Curve Squeal

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Van-vuong Lai - One of the best experts on this subject based on the ideXlab platform.

  • a nonlinear fe model for wheel rail Curve Squeal in the time domain including acoustic predictions
    Applied Acoustics, 2021
    Co-Authors: Van-vuong Lai, Jean-françois Brunel, Olivier Chiello, Marc Anciant, Philippe Dufrenoy
    Abstract:

    Abstract Squeal noise of rail-bound vehicles frequently occurs in Curves with a small radius and is a major nuisance for transport users and local residents. For the quantification of Squeal intensity, a complete vibro-acoustic analysis is developed in this paper. This complete analysis requires time-domain analysis able to introduce non linearities leading to obtain dynamic saturation at the contact zone and a computation of sound radiation of the whole system. For time-domain analysis, a finite element (FE) formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surface combined with unilateral and Coulomb friction laws. Appropriate numerical techniques and reduction strategies are then used in order to solve the non linear discrete equations in dynamic self-sustained conditions. Both the transient approach and linear stability analysis are carried out. For sound radiation calculation, the contact forces calculated from wheel/rail contact model are then used for the calculation of Squeal noise by using a coupled fluid-structure resolution based on boundary element method for the acoustic part and finite element method for the structural part. Results are first discussed in terms of unstable modes which are consistent between transient and stability analysis. Transient calculation shows that the apparent global friction coefficient during stick-slip cycles is slightly smaller than the constant local friction coefficient, and a dynamic saturation Curve with hysteresis considerably different of the quasi-static Curve. Finally the sound radiation calculation showed that the sound power radiated from the wheel is dominant with harmonics coming from the contact non linearities.

  • a full finite element model for the simulation of friction induced vibrations of wheel rail systems application to Curve Squeal noise
    2021
    Co-Authors: Van-vuong Lai, Jean-françois Brunel, Olivier Chiello, Philippe Dufrenoy
    Abstract:

    In this paper, a method is proposed for the modeling of dynamic wheel/rail frictional rolling contact. A full finite element formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surface combined with unilateral and Coulomb friction laws. Appropriate numerical techniques and reduction strategies are used in order to solve the non linear discrete equations in dynamic self-sustained conditions. In addition to the transient approach, a stability analysis allows the determination of unstable modes. This methodology is currently used in realistic wheel/rail contact in Curves to simulate Curve Squeal.

  • identification of instability mechanisms involved in the generation of railway Curve Squeal by point contact models and modal bases
    Forum Acusticum, 2020
    Co-Authors: Van-vuong Lai, Olivier Chiello, Jeanfrancois Brunnel, Philippe Dufrenoy
    Abstract:

    Squeal noise of rail-bound vehicles emitted in tight Curves is characterized by high sound pressure levels at pure medium and high frequencies. The models used to simulate the vibrations that cause this noise differ in particular in terms of the instability mechanisms considered: negative damping introduced into the system due to the decrease in the friction coefficient with the sliding speed or instability with a constant friction coefficient. The objective of the paper is to contribute to the understanding of the instability mechanisms in the case of a constant friction coefficient. A stability analysis of the wheel/rail contact in Curve is performed by using an equivalent point contact model (Hertz?s theory for normal contact and assumption of full sliding equilibrium states for tangential contact). The wheel/rail responses are computed by using wheel and rail modal bases. Results show that even with an assumption of a constant Coulomb friction coefficient, instabilities can indeed occur due to the coupling between normal and tangential dynamics in the wheel/rail system. This coupling can involve two wheel modes or only one when rail dynamics is included. The vertical dynamics of the rail then play an important role in the occurrence of the instability.

  • The critical effect of rail vertical phase response in railway Curve Squeal generation
    International Journal of Mechanical Sciences, 2020
    Co-Authors: Van-vuong Lai, Jean-françois Brunel, Olivier Chiello, Philippe Dufrenoy
    Abstract:

    Squeal of rail-bound vehicles emitted in tight Curves is characterized by high sound pressure levels at pure medium and high frequencies. Many models have been proposed in the literature to explain the occurrence of this noise with different instability mechanisms: negative damping due to falling friction or instability with a constant friction coefficient. The aim of the paper is to contribute to the understanding of the instability mechanisms in the case of a constant friction coefficient. A stability analysis of the wheel/rail contact dynamics in Curve is performed by using an equivalent point contact model combined with wheel and rail modal bases. Results show that even with an assumption of a constant Coulomb friction coefficient, two types of instabilities may occur in the wheel/rail system: classical mode coupling and instabilities due to negative damping added to a single wheel mode when the track dynamical behavior, especially in the vertical direction, is included. For this second type of instabilities, an 1-degree of freedom model can be formulated. By using this model, it is found that the equivalent damper behavior of the infinite track is the origin of these instabilities.

