SIST EN 15461:2008
Railway applications - Noise emission - Characterisation of the dynamic properties of track sections for pass by noise measurements
Railway applications - Noise emission - Characterisation of the dynamic properties of track sections for pass by noise measurements
This WI defines the measuring procedures to assess the dynamic properties of the track and the roughness level of rails. It covers the following subjects:
1. Definition of data acquisition and processing procedures to determine track vibration decay with distance for both vertical and lateral direction under measured excitation;
2. rail roughness measurement protocol application.
Bahnanwendungen - Schallemissionen - Charakterisierung der dynamischen Eigenschaften von Gleisabschnitten für Schallmessungen von vorbeifahrenden Zügen
In der vorliegenden Europäischen Norm wird ein Verfahren zur Charakterisierung des dynamischen Verhaltens der Schienen eines Oberbaus in Bezug auf ihren die Rollgeräusche verursachenden Anteil an der Schallemission festgelegt.
Die vorliegende Europäische Norm beschreibt ein Verfahren zur:
- Gewinnung von Daten zur Körperschallempfindlichkeit einer Schiene;
- Weiterverarbeitung der Messdaten zur Berechnung eines Schätzwertes der Körperschallabklingraten in Gleislängsrichtung im Rahmen eines akustisch wahrnehmbaren und auf die Rollgeräusche zurückzuführenden Frequenzspektrums;
- Darstellung dieses Schätzwertes für einen Vergleich mit der Körperschallabklingrate.
Diese Norm gilt für die Bewertung der Leistungsfähigkeit von Referenzgleisabschnitten zur Messung der durch Schienenfahrzeuge emittierten Schallemissionen im Rahmen von Bauartzulassungsprüfungen.
Das Verfahren gilt nur für die freie Strecke.
Bei der Charakterisierung des Körperschallverhaltens von Gleisen auf Kunstbauten wie Brücken oder Dämmen gilt das Verfahren nicht.
Das Verfahren geht davon aus, dass die in der Schiene verlaufenden Körperschallwellen als Überlagerung zweier – längs und quer verlaufenden – Biegewellen, wie bei einem einfachen Träger gemessen werden können. Obwohl sich die Schiene im Betriebsgleis auf diese Weise nicht hinsichtlich der Gesamtheit aller durch die Messung abgedeckten Frequenzen verhält, ermöglicht diese Vereinfachung die Messung der „Körperschallabklingrate“ zur Erstellung einer Abschätzung des dynamischen Verhaltens des Gleises, das wiederum ein Hauptparameter ist, der die Erzeugung von Rollgeräuschen beeinflusst
Applications ferroviaires - Emission sonore - Caractérisation des propriétés de sections de voie pour le mesurage du bruit au passage
La présente Norme Européenne spécifie une méthode de caractérisation du comportement dynamique de la structure d’une voie, relativement à sa contribution au rayonnement sonore associée au bruit de roulement.
Cette Norme Européenne présente une méthode pour :
a) l’acquisition de données de fonctions de réponse en fréquence mécanique sur une voie ;
b) le traitement des données de mesurage en vue de calculer une estimation des taux de décroissance des vibrations le long des rails dans une gamme de fréquences audibles associées au bruit de roulement ;
c) la présentation de cette estimation pour comparaison avec des limites inférieures de taux de décroissance.
Elle est applicable pour évaluer les performances de sections de voies de référence pour le mesurage du bruit des véhicules ferroviaires dans le cadre d’essais d’homologation.
La méthode n’est pas applicable pour caractériser le comportement vibratoire de voies sur des structures porteuses comme les ponts ou les remblais.
