Non-destructive testing - Ultrasonic testing - Vocabulary (ISO 5577:2017)

This International Standard defines the terminology used in ultrasonic non-destructive testing and forms a common basis for standards and general use.

Zerstörungsfreie Prüfung - Ultraschallprüfung - Terminologie (ISO 5577:2017)

Dieses Dokument legt die Begriffe fest, die bei der zerstörungsfreien Ultraschallprüfung verwendet werden, und bildet somit eine gemeinsame Grundlage für Normen und den allgemeinen Gebrauch. Dieses Dokument behandelt keine Begriffe der zerstörungsfreien Prüfung mit phasengesteuerten Arrays.
ANMERKUNG   Begriffe für zerstörungsfreie Prüfung mit phasengesteuerten Arrays sind in EN 16018 festgelegt.

Essais non destructif - Contrôle par ultrasons - Vocabulaire (ISO 5577:2017)

ISO 5577:2017 définit les termes utilisés pour le contrôle non destructif par ultrasons et constitue une base commune pour les normes et l'usage général. Le présent document n'inclut pas les termes utilisés pour le contrôle par ultrasons en multiéléments.
NOTE Les termes applicables au contrôle par ultrasons en multiéléments sont définis dans l'EN 16018.

Neporušitvene preiskave - Preskušanje z ultrazvokom - Slovar (ISO 5577:2017)

Ta mednarodni standard opredeljuje terminologijo, ki se uporablja pri neporušitvenem preskušanju z ultrazvokom in oblikuje skupno podlago za standarde in splošno uporabo.

General Information

Status
Published
Public Enquiry End Date
09-Aug-2015
Publication Date
11-Jun-2017
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
02-Mar-2017
Due Date
07-May-2017
Completion Date
12-Jun-2017

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SLOVENSKI STANDARD
SIST EN ISO 5577:2017
01-julij-2017
1DGRPHãþD
SIST EN 1330-4:2011
Neporušitvene preiskave - Preskušanje z ultrazvokom - Slovar (ISO 5577:2017)
Non-destructive testing - Ultrasonic testing - Vocabulary (ISO 5577:2017)
Zerstörungsfreie Prüfung - Ultraschallprüfung - Terminologie (ISO 5577:2017)
Essais non destructif - Contrôle par ultrasons - Vocabulaire (ISO 5577:2017)
Ta slovenski standard je istoveten z: EN ISO 5577:2017
ICS:
01.040.19 Preskušanje (Slovarji) Testing (Vocabularies)
19.100 Neporušitveno preskušanje Non-destructive testing
SIST EN ISO 5577:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 5577:2017
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SIST EN ISO 5577:2017
EN ISO 5577
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2017
EUROPÄISCHE NORM
ICS 01.040.19; 19.100 Supersedes EN 1330-4:2010
English Version
Non-destructive testing - Ultrasonic testing - Vocabulary
(ISO 5577:2017)

Essais non destructif - Contrôle par ultrasons - Zerstörungsfreie Prüfung - Ultraschallprüfung -

Vocabulaire (ISO 5577:2017) Terminologie (ISO 5577:2017)
This European Standard was approved by CEN on 28 December 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 5577:2017 E

worldwide for CEN national Members.
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SIST EN ISO 5577:2017
EN ISO 5577:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 5577:2017
EN ISO 5577:2017 (E)
European foreword

This document (EN ISO 5577:2017) has been prepared by Technical Committee ISO/TC 135 "Non-

destructive testing" in collaboration with Technical Committee CEN/TC 138 “Non-destructive testing”

the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by August 2017, and conflicting national standards shall

be withdrawn at the latest by August 2017.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.
This document supersedes EN 1330-4:2010.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 5577:2017 has been approved by CEN as EN ISO 5577:2017 without any modification.