  • dynamic model of wheel rail contact for Curve Squeal simulation
    2018
    Co-Authors: Van-vuong Lai
    Abstract:

    Le bruit de crissement emis par les vehicules guides sur rail dans les courbes serrees (rayon inferieur a 200 m) est caracterise par un niveau de pression acoustique eleve et un spectre de raies a moyennes et hautes frequences. La litterature est riche en modeles de simulation du crissement en courbe. Cependant, le mecanisme d'instabilite est toujours controverse. De plus, les modeles de crissement en courbe existants sont souvent simplifies (lois de pseudo-glissement analytiques ou hypothese de massif semi-infini elastique).Le premier objectif de la these est de contribuer a la comprehension du mecanisme de generation. Pour ce faire, une analyse de stabilite du contact de roulement roue/rail dans le cas du glissement lateral total est realisee en utilisant un modele de contact ponctuel et des bases modales roue et rail. On constate que meme avec une hypothese de coefficient de frottement de Coulomb constant, la flexibilite verticale dynamique du rail joue notamment un role important dans l'occurrence d'instabilite sans "decroissance du coefficient de frottement" ni sans "couplage de modes". Le second objectif de la these est de developper un modele element finis complet de contact roue/rail pour calculer des solutions de reference. Des techniques numeriques appropriees sont developpees pour resoudre les equations discretes non lineaires. Ces methodes sont ensuite appliquees a un modele realiste de contact roue/rail en courbe. On constate que la discretisation de la zone de contact ne modifie pas les mecanismes d'instabilite mais les taux de divergence des modes instables en raison du couplage plus fort entre les degres de liberte de contact normaux.

Philippe Dufrenoy - One of the best experts on this subject based on the ideXlab platform.

  • a nonlinear fe model for wheel rail Curve Squeal in the time domain including acoustic predictions
    Applied Acoustics, 2021
    Co-Authors: Van-vuong Lai, Jean-françois Brunel, Olivier Chiello, Marc Anciant, Philippe Dufrenoy
    Abstract:

    Abstract Squeal noise of rail-bound vehicles frequently occurs in Curves with a small radius and is a major nuisance for transport users and local residents. For the quantification of Squeal intensity, a complete vibro-acoustic analysis is developed in this paper. This complete analysis requires time-domain analysis able to introduce non linearities leading to obtain dynamic saturation at the contact zone and a computation of sound radiation of the whole system. For time-domain analysis, a finite element (FE) formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surface combined with unilateral and Coulomb friction laws. Appropriate numerical techniques and reduction strategies are then used in order to solve the non linear discrete equations in dynamic self-sustained conditions. Both the transient approach and linear stability analysis are carried out. For sound radiation calculation, the contact forces calculated from wheel/rail contact model are then used for the calculation of Squeal noise by using a coupled fluid-structure resolution based on boundary element method for the acoustic part and finite element method for the structural part. Results are first discussed in terms of unstable modes which are consistent between transient and stability analysis. Transient calculation shows that the apparent global friction coefficient during stick-slip cycles is slightly smaller than the constant local friction coefficient, and a dynamic saturation Curve with hysteresis considerably different of the quasi-static Curve. Finally the sound radiation calculation showed that the sound power radiated from the wheel is dominant with harmonics coming from the contact non linearities.

  • a full finite element model for the simulation of friction induced vibrations of wheel rail systems application to Curve Squeal noise
    2021
    Co-Authors: Van-vuong Lai, Jean-françois Brunel, Olivier Chiello, Philippe Dufrenoy
    Abstract:

    In this paper, a method is proposed for the modeling of dynamic wheel/rail frictional rolling contact. A full finite element formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surface combined with unilateral and Coulomb friction laws. Appropriate numerical techniques and reduction strategies are used in order to solve the non linear discrete equations in dynamic self-sustained conditions. In addition to the transient approach, a stability analysis allows the determination of unstable modes. This methodology is currently used in realistic wheel/rail contact in Curves to simulate Curve Squeal.

  • identification of instability mechanisms involved in the generation of railway Curve Squeal by point contact models and modal bases
    Forum Acusticum, 2020
    Co-Authors: Van-vuong Lai, Olivier Chiello, Jeanfrancois Brunnel, Philippe Dufrenoy
    Abstract:

    Squeal noise of rail-bound vehicles emitted in tight Curves is characterized by high sound pressure levels at pure medium and high frequencies. The models used to simulate the vibrations that cause this noise differ in particular in terms of the instability mechanisms considered: negative damping introduced into the system due to the decrease in the friction coefficient with the sliding speed or instability with a constant friction coefficient. The objective of the paper is to contribute to the understanding of the instability mechanisms in the case of a constant friction coefficient. A stability analysis of the wheel/rail contact in Curve is performed by using an equivalent point contact model (Hertz?s theory for normal contact and assumption of full sliding equilibrium states for tangential contact). The wheel/rail responses are computed by using wheel and rail modal bases. Results show that even with an assumption of a constant Coulomb friction coefficient, instabilities can indeed occur due to the coupling between normal and tangential dynamics in the wheel/rail system. This coupling can involve two wheel modes or only one when rail dynamics is included. The vertical dynamics of the rail then play an important role in the occurrence of the instability.

