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SNCF – P. Fodiman Rail Technology Conferences – Noise & Vibrations – 18th November 2015

Which maintenance strategies for a sustainable noise performance of the railway system ?

An analysis of the French case

Pascal Fodiman (SNCF) – [email protected]


SummaryThe rolling noise generation mechanisms – general principles

Rail maintenance -- Reprofiling the rail to improve its lifespan

Rails reprofiling techniques and current practices in France

Current maintenance stratégies on the French national network

Building a dedicated acoustic reprofiling maintenance -- The main underlying topics

A 4 years SNCF Réseau project in cooperation with 2 grinding companies (Speno International & Scheuchzer)

Main results

Conclusion


The rolling noise generation mechanisms General principles

Noise emission of the railway system is depending on both the track and the wheel contributions

The wheel/rail combined roughness is the main excitation parameter at the contact point

The track noise contribution to the system depends on 2 main parameters

The rail acoustic roughness The dynamic response of the track and its damping capacity 40,0

45,0

50,0

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

100 1000 10000Frequency (Hz)

SPL

(dB

ref 2

e-5P

a)

Lp totalLp rail Lp roue Lp traverse

The “acoustic” roughness is a variation of the height of the rail running surface associated with rolling noise excitation, expressed as a function of distance x along the rail (EN 15610)

It is typically referring to surface defects with a wavelength between a few tenths to a few dozens of a centimeter and an amplitude from a few µm to a few dozens of a µm

Grinding the rail with classical maintenance techniques can reduce the acoustic roughness.

This can lead to a noise reduction, with wheels equipped with composite brake blocks or disks, up to 3 dB(A)

Rail acoustic roughness remains a parameter that is variable in time and highly depending on the maintenance state of the rail surface


Rail maintenance Reprofiling the rail to improve its lifespan

Reprofiling techniques are currently used for Initial reprofiling after the construction or renewal track-works, preventive or curative maintenance of the rail

They are known to improve the lifespan of the rail by removing the material or surface defect on the railhead, such as

• the decarburized surface layer responsible of fatigue crack generation • the material defects (head checking, squats) • the geometrical defects (ballast footprints, wheel spin of traction engines)

resulting either from the construction or renewal trackworks, or train operation Enhancing the longitudinal and transversal geometry of worn rail Delaying the emergence of corrugation

They contribute to reduce environmental noise however not during the trackworks (!), and only after a stabilisation period after the grinding operation

Cor

ruga

tion

Bal

last

foot

prin

tsH

ead-

chec

king

squa

ts


Rails reprofiling techniques and Current practices in FranceGrinding

The most common in France The main drawback against noise • the rotating stone create a periodic mark on the rail surface • deeper than the mean acoustic roughness • which generate a tonal noise related to the working speed of the

grinding trainset Milling

Experimental approach Strong limitation of the wavelength tonal effect

High-speed grinding Not suitable for classical maintenance High implementation costs

Alternative or complementary techniques (finishing passes) (Experimental )

Oscillating grinding Tangential reprofiling High-speed grinding (not suitable for rail classical maintenance) Longitudinal strip finishing pass as a complement to grinding or milling

Grin

ding

wav

elen

gth

Long

itudi

nal s

trip

Grin

ding


There is no dedicated acoustic maintenance policy in France at the present time There is « classical » grinding policy

a preventive grinding policy with the following periods A curative grinding policy when necessary

The main parameter under control are The grinding trainset speed The applied effort on the rail surface (steered by the intensities provided in the rotating electric motors) The stone rotating speed (constant) The number of the stones The stone material (stiffness)

Current maintenance stratégies on the French national network

UIC classification Periodicity

Tracks (≥ 220kph) Tracks (< 220kph)

1 & 212 months

24 months

3 & 4 48 months

5 & 6 (≥ 160kph) 48 months 48 months

5 & 6 (< 160 kph) reserved reserved

7 to 9


Building a dedicated acoustic reprofiling maintenance The main topics

Principles Monitoring of the rail acoustic level of the rail

Planning of periodic grinding operations as soon as a maximum acoustic level is been reached

The main questions are How frequently shall the rail be reprofiled for acoustic purposes ?

How to insert the periods for acoustics in a classical maintenance scheme ?

Is there an opportunity to optimise the reprofiling parameters for both « classical » and « acoustic » purposes ?

How to settle industrial and cost saving methods

Secondary questions are: What about coupling effects on the track (roughness and track stiffness) ?

Should the grinding trainsets be improved and how ?