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SIST EN ISO 5577:2017
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SIST EN ISO 5577:2017
INTERNATIONAL ISO
STANDARD 5577
Second edition
2017-02
Non-destructive testing — Ultrasonic
testing — Vocabulary
Essais non destructif — Contrôle par ultrasons — Vocabulaire
Reference number
ISO 5577:2017(E)
ISO 2017
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SIST EN ISO 5577:2017
ISO 5577:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 5577:2017
ISO 5577:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms related to frequencies, waves and pulses ................................................................................................................. 1

3.1 Frequencies ................................................................................................................................................................................................ 1

3.2 Waves and pulses .................................................................................................................................................................................. 2

3.3 Types of waves ........................................................................................................................................................................................ 4

4 Terms related to sound .................................................................................................................................................................................. 5

4.1 Sound generation and reception ............................................................................................................................................. 5

4.2 Sound propagation .............................................................................................................................................................................. 6

4.3 Loss of sound pressure .................................................................................................................................................................... 9

4.4 Sound waves at interfaces ............................................................................................................................................................. 9

5 Terms related to test equipment ......................................................................................................................................................12

5.1 Instrument ...............................................................................................................................................................................................12

5.2 Probes ..........................................................................................................................................................................................................15

5.3 Combined equipment .....................................................................................................................................................................20

5.4 Calibration, reference and test blocks ..............................................................................................................................21

6 Terms related to ultrasonic testing ................................................................................................................................................22

6.1 Testing techniques ............................................................................................................................................................................22

6.2 Test object ................................................................................................................................................................................................26

6.3 Coupling .....................................................................................................................................................................................................28

6.4 Reflectors ..................................................................................................................................................................................................28

6.5 Signals and indications .................................................................................................................................................................29

6.6 Presentations .........................................................................................................................................................................................31

6.7 Location ......................................................................................................................................................................................................35

6.8 Evaluation of indications .............................................................................................................................................................36

Bibliography .............................................................................................................................................................................................................................38

© ISO 2017 – All rights reserved iii
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SIST EN ISO 5577:2017
ISO 5577:2017(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,

as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www . i so .org/ iso/ foreword .html.

ISO 5577 was prepared by the European Committee for Standardization (CEN) Technical Committee

CEN/TC 138, Non-destructive testing, in collaboration with ISO Technical Committee TC 135, Non-

destructive testing, Subcommittee SC 3, Ultrasonic testing, in accordance with the Agreement on

technical cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 5577:2000), which has been technically

revised with changes to terms and definitions and structure.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 5577:2017
INTERNATIONAL STANDARD ISO 5577:2017(E)
Non-destructive testing — Ultrasonic testing — Vocabulary
1 Scope

This document defines the terms used in ultrasonic non-destructive testing and forms a common basis

for standards and general use. This document does not cover terms used in ultrasonic testing with

phased arrays.
NOTE Terms for phased array ultrasonic testing are defined in EN 16018.
2 Normative references
There are no normative references in this document.
3 Terms related to frequencies, waves and pulses

For the purposes of this document, the terms and definitions given in this clause and those given in

Clauses 4, 5 and 6 for sound, test equipment and ultrasonic testing apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1 Frequencies
3.1.1
frequency
number of cycles per second
Note 1 to entry: Expressed in Hertz (Hz).
3.1.2
nominal frequency
probe frequency
frequency (3.1.1) of the probe (5.2.1) as stated by the manufacturer
3.1.3
test frequency
effective ultrasonic frequency of a system used to test a material or object
3.1.4
frequency spectrum
distribution of amplitude (3.2.2) in relation to frequency (3.1.1)
Note 1 to entry: See Figure 1.
3.1.5
centre frequency
arithmetic mean of the cut-off frequencies
Note 1 to entry: See Figure 1.
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3.1.6
peak frequency
frequency (3.1.1) at which the maximum amplitude is observed
Note 1 to entry: See Figure 1.
3.1.7
cut-off frequency

frequency (3.1.1) at which the amplitude (3.2.2) of transmitted signal has dropped by a specified amount

from the amplitude at peak frequency (3.1.6), for example, by 3 dB
Note 1 to entry: See Figure 1.
3.1.8
bandwidth

width of the frequency spectrum (3.1.4) between the upper and lower cut-off frequency