  • The critical effect of rail vertical phase response in railway Curve Squeal generation
    International Journal of Mechanical Sciences, 2020
    Co-Authors: Van-vuong Lai, Jean-françois Brunel, Olivier Chiello, Philippe Dufrenoy
    Abstract:

    Squeal of rail-bound vehicles emitted in tight Curves is characterized by high sound pressure levels at pure medium and high frequencies. Many models have been proposed in the literature to explain the occurrence of this noise with different instability mechanisms: negative damping due to falling friction or instability with a constant friction coefficient. The aim of the paper is to contribute to the understanding of the instability mechanisms in the case of a constant friction coefficient. A stability analysis of the wheel/rail contact dynamics in Curve is performed by using an equivalent point contact model combined with wheel and rail modal bases. Results show that even with an assumption of a constant Coulomb friction coefficient, two types of instabilities may occur in the wheel/rail system: classical mode coupling and instabilities due to negative damping added to a single wheel mode when the track dynamical behavior, especially in the vertical direction, is included. For this second type of instabilities, an 1-degree of freedom model can be formulated. By using this model, it is found that the equivalent damper behavior of the infinite track is the origin of these instabilities.

  • Transient models for Curve Squeal noise
    Journal of Sound and Vibration, 2017
    Co-Authors: Jean-françois Brunel, Jean-Luc Munoz, Moussa Nait-abdelaziz, Philippe Dufrenoy, François Demilly
    Abstract:

    The paper deals with numerical models of railway wheel noise occurring in narrow Curves. Curve Squeal is presumed to issue from a lateral creepage of the wheels on the rail head. The frequency range is from around 400 to almost 8000 Hz, with noise levels up to 120 dB close to the wheel. Lateral friction forces are induced on the wheel–rail contact area (typically stick-slip forces). Due to nonlinearities of friction forces, a transient analysis of the lateral creepage of the wheel is performed by using an axi-harmonic model. Results give a reduced number of excited modes. It is shown that Squealing modes have 3, 4 and 5 nodal diameters. These results agree with experimental investigations of Squeal noise measurements. An extension of the transient model is finally discussed. It consists to study the efficiency of a noise attenuation system made of a metallic ring inserted into grooves machined into the wheel.

Lai Van-vuong - One of the best experts on this subject based on the ideXlab platform.

  • A full finite element model for the simulation of friction-induced vibrations of wheel/rail systems: application to Curve Squeal noise
    HAL CCSD, 2019
    Co-Authors: Lai Van-vuong, Chiello Olivier, Brunel Jean-françois, Dufrenoy Philippe
    Abstract:

    13th International Workshop on Railway Noise, GAND, BELGIQUE, 16-/09/2019 - 20/09/2019In this paper, a method is proposed for the modeling of dynamic wheel/rail frictional rolling contact. A full finite element formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surface combined with unilateral and Coulomb friction laws. Appropriate numerical techniques and reduction strategies are used in order to solve the non linear discrete equations in dynamic self-sustained conditions. In addition to the transient approach, a stability analysis allows the determination of unstable modes. This methodology is currently used in realistic wheel/rail contact in Curves to simulate Curve Squeal

  • Simulation dynamique du contact roue/rail en courbe : application au bruit de crissement
    2018
    Co-Authors: Lai Van-vuong
    Abstract:

    Le bruit de crissement émis par les véhicules guidés sur rail dans les courbes serrées (rayon inférieur à 200 m) est caractérisé par un niveau de pression acoustique élevé et un spectre de raies à moyennes et hautes fréquences. La littérature est riche en modèles de simulation du crissement en courbe. Cependant, le mécanisme d'instabilité est toujours controversé. De plus, les modèles de crissement en courbe existants sont souvent simplifiés (lois de pseudo-glissement analytiques ou hypothèse de massif semi-infini élastique).Le premier objectif de la thèse est de contribuer à la compréhension du mécanisme de génération. Pour ce faire, une analyse de stabilité du contact de roulement roue/rail dans le cas du glissement latéral total est réalisée en utilisant un modèle de contact ponctuel et des bases modales roue et rail. On constate que même avec une hypothèse de coefficient de frottement de Coulomb constant, la flexibilité verticale dynamique du rail joue notamment un rôle important dans l'occurrence d'instabilité sans "décroissance du coefficient de frottement" ni sans "couplage de modes". Le second objectif de la thèse est de développer un modèle élément finis complet de contact roue/rail pour calculer des solutions de référence. Des techniques numériques appropriées sont développées pour résoudre les équations discrètes non linéaires. Ces méthodes sont ensuite appliquées à un modèle réaliste de contact roue/rail en courbe. On constate que la discrétisation de la zone de contact ne modifie pas les mécanismes d'instabilité mais les taux de divergence des modes instables en raison du couplage plus fort entre les degrés de liberté de contact normaux.Squeal noise of railbound vehicles emitted in tight Curves (radius lower than 200m) is characterized by high sound pressure levels at pure medium and high frequencies. State-of-the-art abounds with models trying to simulate Curve Squeal. However the instability mechanisms are still controversial. In addition, existing Curve Squeal models are often simplified (analytical frictional contact laws or elastic half-space assumption). The first aim of the thesis is to contribute to a clarification of the possible generation mechanisms. For this purpose, a stability analysis of wheel/rail rolling contact in the case of lateral full sliding is performed by using a point-contact model and wheel/rail modal bases. It is found that, even with a constant Coulomb friction coefficient, the rail vertical flexibility is notably found to play an important role on the instability occurrence without "falling friction" nor without "mode-coupling". The second aim of the thesis is to develop a full Finite Element model of wheel/rail contact in order to compute reference solutions and especially to verify the effects of the simplifications carried out in the point-contact model. Appropriate numerical techniques are used in order to solve the nonlinear discrete equations. In order to reduce the computational effort, reduction strategies are proposed for both domains. The methods are then applied in a realistic wheel/rail model in Curve. It is found that the discretization of the contact zone does not substantially modify the instability mechanisms but the divergence rates of the unstable modes due to a stronger coupling between the normal contact degrees of freedom

