Time-domain modelling of curve squeal: a fast model for one- and two-point wheel/rail contact
Doktorsavhandling, 2017

Curve squeal is a type of railway noise that may arise when a railway vehicle negotiates a relatively tight curve. A single frequency, corresponding to a wheel mode, dominates the radiated sound, which makes squeal a very tonal noise. The high number of tight curves in cities and urban areas, its tonal nature and high noise levels make squeal a significant source of noise pollution. The rising awareness of the impact of noise on public health increases the need to address the squeal problem. Consequently, there is an increased need for practical simulation tools. In this thesis, a computationally fast squeal model formulated in the time domain is proposed. The computational efficiency is achieved by modelling the tangential contact with a point-contact model, which considers the contact variables globally. The friction model and the contact compliance are defined in a rigorous manner using Kalker's variational theory. Validation results show that the contact model is valid up to at least 5 kHz. The proposed model is further extended to include the effects of spin creepage, contact angle and two-point wheel/rail contact. Spin creepage is treated as a contact property with its influence included in the friction model. Additionally, the model is also extended with an existing model for sound radiation from the railway wheel. Parameter studies show a strong influence of parameters that influence the dynamics coupling responsible for squeal: the contact angle, friction and the wheel/rail contact position. These parameters influence both squeal occurrence, amplitudes and frequency. Spin, however, influences only squeal amplitudes. With the wheel being a significant factor in curve squeal, the influence of the wheel modal damping is also investigated. To mitigate squeal in a specific case, all modes that are susceptible to squeal in that case have to be damped. Otherwise, squeal may shift to another mode and develop even higher amplitudes. The amount of modal damping required to prevent squeal is relatively low. Finally, a two-point wheel/rail contact case is analysed. Results show that squeal can occur on curve-outer wheels. The two-point-contact case is relatively complicated: squeal is the result of a combination of the dynamic interplay of the two contact points and the presence of two closely spaced wheel modes.

tangential point-contact model

non-Hertzian contact

Curve squeal

time domain

two-point contact

rolling contact

dynamics coupling

frictional instability

SB-H4, Sven Hultins gata 6, Chalmers
Opponent: Prof. David J. Thompson, ISVR, University of Southampton, UK

Författare

Ivan Zenzerovic

Chalmers, Bygg- och miljöteknik, Teknisk akustik

Towards an engineering model for curve squeal

Notes on Numerical Fluid Mechanics and Multidisciplinary Design,; Vol. 126(2015)p. 433-440

Paper i proceeding

An engineering time-domain model for curve squeal: Tangential point-contact model and Green's functions approach

Journal of Sound and Vibration,; Vol. 376(2016)p. 149-165

Artikel i vetenskaplig tidskrift

Zenzerovic, I., Kropp, W., Pieringer, A. Influence of spin creepage and contact angle on curve squeal: a numerical approach

Zenzerovic, I., Kropp, W., Pieringer, A. Time-domain investigation of curve squeal in the presence of two wheel/rail contact points

Nowadays, more people live in large urban areas than ever before. The urban population is steadily growing and so are cities. This growth leads to more traffic and, in particular, more people using public transport for daily commutes. Trams and metro systems are popular means of city transport. However, they do not come without consequences: railway noise levels are often high and disruptive.

Curve squeal is a kind of railway noise that develops in tight curves. By nature, curve squeal is tonal and usually very loud which, in combination, make it very disturbing. Since the incidence of tight curves is highest in cities and urban areas, squeal affects many people. But besides than being just a disturbance, squeal also negatively affects public health. Therefore, high importance is laid on its prevention.

Squeal has to be first well understood before it can be prevented. Engineers must be able to simulate squeal events to identify its characteristics, severity and what influences it. To enable engineers to better understand and evaluate squeal, tools for its simulation are needed. Such a tool is developed in this thesis. It can simulate a wide range of cases and is suitable for everyday engineering use. Different squeal events and even the application of squeal prevention measures can be analysed.

The proposed tool is a significant step towards a squeal simulation package suitable for the railway industry. It can also facilitate further advances in the understanding of squeal. In the long term, the improved knowledge on curve squeal will lead to better practical squeal prevention measures.

Ämneskategorier

Maskinteknik

Farkostteknik

Strömningsmekanik och akustik

Styrkeområden

Transport

ISBN

978-91-7597-647-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4328

Utgivare

Chalmers tekniska högskola

SB-H4, Sven Hultins gata 6, Chalmers

Opponent: Prof. David J. Thompson, ISVR, University of Southampton, UK