EN IEC 61400-8:2024

SLOVENSKI STANDARD
01-oktober-2024
Sistemi za proizvodnjo energije na veter - 8. del: Projektiranje delov konstrukcije
vetrnih turbin (IEC 61400-8:2024)
Wind energy generation systems - Part 8: Design of wind turbine structural components
(IEC 61400-8:2024)
Windenergieanlagen – Teil 8: Design von Windenergieanlagen-Strukturkomponenten
(IEC 61400-8:2024)
Systèmes de génération d'énergie éolienne - Partie 8: Conception des composants
structurels des éoliennes (IEC 61400-8:2024)
Ta slovenski standard je istoveten z: EN IEC 61400-8:2024
ICS:
27.180 Vetrne elektrarne Wind turbine energy systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61400-8

NORME EUROPÉENNE
EUROPÄISCHE NORM August 2024
ICS 27.180
English Version
Wind energy generation systems - Part 8: Design of wind turbine
structural components
(IEC 61400-8:2024)
Systèmes de génération d'énergie éolienne - Partie 8: Windenergieanlagen - Teil 8: Design von
Conception des composants structurels des éoliennes Windenergieanlagen-Strukturkomponenten
(IEC 61400-8:2024) (IEC 61400-8:2024)
This European Standard was approved by CENELEC on 2024-08-07. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61400-8:2024 E

