CEN/TS 13979-2:2011

SLOVENSKI STANDARD
01-november-2011
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Railway applications - Wheelsets and bogies - Monobloc wheels - Technical approval
procedure - Part 2: Cast wheels
Bahnanwendungen - Radsätze und Drehestelle - Vollräder - Technische
Zulassungsverfahren - Teil 2: Gussräder
Applications ferroviaires - Essieux montés et bogies - Roues monobloc - Procédure
d'homologation technique - Partie 2 : Roues en acier moulé
Ta slovenski standard je istoveten z: CEN/TS 13979-2:2011
ICS:
45.040 Materiali in deli za železniško Materials and components
tehniko for railway engineering
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN/TS 13979-2
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
September 2011
ICS 45.040
English Version
Railway applications - Wheelsets and bogies - Monobloc wheels
- Technical approval procedure - Part 2: Cast wheels
Applications ferroviaires - Essieux montés et bogies - Bahnanwendungen - Radsätze und Drehgestelle - Vollräder
Roues monobloc - Procédure d'homologation technique - - Technische Zulassungsverfahren - Teil 2: Gussräder
Partie 2: Roues en acier moulé
This Technical Specification (CEN/TS) was approved by CEN on 3 January 2011 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 13979-2:2011: E
worldwide for CEN national Members.

Contents Page
Forew ord .4
Introduction .5
1 Scope .6
2 Normative references .6
3 Parameters for the definition of the application covered .6
3.1 Parameters for geometric interchangeability .6
3.1.1 Functional requirements .6
3.1.2 Assembly requirements .7
3.1.3 Maintenance requirements .7
3.2 Parameters for thermomechanical assessment .7
3.3 Parameters for mechanical assessment .7
3.4 Parameters for acoustic assessment .8
4 Description of the wheel to be approved .8
5 Assessment of the geometric interchangeability .8
6 Assessment of the thermomechanical behaviour .8
6.1 General procedure .8
6.2 First stage – Braking bench test .9
6.2.1 Test procedure .9
6.2.2 Decision criteria .9
6.3 Second stage – Wheel fracture bench test .10
6.3.1 General .10
6.3.2 Test procedure .10
6.3.3 Decision criterion .10
6.4 Third stage – Field braking test .10
6.4.1 General .10
6.4.2 Test procedure .10
6.4.3 Decision criteria .10
7 Assessment of the mechanical behaviour .11
7.1 General procedure .11
7.2 First stage - Calculation .11
7.2.1 Applied forces .11
7.2.2 Calculation procedure .12
7.2.3 Preliminary assessment criterion .13
7.3 Second stage – Bench test .13
7.3.1 General .13
7.3.2 Definition of bench loading and of the test procedure .13
7.3.3 Decision criteria .13
8 Assessment of the acoustic behaviour .13
8.1 General procedure .13
8.2 Calculation procedure .14
8.3 Field measurements .14
8.4 Decision criteria .14
9 Technical approval documents .15
Annex A (normative) Assessment of the thermomechanical behaviour .16
A.1 Assessment flow chart .16
A.2 Braking bench test procedure .17
A.2.1 Principle of the test . 17
A.2.2 Definition of braking . 17
A.2.3 Method of measuring the decision criteria . 17
A.2.4 Tests and measurements . 18
A.2.5 Anomalies . 19
A.3 Wheel fracture bench test procedure . 19
A.3.1 Principle of the test . 19
A.3.2 Definition of drag braking . 19
A.3.3 Pre-cracking of the rim . 20
A.3.4 Tests and measurements . 20
A.3.5 Anomalies . 21
A.4 Field braking test procedure . 21
A.4.1 Principle of the test . 21
A.4.2 Definition of braking . 21
A.4.3 Method of measurement of the decision criteria . 21
A.4.4 Tests and measurements . 22
A.4.5 Anomalies . 23
Annex B (normative) Flow chart of the mechanical behaviour assessment . 24
Annex C (informative) Mechanical behaviour – Finite element code assessment. 25
Annex D (informative) Mechanical behaviour – Bench loading and test procedure. 26
D.1 Principle of bench loading and test procedure . 26
D.2 Definition of loading . 27
D.2.1 General . 27
D.2.2 Measurement of the stresses during field tests . 27
D.3 Fatigue bench test . 27
D.3.1 Method 1 – Random fatigue test . 27
D.3.2 Method 2 – Single-stage fatigue test . 29
Annex E (informative) Assessment of the acoustic behaviour . 31
E.1 Assessment flow chart . 31
