Basic Principles Ultrasonic Krautkramer

Basic Principles of Ultrasonic Testing

Basic Principles ofBasic Principles ofUltrasonic TestingUltrasonic Testing

Theory and PracticeTheory and Practice

Krautkramer NDT Ultrasonic Systems

Basic Principles of Ultrasonic TestingE l f ill tiExamples of oscillation

ball on pendulum rotatingball ona spring

pendulum rotatingearth



PulseThe ball starts to oscillate as soon as it is pushed

Pulse


p


OscillationOscillation


Basic Principles of Ultrasonic TestingMovement of the ball over time



Frequencyeque cy

Time

One full ill ti T

From the duration of one oscillation T th f f ( b f oscillation TT the frequency f (number of oscillations per second) is calculated:



The actual displacement a is termed as:

a180 36090 270

Time0

Phase


Basic Principles of Ultrasonic TestingSpectrum of sound

Frequency range Hz Description ExampleFrequency range Hz Description Example

0 20 Infrasound Earth quake0 - 20 Infrasound Earth quake

20 - 20.000 Audible sound Speech, music

20 000 Ul d B Q l> 20.000 Ultrasound Bat, Quartz crystal


Basic Principles of Ultrasonic TestingAt i t t

gas liquid solid

Atomic structures

gas liquid solid

low density weak bonding forces

medium density medium bonding

high density strong bonding forcesweak bonding forces medium bonding

forcesstrong bonding forces

crystallographic structure


Basic Principles of Ultrasonic TestingU d t di tiUnderstanding wave propagation:

Spring = elastic bonding forceBall = atom



T

distance travelleddistance travelled



TDuring one oscillation T the wave f t t b th di t T front propagates by the distance :

Distance travelled

From this we derive:

or Wave equation


Basic Principles of Ultrasonic TestingSound propagation

Di i f ill i

Direction of propagationLongitudinal waveDirection of oscillation


Basic Principles of Ultrasonic TestingSound propagation

Direction of propagationTransverse waveDirection of oscillationDirection of oscillation


Basic Principles of Ultrasonic TestingWave propagationLongitudinal waves propagate in all kind of materials.Longitudinal waves propagate in all kind of materials.Transverse waves only propagate in solid bodies. Due to the different type of oscillation, transverse wavesDue to the different type of oscillation, transverse wavestravel at lower speeds.Sound velocity mainly depends on the density and E-

d l f th t i lmodulus of the material.

AirWaterSteel, long

330 m/s1480 m/s

5920 m/sSteel, trans 3250 m/s


Basic Principles of Ultrasonic TestingReflection and Transmission

A d t h i t i lAs soon as a sound wave comes to a change in material characteristics ,e.g. the surface of a workpiece, or an internal inclusion, wave propagation will change too:


Basic Principles of Ultrasonic TestingB h i t i t fBehaviour at an interface

Medium 1 Medium 2

Incoming wave Transmitted waveIncoming wave Transmitted wave

Reflected wave

Interface


Basic Principles of Ultrasonic TestingReflection + Transmission: Perspex - Steel

1,87

Incoming wave Transmitted wave

,

1 0Incoming wave Transmitted wave1,00,87

Reflected wave

Perspex Steel


Basic Principles of Ultrasonic TestingReflection + Transmission: Steel - Perspex

1 0Incoming wave Transmitted wave

0 13

1,0

0,13

-0,87R fl t d

Perspex SteelReflected wave


Basic Principles of Ultrasonic TestingA lit d f d t i iAmplitude of sound transmissions:

Water - Steel Copper - Steel Steel - Air

Strong reflection No reflection Strong reflection ith i t d h

pp

Double transmission Single transmission with inverted phase No transmission


Basic Principles of Ultrasonic TestingPi l t i Eff tPiezoelectric Effect

+Battery

+y

Piezoelectrical Crystal (Quartz)



++

The crystal gets thicker, due to a distortion of the crystal lattice



++

The effect inverses with polarity change


Basic Principles of Ultrasonic TestingPi l t i Eff t

S d

Piezoelectric Effect

Sound wave with

frequency f

U(f)

An alternating voltage generates crystal oscillations at the frequency f



Sh t lShort pulse( < 1 s )

A short voltage pulse generates an oscillation at the crystals resonantfrequency f0


q y 0

Basic Principles of Ultrasonic TestingR ti f lt iReception of ultrasonic waves

A sound wave hitting a piezoelectric crystal induces crystalA sound wave hitting a piezoelectric crystal, induces crystal vibration which then causes electrical voltages at the crystal surfaces.

Electrical Piezoelectrical Ult ienergyPiezoelectrical crystal Ultrasonic wave


Basic Principles of Ultrasonic TestingUltrasonic Probes

socket Delay / protecting facesocketcrystalDamping

Delay / protecting faceElectrical matchingCable Damping

Straight beam probe Angle beam probeTR-probe


St a g t bea p obe g e bea p obep obe

Basic Principles of Ultrasonic TestingRF signal (short)

100100 ns


Basic Principles of Ultrasonic TestingRF signal (medium)


Basic Principles of Ultrasonic TestingSound field

Focus Angle of divergenceCrystalAccoustical axisAccoustical axis

D0

6

N

D0

Near field Far field


Basic Principles of Ultrasonic TestingUltrasonic Instrument

0 2 4 8 106


0 2 4 8 106


++-Uh

0 2 4 8 106


0 2 4 8 106


+ -+Uh

0 2 4 8 106



+

-Uv

-

+ -Uh

0 2 4 8 106


0 2 4 8 106

Basic Principles of Ultrasonic TestingBlock diagram: Ultrasonic Instrument

amplifier

horizontal IPscreen

sweep

clock

BE

clock

pulser

work piece

probepulser


p

Basic Principles of Ultrasonic TestingSound reflection at a flaw

s

ProbeProbe

Flaw Sound travel path

Work piece


Basic Principles of Ultrasonic TestingPlate testing

IP

BE

F

delaminationplate 0 2 4 6 8 10pIP = Initial pulseF = FlawBE Backwall echoBE = Backwall echo


Basic Principles of Ultrasonic TestingWall thickness measurement

ss

0 2 4 6 8 10Corrosion 0 2 4 6 8 10Corrosion


Basic Principles of Ultrasonic TestingThrough transmission testing

Th h i i i lThrough transmission signal

1 1T R

2T R0 2 4 6 8 10

2 2T R

Flaw


Basic Principles of Ultrasonic TestingWeld inspection

a = s sina' = a - xF = probe anglea = a - xd' = s cos

s probe angles = sound patha = surface distancea = reduced surface distanced = virtual depth0 20 40 60 80 100

ad = 2T - t'

d virtual depthd = actual depthT = material thickness

a'd

x

s

dLack of fusionWork piece with welding


Basic Principles of Ultrasonic TestingStraight beam inspection techniques:

Direct contact, Direct contact, Fixed delaysingle element probe dual element probe

Fixed delay

Immersion testingThrough transmission



1 2

Immersion testing

surface =

1 2

water delaysound entry

backwall flaw

IE IEIP IP1 2IE IE

BE BE

0 2 4 6 8 10 0 2 4 6 8 10

F


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Basic Principles Ultrasonic Krautkramer