oSIST prEN 17149-3:2023
(Main)Railway applications - Strength assessment of rail vehicle structures - Part 3: Fatigue strength assessment based on cumulative damage
Railway applications - Strength assessment of rail vehicle structures - Part 3: Fatigue strength assessment based on cumulative damage
This document describes a procedure for fatigue strength assessment based on cumulative damage of rail vehicle structures that are manufactured, operated and maintained in accordance with standards valid for rail system applications.
This document is applicable for variable amplitude load data with total number of cycles higher than 10 000 cycles.
An endurance limit approach is outside the scope of this document.
The assessment procedure is restricted to ferrous materials and aluminium.
This document does not define design load cases.
This document is not applicable for corrosive conditions or elevated temperature operation in the creep range.
This document is applicable to all kinds of rail vehicles; however it does not define in which cases a fatigue strength assessment using cumulative damage is to be applied.
Bahnanwendungen - Festigkeitsnachweis von Schienenfahrzeugstrukturen - Teil 3: Betriebsfestigkeitsnachweis
Applications ferroviaires - Évaluation de la résistance des structures de véhicule ferroviaire - Partie 3 : Évaluation de la résistance à la fatigue basée sur la méthode des dommages cumulés
Železniške naprave - Ocenjevanje odpornosti konstrukcije železniških vozil - 3. del: Ocena odpornosti proti utrujenosti na podlagi kumulativne škode
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 17149-3:2023
01-maj-2023
Železniške naprave - Ocenjevanje odpornosti konstrukcije železniških vozil - 3.
del: Ocena odpornosti proti utrujenosti na podlagi kumulativne škode
Railway applications - Strength assessment of rail vehicle structures - Part 3: Fatigue
strength assessment based on cumulative damage
Bahnanwendungen - Festigkeitsnachweis von Schienenfahrzeugstrukturen - Teil 3:
Betriebsfestigkeitsnachweis
Applications ferroviaires - Évaluation de la résistance des structures de véhicule
ferroviaire - Partie 3 : Évaluation de la résistance à la fatigue basée sur la méthode des
dommages cumulés
Ta slovenski standard je istoveten z: prEN 17149-3
ICS:
45.060.01 Železniška vozila na splošno Railway rolling stock in
general
oSIST prEN 17149-3:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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prEN 17149-3:2023 (E)
Contents Page
European foreword . 6
Introduction . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Stress determination . 9
4.1 General. 9
4.2 Parent material . 9
4.3 Welded joints . 9
4.3.1 Modified nominal stresses . 9
4.3.2 Structural stresses and notch stresses . 9
5 Fatigue strength . 9
5.1 Parent material . 9
5.1.1 General. 9
5.1.2 Component fatigue strength Δσ and Δτ . 10
R R
5.1.3 Material properties . 10
5.1.4 Design Parameters . 11
5.1.5 Fatigue strength factors for direct stresses f and for shear stresses f . 13
R,σ R,τ
5.1.6 Correction factor for casting fR,C . 14
5.1.7 S-N curves and methods of cumulative damage rule . 15
5.2 Welded joints . 16
5.2.1 General. 16
5.2.2 Fatigue classes Δσ and Δτ . 16
C C
5.2.3 Component fatigue strength Δσ and Δτ . 17
R R
5.2.4 Influence of thickness f and bending . 17
thick
5.2.5 Residual stress factors f and f . 18
res,σ res,τ
5.2.6 Enhancement factor for post-weld improvement f . 18
post
5.2.7 Quality level factor f . 19
QL
5.2.8 Enhancement factor for the weld inspection class f . 20
CT
5.2.9 S-N curves and methods of cumulative damage rule . 20
5.3 Determination of the fatigue strength of parent material and welded joints by
laboratory tests . 22
6 Partial factors covering uncertainties . 23
6.1 General. 23
6.2 Partial factor for loads γ . 23
L
6.3 Partial factor for the component fatigue strength γ . 24
M
6.3.1 General. 24
6.3.2 Partial factor for the consequence of failure γ . 24
M,S
6.3.3 Partial factor for the inspection during maintenance γ . 25
M,I
6.3.4 Partial factor for the degree of the validation process γ . 26
M,V
7 Procedure of the fatigue strength assessment based on cumulative damage
calculation . 26
2
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7.1 General . 26
7.2 Stress determination . 27
7.3 Determination of the design stress spectrum . 27
7.3.1 Conditioning . 27
7.3.2 Stress history adjustment . 27
7.3.3 Counting . 28
7.3.4 Mean stress adjustment . 28
7.3.5 Omission . 29
7.4 Damage calculation for each single stress component . 29