Železniške naprave - Hrup - Opis dinamičnih lastnosti tirnega odseka za merjenje hrupa vozečih vlakov
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Bahnanwendungen - Schallemissionen - Charakterisierung der dynamischen Eigenschaften von Gleisabschnitten für Schallmessungen von vorbeifahrenden ZügenApplications ferroviaires - Emission sonore - Caractérisation des propriétés de sections de voie pour le mesurage du bruit au passageRailway applications - Noise emission - Characterisation of the dynamic properties of track sections for pass by noise measurements45.060.01Železniška vozila na splošnoRailway rolling stock in general17.140.30Emisija hrupa transportnih sredstevNoise emitted by means of transportICS:Ta slovenski standard je istoveten z:EN 15461:2008SIST EN 15461:2008fr01-julij-2008SIST EN 15461:2008SLOVENSKI
STANDARD
SIST EN 15461:2008
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 15461February 2008ICS 17.140.30; 45.080 English VersionRailway applications - Noise emission - Characterisation of thedynamic properties of track sections for pass by noisemeasurementsApplications ferroviaires - Emission sonore -Caractérisation des propriétés dynamiques de sections devoie pour le mesurage du bruit au passageBahnanwendungen - Schallemission - Charakterisierungder dynamischen Eigenschaften von Gleisabschnitten fürVorbeifahrtgeräuschmessungenThis European Standard was approved by CEN on 28 December 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, 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 STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2008 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 15461:2008: ESIST EN 15461:2008
EN 15461:2008 (E) 2 Contents Page Foreword.3 Introduction.4 1 Scope.4 2 Normative references.4 3 Terms and definitions.5 4 Symbols and abbreviations.6 5 Principles.7 6 Data acquisition.7 6.1 Selection of the test section.7 6.2 Position of the accelerometers.7 6.3 Assembly of the accelerometers.8 6.4 Excitation force.9 6.5 Acquisition system.9 6.6 Acquisition of the FRF.9 6.7 Set of measuring positions.9 6.8 Measurement data to be produced.12 7 Data processing.12 8 Acceptance criteria.13 9 Test report.13 9.1 General.13 9.2 Presentation of the track decay rates.13 Annex A (informative)
Calculation of the decay rates.14 A.1 General.14 A.2 Calculation of the decay rates.14 Annex ZA (informative)
Relationship between this
European
Standard and the Essential Requirements
of EU Directives 96/48/EC and 2001/16 modified by Directive 2004/50/EC.16 Bibliography.18
SIST EN 15461:2008
EN 15461:2008 (E) 3 Foreword This document (EN 15461:2008) has been prepared by Technical Committee CEN/TC 256 “Railway applications”, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by August 2008, and conflicting national standards shall be withdrawn at the latest by August 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive 2001/16 modified by Directive 2004/50/EC. For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, 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 the United Kingdom. SIST EN 15461:2008
EN 15461:2008 (E) 4 Introduction The interaction between the wheels of a railway vehicle and the track during operation is translated by vibrations which, in movement, generate rolling noise.
The vibration response of the track structure determines the level of its sound contribution to this noise. The method assumes that the vibration waves in the rail can be regarded as the superposition of two bending waves, one vertical and the other transverse, of the rail represented as a simple beam.
Although the track rail does not behave in this way over all the frequencies covered by the measurement, this simplification permits the "decay rates" to be measured for an estimation of the dynamic behaviour of the track which is one of the basic parameters influencing the generation of rolling noise. 1 Scope This European Standard specifies a method for characterizing the dynamic behaviour of the structure of a track relative to its contribution to the sound radiation associated with the rolling noise. This European Standard describes a method for: a) acquiring data on mechanical frequency response functions on a track; b) processing measurement data in order to calculate an estimate of the vibration decay rates along the rails in an audible frequency range associated with the rolling noise; c) presenting this estimate for comparison with the lower limits of the decay rates. It is applicable for evaluating the performance of sections of reference tracks for measuring railway vehicle noise within the framework of official approval tests. The method is not applicable for characterizing the vibration behaviour of tracks on loadbearing structures such as bridges or embankments. 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 referenced document (including any amendments) applies EN 61260, Electroacoustics — Octave-band and fractional-octave-band filters (IEC 61260:1995)
EN ISO 266, Acoustics — Normal frequencies (ISO 266:1997) EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:2005) ISO 2041, Vibration and shock — Vocabulary ISO 7626-1, Vibration and shock — Experimental determination of mechanical mobility — Part 1: Basic definitions and transducers
SIST EN 15461:2008
EN 15461:2008 (E) 5 ISO 7626-5, Vibration and shock — Experimental determination of mechanical mobility – Part 5: Measurements using impact excitation with an exciter which is not attached to the structure 3 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply. 3.1 frequency-response function (FRF) frequency-dependent ratio of the motor-response phasor to the phasor of the excitation force (see
ISO 7626-1)
NOTE 1
In this document, the term also refers to the mean spectral amplitude of the FRF in the form of a one-third octave spectrum. NOTE 2
In this standard, the term frequency-response function (FRF) is used to refer generically either to accelerance (accelerometric response/excitation force) or to mobility (speed response/excitation force). The term is not used to refer to receptance (dynamic compliance).
