Yes / Cattle grids are used on roads and tracks to prevent grazing animals from leaving an open space without fencing onto a more controlled area where access to the road from surrounded land is more limited. They are widely used in the UK at the entrances to common and moorland areas where animals are free to roam, but also on private drive entrances. Typically, they consist of a series of metal bars across the road that are spaced so that an animal’s legs would fall through the gaps if it attempted to cross. Below the grid is a shallow pit that is intended to further deter livestock from using that particular crossing point. The sound produced as vehicles cross these devices is a characteristic low frequency “brrrr” where the dominant frequencies relates to the bar passage frequency under the tyres. The sound can be disturbing to riders and their horses and walkers and residents living close by as evidenced by press reports and the need to consider noise aspects in planning for new installations. For this reason and due to the lack of available information on the size and nature of the problem measurements and recordings have been made at a number of sites in Yorkshire in the UK. In addition, questionnaire surveys of residents living close by and façade measurements have also been used to gauge impact. Results show that there is a wide variation in the maximum noise level produced by cattle grids of apparently similar design. This can be related to impact noise produced by the movement of all or part of the grid as the frame comes under impulsive loading as the vehicle crosses. It was further established that some residents living close to the cattle grids were disturbed by the noise, and in some cases vibration, and wanted them removed or suitably modified. / The work was funded by the Bradford Centre for Sustainable Environments, University of Bradford.

Dans un contact pneu/chaussée, le bruit de roulement résulte de l’interaction mécanique entre les aspérités de la chaussée et les pains de la bande de roulement. À l’issue de cette interaction, des forces compressives apparaissent pour repousser les deux corps en contact. Ces forces conduisent à la vibration du pneumatique. Ces vibrations sont à l’origine du bruit rayonné. Le travail de cette thèse s’inscrit dans le cadre de l’évaluation du bruit de roulement. L’objectif est double. Premièrement, il s’agit de comprendre les mécanismes à l’œuvre dans un processus de roulement de deux surfaces rugueuses qui engendrent une vibration puis du bruit. Deuxièmement, on cherche à mettre en évidence l’influence des aspérités de la chaussée sur les forces dynamiques interfaciales et sur le bruit généré. Dans ce contexte, on propose un nouveau modèle 3D de contact dynamique basé sur la décomposition modale de la réponse du pneumatique. Cette nouvelle approche permet de réduire considérablement le temps CPU. Le pneumatique est modélisé par une plaque orthotrope sur fondation élastique. Le problème de contact est résolu par la méthode de pénalité. On a validé ce modèle analytiquement. Cet outil permet de prédire finement ce qui se passe dans la zone de contact. Nous pouvons prédire les forces de contact et les vitesses vibratoires. En outre, il permet de déterminer l’aire de contact et les cartes de pression. À l’échelle locale, les caractéristiques d’un choc sont connues. On est capable de déterminer la force maximale du choc, à partir de l’évolution temporelle de la force de contact, et sa durée mais aussi le pourcentage de temps du choc. / In a tire road contact, the rolling noise results from the mechanical interaction between the asperities of the roadway and the tread pattern. Following this interaction, compressive forces appear to push the two bodies in contact. These forces lead to the vibration of the tyre. These vibrations are the origin of the radiated noise. The work of this thesis falls within the evaluation of rolling noise. The objective is twofold. First, we seek to understanding the mechanisms involved in a rolling process of two rough surfaces that generate vibration and then noise. Second, we aim to show the influence of the road asperities on the interfacial dynamic forces and on the noise generated. In this context, we propose a new 3D model of the dynamic contact based on a modal decomposition of the tyre response. This new approach significantly reduces CPU time. The tyre is modeled by an orthotropic plate on a elastic foundation. The contact problem is solved by the penalty method. This model was validated analytically. This tool allows us to finely predict what happens in the contact area. We can predict contact forces and vibratory velocities. Moreover, it makes it possible to determine the contact area and the pressure maps. At the local scale, the characteristics of a shock are known. We are able not only to determine the maximum force of impact, using time evolution of the contact force, and its duration but also the percentage of shock time.