What is the potential and scope of alternative techniques against acoustics

Roughness acoustic level


CUPERLY (High speed)

MONTMIREY- LE-CHÂTEAU (High speed)

IS-SUR-TILLE (Conventional)

CERGY (Suburban)

VERNEUIL-L’ETANG (Conventional)

ParisStrasbourg

Reims

Dijon

Nancy

3 sites dedicated to High-speed Conventional Suburban traffics

Initial grinding operations between 2011 & 2015

28 acoustic roughness measurements (EN ISO 15610)

17 sets of parameters with various: Grinding train speeds:

• Conventional speeds from 4,5 to 8 kph • High-speed: from 10 to 20 kph

Stone pressure (electrical intensity) Number of grinding cuts: 1 or 2 Kind of grinding stones: standard, smooth depth value of grinding cuts

A 4 years SNCF Réseau project in cooperation with 2 grinding companies (Speno & Scheuchzer)

Test site Nbr of meas.

Campaigns

Grinding date

Test

zone

Nbr. of

cuts

Speed cut 1 (kph)

Speed cut 2 (kph)

Type of stone

Pressure

(A)

Is-sur Tille (Conventional)

917/05/20

11

1

2 5,5

6smooth 21

2standard 22

7 Standard 223

4Smooth 21

8,4 Standard 225

Verneuil-l'Etang (conventional)

321/05/20

151 2 4,5 4,5

standard +

acoustics22

Cergy (suburban) 6/729/05/20

13

1

1 6,5 n.a

Standard 22

2Smooth + tangenti

al24

3smooth+tangenti

al22

4 Smooth 22

Cuperly (high-speed) 328/11/20

13

11

10 n.a

standard LGV

242 14 n.a3

220 20 24

4 10 20 22


Conventional rail – acoustic roughness after grinding ! Influence of the train speed

In most cases, the TSI limit is not reached just after grinding Emergence of rail grinding pattern as a general case, which can be reduced with a second grinding

cut at « low » speed The train speed is highly impacting the IMMEDIATE acoustic performance of the grinding with:

A high amplification of the rail grinding pitch

A wavelength shift : (a higher wavelength when the train speed increases)

An influence of the vibration response of the grinding bogie-set is foreseen


Conventional rail : acoustic roughness after grinding (T0) ! Influence of the grinding stones type and the mechanical pressure

Better results can be achieved with « soft »grinding stones provided that the grinding quality is good (low train speed) In that respect, the optimum for acoustics (soft grinding stones, 2 cuts, low speeds) is hardly compatible with “classical” grinding criteria (aggressive stones, 1 cut, the highest speed possible) seeking productivity in terms of material removal


Conventional rail : acoustic roughness after grinding (T0) ! Influence of the grinding stones

Better results can be achieved with « soft »grinding stones provided that the grinding quality is good (low train speed) In that respect, the optimum for acoustics (soft grinding stones, 2 cuts, low speeds) is hardly compatible with “classical” grinding criteria (aggressive stones, 1 cut, the highest speed possible) seeking productivity in terms of material removal After 39 months however, the discrepancies between the several sets of parameters tend to be reduced


Conventional rail : acoustic roughness after 39 months

With a low train speed, 2 passes, and while using « smooth » stones with an existing trainset A TSI reference acoustic roughness level has been achieved straightforwardly after grinding

After a stabilisation period, depending on the density of the traffic, the acoustic roughness

The acoustic roughness performance is still conforming to the TSI reference track after a period of more than 3 years

After a 3 years period, a differentiated evolution which depends on the wavelength improvement along time for short wavelengths, but degradation for long wavelengths

A wavelength transition domain between 3 and 5 cm


Summary

A test program has been successfully performed in France

several grinding parameter, with an acoustic optimisation have been applied on several test sites

They showed that : The optimisation parameters for acoustics and for classical grinding operation are contradictory • Trains speed is of major influence • The grinding material is also impacting the surface quality against acoustics

A TSI reference track may not be achievable with classical grinding parameters and requires a specific optimisation for acoustic criteria to be reached just after grinding

Relatively to the French track design, provided that some of the grinding parameters are optimised, there may be no need to increase the grinding frequency

CR : A specific grinding scheme may not to be requested after at least a 39 months period (next “rendez-vous” after 48 months) HS : Due to the existing grinding maintenance, a specific acoustic maintenance policy is probably not required

In that respect the principles of the maintenance can be optimised to improve the set of parameters for acoustic purposes without jeopardizing the productivity requirements


Merci de votre attentionThank you for your attention

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