7.4.1 General . 29
7.4.2 Determination of stress spectrum shape factor A . 30
eq
7.4.3 Determination of admissible damage sum D . 30
m
7.4.4 Determination of the utilization for a single stress component U . 31
c
7.5 Assessment of fatigue strength . 32
7.6 Critical plane approach . 33
Annex A (informative) Procedure for determination of mean stress factors for parent
material and welded joints . 35
A.1 General . 35
A.2 Mean stress sensitivity . 35
A.2.1 Parent material . 35
A.2.2 Welded joints . 36
A.3 Determination of mean stress factors . 36
Annex B (informative) Specification example for permissible volumetric defects in steel,
iron and aluminium castings . 40
B.1 General . 40
Annex C (informative) Material factors for parent material . 41
Annex D (normative) Fatigue classes Δσ and Δτ for welded joints based on the nominal
C C
stress approach . 43
D.1 Explanation of the tables for fatigue classes . 43
D.1.1 General . 43
D.1.2 Number in accordance with EN 15085-3:2022, Table B.1 . 43
D.1.3 Sketch of the joint . 43
D.1.4 Joint specific requirements . 44
D.1.5 Potential crack initiation point . 44
D.1.6 Feasibility for inspection . 44
D.1.7 Relevant thickness for the assessment of a welded joint . 44
D.1.8 Material . 44
D.1.9 Fatigue classes Δσ and Δτ . 44
C C
D.1.10 Exponent m and number of cycles at the knee point of the S-N curve N . 45
D
D.1.11 Thickness correction exponents n n and n . 45
σ,┴, σ,|| τ
D.1.12 Lower limit of the plate thickness for the thickness correction t . 45
min
D.1.13 Parameter α used for the determination of f . 45
bend bend
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D.2 Tables of fatigue classes for welded joints . 46
D.3 Determination of fatigue strength based on comparative notch case models . 81
Annex E (informative) Thickness and bending influence on nominal and structural stress
approaches for welded joints . 82
E.1 General. 82
E.2 Influence quantities . 83
E.2.1 Thickness correction factor f . 83
thick
E.2.2 Enhancement factor for bending f . 84
bend
E.3 Methods for application of f in the assessment process . 85
bend
E.3.1 General. 85
E.3.2 General ratio method . 85
E.3.3 Constant ratio method . 86
E.3.4 Comparative notch case model method. 86
Annex F (informative) Stress adjustment due to joint geometry for welded joints for nominal
stress approach . 87
F.1 General. 87
F.2 Methods for stress adjustment . 87
F.2.1 General. 87
F.2.2 Modelling techniques for welded joints . 88
F.2.3 Adjustment in the stress evaluation . 89
Annex G (informative) Application of structural stress approach for welded joints of steel
and aluminium . 94
G.1 General for fatigue stress determination on weld toe . 94
G.2 Fatigue stress determination with Finite Element method . 95
G.2.1 Fatigue stress determination at the weld toe . 95
G.2.2 Fatigue stress determination at the root . 96
G.3 Fatigue strength assessment with structural stresses . 96
Annex H (informative) Application of notch stress approach for welded joints of steel and
aluminium . 98
H.1 General. 98
H.2 Calculation of notch stresses . 98
H.2.1 General. 98
H.2.2 Reference notch radius r for modelling of weld notches . 99
ref
H.2.3 Modelling of nominal weld cross sections . 99
H.2.4 Methods for notch stress calculation . 102
H.3 S-N curves . 103
H.3.1 Direct stress transverse to the weld . 103
H.3.2 Direct stress longitudinal to the weld . 104
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H.3.3 Shear stress . 104
H.3.4 Characteristic values dependent on thickness effect . 104
Annex I (informative) Example for fatigue strength assessment . 105
I.1 Description . 105
I.2 Task . 106
I.3 Assessment . 107
Annex J (informative) Flow chart diagrams of the fatigue strength assessment procedure
. 112
Bibliography . 118
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European foreword
This document (prEN 17149-3:2023) has been prepared by Technical Committee CEN/TC 256 “Railway
applications”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document is part of the series EN 17149 Railway applications — Strength assessment of railway
vehicle structures, which consists of the following parts:
— Part 1: General
— Part 3: Fatigue strength assessment based on cumulative damage
The following part is under preparation:
— Part 2: Static strength assessment
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Introduction
If a fatigue strength assessment is necessary for rail vehicle structures, this assessment may be made with
an endurance limit approach or a cumulative damage approach.