European foreword
The text of document 88/1010/FDIS, future edition 1 of IEC 61400-8, prepared by IEC/TC 88 "Wind
energy generation systems" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 61400-8:2024.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2025-05-07
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2027-08-07
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61400-8:2024 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
ISO 12944-5:2019 NOTE Approved as EN ISO 12944-5:2019 (not modified)
ISO 1461:2022 NOTE Approved as EN ISO 1461:2022 (not modified)
ISO 14713-1:2017 NOTE Approved as EN ISO 14713-1:2017 (not modified)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 61400-1 2019 Wind energy generation systems - Part 1: EN IEC 61400-1 2019
Design requirements
IEC 61400-3-1 2019 Wind energy generation systems - Part 3- EN IEC 61400-3-1 2019
1: Design requirements for fixed offshore
wind turbines
- -  + A11 2020
IEC/TS 61400-3-2 2019 Wind energy generation systems - Part 3- - -
2: Design requirements for floating offshore
wind turbines
IEC 61400-5 2020 Wind energy generation systems - Part 5: EN IEC 61400-5 2020
Wind turbine blades
IEC 61400-6 2020 Wind energy generation systems - Part 6: EN IEC 61400-6 2020
Tower and foundation design requirements
IEC 61400-13 2015 Wind turbines - Part 13: Measurement of EN 61400-13 2016
mechanical loads
ISO/IEC 17025 2017 General requirements for the competence EN ISO/IEC 17025 2017
of testing and calibration laboratories
ISO 148-1 2016 Metallic materials - Charpy pendulum EN ISO 148-1 2016
impact test - Part 1: Test method
ISO 945-1 2019 Microstructure of cast irons - Part 1: EN ISO 945-1 2019
Graphite classification by visual analysis
ISO 1083 2018 Spheroidal graphite cast irons - - -
Classification
ISO 1099 2017 Metallic materials - Fatigue testing - Axial - -
force-controlled method
ISO 1143 2021 Metallic materials - Rotating bar bending - -
fatigue testing
To be published. Stage at time of publication: FprEN IEC 61400-3-2:2024.
ISO 2394 2015 General principles on reliability for - -
structures
ISO 3800 1993 Threaded fasteners; axial load fatigue - -
testing; test methods and evaluation of
results
ISO 6892-1 2019 Metallic materials - Tensile testing - Part 1: EN ISO 6892-1 2019
Method of test at room temperature
ISO 7500-1 2018 Metallic materials - Calibration and EN ISO 7500-1 2018
verification of static uniaxial testing
machines - Part 1: Tension/compression
testing machines - Calibration and
verification of the force-measuring system
ISO 12107 2012 Metallic materials - Fatigue testing - - -
Statistical planning and analysis of data
ISO 12108 2018 Metallic materials - Fatigue testing - - -
Fatigue crack growth method
ISO 12135 2021 Metallic materials - Unified method of test - -
for the determination of quasistatic fracture
toughness
ISO/TR 14345 2012 Fatigue - Fatigue testing of welded - -
components - Guidance
ISO 16269-6 2014 Statistical interpretation of data - Part 6: - -
Determination of statistical tolerance
intervals
ASTM-E466-21 2021 Standard Practice for Conducting Force - -
Controlled Constant Amplitude Axial
Fatigue Tests of Metallic Materials
BS 7910 2013 Guide to methods for assessing the - -
acceptability of flaws in metallic structures
- - Personal fall protection equipment - Anchor CEN/TS 16415 2013
devices - Recommendations for anchor
devices for use by more than one person
simultaneously
- - Execution of steel structures and EN 1090-2 2018
aluminium structures - Part 2: Technical
requirements for steel structures
- - Execution of steel structures and EN 1090-3 2019
aluminium structures - Part 3: Technical
requirements for aluminium structures
- - Founding - Magnetic particle testing EN 1369 2012
- - Founding - Magnetic particle inspection EN 1369 1996
- - Founding - Liquid penetrant testing - Part EN 1371-1 2011
1: Sand, gravity die and low pressure die
castings
- - Founding - Liquid penetrant inspection - EN 1371-1 1997
Part 1: Sand, gravity die and low pressure
die castings
- - Eurocode 3: Design of steel structures - EN 1993-1-8 2007
Part 1-8: Design of joints
- - Eurocode 3: Design of steel structures - EN 1993-1-9 2007
Part 1-9: Fatigue
- - Eurocode 3: Design of steel structures - EN 1993-1-10 2007
Part 1-10: Material toughness and through-
thickness properties
- - Eurocode 9: Design of aluminium EN 1991-1-1 2008
structures - Part 1-1: General structural
rule
- - Eurocode 9: Design of aluminium EN 1999-1-3 2007
structures - Part 1-3: Structures
susceptible to fatigue
- - Ultrasonic examination - Part 3: Spheroidal EN 12680-3 2011
graphite cast iron castings
- - Wind turbines - Protective measures - EN 50308 2004
Requirements for design, operation
and maintenance
DIN 50100 2016 Load controlled fatigue testing - Execution - -
and evaluation of cyclic tests at constant
load amplitudes on metallic specimens and
components
FKM Guideline 2018 Fracture Mechanics Proof of Strength for - -
Engineering Components (FKM – RBM-04-
18)
IIW-Doc. 2259- 2014 Recommendations for fatigue design of - -
152259-15 welded joints and components,
International Institute of Welding
IIW-Doc. XIII- 2010 Guideline for the Fatigue Assessment by - -
2240r2-08/XV- Notch Stress Analysis for Welded
1289r2-08 Structures
VDI 2230-1 2015 Systematic calculation of highly stressed - -
bolted joints - Joints with one cylindrical
bolt
VDI 2230-2 2014 Systematic calculation of high duty bolted - -
joints - Joints with several cylindrical bolts
VDMA 23902 2014 Guideline for fracture mechanical strength - -
assessment of planet carriers made of
nodular cast iron EN-GJS-700-2 for wind
turbine gear boxes, Verband Deutscher
Maschinen- und Anlagenbau e.V.