  • SIMULATION DYNAMIQUE DU CONTACT ROUE/RAIL EN COURBE APPLICATION AU BRUIT DE CRISSEMENT
    HAL CCSD, 2018
    Co-Authors: Lai Van-vuong
    Abstract:

    Squeal noise of rail-bound vehicles emitted in tight Curves (radius lower than 200m) is characterized by high sound pressure levels at pure medium and high frequencies. In urban areas where tight Curves are numerous, Squeal may affect many passengers and local residents and it is necessary to reduce this noise. State-of-the-art abounds with models trying to simulate Curve Squeal. They can be distinguished according to the mechanisms leading to Squeal (negative damping introduced in the system due to the decrease of friction coefficient with the sliding velocity or mode coupling in the case of constant friction coefficient) but also wheel-rail contact models and solution types (time or frequency domain, linear or nonlinear analysis) according to. However, the instability mechanisms are still controversial. In addition, existing Curve Squeal models are often simplified (analytical frictional contact laws or elastic half-space assumption). The first aim of the thesis is to contribute to a clarification of the possible generation mechanisms. For this purpose, a stability analysis of wheel/rail rolling contact in the case of lateral full sliding is performed by using a point-contact model and wheel/rail modal bases. It is found that, even with a constant Coulomb friction coefficient, instabilities can occur because of the coupling between normal and tangential dynamics in wheel/rail system. However, this coupling may involve two wheel modes or only one wheel mode when the rail dynamics is included. The last case corresponds to a specific original mechanism. The rail vertical flexibility is notably found to play an important role on the instability occurrence without "falling friction" nor without "mode-coupling". This role is clarified by proposing a simple model including a single wheel mode and an analytical rail model. It is thus showed how the imaginary part of the complex stiffness of the rail, induced by the phase shift of the propagating wave but also by track damping (supporting pad, rail) plays an critical role in the instability mechanism. The combination of friction and phase shift induces a negative damping which may destabilize the system, leading to self-sustained vibration and Squeal noise. Finally, it is shown that the results obtained with the model are rather coherent with experimental observations. The second aim of the thesis is to develop a full Finite Element model of wheel/rail contact in order to compute reference solutions and especially to verify the effects of the simplifications carried out in the point-contact model of Part I. A finite element formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surfaces. Unilateral contact and Coulomb friction with constant friction coefficient are assumed in the contact zone. This formulation, already used in other problems of structures destabilized by friction, is adapted here to a rolling case. Appropriate numerical techniques are used in order to solve the nonlinear discrete equations in quasi-static and dynamic conditions. In addition to the transient approach, a stability analysis performed around the full sliding equilibrium position allows to determine unstable modes and corresponding frequencies. In order to reduce the computational effort, reduction strategies are proposed for both domains. The first technique uses a classical reduction basis including free-interface normal modes and static contact attachments modes. A second original technique consists in simply adding a residual static contact flexibility to the free-interface normal modes when solving the frictional contact equations (Contact Static Approximation). The method is then tested in the case of frictional rolling contact between two annular cylinders. The quasi-static results show a good agreement with the ones obtained with Kalker's CONTACT software, which is the reference method for the quasi-static wheel/rail contact analysis. In case of full sliding, the stability analysis brings out a mode coupling when the contact zone is laterally shifted from the center of the cylinders. In the unstable configuration, the numerical integration provides solutions in the time domain, which are coherent with the stability results. Concerning the performance of the reduction strategies, the approximate results show a good agreement with the reference ones in both transient and stability analyses. The methods are then applied in a realistic wheel/rail model in Curve. It is found that the discretization of the contact zone does not substantially modify the instability mechanisms in comparison with the results obtained in the first part. However due to a stronger coupling between the normal contact degrees of freedom, the divergence rates of the unstable modes are greater for the finite element-contact model than for the point-contact model. The results of transient dynamics are consistent with the stability analysis and show localized stick/slip oscillations in the contact zone. The average global friction coefficient during stick-slip cycles is lightly smaller than the constant local friction coefficient. Thus, the decrease of the global friction coefficient could be interpreted as a consequence (and not a cause) of the friction-induced vibrations. Moreover, an hysteresis is observed in the average dynamic saturation Curve provided with the finite element model. This result is is significantly different from those obtained with quasi-static Curves. This could be due to the high lateral stiffness resulting from transient contact effects at Squeal frequencies. Nonlinear dynamic analyses with point contact models should thus take into account this effect in order to provide correct limit cycles.Le bruit de crissement émis par les véhicules guidés sur rail dans les courbes serrées (rayon inférieurà 200 m) est caractérisé par un niveau de pression