| 1. |
- Fabre, François, et al.
(författare)
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Sound Radiation from Railway Wheels including Ground Reflections: A half-space formulation for the Fourier Boundary Element Method
- 2021
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 493
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Tidskriftsartikel (refereegranskat)abstract
- Current models for the acoustic radiation from railway wheels assume free field radiation. However, slab tracks are increasingly used for new railway lines. The acoustically hard surface of those tracks makes a re-evaluation of the free field assumption relevant, as such a surface can affect the radiation efficiency of an acoustic radiator. The wheel as the acoustic radiator is most conveniently described in a cylindrical coordinate system, thus making use of its axisymmetry. While this is a viable solution for the structural vibrations, for instance by using the curved Waveguide Finite Element formulation, the axisymmetry breaks when including a reflective plane in the calculation of the acoustic radiation. A convenient method to include an infinitely large, reflective plane is by using half-space Green’s functions in combination with the Boundary Element method. This method can be formulated in cylindrical coordinates using the Fourier series BEM (FBEM). However, the FBEM has not yet been combined with half-space Green’s functions. This paper provides a half-space formulation for the FBEM, which enables e.g. the evaluation of sound radiation of railway wheels over reflective surfaces. Finally, it is shown that the assumption of free field radiation for railway wheels is valid, as there is no major contribution of the reflective plane to the radiation efficiency of the wheel. The developed method is validated against laboratory measurements as well as analytical models.
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| 2. |
- Kropp, Wolfgang, 1959, et al.
(författare)
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The application of dither for suppressing curve squeal
- 2019
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Ingår i: Proceedings of the International Congress on Acoustics. - 2226-7808 .- 2415-1599. ; 2019-September, s. 1551-1558
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Konferensbidrag (refereegranskat)abstract
- Curve squeal is a highly disturbing tonal sound generated by vehicles like railways, metros or trams, when negotiating a sharp curve. The probability that squeal occurs increases with reduced curve radius of the track. Curve squeal noise is attributed to self-excited vibrations caused by stick/slip behaviour due to lateral creepage of the wheel tyre on the top of the rail. With respect to the enormous number of the rolling stock units and the long lifetime of waggons there is an urgent need for a cheap and simple retrofitting measure to reduce curve squeal. The main objective of the paper is therefore to investigate the potential to reduce curve squeal by means of active control in the form of dither in an efficient and robust way. Dither control has been applied in the field of mechanical engineering for systems including non-linear components. There it has been shown to suppress self-excited oscillations very efficiently. The control is an open loop control. It consists in adding a forced vibration to the vibrational system. The demand on this additional signal is that it is higher in frequency than the friction-induced response. From a physical point of view, dither control modifies the effective friction characteristic.
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| 3. |
- Kropp, Wolfgang, 1959, et al.
(författare)
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The application of dither to mitigate curve squeal
- 2021
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 514
-
Tidskriftsartikel (refereegranskat)abstract
- Curve squeal is a highly disturbing tonal sound generated by rail vehicles like trains, metros or trams, when negotiating a sharp curve. The probability that squeal occurs increases with reduced curve radius of the track. Curve squeal noise is attributed to self-excited vibrations caused by stick/slip behaviour due to lateral creepage of the wheel tyre on the top of the rail. With respect to the large number of rolling stock units and the long lifetime of vehicles, there is an urgent need for a cheap and simple retrofitting measure to reduce curve squeal. Therefore, main objective of this paper is to investigate the potential to reduce curve squeal by means of active control in the form of dither in an efficient and robust way. Dither control has been applied in the field of mechanical engineering for systems including non-linear components. There it has been shown to suppress self-excited oscillations very efficiently. The control is an open-loop control. It consists in adding a forced vibration to the vibrational system. A time-domain model has been applied to investigate the mechanisms behind self-excited vibrations leading to curve squeal at the squealing noise rig at Chalmers University of Technology. The analysis showed, that in the presence of constant friction, the coupling between lateral and vertical direction is the driving mechanism for building up self-excited vibrations. Based on this insight, the potential of dither has been investigated. For the case considered here dither has the potential to reduce the overall kinetic energy on the wheel by more than 10 dB and on the rail by more than 20 dB. Further optimisation of dither forces with respect to the radiated sound power might increase this potential.
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| 4. |
- Pieringer, Astrid, 1979, et al.