NOTE 3 The FRF is generally calculated as the interspectrum ratio between the response and the force with the autospectrum.
This estimate of the FRF is called estimate H1. NOTE 4 A set of FRF between a single excitation point and multiple response points or even between a single response point and multiple excitation points may be used.
In this standard, the case of a fixed accelerometer and a mobile instrumented excitation hammer is the easiest to implement.
3.2 accelerance complex ratio of the acceleration at one point in a mechanical system to the force at the same point or at a different point during a single harmonic motion (see also ISO 7626-1 and ISO 2041)
NOTE
Accelerance is an FRF currently expressed as a narrow-band complex spectrum.
It is also used in this standard to express a one-third octave spectrum.
3.3 mobility complex ratio of the speed at one point in a mechanical system to the force at the same point or at a different point during a single harmonic motion (see also ISO 7626-1 and ISO 2041)
NOTE
Mobility is an FRF currently expressed as a narrow-band complex spectrum.
It is also used in this standard to express a one-third octave spectrum.
3.4 direct FRF, FRF at the point of application FRF for which the response is measured at the same position (as close as possible physically with an impact hammer and an accelerometer) and the same direction (see also ISO 7626-1)
NOTE
In this standard, the term refers both to force and response FRF in the vertical and transverse directions. 3.5 transfer FRF FRF for which the response amplitude is measured at a different position to the force application point
NOTE In order to define the FRF, the direction and position of the application force and the response should be mentioned.
SIST EN 15461:2008
EN 15461:2008 (E) 6 3.6 decay rate on the track vibration amplitude decay rate of the vertical or transverse bending waves of the rail as a function of the distance along the rail NOTE It is represented by a one-third octave band spectrum of the values of the decay rate, expressed in decibels per metre (dB/m) representing the attenuation as a function of the distance. 3.7 test section
section of track specifically associated with a particular set of measurement data
3.8 accelerometer position fixed position of the accelerometer(s) for which a complete set of FRF measurements is taken
3.9 structural wave
vibration wave that is propagated along the rail resulting in a deformation of the whole rail section
NOTE For example, vertical and transverse bending waves of the rail behaving like a beam or waves that involve deformation modes in the cross-section of the rail propagating along the rail.
The vibration waves with wavelengths that are smaller than the rail cross-section dimensions, such as the Rayleigh ultrasonic waves or the shear or compression waves in the material are not covered in the definition associated with the subject of this standard. 3.10 one third-octave band spectrum spectrum of the added squared values or the root mean squares of the FRF in each of the normal frequencies one-third octave band (see EN ISO 266). NOTE In this document, also refers to the speed and acceleration vibration spectrum, to the excitation effort spectrum, to the mobility and accelerance FRF spectrum and to the resulting decay rate 3.11 reference track section portion of track used to characterize the rail system noise emission performances that meet the requirements of the interoperability technical specifications from the railway interoperability directives
NOTE These requirements cover the track vibration response via the track decay rate and the acoustic roughness level of the rail.
They are intended to ensure the reproducibility of the measurements 3.12 instrumented hammer instrument with an integrated force transducer for applying an excitation force to the structure
4 Symbols and abbreviations x
position along the track. The reference position x0 = 0 is situated at the measuring point of the direct
FRF, x
differential operator over x, n
number of measuring positions, Dxn
nth interval, xmax
position of the maximum distance considered along the track, SIST EN 15461:2008
EN 15461:2008 (E) 7 A(xn) FRF at position xn along the track, b
response amplitude decay constant, DR
decay rate, FRF
frequency-response function, FFT
fast Fourier transform 5
Principles The decay rates are determined on the basis of an FRF at the application point and a certain number of frequency-response function measurements relative to the position on the rail of the excitation force application point (transfer function). An instrumented hammer shall be used to excite the rail. For the purpose of this standard, an accelerometer shall be fixed to the rail and the measurements shall be taken for various distances from the force application point in relation to it. The full set of FRF shall be measured in the vertical and transverse directions.