acoustique élevé et un spectre de raies à moyennes ethautes fréquences. Dans les zones urbaines où les courbes sont nombreuses, le crissement peut affecterde nombreux passagers et résidents et il est nécessaire de réduire ce bruit. La littérature est riche en mod-èles de simulation du crissement en courbe. Ils se distinguent principalement au niveau des mécanismesd'instabilité conduisant au crissement (amortissement négatif introduit dans le système dû à la diminu-tion du coefficient de frottement avec la vitesse de glissement ou couplage de modes dans le cas d'uncoefficient de frottement constant), mais aussi au niveau des modèles de contact roue/rail et des typesde solution (domaine temporel ou fréquentiel, analyse linéaire ou non linéaire). Cependant, le mécan-isme d'instabilité est toujours controversé. De plus, les modèles de crissement en courbe existants sontsouvent simplifiés (lois de pseudo-glissement analytiques ou hypothèse de massif semi-infini élastique).Le premier objectif de la thèse est de contribuer à la compréhension du mécanisme de génération.Pour ce faire, une analyse de stabilité du contact de roulement roue/rail dans le cas du glissement latéraltotal est réalisée en utilisant un modèle de contact ponctuel et des bases modales roue et rail. On constateque même avec une hypothèse de coefficient de frottement de Coulomb constant, des instabilités peuventse produire en raison du couplage entre la dynamique normale et tangentielle dans les systèmes roue/rail.Ce couplage peut faire intervenir deux modes de roue (couplage de modes classique) ou un seul modede roue lorsque la dynamique du rail est incluse. Il s'agit alors d'un mécanisme spécifique. La flexibilitéverticale du rail joue notamment un rôle important dans l'occurrence d'instabilité sans "décroissancedu coefficient de frottement" ni sans "couplage de modes". Ce rôle est ensuite clarifié par un modèlesimple comprenant un mode de roue et un modèle analytique de rail. On constate alors que la partieimaginaire de la raideur complexe du rail, induite par le déphasage de l'onde de propagation mais aussipar l'amortissement des semelles et du rail, joue un rôle critique dans le mécanisme d'instabilité. Lacombinaison du frottement et de ce déphasage induit un amortissement négatif qui peut alors déstabiliserle système, conduisant à des vibrations auto-entretenues et au bruit de crissement. Il est finalementmontré que les résultats de la modélisation sont cohérents avec les constatations expérimentales.Le second objectif de la thèse est de développer un modèle élément finis complet de contact roue/railpour calculer des solutions de référence. Une formulation par éléments finis autour de la position sta-tionnaire dans un repère eulérien est proposée avec une discrétisation fine de la surface de contact. Deslois non régularisées de contact unilatéral et de frottement avec un coefficient de frottement constant sontutilisées. Cette formulation déjà utilisée dans d'autres types de structures frottantes est ici adaptée au casavec roulement. Des techniques numériques appropriées sont développées pour résoudre les équationsdiscrètes non linéaires dans des conditions quasi-statiques ou dynamiques. Outre l'approche transitoire,une analyse de stabilité réalisée autour de la position d'équilibre en glissement total permet de déterminerles modes et les fréquences instables. Afin de réduire le temps de calcul, des méthodes de réduction sontproposées pour la stabilité et le calcul temporel. La première technique utilise une base réduite classiquede sous-structuration dynamique (Component Mode Synthesis ou CMS) comprenant des modes normauxet des modes statiques d'attache au contact. Une deuxième technique consiste simplement à ajouter uneflexibilité de contact statique résiduelle aux modes normaux lors de la résolution des équations de contactpar frottement (approximation statique du contact). La méthode est ensuite testée dans le cas d'un contact56roulant et frottant entre deux cylindres annulaires. Les résultats quasi statiques montrent un bon accordavec ceux obtenus avec le logiciel CONTACT de Kalker, qui constitue la méthode de référence pour lecontact roue/rail quasi-statique. Dans le cas de glissement total, l'analyse de stabilité fait apparaître uneinstabilité du couplage de modes lorsque la zone de contact est décalée latéralement du plan moyen descylindres. Dans la configuration instable, la solution transitoire est cohérente avec les résultats de stabil-ité. En ce qui concerne les performances des modèles de réduction, les résultats obtenus montrent un bonaccord avec ceux de référence dans l'analyse de stabilité et dans les calculs transitoires. Ces méthodessont ensuite appliquées à un modèle réaliste de contact roue/rail en courbe. On constate que la discréti-sation de la zone de contact ne modifie sensiblement pas les mécanismes d'instabilité. Cependant, enraison du couplage plus fort entre les degrés de liberté de contact normaux, les taux de divergence desmodes instables sont plus élevés avec le modèle éléments finis que pour le modèle de contact ponctuel.Les résultats de la simulation dynamique transitoire sont cohérents avec l'analyse de stabilité et montrentdes oscillations localisées adhérence/ glissement dans la zone de contact. Le coefficient de frottementglobal moyenné pendant les cycles stabilisés est légèrement inférieur au coefficient de frottement localconstant. Ainsi, la diminution du coefficient de frottement global pourrait être interprétée comme uneconséquence (et non une cause) des vibrations auto-entretenues. La courbe de saturation dynamiquemoyenne obtenue avec le modèle éléments finis montre un hystérésis qui est n'est pas obtenu avec lescourbes quasi-statiques. Ce phénomène pourrait être du à l'importante rigidité latérale liée aux effetstransitoires dans la zone de contact. Des analyses non linéaires avec des modèles de contact ponctuelsdevraient ainsi prendre en compte cette cette rigidité pour améliorer la prédiction des cycles limites