The tonal character of the low frequency internal noise in cars is often due to energy transmission through the tyre at the first few eigenfrequencies of the air cavity of the tyre. The first acoustic mode in the air cavity of a typical stationary car tyre is approximately 224 Hz. At this frequency the tyre is comparatively stiff resulting in a high transmission of energy from the road wheel contact to the car body itself. In order to investigate possible means of reducing this effect, the acoustic field inside a tyre is modelled. Theoretically it is found that the pressure inside a tyre and the energy transmission through the tyre to the wheel axle and the car body can be reduced by adding a sound absorbing material inside the tyre. This was confirmed by measurements on stationary as well as rotating tyres with and without added sound absorption. For a rotating tyre there is a split of the natural frequency depending on the rotational speed of the tyre. Measurements in a standard passenger car reveal that the noise level inside the car is rather high in a fairly wide frequency range around 224 Hz at normal velocities. This tonal noise can be reduced by adding sound absorption inside a tyre. Models for the prediction and the reduction of the tonal noise are presented. Measured and predicted results are compared and the agreement is found to be good. It is found that the tonal noise can be reduced by up to 9 dB. The effects of the air cavity resonances on the external noise have also been studied. It is estimated that external tyre noise can be reduced 1 dB by adding a sound absorbing material inside tyres. For a car travelling on a road a strong acoustic field is induced between the floor of the car and the road. The impact of this acoustic field can be reduced by mounting a sound absorbing material underneath the car. It is estimated that the A-weighted sound pressure level close to a running car could be reduced by 3 dB by adding this type sound absorption. It is found that aluminium foam could be a suitable sound absorbing material which could be mounted inside tyres and underneath cars. The acoustic and dynamic properties of various types of aluminium foams are discussed. In particular measurement techniques for determining sound absorption at grazing incidence are investigated. / QC 20100923

Exterior vehicle noise has a very big impact when it comes to environmental noise pollution. Due to the decrease of the other noise sources of a passenger car, like power-train and air turbulence noise in the last decade, the tyre/road noise has become a more important part in the overall noise generation of a vehicle nowadays. It is considered as the main noise source in nearly all driving conditions, especially with increasing vehicle speed. The easiest idea to tackle this pollution is to introduce rules like speed-limits to control the noise at a certain area or time. More interesting, however, is to approach the problem of unwanted noise directly at the source. This Thesis, carried out at Loughborough University, aims to give a better understanding about the basic noise generation mechanisms at the tyre/road interface. Especially, the air related mechanisms of closed cavities are analysed. With the usage of a solid rubber tyre, unique measurements have been carried out and the results are compared to the theories already existing in the literature. These measurements reveal some of the strengths and weaknesses of the current understanding of air related noise generation.

The objective of the present work is to study the vehicle suspension as a vibro-acoustic system of high complexity, consisting of many sub-systems with fundamentally different acoustical properties. In a parallel numerical and experimental modelling effort, important contributions to the understanding of its behaviour have been achieved. These findings are based on a balance between component investigations and global modelling of the complete system; they have been formulated for the transmission of both tyre-road excitation and friction-induced vibrations in the brake system. Initially an experimental study was conducted on a full vehicle test rig studying the broadband interior brake noise problem of, here named, roughness noise. The purpose of the study was twofold: first, to determine if the transmission from the source to the interior of the vehicle was structure-borne; second, to study the complexity of the suspension as a vibro-acoustic system. Parameters a_ecting the vibro-acoustic source were varied to gain understanding of the source mechanisms. This experimental study laid the foundation of the first part of this thesis (paper A) and provided the directions for the second part, the development of a mathematical modelling approach (paper B and C). In these two papers, methods for analysing the complex vibro-acoustic transfer of structure-borne sound in a vehicle suspension system were developed. The last part was then focussed on the wheel rim influence on the vibro-acoustic behaviour (paper D) of the suspension system. As a whole, the work clearly demonstrates that it is possible to conduct component studies of subsystems in the vehicle suspension system; and from these component studies it is possible draw conclusions that very well may avoid severe degradations in the interior noise of future vehicle generations. / <p>QC 20130503</p>