E.2 Calculation procedure . 32
E.2.1 Preliminary comment . 32
E.2.2 Calculation of the wheel modal basis . 32
E.2.3 Selection of the reference track model . 32
E.2.4 Definition of the calculation parameters . 32
E.2.5 Power calculation . 32
E.2.6 Insertion . 33
E.2.7 Calculations of the decision criteria for acoustic technical approval of the wheel . 34
E.2.8 Optional calculations . 34
E.3 Field measurement procedure . 34
E.3.1 Objective and preliminary remark . 34
E.3.2 Recommendations for the operating conditions . 35
E.3.3 Measurement procedure . 38
E.3.4 Analysis of results . 40
Annex F (informative) Drag braking values for interoperability . 44
Bibliography . 45

Foreword
This document (CEN/TS 13979-2:2011) has been prepared by Technical Committee CEN/TC 256 “Railway
applications”, the secretariat of which is held by DIN.
Your attention is drawn to the fact that certain elements in this document may be subject to intellectual
property or similar rights. The CEN and/or CENELEC cannot be held responsible for not identifying such
property rights and providing a warning of their existence.
This document has been prepared as part of a mandate given to CEN by the European Commission and the
European Free Trade Association and provides support for the main requirements of EU Directive
2008/57/CE.
This European Standard is part of a series Railway applications — Wheelsets and bogies — Monobloc wheels
— Technical approval procedure which consists of the following parts:
⎯ Part 1: Forged and rolled wheels;
⎯ Part 2: Cast wheels.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Cyprus, Croatia, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Iceland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Norway, the Netherlands, Poland, Portugal, Romania, Slovakia,
Slovenia, Spain, Sweden, Switzerland and the United Kingdom.
Introduction
Part 1 of this series applies to monobloc wheels manufactured by forging and rolling. This process was the
only authorized process accepted in the UIC regulations that were applicable in the recent past in most of the
European countries.
Cast wheels are commonly used by AAR networks and have been introduced into Europe on some
applications for freight wagons. This standard defines the specified requirements linked to the casting process
for the technical approval of a monobloc wheel. It follows the same methodology as Part 1.
As this standard applies only to freight wagons and supports European interoperability, this standard defines
in the informative Annex F the specific parameters for the thermomechanical assessment of a freight wagon
wheel designed for European interoperability.
The standard describes how to assess the wheel design. To be able to apply the specifications, it is essential
to define the use of the wheel; this standard also states how to define this use.
At least four aspects are described with different purposes:
⎯ a geometric aspect: to allow interchangeability of different solutions for the same application;
⎯ a thermomechanical aspect: to manage wheel deformations and to ensure that braking will not cause
wheels to break;
⎯ a mechanical aspect: to ensure that no fatigue cracks occur in the web;
⎯ an acoustic aspect: to ensure that the solution chosen is as good as the reference wheel, for the use in
question.
For each of these three latter aspects, the rules proposed tend to limit the procedure; thus, the easier the
objectives are to attain by the wheel under study.
This Technical Specification does not cover assessment of the hub nor of the static mechanical dimensioning
of the wheel.
The main content of this standard is derived from Part 1. The only technical differences are linked to the
needs of the cast process for the product.
1 Scope
This Technical Specification defines the requirements for a cast monobloc wheel of a freight railway vehicle
non-powered axle for use on a European network.
It only applies to wheels of new design or new European application.
These requirements are intended to assess the validity of the design choice for the proposed use.
The assessment of these requirements is the technical approval procedure.
