Analysis of train wheel rail noise
Australian Rail Track Corporation
Moderators: Neville Fowkes (University of Western Australia) and Graeme Hocking (Murdoch University)
The effective commencement of ARTC operations occurred on 1 July 1998. ARTC operates as a rail access provider and a rail infrastructure manager. Main activities include:
- Provision of access for train operators over the rail network either owned or leased by the company;
- Management of the Commonwealth's former interstate rail infrastructure and related assets; and
- Management, through a lease, of those sections of the Victorian standard gauge network and related assets that form part of the interstate corridors.
The company's main responsibilities include the provision of equitable access arrangements to the rail network it manages, the provision of train pathway planning services, the provision of a train control function for all trains operating over the network, and the management of a capital investment and infrastructure maintenance program.
ARTC's assets include in excess of 4,400 kms of standard gauge track and associated rail and communications infrastructure, linking the extremities of Parkeston (WA), Whyalla (SA), Broken Hill (NSW), Alice Springs (NT) and Wolesley (Vic.). Leased assets in Victoria (a further 830 kms) extend this asset beyond Wolesley into Melbourne and further on to Albury (NSW/Vic border).
The Problem
Identification and assessment of the physical conditions causing wheel and rail noise during the movement of trains on a rail network. Under certain conditions, rail wheels on trains cause audible sounds (squeals) as the wheel makes contact with rail. The wheel appears to act as a resonator of sound (bell). This phenomenon is often observed on sections of the interstate rail network in the Adelaide Hills area. Previous studies have identified a stick-slip friction cycle as the likely trigger mechanism..
Background
Significant research into noise emanating from what is known as the 'wheel-rail interface' has been undertaken in the past (Grassie and Kalousec). In addition ARTC have commissioned a study (Vipac) of rail wheel noise in the Adelaide Hills region. Detailed measurements of 17 freight train passby events was undertaken adjacent to a curve in the Adelaide Hills track. Acoustical data showed that wheel squeal typically occurred at frequencies of between 2 and 8 kHz with each squeal lasting a few seconds. Maximum noise levels of between 90 and 100 dBA, generated by wheel squeal, near residential areas exceed the NSW EPA rail noise criteria by around 10 to 15 dBA and are likely to cause discomfort.
The various studies referred to below point to several possible sources of the noise. In particular, it is suggested that contact between the wheel flange and the rail will create a ringing noise consistent with resonance in the wheel. The propensity for a wheel to resonate may relate to wheel profile or to the extent to which it is out of shape. Another source of noise is squeal, caused by slippage of the wheel on the rail head. This problem may be exacerbated on curves where load bearing is uneven with less load on the outer wheels. Uneven wheel tracking on curves or because of faulty bogies may also contribute to this noise.
The Vipac study made several recommendations including:
- static impact response testing of train wheels and rail segments to determine the natural frequencies and vibration modes;
- application of a friction modifier such as a flange lubricator on the wheel or tape on the rail;
- application of damping materials such as plate dampers or rubber elements on wheels;
- modification of wheel and rail profiles; and
- improved maintenance of wheels, bogies and rails.
Project Objectives
The tasks for the MISG team can be stated as follows:
- identify the source and cause of the wheel and track noise via a frequency analysis;
- develop models for vibration of the wheel-rail system which can be used to validate the source of the noise; and
- analyse the models and develop strategies to mitigate the noise.
References
Vipac Engineers & Scientists Ltd, May 1999, Freight Train Wheel Squeal Noise Assessment, A consultant's report for ARTC.
Grassie, S. & Kalousek, J., `Rolling Contact Fatigue of Rails: Characteristics, Causes and Treatments', source unknown.
Jones, C. J. C. 1996, `Reduction of noise and ground vibration from freight trains', selected papers presented at S-Tech - a conference on railway speed-up technology, I. of Mech. E. conference transactions 1996-8, Birmingham, pp. 87-97.
Kerr, M., and Lak, A. `Wheelsqueal Problems Solved: a Trackside Solution', source unknown.
Cervello, S., Lucchini, C. & Bracciali A. 1997, `Development of a Vibro-Acoustical Methodology for the Design and Validation of Low Noise Railway Wheel', World Congress on Railway Research, Florence 1997.