Non-destructive testing -- Infrared thermographic testing -- General principles for thermoelastic stress measuring method

This document provides general principles for thermoelastic stress measuring method of infrared thermographic testing in the field of industrial non-destructive testing (NDT).

Essais non destructifs -- Examen par thermographie infrarouge -- Principes généraux de la méthode de mesure des contraintes thermoélastiques

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Publication Date
16-Nov-2020
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5060 - Close of voting Proof returned by Secretariat
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INTERNATIONAL ISO
STANDARD 22290
First edition
2020-11
Non-destructive testing — Infrared
thermographic testing — General
principles for thermoelastic stress
measuring method
Essais non destructifs — Examen par thermographie infrarouge
— Principes généraux de la méthode de mesure des contraintes
thermoélastiques
Reference number
ISO 22290:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 22290:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22290:2020(E)
Contents Page

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

Introduction ..................................................................................................................................................................................................................................v

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Infrared thermographic testing personnel ............................................................................................................................... 1

5 Test Environment ................................................................................................................................................................................................. 1

5.1 Installation environment for the test equipment ...................................................................................................... 1

5.2 Avoidance of disturbances ............................................................................................................................................................ 2

6 Equipment ................................................................................................................................................................................................................... 2

6.1 Configuration ............................................................................................................................................................................................ 2

6.2 Infrared camera ...................................................................................................................................................................................... 2

6.3 Detection of temperature change by thermoelastic effect ................................................................................ 3

7 Measuring method .............................................................................................................................................................................................. 4

7.1 Test object ................................................................................................................................................................................................... 4

7.2 Load condition ......................................................................................................................................................................................... 4

7.2.1 General load condition ................................................................................................................................................ 4

7.2.2 Average value and amplitude of load ............................................................................................................. 4

7.2.3 Load frequency .................................................................................................................................................................. 5

7.3 Imaging method ..................................................................................................................................................................................... 5

7.4 Calibration of stress value ............................................................................................................................................................. 6

8 Implementation and reporting of tests ......................................................................................................................................... 7

8.1 Items described in the NDT procedures ........................................................................................................................... 7

8.2 Items described in the NDT instructions.......................................................................................................................... 7

8.3 Record of test conditions ................................................................................................................................................................ 7

8.4 Report ............................................................................................................................................................................................................. 8

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 22290:2020(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 of the voluntary nature of standards, 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing,

Subcommittee SC 8, Thermographic testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 22290:2020(E)
Introduction

Thermoelastic stress measuring method, which utilizes the thermoelastic properties of materials, is a

“full-field”, “noncontact” technique for surface stress mapping of materials and structures. Unlike the

conventional technique such as strain gauge method, the unique advantage of the method is its ability to

image whole-surface stress (∆(σ +σ )) distribution in specimens easily (ISO 10878).

1 2

Industrial applications of thermoelastic stress measuring method are getting wider along with

remarkable improvement of thermographic technologies. The effectiveness of any application of

thermoelastic stress measuring depends upon proper and correct usage of the method. The purpose of

this document is to provide general principles for the thermoelastic stress measuring method to promote

correct and effective application to various industrial non-destructive testing, such as automobiles,

aerospace products, electronic instruments, medical devices, industrial materials and so on.

© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 22290:2020(E)
Non-destructive testing — Infrared thermographic
testing — General principles for thermoelastic stress
measuring method
1 Scope

This document provides general principles for thermoelastic stress measuring method of infrared

thermographic testing in the field of industrial non-destructive testing (NDT).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 10878, Non-destructive testing — Infrared thermography — Vocabulary

ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel

ISO/TS 25107, Non-destructive testing — NDT training syllabuses

ISO 10880, Non-destructive testing — Infrared thermographic testing — General principles

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 10878 apply.

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

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Infrared thermographic testing personnel

Personnel who are responsible for conducting infrared thermographic testing (TT) including

thermoelastic stress measuring shall meet the following criteria.

a) TT personnel shall have an adequate knowledge of the testing including the basics of infrared

measurement and heat-transfer engineering as required by ISO 9712 and ISO/TS 25107.

b) TT personnel’s visual acuity and colour vision shall meet the requirements of ISO 9712.

5 Test Environment
5.1 Installation environment for the test equipment

Conduct the test in an environment where the temperature, humidity, and atmosphere are appropriate

for the test equipment, including the infrared camera as required by ISO 10880. Be sure to avoid

condensation on the surface of the test object.
© ISO 2020 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 22290:2020(E)

In order to avoid occurrence of image blur due to fluctuation of the field of view, make sure that vibration

is not applied to the infrared camera as much as possible. However, when the vibration period of the

infrared camera is synchronized with the load cycle to the test object, the influence can be reduced by

the position correction technique.
5.2 Avoidance of disturbances

For the avoidance of disturbances, requirements and information are given in ISO 10880.

