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Assessment of the influence of railway track periodicity, load speed and support modelling on the rolling noise emission
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0001-5760-3919
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The presented methodology jointly accounts for the railway track periodicity and the moving load nature at noise predictions. This modelling approaches rail and sleepers employing the Timoshenko beam theory, and it is formulated to be directly implemented into noise software based on irregularity strip technique. By means of precalculated time domain responses with an analytical track model, the periodicity and moving track dynamics are addressed. In the same way, the propagative behaviour in moving conditions of waves along the rail is characterised by comparison of the responses at several positions.Regarding track support modelling, the usual point modelling is substituted by a distributed representation in order to explore the advantages of accounting for the support length. A numerical model fulfils this task and avoids boundary effects utilising infinite elements. Distributed modelling achieves a more realistic representation of the track geometry. It prevents exaggeration of the amplitude at the `pinned-pinned' frequencies without resorting to overestimation of the steel loss factors. This improvement is especially useful when overvalued rail damping leads to predicted track decay rate (TDR) higher than the one experimentally measured.Finally, the impact of periodicity, load speed and support modelling are assessed through the sound power level (SWL) results.  The predictions are performed with a software package, CRoNoS (CAF Rolling Noise Software), developed by CAF S.A. Moving conditions has a limited impact on the SWL, while modelling of the foundation as periodic is important at tracks with hard pad types, and distributed support modelling becomes significant when realistic values of the steel loss factor are used.

Keywords [en]
Rolling noise, Moving load, Periodic foundation, Distributed support, Steel loss factor
National Category
Mechanical Engineering
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-244296OAI: oai:DiVA.org:kth-244296DiVA, id: diva2:1289617
Note

QC 20190220

Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2019-02-20Bibliographically approved
In thesis
1. Development of new techniques for the numerical modelling of railway track dynamics. Application to rolling noise assessment
Open this publication in new window or tab >>Development of new techniques for the numerical modelling of railway track dynamics. Application to rolling noise assessment
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The numerical modelling is widely employed for the prediction of the railway track dynamic behaviour, which is of utmost importance for the characterisation of the undesired medium-high frequency phenomena, such as corrugation, wheel-out-of-roundness and noise emission. This study is devoted to the improvement of railway track numerical modelling, the efficient resolution of the problem in the time domain and the assessment of rolling noise for different approaches of the track modelling.

Regarding the enhancement of the railway track numerical modelling, two main core ideas have led the development of this task. On the one hand, the rail modelling, and on the other hand, the characterisation of the finite length nature of track supports. The proposals of this work include two basic premises, accuracy and computational efficiency.

Firstly, the study makes use of Timoshenko beam theory for the numerical description of the rail. However, the conventional Timoshenko finite element involves drawbacks for the description of the rail dynamic behaviour and the calculation of the wheel-rail interaction in the time domain. These problems are addressed by improving the finite element formulation, which is based on the description of its local displacements.

Secondly, the versatility of numerical methods is exploited to develop a distributed model of support. It substitutes the usual concentrated model, which entails overestimation of the periodicity effects and disruption of the wheel-rail interaction in the time domain.

Thirdly, the advantages of the formulation of numerical models in the frequency domain are explored focusing on the ability to fairly describe the sleeper dynamics, the enhancement of the model boundaries and the realistic modelling of the track components dissipative behaviour. Moreover, the frequency domain response can be used to obtain the wheel-rail interaction in the time domain efficiently, by means of the moving Green's function.

Lastly, this work deals with the assessment of rolling noise, in which particular emphasis is made on the influence of track dynamics in the noise prediction. At this regard, a methodology is proposed to account for the track periodicity, load speed and finite length of supports.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 158
Series
TRITA-SCI-FOU ; 2019:07
Keywords
Track modelling, Timoshenko element, local deformation, distributed supports, moving Green's functions, rolling noise
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-244379 (URN)978-91-7873-102-2 (ISBN)
Public defence
2019-03-15, Salón de Grados, Paseo Manuel Lardizábal, 13, San Sebastián, Spain, 11:00 (English)
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Note

QC 20190220

Available from: 2019-02-21 Created: 2019-02-20 Last updated: 2019-02-21Bibliographically approved

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Blanco, BlasKari, Leif

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