| 1. |
|
|
| 2. |
- Blanco, Blas, et al.
(författare)
-
Assessment of the influence of railway track periodicity, load speed and support modelling on the rolling noise emission
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 3. |
- Casanueva, Carlos, 1981-
(författare)
-
Análisis dinámico de un eje de ferrocarril con capacidad de cambio de ancho automático
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- El objetivo de la presente tesis es la mejora de los actuales ejes de ancho variable para su circulación por vías de alta velocidad (AV) a velocidades de hasta 300km/h. En la actualidad los vehículos con ejes de ancho variable no sobrepasan los 250km/h de velocidad de servicio en vías de AV, lo que supone un claro desaprovechamiento de recursos y dificultades de gestión del tráfico para el gestor de la infraestructura a causa de las distintas velocidades punta de los diferentes trenes. Los modelos ferroviarios convencionales no tienen en cuenta la flexibilidad asociada a los ejes y suponen que éstos son lo suficientemente rígidos como para no necesitar una modelización que tenga en cuenta su deformación estructural. Sin embargo, en los ejes de ancho variable, que poseen tanto mecanismos que permiten el desplazamiento lateral de rueda respecto al cuerpo de eje como mecanismos de bloqueo de dicho desplazamiento, tienen influencia diversas holguras, rozamiento entre superficies, y componentes intermedios entre ruedas y cuerpo de eje. Estos efectos provocan una flexibilización de la conexión entre ruedas y cuerpo de eje que es necesario estudiar. Por otra parte, en el caso de los ejes de ancho variable de cuerpo de eje no rotativo sus menores solicitaciones a fatiga permiten una importante reducción del diámetro del cuerpo de eje. Esto provoca una flexibilidad adicional muy superior a la de los ejes convencionales. Para el estudio de la influencia de este aumento de flexibilidad en el comportamiento dinámico del eje, en primer lugar se determina qué tipo de modelo permite la correcta representación de los efectos presentes en los análisis dinámicos. Además, se analiza en profundidad el comportamiento del eje de ancho variable, para facilitar el posterior estudio y simplificaciones, así como identificar los componentes críticos del mecanismo. En segundo lugar se calculan las relaciones esfuerzo-deformación para los distintos componentes del sistema: conjunto de rodamientos, cuerpo de eje, mecanismos de anclaje, etc. Dichas características se introducen en un modelo multicuerpo simplificado que es capaz de representar tanto ejes de ancho variable flexibles como ejes convencionales flexibles. Por último se realiza un análisis de la influencia de dichas características en el comportamiento dinámico del vehículo, así como el grado de influencia de cada una de ellas. Además se proponen posibles mejoras del sistema para mejorar sus prestaciones a altas velocidades.
|
|
| 4. |
|
|
| 5. |
- Casanueva, Carlos, 1981-, et al.
(författare)
-
Influence of Bearing Flexibility in Rail Vehicle Dynamics
- 2015
-
Ingår i: The international Journal of railway technology. - Edinburgh : Civil-Comp Press. - 2049-5358 .- 2053-602X. ; 4:1, s. 47-67
-
Tidskriftsartikel (refereegranskat)abstract
- Dynamic multibody models for railway vehicles usually assume that the stiffness of the bearings is much higher than that of the primary suspension, neglecting their effect whatsoever. This assumption might not be entirely valid for high speed vehicles, where the primary suspension is stiffer than other rail vehicles; or for more complex systems such as variable gauge wheelsets, where the whole mechanic system might have a higher than expected flexibility. In this paper, a model to obtain the stiffness of a typical configuration of railway bearings is developed and applied to both a high speed vehicle bearing set and a variable gauge wheelset bearing set. The results show that the reduction of lateral stiffness as a result of bearing flexibility can reach up to 35% of its theoretical value. This massive reduction has a major influence on the prediction of the dynamic behaviour of these vehicles, e.g. critical speed or curving performance.
|
|
| 6. |
- Casanueva, Carlos, 1981-, et al.