(författare)
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Transient Modelling of Curve Squeal Considering Varying Contact Conditions
- 2024
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Ingår i: Lecture Notes in Mechanical Engineering. - : Springer. - 2195-4356 .- 2195-4364. ; 14th International Work-shop on Railway Noise, IWRN 2022, s. 491-499, s. 491-499
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Konferensbidrag (refereegranskat)abstract
- Modelling railway curve squeal poses a challenge since the phenomenon is non-linear, transient and complex. This work focusses on the transient effects of varying contact parameters on curve squeal. A previously developed high-frequency tool for the simulation of curve squeal in the time domain during quasi-static curving is extended to account for transient curving and connected to a software for the low-frequency vehicle dynamics. An application of the model demonstrates that time-varying contact parameters such as contact position, lateral creepage, and friction coefficient can lead to an on-and offset of squeal. The history of the wheel/rail dynamics can also have an influence on the occurrence of squeal and the selection of the squeal frequency.
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| 5. |
- Theyssen, Jannik, 1991, et al.
(författare)
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A time-domain model for railway rolling noise
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The poster presents a modelling approach for railway rolling noise prediction developed at Chalmers during a recent PhD project. Rolling noise, which is caused by the roughness-excited vibration of the wheel and the track, is the dominant noise source in a wide range of vehicle speeds. The presented modelling approach is based on the time-domain, non-linear contact model WERAN. The model has been extended with a numerically efficient description of the structural vibration of the wheel and the track based on moving Green's functions. Further, efficient models for the sound radiation from the wheel and track were developed and implemented, again using a Green's functions approach. The Green's functions are computed using combinations of the Waveguide Finite Element method (2.5D FE), the Wavenumber domain Boundary Element Method (WBEM / 2.5D BE), the Fourier domain BEM (FBEM), and spherical harmonics equivalent sources. This model provides a physics-based, time-domain description of the radiated sound based on the combined roughness between the wheel and the rail. There are several possible applications for a time-domain rolling noise model, for example in component design, condition monitoring, and, by auralising the noise, as an effective tool for communication with a broader public.
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| 6. |
- Theyssen, Jannik, 1991, et al.
(författare)
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Calibration and validation of the dynamic response of two slab track models using data from a full-scale test rig
- 2021
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 234
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Tidskriftsartikel (refereegranskat)abstract
- For the development of accurate and reliable simulation models, the procedure of calibration and validation against measurement data is essential. In this paper, a finite element model and a waveguide finite element model of a slab track are calibrated and validated against hammer impact measurement data from a full-scale test rig. The finite element model is three-dimensional, where the rails are modelled as Rayleigh–Timoshenko beams and the concrete slab and support layer are modelled using linear shell elements. In the waveguide finite element model, a constant track cross-section described by two-dimensional finite elements is assumed, and the vibration in the direction perpendicular to the cross-section is described by propagating waves that are decaying exponentially. Measured frequency response functions (FRFs) are compared with the corresponding calculated FRFs from the two modelling approaches. The calibration is conducted in two steps using (i) a parameter study and (ii) a genetic algorithm. For multiple excitation positions and sensor locations, both calibrated models capture the trend of the Single-Input Multiple-Output measurements with rather small deviations compared to the overall dynamic range. This implies that both models can successfully represent the dynamic response of the test rig and can be considered as validated.
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| 7. |
- Theyssen, Jannik, 1991, et al.
(författare)
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Efficient calculation of the three-dimensional sound pressure field around a railway track
- 2022
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The wavenumber domain Boundary Element method (or 2.5D BE) is well suited for calculating the acoustic sound field around structures with a constant cross-section along one dimension, such as noise barriers or railway tracks. By expressing the sound field along this dimension in the wavenumber domain, the numerical model is reduced from a 3D model to a 2D model at each wavenumber. A consequence of the required discrete Fourier domain representation is that the sound field is represented by periodically repeating sections, of which only one section is physically meaningful. The resolution and the number of required wavenumbers increase with this section's desired length and spatial discretization. Describing the sound field adequately to auralising the sound field without disturbing artefacts requires a large number of wavenumbers (and thus 2D BE computations), which is not feasible for large geometries. Here, a method is introduced that allows the calculation of the 3D sound field by solving a single 2D BE problem for a dense frequency spectrum and interpolating at a higher wavenumber. The calculation efficiency is further increased by pre-calculating the acoustic transfer functions between each BE surface element and receiver positions. Combining these two methods allows the efficient calculation of the 3D sound field. The numerical approach is validated compared to a standard 2.5D BEM calculation and an analytical model. Pre-calculated transfer functions to calculate the sound radiation from railway tracks are presented and made available online.
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| 8. |
- Theyssen, Jannik, 1991, et al.