An endurance limit approach is based on the assessment of the stress ranges (e.g. derived from the design
load cases or from measurements) against the applicable endurance limit. Such an approach is applicable
in combination with the loads given in EN 12663 series or EN 13749.
A fatigue strength assessment based on cumulative damage takes into consideration stress spectra with
variable amplitudes and numbers of cycles or stress time histories. This document provides the basic
procedure and criteria for a pragmatic method to be applied for fatigue strength assessments based on
the cumulative damage approach.
This document does not provide any fatigue strength data, procedures or criteria for an endurance limit
approach. The main body of the document is based on the nominal stress approach, but the consideration
of variable amplitudes and number of cycles using methods described in this standard may equally be
applied with the structural stress and the notch stress approach (additional information for these
assessment methods is included as informative annexes).
Within this document the term fatigue strength assessment is always related to the cumulative damage
approach unless otherwise noted.
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1 Scope
This document describes a procedure for fatigue strength assessment based on cumulative damage of
rail vehicle structures that are manufactured, operated and maintained in accordance with standards
valid for rail system applications.
This document is applicable for variable amplitude load data with total number of cycles higher than
10000 cycles.
An endurance limit approach is outside the scope of this document.
The assessment procedure is restricted to ferrous materials and aluminium.
This document does not define design load cases.
This document is not applicable for corrosive conditions or elevated temperature operation in the creep
range.
This document is applicable to all kinds of rail vehicles; however it does not define in which cases a fatigue
strength assessment using cumulative damage is to be applied.
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.
EN 15085-3:2022, Railway applications - Welding of railway vehicles and components - Part 3: Design
requirements
1
prEN 17149-1:2021, Railway applications — Strength assessment of railway vehicle structures — Part 1:
General
ISO/TR 25901-1:2016, Welding and allied processes — Vocabulary — Part 1: General terms
3 Terms and definitions
For the purposes of this document, the terms, definitions, symbols and abbreviations given in
ISO/TR 25901-1:2016 and prEN 17149-1:2021 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
1
At draft stage.
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4 Stress determination
4.1 General
Fatigue loads acting on a component cause fatigue stresses that can be expressed as a stress spectrum.
The stress spectrum used to perform the fatigue strength assessment based on cumulative damage
approach shall be expressed in terms of stress ranges, mean stresses and number of cycles to represent
the design life.
The design stress spectrum shall incorporate any necessary allowance to account for uncertainties in
their values (see 6.2).
NOTE EN 12663 series, EN 15827 and EN 13749 contain information on how to determine design loads for
cumulative damage assessment of rail vehicles.
The combination of the individual stress components direct and shear is considered in 7.5.
4.2 Parent material
The stresses for the parent material shall be determined as described in prEN 17149-1:2021, 5.2.
4.3 Welded joints
4.3.1 Modified nominal stresses
The modified nominal stresses for welded joints shall be determined in accordance with
prEN 17149-1:2021, 5.3.
4.3.2 Structural stresses and notch stresses
For the fatigue strength assessment of welded joints, the structural stress approaches and the notch
stress approach may be applied. For the application of these approaches, the requirements for the
calculation of the relevant stresses and fatigue strength are described in the following informative
annexes:
— Annex G for the structural stress approach and
— Annex H for the notch stress approach.