Note 1 to entry: See Figure 1.
3.1.9
relative bandwidth
ratio of the bandwidth (3.1.8) to the centre frequency (3.1.5), in per cent
Key
X frequency 4 centre frequency
Y amplitude 5 bandwidth at specified amplitude drop
1 peak frequency 6 peak amplitude
2 upper cut-off frequency 7 specified amplitude drop
3 lower cut-off frequency
Figure 1 — Terms related to frequency and bandwidth
3.2 Waves and pulses
3.2.1
ultrasonic wave

any acoustic wave having a frequency (3.1.1) higher than the audible range of the human ear, generally

taken as higher than 20 kHz
2 © ISO 2017 – All rights reserved
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SIST EN ISO 5577:2017
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3.2.2
amplitude
absolute or relative measure of a sound wave’s magnitude
3.2.3
phase
momentary condition of a vibration expressed as an arc measurement or an angle
3.2.4
wavelength
distance between consecutive corresponding points of the same phase (3.2.3)
Note 1 to entry: See Figure 2.
3.2.5
wavefront

continuous surface joining all the most forward points of a wave that have the same phase (3.2.3)

3.2.6
time-of-flight
TOF

time it takes an ultrasonic pulse to travel from the transmitter probe through the test object to the

receiver probe
3.2.7
pulse
electrical or ultrasonic signal of short duration
3.2.8
pulse amplitude
maximum amplitude of a pulse (3.2.7) (peak-to-peak)
Note 1 to entry: For rectified pulses (A-scan), baseline-to-peak.
3.2.9
pulse rise time
time taken for a pulse amplitude (3.2.8) to change between two defined levels
3.2.10
pulse duration

time interval between the leading and trailing edges of a pulse (3.2.7) measured at a defined level below

the peak amplitude
3.2.11
pulse shape

diagramatic representation of the amplitude (3.2.2) of a pulse (3.2.7) as a function of time

3.2.12
pulse envelope

contour of a pulse shape (3.2.11) including all the peaks in terms of amplitude (3.2.2) and time

3.2.13
pulse energy
total energy within a pulse (3.2.7)
3.2.14
pulse reverberation

undesirable vibration at the beginning and end of a pulse (3.2.7) above a defined level

3.2.15
broad-band pulse
pulse (3.2.7) in which the relative bandwidth (3.1.9) is ≥65 %
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3.2.16
medium-band pulse
pulse (3.2.7) in which the relative bandwidth (3.1.9) is >35 % and <65 %
3.2.17
narrow-band pulse
pulse (3.2.7) in which the relative bandwidth (3.1.9) is ≤35 %
3.2.18
pulse repetition frequency
PRF
number of pulses (3.2.7) generated per second, expressed in Hertz (Hz)
3.3 Types of waves
3.3.1
longitudinal wave
compressional wave

wave in which the direction of displacement of particles is in the same direction as the propagation of

the wave
Note 1 to entry: See Figure 2 a).
3.3.2
transverse wave
shear wave

wave in which the direction of displacement of particles is perpendicular to the direction of the

propagation of the wave
Note 1 to entry: See Figure 2 b).
3.3.3
surface wave
Rayleigh wave

wave which propagates on the surface of a material with an effective penetration depth of less than one

wavelength (3.2.4)
3.3.4
creeping wave

wave generated at the first critical angle (4.4.11) of incidence and propagated along the surface as a

longitudinal wave (3.3.1)

Note 1 to entry: It is not influenced by the test object’s surface conditions, nor does the beam follow undulations

on the surface.
3.3.5
plate wave
Lamb wave

wave which propagates within the whole thickness of a plate and which can only be generated at

particular values of angle of incidence, frequency (3.1.1) and plate thickness
3.3.6
plane wave
wave with a planar wave front
3.3.7
cylindrical wave
wave with a cylindrical wave front
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SIST EN ISO 5577:2017
ISO 5577:2017(E)
3.3.8
spherical wave
wave with a spherical wave front
a) Longitudinal wave; compressional wave
b) Transverse wave; shear wave
Key
1 direction of oscillation
2 direction of propagation
λ wavelength
Figure 2 — Types of waves
4 Terms related to sound
4.1 Sound generation and reception
4.1.1
transducer

active element of a probe (5.2.1) which converts electrical energy into sound energy and vice versa

4.1.2
piezo-electric transducer
transducer (4.1.1) made from piezo-electric material
4.1.3
composite transducer
plate consisting of piezo-electric ceramic rods embedded in a polymer matrix
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SIST EN ISO 5577:2017
ISO 5577:2017(E)
4.1.4
electro-magnetic acoustic transducer
EMAT

transducer (4.1.1) which uses magnetostriction or Lorentz force to generate ultrasound in paramagnetic

materials
4.1.5
focusing transducer

piezo-electric transducer (4.1.2) having at least one curved surface, used for focusing the sound

beam (4.2.2)
4.2 Sound propagation
4.2.1
sound field
three-dimensional pressure distribution produced by transmitted sound energy
4.2.2
sound beam
ultrasonic beam

part of the sound field (4.2.1) within which the major part of the ultrasonic energy is transmitted