In contradistinction with road transport exhaust particulate matter (PM) emission, non-exhaust PM emission has not decreased substantially in recent years. One source of non-exhaust PM emission is studded tyre-pavement contact. A-state-of-the-art experimental machines must be developed and improved in order to make a contribution to decrease of non-exhaust PM emission consequently improving human health. This thesis carried out at the department of Machine Design at KTH Royal Institute of Technology deals with redesign of the tribometer available at the department premises to mount and test scaled down studded tyre-pavement PM generation. Three concepts of redesigned tribometer were generated and evaluated against each other, out of which one was selected to be designed in detail, manufactured, assembled and tested. Final concept validation was conduction of an experiment with studded and plain tyres running on a granite sample. PM10 and PM0.5 results were collected and analysed and final redesign of the tribometer was assessed. / I motsats till utsläpp av partiklar från vägtransporter har utsläpp av partiklar från andra källor än avgaser inte minskat avsevärt under de senaste åren. En källa till utsläpp av partiklar utöver avgaser är kontakten mellan dubbdäck och vägbana. Det är nödvändigt att utveckla och förbättra de senaste laborationsmaskinerna för att kunna bidra till att minska icke avgasrelaterade utsläpp och därmed människors hälsa. Denna avhandling, som utförts vid avdelningen för maskinkonstruktion vid KTH (Kungliga Tekniska Högskolan), handlar om att omkonstruera den tribometer som finns tillgänglig vid institutionen för att kunna montera och testa en nedskalad produktion av partiklar från däck och beläggning med dubbdäck. Tre koncept för en omkonstruerad tribometer skapades och utvärderades mot varandra, varav en valdes ut för att konstrueras i detalj, tillverkas, monteras och testas. Den slutliga valideringen av konceptet bestod av att genomföra ett experiment med dubbade och vanliga däck som kördes på ett granitprov. PM10- och PM0.5-resultaten samlades in och analyserades, varpå den slutliga omkonstruktionen av tribometern utvärderades.

Current European legislation aims to limit vehicle noise emissions since many people are exposed to road traffic noise in urban areas. Vehicle pass-by noise is measured according to the international standard ISO 362 in Europe. More recent investigations of urban traffic have led to the proposal of a revised ISO 362 which includes a constant-speed test in addition to the traditional accelerated test in order to determine the pass-by noise value. In order to meet the legal pass-by noise requirements, vehicle manufacturers and suppliers must analyse and quantify vehicle noise source characteristics during the development phase of the vehicle. In addition, predictive tools need to be available for the estimation of the final pass-by noise value. This thesis aims to contribute to the understanding of vehicle pass-by noise and of the characteristics of the vehicle noise sources contributing to pass-by noise. This is supported through an extensive literature review in which current pass-by noise prediction methods are reviewed as well. Furthermore, three vehicle noise sources are replicated experimentally under laboratory conditions. This involves an orifice noise source, represented by a specially designed loudspeaker on a moving trolley, shell noise, represented by a metal cylinder structure, and tyre cavity and sidewall noise, represented by an annular membrane mounted on a tyre-like structure. The experimentally determined directivity characteristics of the acoustically excited noise sources are utilised in the pass-by noise prediction method. The predictive results are validated against experimental measurements of the three vehicle-like noise sources made within an anechoic chamber.

Le secteur des transports représente 50% de la consommation mondiale en produits pétroliers. Une part significative de l'énergie est dissipée par le fonctionnement de la suspension et par la déformation du pneu. La texture de surface de chaussée et son interaction avec le pneu jouent un rôle certain dans cette dissipation d'énergie. Le travail présenté dans ce mémoire est consacré à la modélisation du contact entre un pneu et une chaussée en conditions de roulement dans le but d'évaluer la résistance au roulement. Le choc d'une sphère sur un demi-espace viscoélastique est d'abord étudié. Ensuite, le contact viscoélastique d'un objet roulant sur une surface lisse est modélisé avec une suspension attachant l'objet roulant à une masse qu'il supporte. Enfin, une méthode multipoint linéarisée est proposée pour l'étude du roulement sur une surface rugueuse sans suspension dans un premier temps, et avec suspension dans un second temps. La condition de roulement est introduite. Les surfaces rugueuses sont soit des surfaces composées d'aspérités sphériques, soit des surfaces de chaussées réelles. Les résultats numériques font apparaître une dissymétrie dans la distribution de pression de contact dans la direction du roulement. La force de résistance au roulement, définie comme le couple par rapport à l'axe de l'essieu divisé par le rayon de la roue, est calculée à partir de la distribution de pression. L'influence de différents paramètres sur cette force tels que la vitesse de roulement, la taille des aspérités ainsi que la raideur de la suspension est analysée / The transport accounts for about 50 percent of the fuel consumption. A significant proportion of energy is lost by the suspension and the deformation of the tyre. One of the important factors in the energy loss is the texture of the road and its interaction with the tyre. The present work deals with the numerical modelling of the contact between a tyre and a road in rolling conditions in order to evaluate the rolling resistance. First, the collision of a sphere and a viscoelastic halfspace is studied. Then the viscoelastic contact of a body rolling on an smooth surface is investigated with a suspension between a mass and the rolling body. Finally a linearised multipoint method is proposed for the study of the rolling contact on a rough surface first without suspension and then with a suspension. The rolling condition is introduced in the model. The rough surfaces are surfaces composed of spherical asperities or real road surfaces. Numerical results reveal an asymmetry in the distribution of the contact pressure in the rolling direction. The rolling resistance force, classically defined as the momentum opposing the rolling divided by the radius of the tyre, is calculated using the distribution of the contact pressure. The effects of different parameters on the rolling resistance force such as the rolling speed, the size of the asperities and the stiffness of the suspension are analysed