The decay rates of the vertical and transverse bending waves as a function of the distance shall be calculated on the basis of this set of FRF measurements. The stages of the test method are specified in the following subclauses. 6 Data acquisition 6.1 Selection of the test section The test section shall meet the following conditions: a) the constitution of the track shall be constant over the whole test section for all the parameters that could affect the decay rates. These parameters include the rail cross-sections, the stiffness of the pad beneath the rail, the cant of the rails and the space between the sleepers; b) the test section shall be fitted with long welded rails. Specifically, it shall not have any rail expansion joints. 6.2 Position of the accelerometers Within the test section, each position to which the accelerometer is fixed to the rail shall satisfy the following conditions: a) it shall be located inside the test section, at least 20 m from the centre of the test section; b) it shall be located at the median point of a space between the sleepers; c) the accelerometer shall not be located close to rail supports in an unusual condition; in particular:
1) there shall be no pumping sleeper less than 3 metres from the accelerometer position; 2) there shall be no missing or damaged fastening clip (or fastening of any other type, if necessary) on the supports directly adjacent to the measuring accelerometer position; 3) the accelerometer shall not be located less than 5 m from a rail weld;
SIST EN 15461:2008
EN 15461:2008 (E) 8 4) the accelerometer shall not be located less than 40 m from a rail expansion joint. Three measurements of the direct FRF shall be carried out at three potential accelerometer positions at least, compatible with the requirement of 6.2 c). If at least two of the FRF are similar, it can be regarded that these accelerometer positions are representative of the whole test section, and subsequently can be used for the rest of the measurements. If no accelerometer position is found in the first set of potential positions, others shall be sought, and their direct FRF verified, until a set is identified that does comply. NOTE If no accelerometer position is obtained with this procedure, it is probably because the structure of the test section is not sufficiently homogeneous to be characterized by a single decay rate spectrum. Therefore, another test section should be sought. 6.3 Assembly of the accelerometers The accelerometer(s) shall be fixed: a) in the vertical direction on a longitudinal axis of the rail, preferably on the rail head.
If this is not possible, it (they) should be fixed on the flange of the rail; b) in the transverse direction, on the outside face of the rail head. The accelerometer(s) shall be kept on the rail (either directly with the adhesive, or by a suitable support stuck on) at
...
SLOVENSKI oSIST prEN 15461:2006
PREDSTANDARD
april 2006
Železniške naprave – Hrup – Opis dinamičnih lastnosti tirnega odseka za
merjenje hrupa vozečih vlakov
Railway applications - Noise emission - Characterisation of the dynamic properties
of track sections for pass by noise measurements
ICS 17.140.20; 45.060.01 Referenčna številka
oSIST prEN 15461:2006(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
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EUROPEAN STANDARD
DRAFT
prEN 15461
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2006
ICS
English Version
Railway applications - Noise emission - Characterisation of the
dynamic properties of track sections for pass by noise
measurements
Applications ferroviaires - Emission sonore - Bahnanwendungen - Schallemissionen - Charakterisierung
Caractérisation des propriétés de sections de voie pour le der dynamischen Eigenschaften von Gleisabschnitten für
mesurage du bruit au passage Schallmessungen von vorbeifahrenden Zügen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 256.
If this draft becomes a European Standard, CEN 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.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other language
made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 15461:2006: E
worldwide for CEN national Members.
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prEN 15461:2005 (E)
Contents Page
Foreword .3
Introduction.4
1 Scope.4
2 Normative references.4
3 Terms and definitions .5
4 Symbols and abbreviations .7
5 Test method.7
5.1 Principle.7
6 Data acquisition.11
6.1 Selection of measurement location.11
6.2 Accelerometer location.12
6.3 Measurement system .12
7 Data processing .13
8 Test report .14
8.1 Presentation of track decay rates.14
Annex A (informative) Decay rate calculation.15
A.1 General.15
A.2 Decay rate calculation.15
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 96/48/EC .17
2
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prEN 15461:2005 (E)
Foreword
This document (prEN 15461:2006) 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 has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of Directive 96/46/EC.