4.2.3
beam axis
line through the points of maximum sound pressure at different distances
Note 1 to entry: See Figures 3 b), 8, 9, 10 and 11.
4.2.4
beam profile

curve which shows the signal amplitude along the beam axis (4.2.3) or perpendicular to the beam axis

at a defined distance from the probe (5.2.1)
Note 1 to entry: See Figure 3.
a) Profile along the beam axis
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SIST EN ISO 5577:2017
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b) Profiles perpendicular to the beam axis
Key
1 transducer γ angle of divergence (drop to zero)
2 beam boundary a distance
3 beam axis N near-field length
4 beam width at a given distance P sound pressure
Figure 3 — Beam profiles
4.2.5
beam boundary

boundary of the ultrasonic beam where the sound pressure has fallen to a given fraction of the value on

the beam axis (4.2.3), measured at the same distance from the probe (5.2.1)
Note 1 to entry: See Figures 3 b), 8, 9 and 11.
4.2.6
beam width

dimension of the beam perpendicular to the beam axis (4.2.3) measured between the beam boundaries

at a defined distance from the probe (5.2.1)
Note 1 to entry: See Figure 3 b).
4.2.7
angle of divergence

angle within the far-field (4.2.11) between the beam axis (4.2.3) and the beam boundary (4.2.5)

Note 1 to entry: See Figures 3 b), 8 and 11.
4.2.8
near-field
Fresnel zone

zone of the sound beam (4.2.2) where sound pressure does not change monotonically with distance

because of interference
Note 1 to entry: See Figure 8.
4.2.9
near-field point

position on the beam axis (4.2.3) where the sound pressure reaches a final maximum

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4.2.10
near-field length
distance between the transducer (4.1.1) and the near-field point (4.2.9)
Note 1 to entry: See Figure 3.
4.2.11
far-field
zone of the sound beam (4.2.2) that extends beyond the near-field point (4.2.9)
Note 1 to entry: See Figures 8 and 11.
4.2.12
focal point
focus
point where the sound pressure on the beam axis (4.2.3) is at its maximum
4.2.13
focal distance
focal length
distance from the probe (5.2.1) to the focal point (4.2.12)
Note 1 to entry: See Figures 8 and 11.
4.2.14
focal zone
focal range

zone in sound beam (4.2.2) of a probe (5.2.1) in which the sound pressure remains above a defined level

related to its maximum
4.2.15
length of the focal zone

distance along the beam axis (4.2.3) from the start to the end of the focal zone (4.2.14)

4.2.16
width of the focal zone

dimension of the focal zone (4.2.14) at focal distance (4.2.13) perpendicular to the beam axis (4.2.3)

4.2.17
acoustical properties

characteristic parameters of a material which control the propagation of sound in the material

4.2.18
acoustically anisotropic material

material which has differing sound velocities in differing directions of propagation

4.2.19
sound velocity
velocity of propagation

phase velocity (4.2.20) or group velocity (4.2.21) of a sound wave in a material in the direction of

propagation

Note 1 to entry: In a non-dispersive material, there is no difference between phase and group velocity.

Note 2 to entry: In an anisotropic material, the velocities may depend on the direction of propagation.

4.2.20
phase velocity
velocity of propagation(4.2.19) of a wave front
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4.2.21
group velocity
velocity of propagation (4.2.19) of the acoustic energy
4.3 Loss of sound pressure
4.3.1
attenuation
sound attenuation

decrease of sound pressure when a wave travels through a material, arising from absorption (4.3.4) and

scattering (4.3.3)
4.3.2
attenuation coefficient

coefficient used to express attenuation (4.3.1) per unit of distance travelled, dependent on material

properties, wavelength (3.2.4) and wave type
Note 1 to entry: The attenuation coefficient is usually expressed in dB/m.
4.3.3
scattering

random reflections caused by grain structure and/or by small reflectors (6.4.1) in the beam path