Les enjeux de consommation d'énergie et de sécurité ont fait du frottement entre les pneumatiques et la chaussée une propriété importante lors de la conception de nouveaux pneumatiques. Pour mesurer ces efforts de frottement deux cinématiques sont couramment utilisées : la mise en glissement et le roulement/glissement. Les lois de frottement issues des expériences de mise en glissement sont assez bien interprétées. En revanche, le lien qui existe entre ces lois de frottement et le comportement en roulement/glissement est encore mal compris. En particulier, les modèles de roulement/glissement n'incorporent pas la transition entre frottement statique et frottement dynamique, bien que cette phénoménologie soit bien établie expérimentalement. Dans cette thèse, nous proposons différents modèles de frottement en roulement/glissement qui étendent ceux de la littérature en intégrant explicitement la transition de frottement statique/dynamique. Pour tester ces modéles dans le cas du contact pneu/chaussée, nous avons réalisé des expériences selon les deux cinématiques, sur un contact simplifié élastomère/chaussée. A partir des expériences de mise en glissement, les paramètres de la loi de frottement sont identifiés, en fonction de la force normale appliquée, de la vitesse de glissement et de la nature de la chaussée. Ces résultats sont implémentés dans nos modèles, pour produire des prédictions en roulement/glissement, qui sont finalement comparées avec les mesures obtenues en roulement/glissement. De plus, certaines hypothèses des modèles ont été testées par des expériences de visualisation in situ du contact. En particulier nous confirmons, sur une interface élastomère/verre, la présence simultanée d'une zone collée et d'une zone en glissement en conditions de roulement/glissement. / For safety and energy consumption issues, tyre friction has become an important property when designing tyres. There are two main kinematic conditions which are commonly used to measure friction forces : the onset of sliding and the rolling/sliding. The friction laws which are extracted from the onset of sliding experiments are rather well interpreted. In contrast, the link between those frictions laws and the rolling/sliding behaviour remains incompletely understood. In particular, the rolling/sliding models do not take into account the transition between static friction and dynamic friction, although it is a well-established phenomenology. In this manuscript, we propose diérent models of friction in rolling/sliding, which extend those of the literature by explicitly integrating a static/dynamic friction transition. To test these models in the case of a tyre/road contact, we performed experiment in the two kinematic conditions, on a simpliéd elastomer/road contact. From the onset of sliding experiments, we identify the parameters of the friction law as functions of the applied normal force, the sliding speed and the type of road. These results are used as inputs in our models to predict the rolling/sliding behaviour, and are eventually compared with the corresponding experiments. In addition, we have tested several assumptions made in the models by performing in situ contact imaging experiments. In particular we con_rm, on an elastomer/glass interface, the simultaneous presence of a sticking and a slipping zone in rolling/sliding conditions.