For relationship with the EU Directive, see informative Annex ZA, which is an integral part of this document.
3
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prEN 15461:2005 (E)
Introduction
The rolling interaction between the wheels of a railway vehicle and the track results in vibration that, in turn,
causes rolling noise. The vibration response of the track structure determines the track component of this
noise.
1 Scope
This European Standard specifies a method for characterizing the structural dynamics of a track relative to the
track-radiated component of rolling noise.
This European Standard describes a method for:
acquiring mechanical frequency-response function data at a track site;
post-processing measured data in order to calculate an estimate of the rates of decay of vibration along
the rails in an audible frequency range related to the rolling noise;
presenting this estimate for assessment against lower boundary limits of decay rates.
It is applicable to testing the performance of reference track sections for measuring noise from railway
vehicles for acceptance test purposes.
It is applicable only to open track.
The method is not applicable for characterizing the vibration behaviour of track-supporting structures such as
bridges or embankments.
The method assumes that vibration waves in the rail can be measured as a single propagating vertical
bending wave and a single lateral bending wave of the rail acting as a simple beam. Although the track rail
does not behave in this way throughout the frequency range covered by the measurement, this simplification
allows the "decay rates" to be used an assessment of the dynamic behaviour of the track, which is one of the
key parameters influencing rolling noise generation.
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 referenced
document (including any amendments) applies
WI 00256200, Railway applications — Rail roughness measurements related to noise generation — Definition
1)
and procedures
EN ISO 266:1997, Acoustics — Preferred frequencies
EN ISO IEC 17025:2000, General requirements for the competence of testing and calibration laboratories
1) in preparation
4
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prEN 15461:2005 (E)
ISO 7626-1:1986, Vibration and shock — Experimental determination of mechanical mobility — Part 1: Basic
definitions and transducers
ISO 7626-5 :1994, Vibration and shock — Experimental determination of mechanical mobility — Part 5:
Measurements using impact excitation with an exciter which is not attached to the structure
3 Terms and definitions
For the purposes of this European Standard, the following terms and definitions apply.
3.1
frequency-response function (FRF)
freuqncy-dependent ratio of the motor-response phasor to the phasor of the excitation force (ISO 7626-1)
NOTE 1 In this standard, the term frequency-response function (FRF) is used to refer generically either to accelerance
(acceleration response/excitation force) or to mobility (velocity response/excitation force). The term is not used to refer to
receptance (dynamic compliance) in this document.
NOTE 2 The FRF is generally calculated as the cross spectrum between the response and the force divided by the
auto spectrum of the force. This estimate of the FRF is called an H1 estimate.
NOTE 3 A set of FRFs between a single excitation point and multiple response points or even between a single
response point and multiple excitation points can be used. In this standard, the case of a fixed accelerometer and a roving
instrumented hammer is most easily applicable.
3.2
accelerance
FRF representing the acceleration per unit force, expressed as a spectrum versus frequency (see also ISO
76261)
NOTE In this standard, it is not specifically defined as a complex quantity since the term is used to encompass the
FRFs expressed as a one-third octave spectrum
3.3
mobility
FRF representing the velocity per unit force expressed as a spectrum versus frequency (see also ISO 7626-1)
NOTE In this standard, it is not specifically defined as a complex quantity since the term Is used to encompass the
FRFs expressed as a one-third octave spectrum
3.4
direct FRF, driving-point FRF
FRF for which the response is measured at the same location (as close as physically possible with hammer
and accelerometer) and in the same direction (both force and response vertical or lateral) (see also
ISO 7626-1)
3.5
transfer FRF
FRF for which the response amplitude is measured at a different location from the force application location
NOTE It is strongly recommended that the direction and location of the application force and the response are known
in order to define the FRF.
