1. basic engine

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Basic Principles of

Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

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Examples of oscillation

ball ona spring pendulum rotatingearth

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The ball starts to oscillate as soon as it is pushed

Pulse

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Oscillation

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Movement of the ball over time

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Time

One fulloscillation T

Frequency

From the duration of one oscillation

T the frequency f (number of

oscillations per second) is

calculated:

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Basic Principles of Ultrasonic Testing

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180 36090 270

Phase 

Time 

a

0

The actual displacement a istermed as:

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Spectrum of  sound 

Frequency range Hz Description Example

0 - 20 Infrasound Earth quake 

20 - 20.000 Audible sound Speech, music

> 20.000 Ultrasound Bat, Quartz crystal

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

gas liquid solid

 Atomic structures

• low density

• weak bonding forces

• medium density

• medium bondingforces

• high density

• strong bonding forces

• crystallographicstructure

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Understanding wave propagation:

Spring = elastic bonding forceBall = atom

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

T

Distance travelled

From this we derive:

or Wave equation

During one oscillation T the wave

front propagates by the distance :

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Direction of oscillation

Direction of propagation Longitudinal wave

Sound propagation

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Direction of propagation Transverse wave

Direction of oscillation 

Sound propagation

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Wave propagation

Air

Water

Steel, long

Steel, trans 

330 m/s

1480 m/s

3250 m/s

5920 m/s

Longitudinal waves propagate in all kind of materials.Transverse waves only propagate in solid bodies.

Due to the different type of oscillation, transverse wavestravel at lower speeds.

Sound velocity mainly depends on the density and E-

modulus of the material.

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Basic Principles of Ultrasonic Testing

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Reflection and Transmission 

 As soon as a sound wave comes to a change in materialcharacteristics ,e.g. the surface of a workpiece, or an internal inclusion,

wave propagation will change too:

f

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Behaviour at an interface

Medium 1 Medium 2

Interface

Incoming wave Transmitted wave

Reflected wave

B i P i i l f Ult i T ti

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Reflection + Transmission: Perspex - Steel

Incoming wave Transmitted wave

Reflected wave

Perspex Steel

1,87

1,00,87

B i P i i l f Ult i T ti

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Reflection + Transmission: Steel - Perspex

0,13

1,0

-0,87

PerspexSteel

Incoming wave Transmitted wave

Reflected wave

B i P i i l f Ult i T ti

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

 Amplitude of sound transmissions:

• Strong reflection

• Double transmission

• No reflection

• Single transmission

• Strong reflection

with inverted phase• No transmission

Water - Steel Copper - Steel Steel - Air

B i P i i l f Ult i T ti

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Piezoelectric Effect

Piezoelectrical

Crystal (Quartz)

Battery

+

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

+

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

Piezoelectric Effect

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

+

The effect inverses with polarity change

Piezoelectric Effect

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

 An alternating voltage generates crystal oscillations at the frequency f

U(f)

Sound wavewith

frequency f

Piezoelectric Effect

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

 A short voltage pulse generates an oscillation at the crystal‘s resonant 

frequency f 0 

Short pulse( < 1 µs )

Piezoelectric Effect

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Reception of ultrasonic waves

 A sound wave hitting a piezoelectric crystal, induces crystalvibration which then causes electrical voltages at the crystal

surfaces.

Electrical

energy

Piezoelectrical

crystal Ultrasonic wave

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Ultrasonic Probes

socketcrystal

Damping

Delay / protecting face

Electrical matching

Cable

Straight beam probe Angle beam probeTR-probe

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

100 ns

RF signal (short)

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

RF signal (medium)

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

N

Near field Far field

Focus Angle of divergenceCrystal Accoustical axis

D0 

6 

Sound field

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Ultrasonic Instrument

0 2 4 8 106

Basic Principles of Ultrasonic Testing

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Krautkramer NDT Ultrasonic Systems

0 2 4 8 106

+- Uh

Ultrasonic Instrument

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

0 2 4 8 106

+ -

Uh

Ultrasonic Instrument

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

0 2 4 8 106

+

+

-

-

U

U

h

v

Ultrasonic Instrument

Basic Principles of Ultrasonic Testing

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Basic Principles of Ultrasonic Testing

Krautkramer NDT Ultrasonic Systems

Block diagram: Ultrasonic Instrument

amplifier

work piece

probe

horizontal

sweep

clock

pulser

IP

BE

screen

Basic Principles of Ultrasonic Testing

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as c c p es o U t aso c est g

Krautkramer NDT Ultrasonic Systems

Sound reflection at a flaw

Probe

FlawSound travel path

Work piece

s

Basic Principles of Ultrasonic Testing

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p g

Krautkramer NDT Ultrasonic Systems

Plate testing

delaminationplate

0 2 4 6 8 10

IP

F

BE

IP = Initial pulse

F = Flaw

BE = Backwall echo 

Basic Principles of Ultrasonic Testing

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p g

Krautkramer NDT Ultrasonic Systems

0 2 4 6 8 10

ss

Wall thickness measurement

Corrosion

Basic Principles of Ultrasonic Testing

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p g

Krautkramer NDT Ultrasonic Systems

Through transmission testing

0 2 4 6 8 10

Through transmission signal

1

2

1

2

T

T

R

R

Flaw

Basic Principles of Ultrasonic Testing

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p g

Krautkramer NDT Ultrasonic Systems

Weld inspection

0 20 40 60 80 100

s

aa'

d

x

a = s sinß

a' = a - x

d' = s cosß

d = 2T - t'

s

Lack of fusionWork piece with welding

Fß = probe angle

s = sound path

a = surface distance

a‘ = reduced surface distance

d‘ = virtual depth

d = actual depthT = material thickness

ß

Basic Principles of Ultrasonic Testing

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p g

Krautkramer NDT Ultrasonic Systems

Straight beam inspection techniques:

Direct contact,

single element probe

Direct contact,

dual element probe

Fixed delay

Immersion testingThrough transmission

Basic Principles of Ultrasonic Testing

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Krautkramer NDT Ultrasonic Systems

surface =

sound entry

backwall flaw

1 2water delay

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

IE IEIP IP

BE BEF

1 2

Immersion testing