IEC 61400-8 ®
Edition 1.0 2024-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Wind energy generation systems –

Part 8: Design of wind turbine structural components

Systèmes de génération d'énergie éolienne –

Partie 8: Conception des composants structurels des éoliennes

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180  ISBN 978-2-8322-9063-7

– 2 – IEC 61400-8:2024  IEC 2024
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions, symbols and abbreviated terms . 10
3.1 Terms and definitions . 10
3.2 Symbols and abbreviated terms . 12
4 Reliability considerations . 14
4.1 Approaches to reliability based design . 14
4.2 Models and basic variables for structural verification . 16
4.2.1 Reliability assessment . 16
4.2.2 Material properties . 16
4.3 Partial safety factors and reliability targets . 16
5 Application of loads and analysis models . 17
5.1 Loads models . 17
5.2 Analysis model . 17
5.2.1 General . 17
5.2.2 Load path modelling . 17
5.2.3 Application of load components . 17
5.2.4 Boundary conditions . 18
5.3 Modelling of nonlinear mechanical behaviour . 18
5.3.1 General . 18
5.3.2 Nonlinear stress effects . 18
5.3.3 Application of ultimate loads . 18
5.3.4 Application of fatigue loads . 18
5.4 Partial safety factors . 19
5.5 Partial safety factor for resistance . 21
5.6 Nacelle and hub component considerations . 22
5.6.1 General . 22
5.6.2 Hub structure and bolts . 22
5.6.3 Nacelle front structure (alternatively: mechanical drive-train structure) . 23
5.6.4 Gearbox structure . 23
5.6.5 Yaw structure . 23
5.6.6 Nacelle rear structure . 24
5.6.7 Nacelle cover and spinner . 24
6 Deflection analysis . 24
7 Strength verification. 25
7.1 General . 25
7.2 Determination of stress and strain . 25
7.3 Material properties . 25
7.3.1 Material data . 25
7.3.2 Influence of size . 26
7.4 Static strength assessment . 26
7.4.1 Assessment process . 26
7.4.2 Cast, forged and steel components . 26
7.4.3 Welded structures . 28

IEC 61400-8:2024  IEC 2024 – 3 –
7.4.4 Bolted joints. 28
7.4.5 Fibre reinforced material . 29
7.5 Fatigue strength assessment . 29
7.5.1 Fatigue strength methods . 29
7.5.2 Determination of local stresses . 29
7.5.3 Stress hypothesis for fatigue . 29
7.5.4 S/N curves . 30
7.5.5 Influence on fatigue strength . 30
7.5.6 Partial safety factors for fatigue . 31
7.5.7 Damage accumulation . 32
7.5.8 Bolted joints. 33
7.5.9 Fibre reinforced material . 33
7.6 Fracture mechanics assessment . 33
7.6.1 General . 33
7.6.2 Define objective . 34
7.6.3 Material parameter . 34
7.6.4 Defect model . 35
7.6.5 Structural model . 36
7.6.6 Loading . 36
7.6.7 Strength assessment . 37
7.7 Fracture mechanics-based design . 40
8 Material data for design from testing . 41
8.1 Qualification of material . 41
8.2 Derivation of static strength and impact energy properties (base material) . 41
8.3 Derivation of fatigue strength properties (base material) . 41
8.4 Welded joints . 42
8.5 Cast, forged and steel . 42
8.5.1 Derivation of static strength properties. 42
8.5.2 Fracture toughness . 42
8.5.3 Derivation of fatigue strength properties . 43
8.6 Bolts . 44
8.7 Nacelle cover . 44
9 Model verification and validation . 44
Annex A (informative) Model verification and validation methods . 46
A.1 General . 46
A.2 Verification. 46
A.3 Validation (laboratory testing) . 46
A.4 Validation (field testing) . 46
Annex B (informative) Welded joint stresses . 47
Annex C (informative) S-N curve determination by test, statistical evaluation and
influencing factors . 48
C.1 General . 48
C.2 S-N curve. 48
C.3 Specimens . 48
C.4 Test procedure . 48
C.4.1 General . 48
C.4.2 Finite lifetime . 49
C.4.3 Long life fatigue regime . 49

– 4 – IEC 61400-8:2024  IEC 2024
C.5 Influencing factors of S-N curve . 49
Annex D (informative) Limit state equations . 50
D.1 General . 50
D.2 Yielding failure . 50
D.3 Fatigue limit state equation . 51
D.4 Fatigue assessment based on fracture mechanics . 55
Annex E (informative) Load effect uncertainty computation . 58
Annex F (informative) Considerations for structural elements . 60
F.1 General . 60
F.2 Global and local failures . 60
F.3 Mean stress influence . 61
Bibliography . 63