In addition, care should be taken to minimize the surface temperature change of the test object other

than based on the thermoelastic effect. For example, in order to avoid temperature change due to air

currents, reduce the influence of wind as much as possible.
6 Equipment
6.1 Configuration
Schematic of an example of equipment configuration is shown in Figure 1.

In addition to the infrared camera (key 3 in Figure 1), the measuring equipment is constituted by a

computer or the like which performs camera control, reference signal processing, image processing,

image display and the like (key 7 in Figure 1).

When applying cyclic load to the test object, the material testing machine is required to have the ability

to load the required waveform and frequency (key 1 in Figure 1).
6.2 Infrared camera

An infrared camera shall meet the requirements of ISO 10880. In addition, an infrared camera should

have an infrared measuring wavelength range about 3 μm to 5 μm or about 8 μm to 14 μm to be

capable of measuring extremely small temperature changes. A camera with a frame repetition rate that

provides a sufficient number of frames per cycle of load shall be used. In order to obtain the spatial

resolution necessary for the test, the lens viewing angle of the infrared camera, the number of effective

pixels of the camera and the distance between the camera and the test object shall be considered.

The infrared camera with appropriate temperature resolution should be used in order to obtain the

required stress (the sum of surface principal stresses) resolution.

NOTE In the case of steel, a temperature resolution of about 0,001 K is necessary to obtain 1 MPa stress

resolution. Generally, the temperature resolution can be enhanced by image processing such as image averaging,

using an infrared camera which has about 0,03 K of noise equivalent temperature difference (NETD) value.

2 © ISO 2020 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 22290:2020(E)
Key
1 material testing machine
2 test object
3 infrared camera
4 control signal to infrared camera
5 detector signal from infrared camera
6 reference load or displacement signal from material testing machine
7 computer with signal processing unit and display
F load
t time
Figure 1 — Schematic of an example of equipment configuration
6.3 Detection of temperature change by thermoelastic effect

As signal processing methods for extracting the amount of temperature change with the thermoelastic

effect from
...

INTERNATIONAL ISO
STANDARD 22290
First edition
Non-destructive testing — Infrared
thermographic testing — General
principles for thermoelastic stress
measuring method
PROOF/ÉPREUVE
Reference number
ISO 22290:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 22290:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22290:2020(E)
Contents Page

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

Introduction ..................................................................................................................................................................................................................................v

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

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

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Infrared thermographic testing personnel ............................................................................................................................... 1

5 Test Environment ................................................................................................................................................................................................. 1

5.1 Installation environment for the test equipment ...................................................................................................... 1

5.2 Avoidance of disturbances ............................................................................................................................................................ 2

6 Equipment ................................................................................................................................................................................................................... 2

6.1 Configuration ............................................................................................................................................................................................ 2

6.2 Infrared camera ...................................................................................................................................................................................... 2

6.3 Detection of temperature change by thermoelastic effect ................................................................................ 3

7 Measuring method .............................................................................................................................................................................................. 4

7.1 Test object ................................................................................................................................................................................................... 4

7.2 Load condition ......................................................................................................................................................................................... 4

7.2.1 General load condition ................................................................................................................................................ 4

7.2.2 Average value and amplitude of load ............................................................................................................. 4

7.2.3 Load frequency .................................................................................................................................................................. 5

7.3 Imaging method ..................................................................................................................................................................................... 5

7.4 Calibration of stress value ............................................................................................................................................................. 6

8 Implementation and reporting of tests ......................................................................................................................................... 7

8.1 Items described in the NDT procedures ........................................................................................................................... 7

8.2 Items described in the NDT instructions.......................................................................................................................... 7

8.3 Record of test conditions ................................................................................................................................................................ 7

8.4 Report ............................................................................................................................................................................................................. 8

Bibliography ................................................................................................................................................................................................................................ 9

© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 22290:2020(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 of the voluntary nature of standards, 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing,

Subcommittee SC 8, Thermographic testing.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 22290:2020(E)
Introduction

Thermoelastic stress measuring method, which utilizes the thermoelastic properties of materials, is a

“full-field”, “noncontact” technique for surface stress mapping of materials and structures. Unlike the

conventional technique such as strain gauge method, the unique advantage of the method is its ability

to image whole-surface stress (∆ (σ +σ )) distribution in specimens easily (ISO 10878).

