| 1. |
- Alonso, Asier, et al.
(författare)
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Modelling of rough wheel-rail contact for physical damage calculations
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 436
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the initial steps given in order to obtain a comprehensive physical damage model for the specific case of wheel rail contact wear, which would be able to relate contact conditions, material properties and wear rates. The main advantage of a physical damage wear model is that wheelset and rail manufacturers can perform simulations in order to improve and optimise material properties for different operational cases. The work in this paper focuses on delaminative wear, starting with the importance and modelling of rough contact, and a comparison against classic smooth contact models.
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| 2. |
- Alonso, Asier, et al.
(författare)
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Physical damage mechanisms for uniform wear calculation
- 2018
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Ingår i: Proceedings of the 11th International Conference on Contact Mechanics and Wear of Rail/wheel Systems, CM 2018. - Delft, The Netherlands.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents the initial steps given in order to obtain a comprehensive physical model for the specific case of wheel rail contact, which would be able to relate contact conditions, material properties and wear rates. The main advantage of a physical damage wear model is that wheelset an rail manufacturers can perform simulations in order to improve and optimize material properties for different operational cases. The initial work has focused on delaminative wear, starting with the importance and modelling of rough contact, and a comparison against classic smooth contact models.
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| 3. |
- Blanco, Blas, et al.
(författare)
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Assessment of the influence of railway track periodicity, load speed and support modelling on the rolling noise emission
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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.
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| 4. |
- Blanco, Blas, et al.
(författare)
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Modelling of the track supports with elements over elastic foundation together with dynamic internal degrees of freedom
- 2018
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Ingår i: Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics2018, Pages 3255-326828th International Conference on Noise and Vibration Engineering, ISMA 2018 and 7th International Conference on Uncertainty in Structural Dynamics, USD 2018; Leuven; Belgium; 17 September 2018 through 19 September 2018. - : KU Leuven - Departement Werktuigkunde. - 9789073802995 ; , s. 3255-3268
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Konferensbidrag (refereegranskat)abstract
- Formulation of the Timoshenko elements is improved with the use of internal degrees of freedom (iDOF) representing the local displacements, leading to a new finite element approach specially devoted to the numeric analysis of the track dynamics. The dynamic formulation of the local displacement is proved to correct the frequency content of the track model. Regarding time domain studies, this approach avoids the displacement underestimation and shear discontinuity between elements, which are sources of inaccuracies and irregular behaviour. Those rail sections located above the supports are modelled with Timoshenko element over elastic foundation (TEEF), and the rest with conventional Timoshenko elements (TIM4). By using TEEF prompt disruption of the contact force at support surpassing is avoided, and the frequency response of the track around the `pinned-pinned' frequency is corrected. Moreover the TEEF formulation is extended in order to account for the sleeper pitch rotation, and evaluation of its influence over the track dynamics is performed.
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| 5. |
- Casanueva, Carlos, 1981-
(författare)
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Análisis dinámico de un eje de ferrocarril con capacidad de cambio de ancho automático
- 2010
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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.
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| 6. |
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| 7. |
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| 8. |
- Casanueva, Carlos, 1981-, et al.
(författare)
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Energy Prediction Benchmark for Universal CostModel Calculations
- 2018
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Konferensbidrag (refereegranskat)abstract
- Within the EU project Roll2Rail a Universal Cost Model (UCM) is being developed that accounts for different costs in the railway system affected by the design of the running gear. The objective of the methodology is not to calculate the global LCC of the entire vehicle (with all its components) but to boost the introduction of new technologies in the bogie by calculating the savings or incremental costs on the LCC that could be obtained between technological alternatives. The UCM will allow a more objective comparison of different bogie concepts, for instance in purchasing processes, and thus it includes a trustworthiness analysis that evaluates how accurate the calculations in the UCM are for a given study.When looking at the total life-cycle cost of a railway vehicle, energy consumption accounts for about 5% of the total expenditure. Within this UCM, a methodology has been proposed that allows the calculation of the energy consumption related to the bogie-technology of any railway vehicle. In order to ensure that all the calculation tools developed by the different partners are adequate, a benchmark simulation has been carried out. The benchmark studies a high-speed vehicle composed of two powered units and four non-powered ones, including six conventional bogies and three Jacobs bogies with both mechanical and ED brakes. In order to validate each simulation tool the share of energy consumed is then compared in different concepts, including in the fields of rolling resistance, curve resistance, unstable running resistance, gradient resistance, aerodynamic and turbulent resistance, inertia resistance and energy use of auxiliary elements. It should be stressed that the comparison and validation focuses on bogie-influenced energy consumption.In this paper, the overall UCM methodology is described, with special focus on the energy calculation methodology. The benchmark case is then presented and the energy calculation of all the partners is compared. A discussion on the calibration of the different partners' calculation tools is carried out, including a follow-updiscussion on the relative importance of the different energy consumption concepts in the final energy expenditure. Finally, the trustworthiness analysis is recalibrated according to these results. Closing remarks aregiven addressing the influence of these costs on the UCM.