Figure 1 – Illustration of a nacelle structure, where for example a direct drive generator
is mounted behind the hub . 22
Figure 2 – Idealized elastic plastic stress-strain curve . 27
Figure 3 – Representative S /N curve . 30
Figure 4 – Fracture mechanics calculation – process flow chart . 34
Figure 5 – Idealized crack types . 35
Figure 6 – Failure assessment diagram (FAD) . 37
Figure 7 – Crack growth under cyclic loading by Paris/Erdogan . 39
Figure 8 – Crack propagation and critical crack length in failure assessment diagram . 40
Figure B.1 – Fatigue analysis procedure for the weld toe . 47
Figure D.1 – Haigh diagram with R as the yield stress and R as the tensile limit . 53
e m
Figure E.1 – Model example . 58
Figure F.1 – Locations of failure for local (A) and global (B) failure . 60
Figure F.2 – Local and global failure for two different notch radii . 61
Figure F.3 – Haigh-diagram for evaluation of mean stress influence . 61

Table 1 – Component classes as in IEC 61400-1:2019 . 17
Table 2 – List of potential sources for modelling deviations . 20
Table 3 – Modelling partial safety factor γ : yielding where coefficient of variation
modelling
of yield strength is less than 15 % . 20
Table 4 – Modelling partial safety factor, γ : fatigue of welded details and cast iron . 21
modelling
Table 5 – Minimum resistance partial safety factors, γ , for welded steel for different
M
survival probabilities of the characteristic S-N curve . 21
Table 6 – Minimum resistance partial safety factors γ , for cast iron, forged and steel
M
components (if not utilizing relevant design standards such as EN 1993-1-9) for
different survival probabilities of the characteristic S-N curve. 21
Table 7 – Partial safety factors γ for S/N-curves of cast iron materials . 32
M
Table D.1 – Representative stochastic model for fatigue analysis of cast iron . 55
Table E.1 – Test cases combination. 58
Table E.2 – Result comparison validation vs simplified models and ratio δ
mf
calculation . 59

IEC 61400-8:2024  IEC 2024 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 8: Design of wind turbine structural components

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 61400-8 has been prepared by IEC technical committee 88: Wind energy generation
systems. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
88/1010/FDIS 88/1023/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

– 6 – IEC 61400-8:2024  IEC 2024
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts of the IEC 61400 series, under the general title: Wind energy generation
systems, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

IEC 61400-8:2024  IEC 2024 – 7 –
INTRODUCTION
This part of the IEC 61400 series outlines the minimum requirements for the design of wind
turbine nacelle-based structures and is not intended for use as a complete design specification
or instruction manual.
Several different groups can be responsible for undertaking the various elements of the design,
manufacture, assembly, installation and maintenance of a wind turbine nacelle and for ensuring
that the requirements of this document are met. The division of responsibilities between these
parties is a contractual matter and is outside the scope of this document.
The requirements stated in this document may be altered if it can be sufficiently demonstrated
that the structural integrity of the system is not compromised.
The specific scope of the document is provided in Clause 1. For cases out of the scope of this
document, reference should be made to relevant IEC/ISO standards.

