UTPP1

Ultrasonic TestingUltrasonic TestingPart 1Part 1

Ultrasonic Testing

NDTTraining&Certification

Course Layout Duration : 9 Days 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.

NON-DESTRUCTIVE TESTINGExamination of materials and components in such a way that allows material to be examinated without changing or destroying their usefulness

NDTMost common NDT methods:Penetrant Testing (PT)

Magnetic Particle Testing (MT)

Eddy Current Testing (ET)

Mainly used for surface testing

Radiographic Testing (RT)

Ultrasonic Testing (UT)Mainly used for Internal Testing

NDT

Which NDT method is the best ?Depends on many factors and conditions

NDT

Which method is the best ?Depends on many factors and conditions

Basic Principles of Ultrasonic Testing

To understand and appreciate the capability and limitation of UT

Ultrasonic Inspection Sub-surface detection This detection method uses high frequency sound

waves, typically above 2MHz to pass through a material

A probe is used which contains a piezo electric crystal to transmit and receive ultrasonic pulses and display the signals on a cathode ray tube or digital display

The actual display relates to the time taken for theultrasonic pulses to travel the distance to the interface and back

An interface could be the back of a plate material or a defect

For ultrasound to enter a material a couplant must be introduced between the probe and specimen

Ultrasonic InspectionUltrasonic InspectionUltrasonic testing is a good technique for the detection of plate laminations and thickness surveys

Laminations detected using compression probes

Ultrasonic Inspection

defect

0 10 20 30 40 50

defect echo

Back wall echo

CRT DisplayCompression Probe

Material Thk

initial pulse

Ultrasonic InspectionUT Set, DigitalPulse echo

signals A scan Display

Compression probe Thickness checking the material

Ultrasonic InspectionUltrasonic Inspection

Ultrasonic testing requires high operator for defect identification

Most weld defects detected using angle probes


Angle Probe

UT SetA Scan Display


0 10 20 30 40 50

initial pulse defect echo

CRT Display

sound path

Angle Probe

defect

Surface distance


AdvantagesRapid resultsSub-surface detectionSafeCan detect planar defectCapable of measuring the depth of defectsMay be battery poweredPortable

DisadvantagesTrained and skilled operator requiredRequires high operator skillGood surface finish requiredDifficulty on detecting volumetric defectCouplant may contaminate No permanent record

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

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

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

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

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

Ultrasonic Testing

Principles of Sound

What is Sound ?

A mechanical vibration The vibrations create Pressure Waves Sound travels faster in more elastic

materials Number of pressure waves per second is

the Frequency Speed of travel is the Sound velocity

Sound waves are the vibration of particles in solids liquids or Sound waves are the vibration of particles in solids liquids or gases gases

Particles vibrate about a mean positionParticles vibrate about a mean position

In order to vibrate they require mass and resistance to changeIn order to vibrate they require mass and resistance to change

One cycle

Sound WavesSound Waves

Ultrasonic Sound : mechanical vibration

What is Ultrasonic?

Very High Frequency sound above 20 KHz

20,000 cps

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

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)

fV=

Wavelength Velocity

Frequency

Properties of a sound wave

Velocity (v)How quickly a sound wave travels

Frequency (f)How many vibrations per second Wavelength ()

How far a sound wave advances in completing one cycle

Properties of a sound wave Sound cannot travel

in vacuum Sound energy to be

transmitted / transferred from one particle to another

SOLID LIQUID GAS

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

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

Frequency Frequency : Number of cycles per

second

1 second

1 cycle per 1 second = 1 Hertz



1 second 1 second

THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH

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

Pg 21

DRUM BEAT

Low Frequency Sound

40 Hz

Glass

High Frequency

5 K Hz

ULTRASONIC TESTING

Very High Frequency

5 M Hz

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 (half the wavelength)

High Frequency Sound

fV=

5MHz compression wave probe in steel

mm18.1000,000,5000,900,5 ==

Frequency

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 / fF F

Which of the following compressionalprobe has the highest sensitivity?

1 MHz 2 MHz 5 MHz 10 MHz

10 MHz

Sound travelling through a material Velocity varies according to the material

Compression waves

Steel 5960m/sec

Water 1470m/sec

Air 344m/sec

Copper 4700m/sec

Shear waves

Steel 3245m/sec

Water NA

Air NA

Copper 2330m/sec

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?

AirRemember the formula

= v / f

Sound WaveformsSound travels in different waveforms in

different conditions

Compression waveCompression waveShear waveShear waveSurface waveSurface waveLamb waveLamb wave

Compression / Longitudinal

Vibration and propagation in the same direction / parallel

Travel in solids, liquids and gases

Propagation

Particle vibration

Shear / Transverse Vibration at right angles / perpendicular to

direction of propagation Travel in solids only Velocity 1/2 compression (same material)

Propagation

Particle vibration

Compression v ShearFrequency 0.5MHz 1 MHz 2MHz 4MHz 6MHZ

Compression 11.8 5.9 2.95 1.48 0.98

Shear 6.5 3.2 1.6 0.8 0.54

The smaller the wavelength the better the sensitivity

Sound travelling through a material Velocity varies according to the material

Compression waves

Steel 5960m/sec

Water 1470m/sec

Air 344m/sec

Copper 4700m/sec

Shear waves

Steel 3245m/sec

Water NA

Air NA

Copper 2330m/sec

Surface Wave Elliptical vibration Velocity 8% less than shear Penetrate one wavelength deep

Easily dampened by heavy grease or wet finger

Follows curves but reflected by sharp corners or surface cracks

Lamb / Plate Wave Produced by the manipulation of surface

waves and others Used mainly to test very thin materials /

plates Velocity varies with plate thickness and

frequencies

SYMETRIC ASSYMETRIC

Ultrasonic TestingCourse LayoutNON-DESTRUCTIVE TESTINGNDTNDTNDTBasic Principles of Ultrasonic TestingBasic Principles of Ultrasonic TestingBasic Principles of Ultrasonic TestingBasic Principles of Ultrasonic TestingThickness / depth measurementUltrasonic TestingWhat is Sound ?UltrasonicAcoustic SpectrumSoundProperties of a sound waveProperties of a sound waveVelocityFrequencyFrequencyWavelength and frequencyHigh Frequency SoundFrequencySound travelling through a materialSound Waveforms Compression / LongitudinalShear / TransverseCompression v ShearSound travelling through a materialSurface WaveLamb / Plate Wave

UTPP1

Documents

Transcript of UTPP1