 5960 m/sV Compression in water : 1470 m/sV Compression in air : 330 m/s
STEEL WATER AIR
5 M Hz
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Velocity
4 times
What is the velocity difference in steel compared with in water?
If the frequency remain constant, in what material does sound has the highest velocity, steel, water, or air?
SteelIf the frequency remain constant, in what material does sound has the shortest wavelength, steel, water, or air?
Air
Remember the formula
= v / f
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DRUM BEAT
Low Frequency Sound
40 Hz
Glass
High Frequency
5 K Hz
ULTRASONIC TESTING
Very High Frequency
5 M Hz
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Ultrasonic• Sound : mechanical vibration
What is Ultrasonic?
Very High Frequency sound – above 20 KHz
20,000 cps
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Acoustic Spectrum
0 10 100 1K 10K 100K 1M 10M 100m
Sonic / Audible
Human
16Hz - 20kHz
Ultrasonic
> 20kHz = 20,000Hz
Ultrasonic Testing
0.5MHz - 50MHz Ultrasonic : Sound with frequency above 20 KHz
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Frequency• Frequency : Number of cycles per
second
1 second
1 cycle per 1 second = 1 Hertz
18 cycle per 1 second = 18 Hertz
3 cycle per 1 second = 3 Hertz
1 second 1 second
THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH
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Frequency
• 1 Hz = 1 cycle per second• 1 Kilohertz = 1 KHz = 1000Hz• 1 Megahertz = 1 MHz = 1000 000Hz
20 KHz = 20 000 Hz
5 M Hz = 5 000 000 Hz
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Sound waves are the vibration of particles in solids, liquids or gases.
Particles vibrate about a mean position.
One cycle
Displacement
The distance taken to complete one cycle
wavelength
wavelength
Wavelength
Wavelength is the distance required to complete a cycle.
Copyright © 2004 WI Ltd
f
V
Velocity
Frequency
Wavelength
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Frequency & Wavelength
1 M Hz 5 M Hz 10 M Hz 25 M Hz
Which probe has the smallest wavelength?
SMALLESTLONGEST
Which probe has the longest wavelength?
= v / f
F F
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Wavelength is a function of frequency and velocity.
5MHz compression wave probe in steel
mm18.1000,000,5
000,900,5
Therefore:
f
V V
for
or V f
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• Which of the following compressional probe has the highest sensitivity?
• 1 MHz
• 2 MHz
• 5 MHz
• 10 MHz
10 MHz
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Wavelength and frequency• The higher the frequency the smaller the
wavelength
• The smaller the wavelength the higher the sensitivity
• Sensitivity : The smallest detectable flaw by the system or technique
• In UT the smallest detectable flaw is ½ (half the wavelength)
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The Sound Beam
• Dead Zone
• Near Zone or Fresnel Zone
• Far Zone or Fraunhofer Zone
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The Sound Beam
NZ FZ
Distance
Intensity varies
Exponential Decay
Main Beam
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Main Lobe
Side Lobes
Near Zone
Main Beam
The main beam or the centre beam has the highest intensity of sound energy
Any reflector hit by the main beam will reflect the high amount of energy
The side lobes has multi minute main beams
Two identical defects may give different amplitudes of signals
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Sound BeamNear Zone• Thickness
measurement• Detection of defects• Sizing of large
defects only
Far Zone• Thickness
measurement• Defect detection• Sizing of all defects
Near zone length as small as possible
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Near Zone
V
fD
f
V
D
4Near Zone
4Near Zone
2
2
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Near Zone
• What is the near zone length of a 5MHz compression probe with a crystal diameter of 10mm in steel?
mm
V
fD
1.21
000,920,54
000,000,510
4Near Zone
2
2
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Near Zone
• The bigger the diameter the bigger the near zone
• The higher the frequency the bigger the near zone
• The lower the velocity the bigger the near zone
Should large diameter crystal probes have a high or low frequency?
V
fDD
4
4Near Zone
22
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1 M Hz 5 M Hz
1 M Hz
5 M Hz
Which of the above probes has the longest Near Zone ?
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Near Zone
• The bigger the diameter the bigger the near zone
• The higher the frequency the bigger the near zone
• The lower the velocity the bigger the near zone
Should large diameter crystal probes have a high or low frequency?
V
fDD
4
4Near Zone
22
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Beam Spread• In the far zone sound pulses spread out
as they move away from the crystal
Df
KV
D
KSine or
2
/2
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Beam Spread
Df
KV
D
KSine or
2
Edge,K=1.2220dB,K=1.08
6dB,K=0.56
Beam axis or Main Beam
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Beam Spread
• The bigger the diameter the smaller the beam spread
• The higher the frequency the smaller the beam spread
Df
KV
D
KSine or
2
Which has the larger beam spread, a compression or a shear wave probe?
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Beam Spread• What is the beam spread of a 10mm,5MHz
compression wave probe in steel?
o
Df
KVSine
35.7 1278.0
105000
592008.1
2
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1 M Hz 5 M Hz
1 M Hz
5 M Hz
Which of the above probes has the Largest Beam Spread ?
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Beam Spread
• The bigger the diameter the smaller the beam spread
• The higher the frequency the smaller the beam spread
Df
KV
D
KSine or
2
Which has the larger beam spread, a compression or a shear wave probe?
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Testing close to side walls
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