– 8 – IEC 61400-8:2024  IEC 2024
WIND ENERGY GENERATION SYSTEMS –

Part 8: Design of wind turbine structural components

1 Scope
This part of IEC 61400 outlines the minimum requirements for the design of wind turbine
nacelle-based structures and is not intended for use as a complete design specification or
instruction manual. This document focuses on the structural integrity of the structural
components constituted within and in the vicinity of the nacelle, including the hub, mainframe,
main shaft, associated structures of direct-drives, gearbox structures, yaw structural connection,
nacelle enclosure. It also addresses connections of the structural components to control and
protection mechanisms, as well as structural connections of electrical units and other
mechanical systems. This document focuses primarily on ferrous material-based nacelle
structures but can apply to other materials also as appropriate. The design of bolted and welded
joints in the nacelle structures is included, as well as cast and forged components. Material
testing requirements to use in the design process for nacelle structures are specified. While the
structural connections of the gearbox and the main shaft are in the scope, the design of the
gears and bearings are not included.
The safety level of the wind turbine designed according to this document shall be at or exceed
the level inherent in IEC 61400-1:2019. Probabilistic methods to calibrate partial safety factors
and for use in the design process are provided.
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.
IEC 61400-1:2019, Wind energy generation systems – Part 1: Design requirements
IEC 61400-3-1:2019, Wind energy generation systems – Part 3: Design requirements for fixed
offshore wind turbines
IEC TS 61400-3-2:2019, Wind energy generation systems – Part 3-2: Design requirements for
floating offshore wind turbines
IEC 61400-5:2020, Wind energy generation systems – Part 5: Wind turbine blades
IEC 61400-6:2020, Wind energy generation systems − Part 6: Tower and foundation design
requirements
IEC 61400-13:2015, Wind turbines – Part 13: Measurement of mechanical loads
ISO/IEC 17025:2017, General requirements for the competence of testing and calibration
laboratories
ISO 148-1:2016, Metallic materials – Charpy pendulum impact test – Part 1: Test method
ISO 945-1:2019, Microstructure of cast irons – Part 1: Graphite classification by visual analysis

IEC 61400-8:2024  IEC 2024 – 9 –
ISO 1083:2018, Spheroidal graphite cast irons – Classification
ISO 1099:2017, Metallic materials – Fatigue testing – Axial force-controlled method
ISO 1143:2021, Metallic materials – Rotating bar bending fatigue testing
ISO 2394:2015, General principles on reliability for structures
ISO 3800:1993, Threaded fasteners – Axial load fatigue testing – Test methods and evaluation
of results
ISO 6892-1:2019, Metallic materials – Tensile testing – Part 1: Method of test at room
temperature
ISO 7500-1:2018, Metallic materials – Calibration and verification of static uniaxial testing
machines – Part 1: Tension/compression testing machines – Calibration and verification of the
force-measuring system
ISO 12107:2012, Metallic materials – Fatigue testing – Statistical planning and analysis of data
ISO 12108:2018, Metallic materials – Fatigue testing – Fatigue crack growth method
ISO 12135:2021, Metallic materials – Unified method of test for the determination of quasistatic
fracture toughness
ISO/TR 14345:2012, Fatigue − Fatigue testing of welded components − Guidance
ISO 16269-6:2014, Statistical interpretation of data − Part 6: Determination of statistical
tolerance intervals
ASTM-E466-21:2021, Standard Practice for Conducting Force Controlled Constant Amplitude
Axial Fatigue Tests of Metallic Materials
BS 7910:2013, Guide to methods for assessing the acceptability of flaws in metallic structures
CEN/TS 16415:2013, Personal fall protection equipment – Anchor devices – Recommendations
for anchor devices for use by more than one person simultaneously
EN 1090-2:2018, Execution of steel structures and aluminium structures – Part 2: Technical
requirements for steel structures
EN 1090-3:2019, Execution of steel structures and aluminium structures – Part 3: Technical
requirements for aluminium structures
EN 1369:2012, Founding – Magnetic particle testing
EN 1369:1996, Founding – Magnetic particle inspection
EN 1371-1:2011, Founding – Liquid penetrant testing – Part 1: Sand, gravity die and low
pressure die castings
EN 1371-1:1997, Founding – Liquid penetrant inspection – Part 1: Sand, gravity die and low
pressure die castings
EN 1993-1-8:2007, Eurocode 3: Design of steel structures – Part 1-8: Design of joints