This Technical Specification does not address the quality requirements for cast wheels. These quality
requirements are defined in Technical Specification CEN/TS 15718.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the reference document
(including any amendments) applies.
EN 13103, Railway applications — Wheelsets and bogies — Non-powered axles — Design method
CEN/TS 15718, Railway applications — Wheelsets and bogies — Product requirements for cast wheels
3 Parameters for the definition of the application covered
The application for which the wheel is to be approved shall be defined by the following parameters.
If the application parameters are changed for an approved wheel, the customer and supplier shall review the
assessments.
3.1 Parameters for geometric interchangeability
The application shall be defined by geometric interchangeability parameters divided into three categories
according to whether they are linked to functional, assembly or maintenance requirements.
3.1.1 Functional requirements
⎯ the nominal tread diameter that influences the buffer height and the loading gauge;
⎯ the maximum rim width linked to the points and crossing and the track brakes;
⎯ the tread profile outside the conical part of the tread;
⎯ the position of the rim internal surface relative to the corresponding surface of the hub;
⎯ the conicity of the hub bore;
⎯ the space required for disc brakes mounted on the wheel;
⎯ the space needed on the bogie frame, braking equipment and suspension equipment.
3.1.2 Assembly requirements
⎯ the bore diameter;
⎯ the hub length to ensure overhanging of the hub on the wheelseat.
3.1.3 Maintenance requirements
⎯ the wear limit diameter or the last reprofiling diameter;
⎯ the wear groove shape;
⎯ the geometry of the area for wheel clamping on reprofiling machines;
⎯ the position and shape of the hole and groove for displacement under oil pressure (where required);
⎯ the general rim shape to allow ultrasonic measurement of residual stresses in wheels braked by shoes.
3.2 Parameters for thermomechanical assessment
The application shall be defined by:
⎯ the maximum braking energy created by the friction of the brake shoes on the tread surface. This energy
may be defined by a power P , a time t and a train speed V during drag braking. If it is defined by other
a a a
parameters (for braking to a stop, for example), these parameters are defined by agreement between the
customer and the supplier. Required values of P for European interoperability are given in informative
a
Annex F;
NOTE For interoperable freight rolling stock, the thermomechanical behaviour does not need to be verified when
braking to a stop, but only when drag braking, because of the lower energy in braking to a stop.
⎯ the type of brake shoes applied to the wheel (nature, dimensions and number).
3.3 Parameters for mechanical assessment
The application shall be defined by:
⎯ the maximum vertical static force per wheelset;
⎯ the type of service to be provided by the vehicles that will be fitted with the wheels to be approved:
⎯ description of the lines: geometric quality of the tracks, curve parameters, maximum speeds;
⎯ running times on these lines;
⎯ the calculated service life of the wheel, in kilometres.
3.4 Parameters for acoustic assessment
The application shall be defined by all the parameters influencing the noise emitted by the wheel and not
directly involved in the design of the wheel to be approved, such as:
⎯ the reference track on which the wheel is to run;
⎯ the reference wheel to which the design will be compared;
⎯ the reference rolling stock and one or more reference speeds;
⎯ one or two surface roughness spectra representative of the range of operational values of the wheel
under test.
4 Description of the wheel to be approved
The designer of the wheel to be approved shall supply documentation comprising:
⎯ the description of the fabrication process (casting, shot peening, heat treatment, machining condition);
⎯ the definition of the wheel geometry (drawing);
⎯ the following fabrication parameters:
⎯ geometric tolerances;
⎯ surface finishes;
⎯ steel grade;
⎯ the parameters for defining the application for which the approval is requested.
At the end of this technical approval procedure and before being put into service, a wheel shall be subjected
to product qualification as defined in Technical Specification CEN/TS 15718.
5 Assessment of the geometric interchangeability
The wheel design shall conform to the requirements of 3.1.
6 Assessment of the thermomechanical behaviour
6.1 General procedure
This assessment may comprise three stages.
