| 1. |
- Pieringer, Astrid, 1979
(författare)
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A numerical investigation of curve squeal in the case of constant wheel/rail friction
- 2014
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 333:18, s. 4295-4313
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Tidskriftsartikel (refereegranskat)abstract
- Curve squeal is commonly attributed to self-excited vibrations of the railway wheel, which arise due to a large lateral creepage of the wheel tyre on the top of the rail during curving. The phenomenon involves stick/slip oscillations in the wheel/rail contact and is therefore strongly dependent on the prevailing friction conditions. The mechanism causing the instability is, however, still a subject of controversial discussion. Most authors introduce the negative slope of the friction characteristic as a source of the instability, while others have found that squeal can also occur in the case of constant friction due to the coupling between normal and tangential dynamics. As a contribution to this discussion, a detailed model for high-frequency wheel/rail interaction during curving is presented in this paper and evaluated in the case of constant friction. The interaction model is formulated in the time domain and includes the coupling between normal and tangential directions. Track and wheel are described as linear systems using pre-calculated impulse response functions that are derived from detailed finite element models. The nonlinear, non-steady state contact model is based on an influence function method for the elastic half-space. Real measured wheel and rail profiles are used. Numerical results from the interaction model confirm that stick/slip oscillations occur also in the case of constant friction. The choice of the lateral creepage, the value of the friction coefficient and the lateral contact position on the wheel tread are seen to have a strong influence on the occurrence and amplitude of the stick/slip oscillations. The results from the interaction model are in good qualitative agreement with previously published findings on curve squeal.
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| 2. |
- Pieringer, Astrid, 1979, et al.
(författare)
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A time-domain model for coupled vertical and tangential wheel/rail interaction - a contribution to the modelling of curve squeal
- 2012
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Ingår i: Notes on Numerical Fluid Mechanics and Multidisciplinary Design. - Tokyo : Springer Japan. - 1612-2909 .- 1860-0824. ; 118, s. 221-229
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Konferensbidrag (refereegranskat)abstract
- Lateral forces due to frictional instability are seen as the main reason for the occurrence of curve squeal. Predicting squeal requires thus to describe the high-frequency wheel/rail interaction during curving including the coupling between vertical and lateral directions. In this article, a time-domain approach is presented which includes both vertical and lateral forces and takes into account the non-linear processes in the contact zone. Track and wheel are described as linear systems using pre-calculated impulse response functions. The non-linear, non-steady state contact model is based on an influence function method for the elastic half-space, includes a velocity-dependent friction coefficient and accounts for surface roughness. First results from the interaction model demonstrate the functioning of the approach.
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| 3. |
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| 4. |
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| 5. |
- Pieringer, Astrid, 1979, et al.
(författare)
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Investigation of the dynamic contact filter effect in vertical wheel/rail interaction using a 2D and a 3D non-Hertzian contact model
- 2011
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 271:1-2, s. 328-338
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Tidskriftsartikel (refereegranskat)abstract
- Rolling noise is excited by the roughness of the wheel/rail running surfaces. The contact patch acts as a filter attenuating the excitation at wavelengths that are short in comparison with its length. Additionally, the excitation depends on the variations in roughness profile height across the width of the contact. While most available wheel/rail interaction models include the contact filter effect by roughness pre-processing, a time-domain model is presented in this paper that includes the contact filter effect dynamically by an appropriate two-dimensional (2D) or three-dimensional (3D) non-Hertzian contact model. The 2D contact model is based on a Winkler bedding, while wheel and rail are locally approximated by elastic half-spaces in the 3D contact model. The wheel/rail interaction model is applied to evaluate the contact filter effect for different sets of roughness data measured in several parallel lines. It is found that the 3D contact model gives, as a general tendency, a contact force level several dB lower than the 2D model. The differences increase with a decrease in correlation between the roughness on parallel lines and vary significantly with the choice of roughness line in the 2D model.
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| 6. |
- Pieringer, Astrid, 1979
(författare)
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On the modelling of wheel/rail noise
- 2013
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Ingår i: AIA-DAGA 2013 Conference on Acoustics, Meran, Italy, March 18-21, 2013.
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Konferensbidrag (refereegranskat)
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| 7. |
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| 8. |
- Pieringer, Astrid, 1979, et al.
(författare)
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The influence of contact modelling on simulated wheel/rail interaction due to wheel flats
- 2014
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 314:1-2, s. 273-281
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Tidskriftsartikel (refereegranskat)abstract
- Most available wheel/rail interaction models for the prediction of impact forces caused by wheel flats use a Hertzian spring as contact model and do not account for the changes in contact stiffness due to the real three-dimensional wheel flat geometry. In the literature, only little information is available on how this common simplification influences the calculation results. The aim of this paper is to study the influence of contact modelling on simulated impact forces due to wheel flats in order to determine the errors introduced by simplified approaches. For this purpose, the dynamic wheel/rail interaction is investigated with a time-domain model including a three-dimensional (3D) non-Hertzian contact model based on Kalker's variational method. The simulation results are compared with results obtained using a two-dimensional (2D) non-Hertzian contact model consisting of a Winkler bedding of independent springs or alternatively a single non-linear Hertzian contact spring. The relative displacement input to the Hertzian model is either the wheel profile deviation due to the wheel flat or the pre-calculated vertical wheel centre trajectory. Both the 2D model and the Hertzian spring with the wheel centre trajectory as input give rather similar results to the 3D model, the former having the tendency to slightly underestimate the maximum impact force and the latter to slightly overestimate. The Hertzian model with the wheel profile deviation as input can however lead to large errors in the result. Leaving aside this contact model, the correct modelling of the longitudinal geometry of the wheel flat is actually seen to have a larger influence on the maximum impact force than the choice of contact model.