4.3.4
absorption

part of the attenuation (4.3.1) resulting from transformation of ultrasonic energy into other types of

energy, for example, thermal energy
4.4 Sound waves at interfaces
4.4.1
interface

boundary between two materials, in acoustic contact, having different acoustic properties

Note 1 to entry: See Figure 4.
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ISO 5577:2017(E)
Key
1 interface 6 angle of incidence
2 direction of incident wave 7 angle of reflection
3 direction of refracted wave 8 medium 1
4 direction of reflected wave 9 medium 2
5 angle of refraction
Figure 4 — Refraction and reflection of waves
4.4.2
angle of incidence

angle between the direction of the incident wave and the normal to the interface (4.4.1)

Note 1 to entry: See Figure 4.
4.4.3
reflection

change of the direction of sound propagation within the same material when impinging on an

interface (4.4.1)
Note 1 to entry: See Figure 4.
4.4.4
refraction

change of the direction of sound propagation when passing obliquely through the interface (4.4.1)

between two materials of differing sound velocities
Note 1 to entry: See Figure 4.
4.4.5
angle of reflection

angle between the direction of the reflected wave and the normal to the interface (4.4.1)

Note 1 to entry: See Figure 4.
4.4.6
angle of refraction

angle between the direction of the refracted wave and the normal to the interface (4.4.1)

Note 1 to entry: See Figure 4.
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4.4.7
acoustical impedance
ratio of sound pressure to particle displacement velocity

Note 1 to entry: In a material with perfect elastic properties for a plane longitudinal wave, it is equal to the

product of sound velocity (4.2.19) and density.
4.4.8
reflection coefficient

ratio of reflected sound pressure to incident sound pressure at a reflecting surface

Note 1 to entry: The corresponding transmission coefficient is defined in 4.4.9.
4.4.9
transmission coefficient

ratio of sound pressure transmitted through an interface (4.4.1) to the incident sound pressure

Note 1 to entry: The corresponding reflection coefficient is defined in 4.4.8.
4.4.10
refractive index
ratio of the sound velocities of two materials in contact
4.4.11
critical angle

angle of incidence (4.4.2) at which the angle of refraction (4.4.6) is 90° for a defined wave type

Note 1 to entry: For longitudinal (3.3.1) and transverse waves (3.3.2), there are two different critical angles.

4.4.12
total reflection

reflection (4.4.3) which occurs when the angle of incidence (4.4.2) is greater than the critical angles

(4.4.11) or if the reflection coefficient (4.4.8) is unity
4.4.13
corner reflection

reflection (4.4.3) of ultrasonic waves (3.2.1) in a corner formed by two or three coincident, mutually

perpendicular surfaces
Note 1 to entry: See Figure 5.
Key
α and β angles of incidence
Figure 5 — Corner reflection
4.4.14
wave mode conversion
change of wave mode to another by refraction (4.4.4) or reflection (4.4.3)
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4.4.15
edge effect

phenomenon resulting from the diffraction of an ultrasonic wave (3.2.1) by the edges of a reflector (6.4.1)

4.4.16
beam displacement
displacement of the beam due to reflection (4.4.3) from a surface of a solid
Note 1 to entry: It mainly depends on frequency (3.1.1) and angle.
Note 2 to entry: See Figure 6.
Key
1 beam displacement due to reflection
Figure 6 — Beam displacement
4.4.17
acoustic shadow

region in an object which cannot be reached by ultrasonic waves (3.2.1) travelling in a given direction

because of the geometry of the object or a discontinuity in it
Note 1 to entry: See Figure 7.
Key
1 acoustic shadow
Figure 7 — Acoustic shadow
5 Terms related to test equipment
5.1 Instrument
5.1.1
ultrasonic instrument

instrument used together with the probe or probes (5.2.1), which transmits, receives, processes and

displays ultrasonic signals for non-destructive testing purposes
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5.1.2
transmitter
electrical device which generates the transmitter pulses (5.1.3)
5.1.3
transmitter pulse

electrical pulse generated by the ultrasonic instrument (5.1.1) for exciting the transducer (4.1.1)

5.1.4
receiver

electrical device which amplifies or converts signals coming from the ultrasonic probe into usable signals

5.1.5
amplifier
electronic device which converts
...

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