The flowchart for this assessment is shown in normative Annexe A. It shall be noted that stages 1 and 2 can
occur in any order as they are both mandatory for cast wheels. The following text maintains the same order as
EN 13979-1; however, it shall be noted that the sequence shown in Annex A may be preferable in practice.
For each of the three stages, the test shall be carried out on a new rim (nominal tread diameter) and a worn
rim (wear limit tread diameter).
In each case (new rim and worn rim), the web geometry of the tested wheels shall be the least favourable for
thermomechanical behaviour within the geometric tolerance ranges. The wheel designer shall prove by
numeric simulation that the tested wheels give the worst results. If that is not the case, the numeric simulation
shall allow correction of the results to correspond with those that would be obtained on wheels in the most
unfavourable geometric conditions.
NOTE For the moment, the calculation codes and thermomechanical parameters are too imprecise and not well
known enough to be used as assessment parameters in a standard. In future, if this situation develops, a
thermomechanical calculation should be made as the first stage of the assessment.
6.2 First stage – Braking bench test
6.2.1 Test procedure
The test method and the measurements to be made are given in normative Annex A.
The power to be applied during this test shall be equal to 1,2 P (P is defined in 3.2). The duration of each
a
a
drag braking period and the train speed are those defined in 3.2 (t and V ).
a a
6.2.2 Decision criteria
Three criteria shall be met simultaneously for the wheel with the new rim and the wheel with the worn rim.
Wheel with new rim:
⎯ maximum lateral displacement of the rim during braking: + 3 / -1 mm;
⎯ level of residual stress in the rim after cooling:
⎯ σ ≤ + Σ N/mm as the average of three measurements;
r n r
⎯ σ ≤ + (Σ + 50) N/mm for each measurement;
i n r
⎯ maximum lateral displacement of the rim after cooling: + 1,5 / - 0,5mm.
Wheel with worn rim:
⎯ maximum lateral displacement of the rim during braking: + 3 / -1 mm;
⎯ level of residual stress in the rim after cooling:
⎯ σ ≤ +(Σ + 75) N/mm as the average of three measurements;
r w r
⎯ σ ≤ +(Σ + 100) N/mm for each measurement;
i w r
⎯ maximum lateral displacement of the rim after cooling: + 1,5 / - 0,5mm.
For steel grade CER7, a value of Σr = 200 N/mm is adopted. For CER8, the value of Σr shall be determined.
The lateral displacement is positive if the distance between the two inner faces of the wheel of the wheelset
increases.
For domestic traffic, if the track tolerances differ from general tolerances used in Europe, other values of
lateral displacement may be agreed between the parties concerned.

6.3 Second stage – Wheel fracture bench test
6.3.1 General
This second stage is mandatory for cast wheels due to the currently limited European experience on those
products.
6.3.2 Test procedure
The test procedure is given in normative Annex A.
6.3.3 Decision criterion
The tested wheels shall not fracture.
6.4 Third stage – Field braking test
6.4.1 General
This third stage shall be proceeded with if one of the results of the first stage does not meet the decision
criteria and the wheel is not rejected after the second stage.
6.4.2 Test procedure
The test method and the measurements to be taken are given in normative Annex A.
The power to be taken into account for this test is 1,2 P (P is defined in 3.2). The duration of each drag
a a
braking and the running speed of the train are those defined in 3.2 (t and V ).
a a
6.4.3 Decision criteria
Three criteria shall be met simultaneously for the wheel with the new rim and the wheel with the worn rim.
Wheel with new rim:
⎯ maximum lateral displacement of the rim during braking: + 3 / -1 mm;
⎯ level of residual stress in the rim after the tests and after cooling:
⎯ σ ≤ + (Σ - 50) N/mm as the average of the three measurements;
r n r
⎯ σ ≤ + Σ N/mm for each of the measurements;
i n r
⎯ maximum lateral displacement of the rim after cooling: + 1,5 /- 0,5 mm.