– 10 – IEC 61400-8:2024  IEC 2024
EN 1993-1-9:2007, Eurocode 3: Design of steel structures – Part 1-9: Fatigue
EN 1993-1-10:2007, Eurocode 3: Design of steel structures – Part 1-10: Material toughness
and through-thickness properties
EN 1999-1-1:2008, Eurocode 9: Design of aluminium structures – Part 1-1: General structural
rule
EN 1999-1-3:2007, Eurocode 9: Design of aluminium structures – Part 1-3: Structures
susceptible to fatigue
EN 12680-3:2011, Ultrasonic examination – Part 3: Spheroidal graphite cast iron castings
EN 50308:2004, Wind turbines − Protective measures − Requirements for design, operation
and maintenance
DIN 50100:2016, Load controlled fatigue testing – Execution and evaluation of cyclic tests at
constant load amplitudes on metallic specimens and components
FKM Guideline, Fracture Mechanics Proof of Strength for Engineering Components, 2018 (FKM
– RBM-04-18)
IIW-Doc. 2259-152259-15, Hobbacher A., Recommendations for fatigue design of welded joints
and components, International Institute of Welding, 2014
IIW-Doc. XIII-2240r2-08/XV-1289r2-08, Fricke W., Guideline for the Fatigue Assessment by
Notch Stress Analysis for Welded Structures, 2010
VDI 2230-1:2015, Systematic calculation of highly stressed bolted joints – Joints with one
cylindrical bolt
VDI 2230-2:2014, Systematic calculation of high duty bolted joints – Joints with several
cylindrical bolts
VDMA 23902:2014, Guideline for fracture mechanical strength assessment of planet carriers
made of nodular cast iron EN-GJS-700-2 for wind turbine gear boxes, Verband Deutscher
Maschinen- und Anlagenbau e.V.
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions 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 Terms and definitions
3.1.1
basquin equation
power law representation of S-N curves

IEC 61400-8:2024  IEC 2024 – 11 –
3.1.2
component capacity
maximum static stress the component can withstand
3.1.3
damage equivalent load
equivalent constant range load
load which when repeated a certain number of cycles, causes the same amount of damage as
the original combination of several loads and cycles
3.1.4
defect model
model which is used to substitute the geometrical dimensions of an idealized defect type
3.1.5
design life
minimum intended life of the structure, as used in the design process that the structure shall
survive under fatigue
3.1.6
design load
mechanical loads whether dynamic or static that the structure shall withstand in its design life
3.1.7
failure assessment diagram
FAD
diagram which is used to check if there is any risk of brittle failure of plastic collapse while
performing a fracture mechanic strength assessment
3.1.8
fail-safe
design property of a structure or system which prevents its failure
3.1.9
global stresses
stresses in terms of nominal stresses which are applicable for simple continuous structures
(e.g. beams, shells, plates), where the stress can be derived out of sectional forces by analytical
methods
Note 1 to entry: Notch factors may need to be considered.
3.1.10
impact energy
energy absorbed/required to break a V-notched test sample on pendulum impact testing
machine
3.1.11
limit state
state of a structure beyond which it no longer satisfies the design requirements
3.1.12
local stresses
local stress analysis points at specific regions of a global structure (e.g. at radii, notches) with
consideration of the notch shape

– 12 – IEC 61400-8:2024  IEC 2024
3.1.13
mode I
failure mode I
crack opening mode (in tensile direction) in accordance with FKM Guideline of fracture
mechanics or BS 7910
3.1.14
Paris-Erdogan equation
equation used to compute the cyclic crack growth behaviour
3.1.15
primary structures
structures which are in the main force flow of the nacelle structure (e.g. the planet carrier of the
gearbox)
3.1.16
S-N curve
relation between the number of stress cycles a material can undergo before failure
3.1.17
safe-life
design life period of a system after which it should be removed from service
3.1.18
secondary structures
structures which are not in the main force flow of the nacelle structure (e.g. the housing of the
gearbox)
3.1.19
structural model
model oriented to the shape and dimensions of the defect surrounding structure
3.2 Symbols and abbreviated terms
COV coefficient of variation
EPFM elastic plastic fracture mechanics
FAD failure assessment diagram
FE finite element
FEA finite element analysis
LEFM linear elastic fra
...