stage 6 triennial report 1 July 2009–30 June 2012 ... - CHARMEC

Vibrations and noise – Vibrationer och buller (VB) – Schwingungen und Geräusche – Vibrations et bruit
VB11. ABATEMENT OF CURVE SQUEAL NOISE FROM TRAINS
Reduktion av kurvskrikljud från tåg
Verminderung des Quitschens von Zûgen in Kurven
Réduction du grincement ferroviaire dans les courbes
Project leaders Professor Wolfgang Kropp and
and supervisors Dr Astrid Pieringer,
Civil and Environmental
Engineering/
Division of Applied Acoustics
Doctoral candidate Mr Ragnar Vidarsson, MSc
(2011-01-15 – 2011-06-30)
Mr Ivan Zenzerovic, MSc
(from 2012-06-01)
Period 2011-01-01 – 2012-06-30
(– 2017-05-31)
Chalmers budget Stage 6: ksek 1200
(excluding university Stage 7: ksek 2 775
basic resources)
Industrial interests Stage 6: ksek 200
in-kind budget Stage 7: ksek 200
(Bombardier Transportation)
From the left: Dr Astrid Pieringer, Professor Wolfgang Kropp and
PhD student Ivan Zenzerovic from projects VB10 and VB11
Curve squeal is a highly disturbing tonal sound generated
by railway cars, metros and trams when they negotiate a
sharp curve. For curves with a radius of 200 m and below,
curve squeal noise is common. In addition, such tight
curves are situated mainly in urban areas where many
people live close to the tracks, see photo on page 35. The
noise is also a comfort issue for the passengers inside the
vehicles.
Curve squeal noise is commonly attributed to selfexcited
vibrations of the railway wheel, which are induced
either by stick/slip behaviour due to lateral creepage of
the wheel tyre on the top of the rail or by contact on the
wheel flange. Practical solutions to reduce the noise have
been wheel damping and friction modifiers. However, it
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is desirable to gain a fundamental understanding of the
mechanisms and causes of the squeal in order to find, if
possible, appropriate vehicle and track designs to avoid
or abate the generation of squeal noise. It should then be
possible to predict not only the likelihood of noise but also
its amplitude.
Project vb11 will be divided into four parts: (i) a further
extension of the time-domain model developed in project
vb10, (ii) an experimental validation of the model, (iii) an
extensive study to identify the essential parameters (and
their complex interaction) responsible for curve squeal,
and (iv) an investigation of the potential to reduce curve
squeal by design changes to track and wheel. Like project
vb10, this project is also being run in co-operation with
project ts11.
A measurement campaign on the sl line at Alvik – Stora
Mossen in Stockholm has been run, and included measurements
of both noise and vibration (vertical and lateral accelerations
of the inner rail on a curve). The average speed
of the accelerating trains was in the order of 20 km/h. The
maxima in the spectrograms were compared
with the frequencies of the wheel’s axial eigenmodes,
which are often the cause of the squealing,
and in certain cases a good agreement was
found. Acceleration signals with a strong sawtooth
shape were observed, possibly indicating
stick/slip or flange climbing.
As part of the preparatory work for project
vb11, the model for the prediction of squeal
noise developed in project vb10 was extended
so that it now contains the whole chain from
time-domain calculation of contact forces
between wheel and rail, over wheel vibration,
to radiated sound from the wheel. A Boundary Element
Model (bem) of the wheel has also been set up and tested
with an in-house bem code. This model was found to be
computationally very costly. However, this can be compensated
for by an approach where transfer functions from
point forces on the wheel (radial and tangential) to the
complex sound pressure at reference points in the field are
precalculated. Based on these transfer functions, the sound
field radiated from a vibrating wheel can be simulated very
efficiently.
The reference group for project vb11 has members from
Bombardier Transportation (in Germany, Sweden and
Switzerland), Interfleet Technology, sl and Trafikverket.
The research plan for the project is dated 2010-05-15. The
work has been delayed by the resignation of the original
doctoral candidate and the recruitment of his successor.