Wheel with worn rim:
⎯ maximum lateral displacement of the rim during braking: + 3 /-1 mm;
⎯ level of residual stress in the rim after the tests and after cooling:
⎯ σ = + Σ N/mm as the average of the three measurements;
r w r
⎯ σ = + (Σ + 50) N/mm for each of the measurements;
i w r
⎯ maximum lateral displacement of the rim after cooling: + 1,5 /- 0,5 mm;
⎯ For steel grade CER7, a value of Σr = 200 N/mm is adopted. For CER8, the value of Σr shall be
determined.
The lateral displacement is positive if the distance between the two inner faces of the wheel of the wheelset
increases.
For domestic traffic, if the track tolerances differ from the general tolerances used in Europe, other values of
lateral displacement may be agreed between the parties concerned.
7 Assessment of the mechanical behaviour
7.1 General procedure
This assessment shall comprise two stages. The purpose of this assessment is to ensure that there will be no
risk of fatigue cracking either in the wheel web or in its connections with the hub or the rim during the service
life of the wheel.
Both for the calculation and the test, the wheel geometry shall be the least favourable with regard to the
mechanical behaviour. If that is not the case for the test, the test parameters shall be corrected by the
calculation.
The flowchart for this assessment is shown in normative Annex B.
7.2 First stage - Calculation
7.2.1 Applied forces
Conventional forces shall be used. They are calculated on the basis of the value of load P. Load P is defined
in EN 13103. It is half the vertical force per wheelset on the rail.
On the basis of the parameters necessary for the mechanical assessment defined in 3.3, additional forces
shall be used if these parameters generate greater forces (for example, curve parameters, frozen track, etc.).
Three load cases shall be considered (see Figure 1):
⎯ Case 1: straight track (centred wheelset)
F = 1,25 P
z
F = 0
y1
⎯ Case 2: curve (flange pressed against the rail)
F = 1,25 P
z
F = 0,6 P for non-guiding wheelsets
y2
⎯ Case 3: negotiation of points and crossings (inside surface of flange applied to the rail)
F = 1,25 P
z
F = 0,6 F = 0,36 P for non-guiding wheelsets.
y3 y2
Dimensions in millimetres
Key
1 Straight track
2 Curve
3 Negotiation of points and crossings
Figure 1 — Application points of the different forces
7.2.2 Calculation procedure
A finite element calculation code shall be used to determine the stresses. The validity of the code shall be
proven and the choice of parameters having a critical influence on the results shall be justified. Informative
Annex C gives one method of demonstrating this.
The stresses shall be analysed as follows:
⎯ determination of the principal stresses at all points in the mesh (nodes) for each of the three load cases;
⎯ assessment, for each node, of the maximum principal stress for the three load cases (σ ) and of the
max
direction of this principal stress;
⎯ assessment, for each node, of the minimum stress equal to the lowest normal stress in the direction of
σ , for the three load cases (σ );
max min
⎯ calculation for each node of:
Δσ = σ - σ
max min
7.2.3 Preliminary assessment criterion
The range of dynamic stress Δσ shall be less than the permissible stresses at all points of the web.
For the permissible range of dynamic stresses, a value (in the shot-peened condition), A = 290 N/mm is
adopted.
7.3 Second stage – Bench test
7.3.1 General
This second stage shall be carried out irrespective of the results of the first stage.
7.3.2 Definition of bench loading and of the test procedure
They shall be agreed between the designer of the wheel and the appointed Notified Body.
The loading and the test procedure shall reproduce in the web the stresses representative (direction, level and
number of cycles) of those the wheel is subjected to throughout its entire life.
Informative Annex D gives one method of doing this.
7.3.3 Decision criteria
Four wheels shall be tested.
No fatigue cracks shall be observed after the test. A fault is considered to be a crack if its length is greater
than or equal to 1 mm.
8 Assessment of the acoustic behaviour
8.1 General procedure
The assessment of the acoustic behaviour of a wheel is widely dependent on several parameters that are not
directly related to the design of the particular wheel to be approved. This is why the result of a new wheel
design shall be compared with that of a rail system/reference wheel for a given state of maintenance of the rail
surface.