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| 9. |
- Pieringer, Astrid, 1979
(författare)
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Time-domain modelling of high-frequency wheel/rail interaction
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The interaction between wheel and rail is the predominant source of noise emission from railway operations in a wide range of conventional speeds. On the one hand, this wheel/rail noise concerns rolling noise and impact noise caused by the vertical interaction excited by roughness and discrete irregularities of the wheel/rail running surfaces, respectively. On the other hand, it concerns squeal noise generated by the tangential interaction due to frictional instability. The aim of this thesis is to develop a model for the combined vertical and tangential wheel/rail interaction induced by roughness, discrete irregularities or frictional instability. This is the main step in the formulation of a combined prediction model for the three different types of wheel/rail noise, which can be used as a design tool for noise reduction. In order to include the non-linearities in the contact zone, the interaction model presented in this thesis is formulated in the time domain. Wheel and track models are represented by Green’s functions, which leads to a computationally efficient formulation and allows the inclusion of detailed contact models. A two-dimensional (2D) vertical contact model consisting of a bedding of independent springs, and a three-dimensional (3D) vertical and tangential model based on an influence-function method for the elastic half-space, are considered. Non-Hertzian and transient effects are taken into account. In the thesis, the vertical interaction model has been applied for excitation by wheel/rail roughness and by wheel flats. In the former case, the model has been validated against existing established models. In the latter case, encouraging agreement with field measurements has been found. Results from simulations carried out with both the 2D and the 3D contact models for excitation by detailed measured roughness data indicate that significant errors may occur in the calculated contact forces, when the 3D roughness distribution is represented by the roughness on only one longitudinal line. The errors increase with a decrease in roughness correlation across the width of the contact. Frictional instabilities during curve negotiation have been investigated with the combined vertical/tangential interaction model. For both a constant friction law and a friction curve falling with the sliding velocity, stick/slip oscillations were observed. While the model is not yet considered completely reliable in the case of a falling friction curve due to the possibility of multiple solutions, the results in the case of constant friction are in good qualitative agreement with previouslypublished findings on curve squeal.
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| 10. |
- Torstensson, Peter, 1981, et al.
(författare)
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Simulation of rail roughness growth on small radius curves using a non-Hertzian and non-steady wheel-rail contact model
- 2012
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Ingår i: 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2012; Chengdu; China; 27 August 2012 through 30 August 2012. ; , s. 223-230
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Konferensbidrag (refereegranskat)abstract
- A time-domain model for the prediction of long-term rail roughness growth on small radius curves is presented. Both lowfrequency vehicle dynamics due to curving and high-frequency vehicle-track dynamics excited by short-wavelength rail irregularities are accounted for. The influence of non-Hertzian and non-steady effects in the wheel-rail contact model on rail wear is studied. The model features a refined contact detection algorithm that accounts for wheelset yaw angle as well as surface irregularities and structural flexibilities of wheelset and rail. The development of corrugation on a small radius curve is found to be highly influenced by the wheel-rail friction coefficient. For vehicle speed 25 km/h and friction coefficient 0.3, predictions of long-term roughness growth on the low rail generated by the leading wheelset show decreasing magnitudes in the entire studied wavelength interval. For friction coefficient 0.6, roughness growth is found at several wavelengths. The corresponding calculation for the high rail contact indicates no roughness growth generated by the trailing wheelset independent of friction coefficient. The importance of accounting for the phase between the calculated wear and the present rail irregularity is demonstrated.
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| 11. |
- Torstensson, Peter T, 1981, et al.
(författare)
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Simulation of rail roughness growth on small radius curves using a non-Hertzian and non-steady wheel–rail contact model
- 2014
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 314:1-2, s. 241-253
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Tidskriftsartikel (refereegranskat)abstract
- A time-domain model for the prediction of long-term growth of rail roughness (corrugation) on small radius curves is presented. Both low-frequency vehicle dynamics due to curving and high-frequency vehicle–track dynamics excited by short-wavelength rail irregularities are accounted for. The influence of non-Hertzian and non-steady effects in the wheel–rail contact model on rail wear is studied. The model features a contact detection method that accounts for wheelset yaw angle as well as surface irregularities and structural flexibilities of wheelset and rail. The development of corrugation on a small radius curve is found to be highly influenced by the wheel–rail friction coefficient. For vehicle speed 25 km/h and friction coefficient 0.3, predictions of long-term roughness growth on the low rail show decreasing magnitudes in the entire studied wavelength interval. For friction coefficient 0.6, roughness growth is found at several wavelengths. The corresponding calculation for the high rail contact of the trailing wheelset indicates no roughness growth independent of friction coefficient. The importance of accounting for the phase between the calculated wear and the present rail irregularity is demonstrated.
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| 12. |
- Torstensson, Peter, 1981, et al.
(författare)
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Towards a model for prediction of railway tread brake noise
- 2014
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Ingår i: The ISMA conference on Noise and Vibration Engineering (ISMA2014), 15 - 17 September 2014, Leuven. - 9789073802919 ; , s. 3543-3556
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Konferensbidrag (refereegranskat)abstract
- A model for complex linear stability analysis of railway tread brakes has been developed. It accounts forinertial effects due to wheel rotation as well as damping provided by tangential wheel–rail contact forces.Kinematic constraint equations are used to model the normal brake–wheel contact. For a brake–wheelfriction coefficient higher than 0.2, unstable vibrations develop for several system eigenmodes in thefrequency range above 6 kHz. The required level of brake–wheel friction at onset of instability isinfluenced by the wheel profile and the tangential wheel–rail contact damping. The present workconstitutes the first step in the development of a prediction model for railway tread brake noise.
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