(författare)
-
Efficient calculation of the three-dimensional sound pressure field around a slab track
- 2024
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Ingår i: Acta Acustica. - 2681-4617 .- 1022-4793. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The wavenumber domain Boundary Element (2.5D BE) method is well suited to calculate the acoustic sound field around structures with a constant cross-section along one dimension, such as noise barriers or railway track. By expressing the sound field along this dimension in wavenumber domain, the numerical model is reduced from a 3D model to 2D model at each wavenumber. A consequence of the required discrete Fourier domain representation is that the sound field is represented by periodically repeating sections, of which only one section is physically meaningful. The resolution and the number of required wavenumbers increases with the desired length and spatial discretisation of this section. Describing the sound field adequately to auralise the sound without disturbing artefacts requires a large number of wavenumbers (and thus 2D BE computations), which is not feasible for large geometries. Here, a method is introduced that allows the calculation of the 3D sound field by solving a single 2D BE problem for a dense frequency spectrum and interpolating at higher wavenumbers. The calculation efficiency is further increased by precalculating the acoustic transfer functions between each BE surface element and receiver positions. Combining these two methods allows for efficient calculation of the 3D sound field around acoustically rigid structures such as slab tracks. The numerical approach is validated by comparison with a standard 2.5D BEM calculation and an analytical solution. Precalculated transfer functions to calculate the sound radiation from railway track, which are made available online, are illustrated. An example application is presented.
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| 9. |
- Theyssen, Jannik, 1991
(författare)
-
Modelling the acoustic performance of slab tracks
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transport is a major contributor to anthropogenic greenhouse gas emissions. Railway transport has a small footprint compared to other means of transport. This is one reason for the construction of new high-speed railway lines world-wide. These lines are often constructed using slab track technology, in which the traditional track configuration of concrete sleepers and ballast is replaced by concrete slabs. In earlier work, it has been found that traffic on slab tracks has higher noise emissions than on ballasted tracks. Rolling noise, radiated from wheels and track, is an important contributor to these noise emissions. To predict the acoustic performance of slab tracks, first, a model for the high-frequency vibration in these tracks is necessary, for which there is currently no standard solution. Further, the effect of the reflective slab track surface on the wheel radiation has not been researched. In this work, a model for the high-frequency vibrations and acoustic radiation of slab tracks has been developed and implemented. The validity of the dynamic model has been tested on a full-scale test rig. The developed model was then used for researching the influence of track parameters on noise emission. In this investigation, the rail pad stiffness was identified to have a major influence. Besides, a model for the sound radiation of railway wheels over hard reflective surfaces was developed, implemented, and validated. The effect of the slab track surface on the radiation efficiency of the vibrating wheel was evaluated and found negligible. The developed models are steps towards predicting the rolling noise generated by rail vehicles on slab tracks, which is significant both for the planning of new lines and the investigation of potential abatement measures.
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| 10. |
- Theyssen, Jannik, 1991, et al.
(författare)
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On the efficient simulation of pass-by noise signals from railway wheels
- 2023
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Ingår i: Journal of Sound and Vibration. - 1095-8568 .- 0022-460X. ; 564
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Tidskriftsartikel (refereegranskat)abstract
- The article presents an approach for calculating pass-by sound pressure radiated from railway wheels in the time domain using moving Green's functions. The Green's functions are obtained by using Finite Element (FE) and Boundary Element (BE) methods in the frequency domain, subsequent inverse Fourier transform, followed by convolution with a time series of rolling contact forces to obtain the pass-by time signals. However, traditional BE methods are computationally expensive due to the low structural damping of the wheel, necessitating a high frequency resolution. To overcome this issue, a modal approach is introduced in which the pass-by sound radiated by each wheel mode is calculated separately. This approach incorporates the dynamic response of the wheel in the time-domain processing and thus reduces the cost of the BE solution. A modal source signal is introduced to describe the excitation of each mode at each time step. The sound field radiated by unit modal amplitudes is calculated in BE and subsequently approximated by spherical harmonic (SH) equivalent sources, which allows for efficiently calculating acoustic transfer functions for varying relative positions of the wheel and a stationary receiver. Convolution of the source signal with the moving acoustic transfer function produces the pass-by pressure signal. The article investigates the directivity of the radiation from each mode and finds that most modes, including those with dominant radial deflection, radiate in mostly axial direction at high frequencies. Modes that dominate the pass-by pressure level are identified, both in frequency bands and with respect to the relative positioning of the wheel to the receiver. Finally, it is found that an SH expansion order of approximately 30 is required to satisfy the employed error measures, although lower orders may suffice for an auralisation of the signal.
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