5 Fatigue strength
5.1 Parent material
5.1.1 General
This clause describes the method to derive the fatigue strength of parent material under the following
conditions:
— materials used such as construction steel, weldable cast steel, cast iron (GJS and ADI), wrought steel,
cast aluminium, and wrought aluminium;
— application temperature up to 100 °C for aluminium and up to 200 °C for steel;
— plane stress tensor on the components surface (no significant stress component perpendicular to the
surface, e.g. press fit connection).
The restrictions defined above are met with most applications of parent material for rail vehicles, in
which case a simplified assessment method is appropriate. If the scope of the application is exceeded, an
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assessment method shall be chosen which accounts for the specific application (e.g. high temperatures
and 3-dimensional stress states).
Annex C gives an overview over the applicable material factors.
5.1.2 Component fatigue strength Δσ and Δτ
R R
The fatigue strength is specified by S-N curves, which define the values of the component fatigue strength
2
expressed as stress range Δσ and Δτ (in N/mm , unless stated otherwise) related to:
R R
6
— N =10 ,
C
— stress ratio R = R=−1,
στ
— survival probability of P= 97,5 %,
s
— membrane stresses.
The values of the component fatigue strength are determined with Formula (1) and Formula (2):
6
∆σ N =10, R =−=1 Rf⋅⋅⋅ f f (1)
( )
R C σ m R,σ SR,σ R,C
6
∆τ N =10, R =−1 =Rf⋅ ⋅ f ⋅⋅f f (2)
( )
R C τ m R,τ R,σ SR,τ R,C
5.1.3 Material properties
5.1.3.1 Tensile strength in accordance with material standards R
m,N
R is the nominal tensile strength in accordance with the material standards considering the actual
m,N
sheet thickness. For machined components, the thickness before machining (semi-finished product) shall
be considered.
For rolled sheets and extrusions an anisotropy factor f shall be considered in the direction transverse to
A
the main direction of rolling in accordance with Table , unless this is already considered or explicitly
excluded in the material standard or component specification. For other material applications f =1,0 .
A
R = fR⋅ (3)
m A mN,
Table 1 — Anisotropy factor f for steel and aluminium
A
Material R f
m,N A
2
[N/mm ]
Rolled Steel ≤ 600 0,9
> 600 ≤ 900 0,86
Rolled sheets and extrusions of aluminium ≤ 200 1,0
> 200 ≤ 400 0,95
> 400 ≤ 600 0,9
All other material applications Any value 1,0
Heat-affected zone Any value 1,0
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For heat-affected zones in the vicinity of welded joints the nominal tensile strength for the heat-affected
zone R shall be used instead of R . The value for R shall be derived from technical literature (e.g.
m,HAZ m m,HAZ
[2], [5], [57], [58]).
5.1.3.2 Tensile strength specified by drawing or specification R
m,S
As an alternative to a material standard, the mechanical properties may be specified by the drawing or
specification.
R is the tensile strength in accordance with a drawing or component specification. If higher values than
m,S
those defined in the material standards are specified for R and the values are checked only by random
m,S
testing, then the specified values are not sufficiently reliable and therefore would be non-conservative to
use for the purposes of a fatigue strength assessment. To perform a fatigue strength assessment with a
survival probability of P = 97,5 % the tensile strength R defined by the drawing or component
S m,S
specification shall be reduced in accordance with Formula (4):
R = f ⋅R (4)
m RmS, mS,
If the strength value is checked by three random tests (e.g. hardness test or tensile test) a value of
f = 0,94 is applicable. For other numbers of tests, this value shall be adjusted in accordance with
Rm,S
technical literature (e.g. [2]).
If a validated P = 97,5 % value within the component is available, f may be set to 1,0.
S Rm,S
NOTE Strength values verified with 3.1 certificate in accordance with EN 10204 are examples for such values.
The R values defined in material standards for a given wall thickness may be used for the purposes of
m,N
fatigue strength assessment with a survival probability of P = 97,5 %.
S
5.1.3.3 Influence of technological size
...
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