(författare)
-
Simple flexible wheelset model for low-frequency instability simulations
- 2014
-
Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : Sage Publications. - 0954-4097 .- 2041-3017. ; 228:2, s. 169-181
-
Tidskriftsartikel (refereegranskat)abstract
- As a general rule, the multi-body simulation models used by railway vehicle designers consider the wheelsets to be fully rigid, thus leading to possible errors when calculating the critical speed of the vehicle under study. This article suggests a wheelset model that takes into account wheelset flexibility for the study of dynamic stability. The model is simple to implement, easily parameterised, and can be applied to both conventional and variable gauge wheelsets. The parameters corresponding to wheelset flexibility that most influence the critical speed of high-speed and variable gauge vehicles are also analysed.
|
|
| 7. |
- Casanueva, Carlos, 1981-, et al.
(författare)
-
The Influence of Bearing Flexibility on High Speed Vehicles
- 2012
-
Ingår i: Proceedings of the First International Conference on Railway Technology. - Stirlingshire, UK : Civil-Comp Press. ; , s. Paper 25-
-
Konferensbidrag (refereegranskat)abstract
- Railway multibody models usually ignore the flexibility of the rolling bearings, assuming that it is much smaller than the flexibility of the primary suspension elements. However, this assumption is not necessarily valid for high speed vehicles, which have a much stiffer primary suspension. In this paper a model to obtain the stiffness parameters of a typical configuration of railway bearings is developed and applied to a high speed vehicle bearing system.In this paper a bearing model has been developed, which takes into account the real geometry of the bearings and races for a more precise calculation of the forces transmitted through the different contact patches.It has been demonstrated that the interaction of rollers and races can never be considered as Hertzian contact, as the shape of the contact area goes from ellipsoidal to trapezoidal as the load increases, including a mixed contact shape when only one of the roller end is in contact with the race. Hertzian contact implies a unique type of contact through all the loading cases, with a loss of precision in the areas where it does not behave in this way. The methodology has been applied to a bearing set used in high speed vehicles, with the following results:The stiffness matrix of the bearing set has been obtained. Individual stiffness values are highly dependent on the mounting clearance. A priori, this dependence cannot be neglected for high speed dynamic analyses.The inclusion of bearing stiffness in a high speed vehicle can affect the theoretical values of the primary suspension, i.e. reduce longitudinal stiffness up to 10% or lateral stiffness up to 32%. This effect will decrease the dynamic stability of the vehicle.It can also affect the transmission of the lateral force, displacing the lateral force position closer to the wheelset axis. This effect, which is positive for the dynamic behaviour of the vehicle, is negligible for the stiffness values of the primary suspension and the bearing set of the studied vehicle.Moreover, a polyvalent and adaptable bearing model has been developed that allows the calculation of various characteristics and variables. This model can be further used for other studies that need individual roller characteristics, such as contact geometry or maximum pressures in the races.
|
|
| 8. |
- Conde Mellado, Alberto, et al.
(författare)
-
A lateral active suspension for conventional railway bogies
- 2009
-
Ingår i: Vehicle System Dynamics. - : Taylor & Francis. - 0042-3114 .- 1744-5159. ; 47:1, s. 1-14
-
Tidskriftsartikel (refereegranskat)abstract
- The present paper describes an active centring system for railway vehicles. The proposed solution is based on lateral pneumatic actuators placed between bogie and car body connected to the vertical secondary suspension air springs. The objective of the developed centring system is twofold: the improvement of the curving behaviour of the train and the decrease of the lateral acceleration perceived by the passenger in curve negotiation thanks to the reduction of the ‘souplesse’ coefficient. The system is described in detail in the paper. Results from simulations are included considering a bidimensional model of the vehicle, and a detailed model of the air spring and control valves. The performance in curve negotiation of a vehicle equipped with this system and a conventional one is compared. Specifically, lateral displacements of the secondary suspension, roll angle and lateral accelerations are analysed. The results show noticeable performance improvements in the vehicle curving behaviour. The proposed centring system can be implemented in a conventional bogie without special design requirements; and due to the low air consumption, additional pressurised reservoirs are not required.
|
|