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prEN 15461:2005 (E)
3.6
track decay rate
the rate of attenuation of vibration amplitude of either vertical or lateral bending wave motion in the rail as a
function of the distance along the rail
NOTE It is represented by a one-third octave spectrum of values expressed in decibels per metre (dB/m)
representing attenuation over distance
3.7
test section
specific section of track that is associated with a particular set of measurements
3.8
centre of test section
midpoint of the test section
3.9
accelerometer location
fixed position of the accelerometer(s) for which a full set of FRF measurements is taken
3.10
structural waves
vibration waves that are propagated along the rail resulting in a deformation of the whole rail section
NOTE For example, vertical and or lateral bending waves of the rail acting like a beam or waves that involve modes
of cross-sectional deformation of the rail and propagate along the rail. Waves of vibration with wavelengths very much
shorter than the cross-section dimensions of the rail, such as ultrasonic Rayleigh waves or shear and compression waves
in the rail material are not included in the definition for the purposes of this standard.
3.11
one-third octave spectrum
vibration spectra of velocity or acceleration, excitation force spectra, FRF spectra of either mobility or
accelerance and the resulting decay rates
NOTE However, the definition is standardized and relates to a spectrum of the summed squared values or the root
mean squares of the FRFs in each of the preferred one-third octave frequency bands (see EN ISO 266)
3.12
narrow-band spectrum
any spectrum expressed in terms of frequency bandwidth smaller than one-third octave band, either a
proportional bandwidth or constant bandwidth such as might be produced by a Fast Fournier Transform (FFT)
3.13
frequency analyser
a digital device for acquiring the signals from transducers and processing the signals to produce either a
narrow-band spectrum or a one-third octave band spectrum
NOTE 1 The system supplies at least two simultaneous channels.
NOTE 2 The signals are filtered by anti-aliasing filters before being sampled digitally (see ISO 7626-5 for more details).
3.14
reference track (section)
see definition in WI 00256200
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prEN 15461:2005 (E)
3.15
instrumented hammer
a device to apply the excitation impact on the rail with a built-in force transducer. The usable frequency range
depends on the duration of the force pulse generated
NOTE The excitation bandwidth is controlled by the choice of hammer mass and the stiffness of the tip (see
ISO 7626-5 for more details).
4 Symbols and abbreviations
x position along the track
dx differential operator on x
Δx interval on x
x position at maximum distance considered along the track
max
A(x) FRF at the position x along the track
β decay constant of the response amplitude
Δ decay rate
FRF frequency-response f unction
FFT Fast Fourier Transform
5 Test method
5.1 Principle
The decay rates are determined on the basis of a point FRF and a number of frequency-response function
measurements relative to the location on the rail of the excitation force application point. An instrumented
hammer shall be used to excite the rail. An accelerometer located at a number of positions along the rail at
different distances from the excitation point shall be used to measure the response. Rather than apply the
excitation at a single point and relocate the accelerometer along the rail, it is advisable to fix the
accelerometer at a specific position and move the excitation point to a series of locations along the rail.
The whole set of FRFs shall be measured successively for lateral and vertical excitation and the response
directions.
The measurements shall be carried out with the fixed accelerometers at the same time in the vertical and
lateral directions (see Figure 1) or by using successive positions of the accelerometers in the directions
(vertical and lateral) corresponding to that of the application force. In each case, the accelerometer(s) shall be
secured on the rail (either directly with the adhesive, or by a suitable glued stud) at the locations shown in
Figure 1.
NOTE It is preferable to isolate the transducer from the rail electrically in order to maintain the integrity of the
measuring system.
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prEN 15461:2005 (E)
The accelerometer(s) shall be fixed:
in the vertical direction on the longitudinal axis of the rail, preferably on the rail head. If this is not
possible, it (they) should be fixed under the rail foot;
in the transverse direction, on the outside face of the rail head preferably. If this is not possible, it (they)
should be fixed on the gauge face of the rail.
Key
1 F
vertical
2 F
lateral
3 Accelerometer
Figure 1 — Position of the accelerometers on the rail cross-section
A force pulse is applied to the rail head in each direction with an instrumented hammer fitted with a tip of
appropriate hardness to ensure a good quality measurement of the force and the response in a frequency
range of 50 Hz to 6 000 Hz.
NOTE A hardened steel tip with a light hammer is required in practice to obtain good quality measurements at the
up
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