Die Kontaktverhältnisse zwischen Reifen und Fahrbahn bestimmen die maximal übertragbaren Beschleunigungs-, Brems- und Seitenkräfte des Fahrzeugs und sind daher für die Fahrsicherheit von großer Bedeutung. In dieser Arbeit wird ein Modell zur numerisch effizienten Simulation der hochfrequenten Dynamik einzelner Reifenprofilblöcke entwickelt. Der vorgestellte Modellansatz nutzt einerseits die Vorteile der Finite-Elemente-Methode, welche die Bauteilstruktur detailliert auflösen kann, bei der jedoch lange Rechenzeiten in Kauf genommen werden. Andererseits profitiert der vorgestellte Modellansatz von den Vorteilen stark vereinfachter Mehrkörpersysteme, welche die Berechnung der hochfrequenten Dynamik und akustischer Phänomene erlauben, jedoch strukturdynamische Effekte und das Kontaktverhalten in der Bodenaufstandsfläche des Reifens nur begrenzt abbilden können. Das hier vorgestellte Modell berücksichtigt in einem modularen Ansatz die Effekte der Strukturdynamik, der lokalen Reibwertcharakteristik, der nichtlinearen Wechselwirkungen durch den Kontakt mit der rauen Fahrbahnoberfläche und des lokalen Verschleißes. Die erforderlichen Modellparameter werden durch geeignete Experimente bestimmt. Ein Schwerpunkt der Arbeit liegt in der Untersuchung reibungsselbsterregter Profilblockschwingungen bei Variation der Modell- und Prozessparameter. Zur realistischen Betrachtung des Reifenprofilblockverhaltens erfolgt eine Erweiterung des Modells um eine Abrollkinematik, die tiefere Einblicke in die dynamischen Vorgänge in der Bodenaufstandsfläche des Reifens ermöglicht. Diese Simulationen lassen eine Zuordnung der aus der Literatur bekannten zeitlichen Abfolge von Einlaufphase, Haftphase, Gleitphase und Ausschnappphase zu. Es zeigen sich bei bestimmten Kombinationen aus Fahrzeuggeschwindigkeit und Schlupfwert ausgeprägte Stick-Slip-Schwingungen im akustisch relevanten Frequenzbereich. Das Modell erlaubt die Untersuchung des Einflusses der Profilblockgeometrie, der Materialparameter, der Fahrbahneigenschaften sowie der Betriebszustände auf den resultierenden Reibwert, auf das lokale Verschleißverhalten sowie auf das Auftreten hochfrequenter reibungsselbsterregter Schwingungen. Somit ermöglicht das Modell ein vertieftes Verständnis der Vorgänge im Reifen-Fahrbahn-Kontakt und der auftretenden Wechselwirkungen zwischen Struktur- und Kontaktmechanik. Es kann eine Basis für zukünftige Optimierungen des Profilblocks zur Verbesserung wesentlicher Reifeneigenschaften wie Kraftschlussverhalten, Verschleiß und Akustik bilden. / The contact conditions between tyre and road are responsible for the maximum acceleration, braking and side forces of a vehicle. Therefore, they have a large impact on the driving safety. Within this work a numerically efficient model for the simulation of the high-frequency dynamics of single tyre tread blocks is developed. The presented modelling approach benefits the advantage of the finite element method to resolve the component structure in detail. However, a long computation time is accepted for these finite element models. Moreover, the presented modelling approach makes use of the advantage of simplified multibody systems to calculate the high-frequency dynamics and acoustic phenomena. However, structural effects and the contact behaviour in the tyre contact patch can be covered only to a minor degree. The model treated here considers the effects of structural dynamics, the local friction characteristic, the non-linear interaction due to the contact with the rough road surface and local wear. The required model parameters are determined by appropriate experiments. One focus of this work is the investigation of self-excited tread block vibrations under variation of the model and process parameters. In order to realistically investigate the tread block behaviour the model is extended with regard to rolling kinematics which provides a deeper insight into the dynamic processes in the tyre contact patch. The corresponding simulations allow the allocation of the run-in phase, sticking phase, sliding phase and snap-out which is reported in the literature. For certain combinations of vehicle velocity and slip value pronounced stick-slip vibrations occur within the acoustically relevant frequency range. The model enables to study the influence of the tread block geometry, the material properties, the road surface characteristics and the operating conditions on the resulting tread block friction coefficient, local tread block wear and the occurrence of high-frequency self-excited vibrations. The simulation results provide a distinct understanding of the processes in the tyre/road contact and the interactions between structural mechanics and contact mechanics. They can be a basis for future tread block optimisations with respect to essential tyre properties such as traction, wear and acoustic phenomena.