A schematic diagram representing the acoustic approval procedure for the wheel is given in informative Annex
E. The acoustic technical approval of the wheel may be obtained by a calculation if the type of wheel to be
approved allows reliable results to be obtained and/or from field measurements if requested:
⎯ case 1: a procedure based on calculations is considered adequate. This concerns monobloc
axisymmetric wheels of "standard" diameter (greater than or equal to 800 mm) for which the numerical
1)
calculations have already been validated ;
⎯ case 2: a procedure based on calculations and supplemented by an experimental modal analysis of the
wheel may be selected. This procedure concerns non-axisymmetric monobloc wheels (except for those

1) This procedure has been validated by ERRI reports [2] and [3] and the model has been simplified for the specific
requirements of the test for the technical approval.
with holes) and small diameter (less than 800 mm) monobloc wheels for which retuning of the calculated
modal base is required (e.g. when absorbing devices are mounted on the wheel). This retuning is due to
results of an experimental modal analysis of the wheel;
⎯ case 3: a range of measurements is required for the acoustic technical approval of the wheel. This
procedure concerns non-monobloc wheels with holes, non-axisymmetric wheels, wheels with
shielding devices, for which the calculation approach is not yet a sufficiently reliable approval
criterion.
8.2 Calculation procedure
This shall be applied in case 1 or 2 defined in 8.1. A calculation procedure is given in informative Annex E.
8.3 Field measurements
The field measurements shall be carried out in the following cases:
⎯ the calculation procedure has not been carried out or is unable to be carried out in a reliable enough
manner (case 3 of 8.1);
⎯ the calculation procedure has been carried out but has not led to acoustic technical approval of the wheel.
2)
A field measurement procedure is detailed in informative Annex E .

8.4 Decision criteria
RT
ref ref
If L represents the average acoustic pressure level emitted at a distance of 3 m from the track:
SW
ref ref
⎯ by a reference wheel W ;
ref
⎯ on a reference track T ;
ref
⎯ at a reference speed S ;
ref
⎯ for a reference roughness spectrum R ;
ref
R T
ref ref
W represents the new wheel design and L its noise emission level in the same conditions as the
opt
S W
ref opt
R
T
ref
ref
reference wheel, the performance indicator G is given for:
S
ref
R R T RT
T
ref ref ref ref ref
ref
G = L - L
S W
S SW
ref ref opt ref ref
In the following text, and to simplify the notations, it is assumed that the values of G and L in the above
equation are expressed for the fixed parameters of speed, track and roughness. The above equation may
then be written as:
GL=−L
WW
opt ref
2) Numerical calculations using the TWINS model developed at ERRI have been validated.

This expression may be evaluated both globally and on a 1/3 octave band. With the new notations, this
expression is written as:
ii i
GL=−L
ref
W
opt
where
i  is the 1/3 octave considered in the frequency range [100, 5000 Hz].
Considering that the new wheel shall be quieter than the reference wheel, the acceptance criteria may be
written as:
G= L − L
W W
opt ref
i i i
G = L − L
W W
opt ref
Thus, the acceptance criterion shall be the total noise radiation gain between the reference wheel and the
optimized wheel, assessed on a reference track, with a reference roughness spectrum. It is expressed in
i
dB(A) for the global value G supplemented by a 1/3 octave band analysis G .
ST, ST,
ref ref
In both cases (calculations and field test), the acoustic acceptance criteria are applied to the wheel under test:
i
calculation of the global noise gain thresholds, G , and by 1/3 octave band, G , according to the
ST, ST,
ref ref
standards and regulations. These thresholds are based on the reference system noise radiation and their
minimum value is zero.
9 Technical approval documents
A file shall be built up as the technical approval procedure is progressed. It shall comprise the following parts:
a) identification of the wheel: drawing, material, etc.;
b) definition of the application covered by the approval;
c) geometric assessment documents;
d) thermomechanical assessment documents;
e) mechanical assessment documents;
f) acoustic assessment documents.