Luis Baeza - One of the best experts on this subject based on the ideXlab platform.

  • study of railway Curve Squeal in the time domain using a high frequency vehicle track interaction model
    Journal of Sound and Vibration, 2018
    Co-Authors: Juan Ginernavarro, F.d. Denia, Jose Martinezcasas, Luis Baeza
    Abstract:

    Abstract Railway Curve Squeal is an intense tonal and annoying type of noise commonly attributed to self-excited vibrations during curving. The mechanisms for its generation remain unclear and it is still a subject of discussion among researchers. Most of them have considered the falling behaviour of the friction coefficient with the slip velocity essential for reenergising the system. Recently, some authors have found that Squeal can also appear even for constant friction coefficient through the wheel modal coupling between the normal and tangential directions caused by the wheel/rail contact. This paper particularly evaluates whether the latter mechanism is sufficient to find Squeal in curving conditions. The introduction of flexibility in the railway subsystems is required to widen the domain to the high-frequency range in which Squeal occurs. One single flexible and rotatory wheelset is considered and suitable forces are prescribed at the primary suspension seats in the current investigation. The rails are modelled through the Moving Element Method (MEM), permitting to extend the range of validity of beam models usually utilised in the literature. This work extends the formulation to rails supported by a viscoelastic Winkler bedding. Both wheelset and track models are coupled by means of a non-linear and unsteady wheel/rail contact model based on Kalker's Variational Theory. Simulation results for different track curvatures and friction coefficients are presented and discussed, showing tonal peaks in the tangential contact forces of the inner wheel. These results can be associated with Squeal according to the characterisation of this phenomenon, indicating that Squeal can be found in curving conditions using advanced dynamic interaction models even with constant friction coefficient.

  • Study of railway Curve Squeal in the time domain using a high-frequency vehicle/track interaction model
    Journal of Sound and Vibration, 2018
    Co-Authors: Juan Giner-navarro, José Martínez-casas, F.d. Denia, Luis Baeza
    Abstract:

    Abstract Railway Curve Squeal is an intense tonal and annoying type of noise commonly attributed to self-excited vibrations during curving. The mechanisms for its generation remain unclear and it is still a subject of discussion among researchers. Most of them have considered the falling behaviour of the friction coefficient with the slip velocity essential for reenergising the system. Recently, some authors have found that Squeal can also appear even for constant friction coefficient through the wheel modal coupling between the normal and tangential directions caused by the wheel/rail contact. This paper particularly evaluates whether the latter mechanism is sufficient to find Squeal in curving conditions. The introduction of flexibility in the railway subsystems is required to widen the domain to the high-frequency range in which Squeal occurs. One single flexible and rotatory wheelset is considered and suitable forces are prescribed at the primary suspension seats in the current investigation. The rails are modelled through the Moving Element Method (MEM), permitting to extend the range of validity of beam models usually utilised in the literature. This work extends the formulation to rails supported by a viscoelastic Winkler bedding. Both wheelset and track models are coupled by means of a non-linear and unsteady wheel/rail contact model based on Kalker's Variational Theory. Simulation results for different track curvatures and friction coefficients are presented and discussed, showing tonal peaks in the tangential contact forces of the inner wheel. These results can be associated with Squeal according to the characterisation of this phenomenon, indicating that Squeal can be found in curving conditions using advanced dynamic interaction models even with constant friction coefficient.

  • A State-of-the-Art Review of Curve Squeal Noise: Phenomena, Mechanisms, Modelling and Mitigation
    Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 2018
    Co-Authors: David Thompson, Giacomo Squicciarini, Bo Ding, Luis Baeza
    Abstract:

    Curve Squeal is an intense tonal noise occurring when a rail vehicle negotiates a sharp Curve. The phenomenon can be considered to be chaotic, with a widely differing likelihood of occurrence on different days or even times of day. The term Curve Squeal may include several different phenomena with a wide range of dominant frequencies and potentially different excitation mechanisms. This review addresses the different Squeal phenomena and the approaches used to model Squeal noise; both time-domain and frequency-domain approaches are discussed and compared. Supporting measurements using test rigs and field tests are also summarised. A particular aspect that is addressed is the excitation mechanism. Two mechanisms have mainly been considered in previous publications. In many early papers the Squeal was supposed to be generated by the so-called falling friction characteristic in which the friction coefficient reduces with increasing sliding velocity. More recently the mode coupling mechanism has been raised as an alternative. These two mechanisms are explained and compared and the evidence for each is discussed. Finally, a short review is given of mitigation measures and some suggestions are offered for why these are not always successful.

