ISO 12108:2018
(Main)Metallic materials — Fatigue testing — Fatigue crack growth method
Metallic materials — Fatigue testing — Fatigue crack growth method
This document describes tests for determining the fatigue crack growth rate from the fatigue crack growth threshold stress-intensity factor range, ΔKth, to the onset of rapid, unstable fracture. This document is primarily intended for use in evaluating isotropic metallic materials under predominantly linear-elastic stress conditions and with force applied only perpendicular to the crack plane (mode I stress condition), and with a constant force ratio, R.
Matériaux métalliques — Essais de fatigue — Méthode d'essai de propagation de fissure en fatigue
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INTERNATIONAL ISO
STANDARD 12108
Third edition
2018-07
Metallic materials — Fatigue testing —
Fatigue crack growth method
Matériaux métalliques — Essais de fatigue — Méthode d'essai de
propagation de fissure en fatigue
Reference number
©
ISO 2018
© ISO 2018
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 4
4.1 Symbols . 4
4.2 Abbreviated terms for specimen identification . 5
5 Apparatus . 5
6 Specimens . 6
6.1 General . 6
6.2 Crack plane orientation . 6
6.3 Starter notch precracking details. 8
6.4 Stress-intensity factor .10
6.5 Specimen size .10
6.6 Specimen thickness .10
6.7 Residual stress . .10
7 Procedure.11
7.1 Fatigue precracking .11
7.2 Crack length measurement .11
−5
7.3 Constant-force-amplitude, Κ-increasing, test procedure for da/dN > 10 mm/cycle .12
−5
7.4 K-decreasing procedure for da/dN < 10 mm/cycle .13
8 Crack length measurement .15
8.1 Resolution .15
8.2 Interruption .15
8.3 Static force .15
8.4 Measurement interval .15
8.5 Symmetry.16
8.6 Out-of-plane cracking .16
8.7 Crack tip bifurcation .16
8.8 Non-visual crack length measurement .16
8.9 Visual crack length measurement .16
9 Calculations.16
9.1 Crack-front curvature .16
9.2 Determining the fatigue crack growth rate .17
9.2.1 General.17
9.2.2 Secant method .17
9.2.3 Incremental polynomial method .18
9.3 Determination of the fatigue crack growth threshold .18
10 Test report .18
10.1 General .18
10.2 Material .18
10.3 Test specimen .19
10.4 Precracking terminal values .19
10.5 Test conditions .19
10.6 Test analysis .20
10.7 Presentation of results .20
Annex A (normative) Compact tension (CT) specimen .27
Annex B (normative) Centre crack tension (CCT) specimen .32
Annex C (normative) Single edge notch tension (SENT) specimen .38
Annex D (normative) Single edge notch bend (SENB) specimens .41
Annex E (informative) Non-visual crack length measurement methodology — Electric
[9][12][36]
potential difference .48
Bibliography .51
iv © ISO 2018 – All rights reserved
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 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals,
Subcommittee SC 4, Fatigue, fracture and toughness 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.
This third edition cancels and replaces the second edition (ISO 12108:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— The document has been reorganized to move the formulae and drawings for each of the test
specimens from the main body of the document into a separate normative annex for each specimen.
— Guidance on the effects of residual stress on fatigue crack growth rate data has been expanded.
Introduction
This document is intended to provide specifications for generation of fatigue crack growth rate data.
Test results are expressed in terms of the fatigue crack growth rate as a function of crack-tip stress-
[15][16][17]
intensity factor range, ΔK, as defined by the theory of linear elastic fracture mechanics
[18][19][20]
. Expressed in these terms, the results characterize a material's resis
...
INTERNATIONAL ISO
STANDARD 12108
Third edition
2018-07
Metallic materials — Fatigue testing —
Fatigue crack growth method
Matériaux métalliques — Essais de fatigue — Méthode d'essai de
propagation de fissure en fatigue
Reference number
©
ISO 2018
© ISO 2018
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 4
4.1 Symbols . 4
4.2 Abbreviated terms for specimen identification . 5
5 Apparatus . 5
6 Specimens . 6
6.1 General . 6
6.2 Crack plane orientation . 6
6.3 Starter notch precracking details. 8
6.4 Stress-intensity factor .10
6.5 Specimen size .10
6.6 Specimen thickness .10
6.7 Residual stress . .10
7 Procedure.11
7.1 Fatigue precracking .11
7.2 Crack length measurement .11
−5
7.3 Constant-force-amplitude, Κ-increasing, test procedure for da/dN > 10 mm/cycle .12
−5
7.4 K-decreasing procedure for da/dN < 10 mm/cycle .13
8 Crack length measurement .15
8.1 Resolution .15
8.2 Interruption .15
8.3 Static force .15
8.4 Measurement interval .15
8.5 Symmetry.16
8.6 Out-of-plane cracking .16
8.7 Crack tip bifurcation .16
8.8 Non-visual crack length measurement .16
8.9 Visual crack length measurement .16
9 Calculations.16
9.1 Crack-front curvature .16
9.2 Determining the fatigue crack growth rate .17
9.2.1 General.17
9.2.2 Secant method .17
9.2.3 Incremental polynomial method .18
9.3 Determination of the fatigue crack growth threshold .18
10 Test report .18
10.1 General .18
10.2 Material .18
10.3 Test specimen .19
10.4 Precracking terminal values .19
10.5 Test conditions .19
10.6 Test analysis .20
10.7 Presentation of results .20
Annex A (normative) Compact tension (CT) specimen .27
Annex B (normative) Centre crack tension (CCT) specimen .32
Annex C (normative) Single edge notch tension (SENT) specimen .38
Annex D (normative) Single edge notch bend (SENB) specimens .41
Annex E (informative) Non-visual crack length measurement methodology — Electric
[9][12][36]
potential difference .48
Bibliography .51
iv © ISO 2018 – All rights reserved
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 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals,
Subcommittee SC 4, Fatigue, fracture and toughness 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.
This third edition cancels and replaces the second edition (ISO 12108:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— The document has been reorganized to move the formulae and drawings for each of the test
specimens from the main body of the document into a separate normative annex for each specimen.
— Guidance on the effects of residual stress on fatigue crack growth rate data has been expanded.
Introduction
This document is intended to provide specifications for generation of fatigue crack growth rate data.
Test results are expressed in terms of the fatigue crack growth rate as a function of crack-tip stress-
[15][16][17]
intensity factor range, ΔK, as defined by the theory of linear elastic fracture mechanics
[18][19][20]
. Expressed in these terms, the results characterize a material's resis
...
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