Annex A
(normative)
Assessment of the thermomechanical behaviour
A.1 Assessment flow chart
Figure A.1
A.2 Braking bench test procedure
A.2.1 Principle of the test
The braking bench test consists of making 10 drag brakings on a wheel and measuring their effects on the
development of residual stresses in the rim, on the maximum lateral displacement of the rim during braking
and on the residual lateral displacement of the rim after cooling.
A.2.2 Definition of braking
The parameters of the drag braking cycles are obtained from the parameters defining the application (see
3.2):
⎯ nominal braking power P = 1,2 P ;
b a
⎯ duration of braking t = t ;
b a
⎯ linear speed of the wheel V = V ;
b a
⎯ type of brake shoes;
⎯ speed of simulated wind: V /2 measured 700 mm from the axle with the unit at a halt.
a
During the cycles, variations in these parameters shall remain within the following ranges:
⎯ instantaneous power: ± 10 % P ;
b
⎯ average power: ± 5 % P ;
b
⎯ duration of braking: ± 2 % t ;
b
⎯ linear speed: ± 2 % V .
b
The test shall be driven by the instantaneous braking power that shall be maintained within the range given
above for the duration of the test.
Control is effected:
⎯ either on the basis of measuring the braking torque;
⎯ or on the basis of measuring the tangential forces between the wheel and brake shoes and measuring the
speed.
Following agreement between the parties involved, the effect of the wind may be taken into account by a
calculation that modifies the parameters used or measured during the test.
A.2.3 Method of measuring the decision criteria
A.2.3.1 Measurement of lateral displacements
The lateral displacements of the rim are measured on the internal lateral face of the rim at the wear limit
diameter level with one face of the hub being used as a reference.
The measurement of the displacement during braking shall allow the extremes of displacement occurring
during the ten braking cycles to be obtained.
The residual displacement after cooling is equal to the average of three measurements carried out at 120°
intervals around the rim.
The measurement accuracy shall be at least ± 0,1 mm.
NOTE The maximum value of the displacement may appear some minutes after braking has stopped.
A.2.3.2 Measurement of residual stresses
The residual stresses are measured by a destructive method as described in CEN/TS 15718, Annex C.
NOTE Other techniques (for example, relative ultrasonic methods) for measuring residual stress in the wheel may be
employed where they are proven to give an equivalent and consistent level of accuracy and repeatability.
A.2.4 Tests and measurements
A.2.4.1 Measurements before tests
The parameters of the geometric definition of the wheel shall be recorded.
The brake shoes shall be worn in with a braking power not exceeding 1,2 P /2 until the contact surface
a
between the wheel and the shoe is equal to at least 80 % of the total shoe surface.
A.2.4.2 Braking tests
The ten drag braking cycles are carried out successively.
At the beginning of each cycle, the wheel rim temperature (measured at mid-thickness of the rim on the
external face) shall be less than 50 °C.
Cooling of the wheel may be accelerated by water spraying as soon as the rim temperature is lower than
200 °C.
Before each braking cycle, the position of the brake shoes shall be checked to ensure that there is at least
10 mm between the external face of the brake shoe and the external face of the rim.
During each cycle, the following shall be measured:
⎯ instantaneous power;
⎯ linear speed;
⎯ lateral displacement of the rim;
⎯ temperature of the web-rim fillet (optional);
⎯ duration of the braking cycle;
⎯ parameters of the simulated wind.
The average power is calculated at the end of each cycle.
The brake shoes shall be changed when they are half-worn or after 5 braking cycles. New shoes shall be
worn in as described in A.2.4.1.
NOTE Measurement of the rim temperature is not mandatory, but may in certain cases explain aberrant residual
stresses. Monitoring of the power level is mandatory and replaces monitoring of the pressure in the brake cylinder
because of the variations in the coefficient of friction between the wheel and the brake shoe.
A.2.4.3 Measurements after the braking cycles
After 10 braking cycles and complete cooling down of the wheel, the following shall be measured:
⎯ the residual stresses at the same points as before the braking cycles;
⎯ the residual lateral displacement of the rim.
A.2.5 Anomalies
If a power-monitoring anomaly occurs during the cycles, the test shall be restarted with a different wheel
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