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| 9. |
- Casanueva, Carlos, 1981-, et al.
(författare)
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Influence of Bearing Flexibility in Rail Vehicle Dynamics
- 2015
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Ingår i: The international Journal of railway technology. - Edinburgh : Civil-Comp Press. - 2049-5358 .- 2053-602X. ; 4:1, s. 47-67
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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.
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| 10. |
- Casanueva, Carlos, 1981-, et al.
(författare)
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Simple flexible wheelset model for low-frequency instability simulations
- 2014
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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
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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.
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| 11. |
- Casanueva, Carlos, 1981-, et al.
(författare)
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The Influence of Bearing Flexibility on High Speed Vehicles
- 2012
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Ingår i: Proceedings of the First International Conference on Railway Technology. - Stirlingshire, UK : Civil-Comp Press. ; , s. Paper 25-
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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.
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| 12. |
- Olza, Sheila, et al.
(författare)
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The role of nanochitin in biologically-active matrices for tissue engineering : where do we stand?
- 2023
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Ingår i: Journal of materials chemistry. B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 11:25, s. 5630-5649
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Forskningsöversikt (refereegranskat)abstract
- Our regard to the use of chitin as a material has drastically changed since its discovery, 210 years ago. From an intractable material because of its insolubility in common solvents, it became one of the most important raw materials serving as a source of chitosan (its main derivative), and more recently, as source of nanometric forms: nanocrystals and nanofibers. Nanoscale chitin forms are remarkable high-value compounds for nanomaterials' development, due to their intrinsic biological and mechanical properties, as well as their potential as eco-friendly components to valorize the plentiful by-products of the seafood industry. Lately, these nanochitin forms have been widely used as nanofillers in polymer nanocomposites, and in particular, in natural biologically-active matrices for the development of biomaterials. The recent progresses achieved in the last two decades concerning the use of nanoscale chitin in biologically-active matrices for tissue engineering is highlighted in this review. First, an overview on the use of nanochitin in the different biomedical fields is presented and discussed. Then, the state-of-the-art regarding the development of biomaterials based on chitin nanocrystals or nanofibers is described in the context of the role of nanochitin in biologically-active matrices namely polysaccharides (chitin, chitosan, cellulose, hyaluronic acid, alginate), proteins (silk, collagen, gelatin) and others (lignin). Finally, major conclusions and perspectives on the use of nanochitin as an increasingly important raw material are described.
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| 13. |
- Shahzamanian Sichani, Matin, 1986-
(författare)
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On Efficient Modelling of Wheel-Rail Contact in Vehicle Dynamics Simulation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The wheel-rail contact is at the core of all research related to vehicletrackinteraction. This tiny interface governs the dynamic performanceof rail vehicles through the forces it transmits and, like any high stressconcentration zone, it is subjected to serious damage phenomena. Thus,a clear understanding of the rolling contact between wheel and rail is keyto realistic vehicle dynamics simulation and damage analysis.In a multi-body dynamics simulation, the demanding contact problemshould be evaluated at about every millisecond for several wheel-rail pairs.Hence, a rigorous treatment of the contact is highly time-consuming.Simplifying assumptions are therefore made to accelerate the simulationprocess. This gives rise to a trade-o between the accuracy and computationaleciency of the contact model in use.Conventionally, Hertz+FASTSIM is used for calculation of the contactforces thanks to its low computational cost. However, the elliptic patchand pressure distribution obtained by Hertz' theory is often not realisticin wheel-rail contact. Moreover, the use of parabolic traction bound inFASTSIM causes considerable error in the tangential stress estimation.This combination leads to inaccurate damage predictions.Fast non-elliptic contact models are proposed by others to tacklethis issue while avoiding the tedious numerical procedures. The studiesconducted in the present work show that the accuracy of these models iscase-dependent.To improve the accuracy of non-elliptic patch and pressure estimation,a new method is proposed. The method is implemented in an algorithmnamed ANALYN. Comparisons show improvements in patch and, particularly,pressure estimations using ANALYN.In addition, an alternative to the widely-used FASTSIM is developed, named FaStrip. Unlike FASTSIM, it employs an elliptic traction boundand is able to estimate the non-linear characteristic of tangential stressdistribution. Comparisons show more accurate estimation of tangentialstress and slip velocity distribution as well as creep forces with FaStrip.Ultimately, an ecient non-elliptic wheel-rail contact model consistingof ANALYN and FaStrip is proposed. The reasonable computationalcost of the model enables it to be used on-line in dynamics simulationand its accuracy can improve the damage predictions.
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