  • investigation of railway Curve Squeal using a combination of frequency and time domain models
    Proceedings of the 12th International Workshop on Railway Noise 12-16 September 2016 Terrigal Australia, 2018
    Co-Authors: Astrid Pieringer, Peter Torstensson, Juan Pedro Romera Giner, Luis Baeza
    Abstract:

    Railway Curve Squeal arises from self-excited vibrations during curving. In this paper, a frequency- and a time-domain approach for Curve Squeal are compared. In particular, the capability of the frequency-domain model to predict the onset of Squeal and the Squeal frequencies is studied. In the frequency-domain model, linear stability is investigated through complex eigenvalue analysis. The time-domain model is based on a Green’s function approach and uses a convolution procedure to obtain the system response. To ensure comparability, the same submodels are implemented in both Squeal models. The structural flexibility of a rotating wheel is modelled by adopting Eulerian coordinates. To account for the moving wheel–rail contact load, the so-called moving element method is used to model the track. The local friction characteristics in the contact zone are modelled in accordance with Coulomb’s law with a constant friction coefficient. The frictional instability arises due to geometrical coupling. In the time-domain model, Kalker’s non-linear, non-steady state rolling contact model including the algorithms NORM and TANG for normal and tangential contact, respectively, is solved in each time step. In the frequency-domain model, the normal wheel/rail contact is modelled by a linearization of the force-displacement relation obtained with NORM around the quasi-static state and full-slip conditions are considered in the tangential direction. Conditions similar to those of a Curve on the Stockholm metro exposed to severe Curve Squeal are studied with both Squeal models. The influence of the wheel-rail friction coefficient and the direction of the resulting creep force on the occurrence of Squeal is investigated for vanishing train speed. Results from both models are similar in terms of the instability range in the parameter space and the predicted Squeal frequencies.

  • investigation of railway Curve Squeal using a combination of frequency and time domain models
    Proceedings of the 12h International Workshop on Railway Noise (IWRN12) Terrigal Australia September 12-16, 2016
    Co-Authors: Astrid Pieringer, Peter Torstensson, Juan Pedro Romera Giner, Luis Baeza
    Abstract:

    Railway Curve Squeal arises from self-excited vibrations during curving. In this paper, a frequency- and a timedomain approach for Curve Squeal are compared. In particular, the capability of the frequency-domain model to predict the onset of Squeal and the Squeal frequencies is studied. In the frequency-domain model, linear stability is investigated through complex eigenvalue analysis. The time-domain model is based on a Green's functions approach and uses a convolution procedure to obtain the system response. To ensure comparability, the same submodels are implemented in both Squeal models. The structural flexibility of a rotating wheel is modelled by adopting Eulerian coordinates. To account for the moving wheel‒rail contact load, the so-called moving element method is used to model the track. The local friction characteristics in the contact zone is modelled in accordance with Coulomb's law with a constant friction coefficient. The frictional instability arises due to geometrical coupling. In the time-domain model, Kalker's non-linear, non-steady state rolling contact model including the algorithms NORM and TANG for normal and tangential contact, respectively, is solved in each time step. In the frequency-domain model, the normal wheel/rail contact is modelled by a linearization of the force-displacement relation obtained with NORM around the quasi-static state and full-slip conditions are considered in tangential direction. Conditions similar to those of a Curve on the Stockholm metro exposed to severe Curve Squeal are studied with both Squeal models. The influence of the wheel-rail friction coefficient and the direction of the resulting creep force on the occurrence of Squeal is investigated for vanishing train speed. Results from both models are similar in terms of the instability range in the parameter space and the predicted Squeal frequencies.

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  • the application of dither for suppressing Curve Squeal
    23rd International Congress on Acoustics: Integrating 4th EAA Euroregio ICA 2019 Aachen, 2019
    Co-Authors: Wolfgang Kropp, Arthur Aglat, Jannik S Theyssen, Astrid Pieringer
    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.

  • influence of spin creepage and contact angle on Curve Squeal a numerical approach
    Journal of Sound and Vibration, 2018
    Co-Authors: Ivan Zenzerovic, Wolfgang Kropp, Astrid Pieringer
    Abstract:

    Abstract Curve Squeal is a loud tonal sound that may arise when a railway vehicle negotiates a tight Curve. Due to the nonlinear nature of Squeal, time-domain models provide a higher degree of accuracy in comparison to frequency-domain models and also enable the determination of Squeal amplitudes. In the present paper, a previously developed engineering time-domain model for Curve Squeal is extended to include the effects of the contact angle and spin creepage. The extensions enable the evaluation of more realistic Squeal cases with the computationally efficient model. The model validation against Kalker's variational contact model shows good agreement between the models. Results of studies on the influence of spin creepage and contact angle show that the contact angle has a significant influence on the vertical-lateral dynamics coupling and, therefore, influences both Squeal amplitude and frequency. Spin creepage mainly influences processes in the contact, therefore influencing the tangential contact force amplitude. In the combined spin-contact angle study the spin creepage value is kinematically related to the contact angle value. Results indicate that the influence of the contact angle is dominant over the influence of spin creepage. In general, results indicate that the most crucial factors in Squeal are those that influence the dynamics coupling: the contact angle, wheel/rail contact positions and friction.