1 2

Industrial applications of thermoelastic stress measuring method are getting wider along with

remarkable improvement of thermographic technologies. The effectiveness of any application of

thermoelastic stress measuring depends upon proper and correct usage of the method. The purpose of

this document is to provide general principles of the thermoelastic stress measuring method to promote

correct and effective application to various industrial non-destructive testing, such as automobiles,

aerospace products, electronic instruments, medical devices, industrial materials and so on.

© ISO 2020 – All rights reserved PROOF/ÉPREUVE v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 22290:2020(E)
Non-destructive testing — Infrared thermographic
testing — General principles for thermoelastic stress
measuring method
1 Scope

This document provides general principles for thermoelastic stress measuring method of infrared

thermographic testing in the field of industrial non-destructive testing (NDT).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 10878, Non-destructive testing — Infrared thermography — Vocabulary

ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel

ISO/TS 25107, Non-destructive testing — NDT training syllabuses

ISO 10880, Non-destructive testing — Infrared thermographic testing — General principles

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 10878 apply.

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

— ISO Online browsing platform: available at https:// www. iso. org/o bp
— IEC Electropedia: available at http:// www.e lectropedia. org/
4 Infrared thermographic testing personnel

Personnel who are responsible for conducting infrared thermographic testing (TT) including

thermoelastic stress measuring shall meet the following criteria.

a) TT personnel shall have an adequate knowledge of the testing including the basics of infrared

measurement and heat-transfer engineering as required by ISO 9712 and ISO/TS 25107.

b) TT personnel’s visual acuity and colour vision shall meet the requirements of ISO 9712.

5 Test Environment
5.1 Installation environment for the test equipment

Conduct the test in an environment where the temperature, humidity, and atmosphere are appropriate

for the test equipment, including the infrared camera as required by ISO 10880. Be sure to avoid

condensation on the surface of the test object.
© ISO 2020 – All rights reserved PROOF/ÉPREUVE 1
---------------------- Page: 6 ----------------------
ISO 22290:2020(E)

In order to avoid occurrence of image blur due to fluctuation of the field of view, make sure that vibration

is not applied to the infrared camera as much as possible. However, when the vibration period of the

infrared camera is synchronized with the load cycle to the test object, the influence can be reduced by

the position correction technique.
5.2 Avoidance of disturbances

For the avoidance of disturbances, requirements and information are given in ISO 10880.

In addition, care should be taken to minimize the surface temperature change of the test object other

than based on the thermoelastic effect. For example, in order to avoid temperature change due to air

currents, reduce the influence of wind as much as possible.
6 Equipment
6.1 Configuration
Schematic of an example of equipment configuration is shown in Figure 1.

In addition to the infrared camera (key 3 in Figure 1), the measuring equipment is constituted by a

computer or the like which performs camera control, reference signal processing, image processing,

image display and the like (key 7 in Figure 1).

When applying cyclic load to the test object, the material testing machine is required to have the ability

to load the required waveform and frequency (key 1 in Figure 1).
6.2 Infrared camera

An infrared camera shall meet the requirements of ISO 10880. In addition, an infrared camera should

have an infrared measuring wavelength range about 3 μm to 5 μm or about 8 μm to 14 μm to be

capable of measuring extremely small temperature changes. A camera with a frame repetition rate that

provides a sufficient number of frames per cycle of load shall be used. In order to obtain the spatial

resolution necessary for the test, the lens viewing angle of the infrared camera, the number of effective

pixels of the camera and the distance between the camera and the test object shall be considered.

The infrared camera with appropriate temperature resolution should be used in order to obtain the

required stress (the sum of surface principal stresses) resolution.

NOTE In the case of steel, a temperature resolution of about 0,001 K is necessary to obtain 1 MPa stress

resolution. Generally, the temperature resolution can be enhanced by image processing such as image averaging,

using an infrared camera which has about 0,03 K of noise equivalent temperature difference (NETD) value.

2 PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 22290:2020(E)
Key
1 material testing machine
2 test object
3 infrared camera
4 control signal to infrared camera
5 detector signal from infrared camera
6 reference load or displacement signal from material testing machine
7 computer with signal processing unit and display
F load
t time
Figure 1 — Schematic of an example of equipment configuration
6.3 Detection of temperature change by thermoelastic effect

As signal processing methods for extracting the amount of temperature change with the thermoelastic

effect from the time series of temperature data, “temperature difference image technique” or “lock-in

techniqu
...

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