  • investigation of railway Curve Squeal using a combination of frequency and time domain models
    Proceedings of the 12th International Workshop on Railway Noise 12-16 September 2016 Terrigal Australia, 2018
    Co-Authors: Astrid Pieringer, Peter Torstensson, Juan Pedro Romera Giner, Luis Baeza
    Abstract:

    Railway Curve Squeal arises from self-excited vibrations during curving. In this paper, a frequency- and a time-domain approach for Curve Squeal are compared. In particular, the capability of the frequency-domain model to predict the onset of Squeal and the Squeal frequencies is studied. In the frequency-domain model, linear stability is investigated through complex eigenvalue analysis. The time-domain model is based on a Green’s function approach and uses a convolution procedure to obtain the system response. To ensure comparability, the same submodels are implemented in both Squeal models. The structural flexibility of a rotating wheel is modelled by adopting Eulerian coordinates. To account for the moving wheel–rail contact load, the so-called moving element method is used to model the track. The local friction characteristics in the contact zone are modelled in accordance with Coulomb’s law with a constant friction coefficient. The frictional instability arises due to geometrical coupling. In the time-domain model, Kalker’s non-linear, non-steady state rolling contact model including the algorithms NORM and TANG for normal and tangential contact, respectively, is solved in each time step. In the frequency-domain model, the normal wheel/rail contact is modelled by a linearization of the force-displacement relation obtained with NORM around the quasi-static state and full-slip conditions are considered in the tangential direction. Conditions similar to those of a Curve on the Stockholm metro exposed to severe Curve Squeal are studied with both Squeal models. The influence of the wheel-rail friction coefficient and the direction of the resulting creep force on the occurrence of Squeal is investigated for vanishing train speed. Results from both models are similar in terms of the instability range in the parameter space and the predicted Squeal frequencies.

  • an engineering time domain model for Curve Squeal tangential point contact model and green s functions approach
    Journal of Sound and Vibration, 2016
    Co-Authors: Ivan Zenzerovic, Wolfgang Kropp, Astrid Pieringer
    Abstract:

    Curve Squeal is a strong tonal sound that may arise when a railway vehicle negotiates a tight Curve. In contrast to frequency-domain models, time-domain models are able to capture the nonlinear and transient nature of Curve Squeal. However, these models are computationally expensive due to requirements for fine spatial and time discretization. In this paper, a computationally efficient engineering model for Curve Squeal in the time domain is proposed. It is based on a steady-state point-contact model for the tangential wheel/rail contact and a Green's functions approach for wheel and rail dynamics. The Squeal model also includes a simple model of sound radiation from the railway wheel from the literature. A validation of the tangential point-contact model against Kalker's transient variational contact model reveals that the point-contact model performs well within the Squeal model up to at least 5 kHz. The proposed Squeal model is applied to investigate the influence of lateral creepage, friction and wheel/rail contact position on Squeal occurrence and amplitude. The study indicates a significant influence of the wheel/rail contact position on Squeal frequencies and amplitudes. Friction and lateral creepage show an influence on Squeal occurrence and amplitudes, but this is only secondary to the influence of the contact position.

  • Curve Squeal of rail vehicles linear stability analysis and non linear time domain simulation
    Proceedings of the Third International Conference on Railway Technology: Research Development and Maintenance J. Pombo (Editor) Civil-Comp Press Stirl, 2016
    Co-Authors: Astrid Pieringer, Peter Torstensson, Juan Pedro Romera Giner
    Abstract:

    Railway Curve Squeal arises from self-excited vibrations during curving. In this paper, a combination of a frequency-and a time-domain approach for Curve Squeal is applied in order to compare and evaluate the two different approaches. In the frequency-domain, linear stability is investigated through complex eigenvalue analysis. The time-domain model is based on a Green's functions approach and uses a convolution procedure to obtain the system response. To ensure comparability, the same submodels are implemented in both Squeal models. The wheel model includes a single flexible wheel and accounts for inertia effects due to rotation adopting Eulerian coordinates. The track is modelled using the moving element method technique corresponding to a finite element mesh that travels with the vehicle speed. Coulomb's law with a constant friction coefficient is applied to model the local friction characteristics in the contact zone. The frictional instability arises due to geometrical coupling. The rolling contact model applied is Kalker's variational method in the time domain and a linearized version of this method in the frequency domain. Conditions similar to those of a Curve on the Stockholm metro exposed to severe Curve Squeal are studied with both Squeal models. The influence of the wheel-rail friction coefficient and the direction of the resulting creep force on the occurrence of Squeal is investigated for vanishing train speed. The results of both models show similar tendencies, but differ in the predicted Squeal frequencies.

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