Tesis sobre el tema "Tyred wheels"

Diploma work describes in its theoretical part particular types of pairs of wheels used on railway vehicles in Czech Republic as well as their components and assembly instructions. Practical part describes workplace for wheels in reparation DPOV, a.s. at repairing centre Nymburk, its facilities and repairing possibilities by total repair of pairs of wheels. Practical part brings at the end particular report with results of pairs of wheels measuring.

The ring-rolling process was first developed in the UK in the mid nineteenth century and is still widely used as the preferred method of forming seamless rings for many aerospace and automotive applications, as well as for producing railway wheels and tyres. This thesis describes the development of a finite element based mathematical model that can be used to simulate the process. The model has been developed with the intention of practical application within railway wheel manufacturer Adtranz New Wheel Products Division. A detailed review of previous research on the process is presented. The key observation from that review is that all attempts at modelling ring rolling have suffered from severe run time difficulties which are predominantly due to lack of constraint and the large number of increments required to complete a simulation. Based on this fact the focus of development activities has been on identifying ways in which the simulation can be run in realistic time frames. The usefulness of a simplified 2D method is assessed, with the conclusion that while some beneficial information might be gained by such an approach, 3D simulation is the only way of fully representing material deformation during the process. Attempts at improving run time of 3D modelling have focused on two main areas. Firstly an efficient arbitrary Lagrangian Eulerian finite element flow formulation has been adopted. This gives the advantages of allowing mesh density to be concentrated on roll gap regions, and removing some of the convergence problems associated with frequent contact changes. Secondly the issue of solution of the discretised flow formulation equations is examined in some detail. A range of well known solution methods are considered as potential ways of improving on direct methods, with limited success. Significant potential benefits are found to result however from a new approach, the successive preconditioned conjugate gradient method. This method, together with tests of its effectiveness, is described in some detail. The resulting model is tested against experimental work performed by previous authors. Attempts to integrate the work into Adtranz are also described. These have included consideration of usability and management issues, and illustrative case studies.

This thesis reports the investigation into the modelling and simulation of an aircraft tyre and wheel assembly in finite element environment. The finite element simulations basing on aircraft tyre test and operational scenarios could predict the loads transferred from tyre and the stresses distributed to the wheel rim. The virtual analysis could assess the safety criteria of different tyre structures, which would lead to the cost and time circle reduction in tyre R&D process. An H41x16.0R20 radial ply aircraft test tyre and its corresponding test wheel, provided by Dunlop Aircraft Tyres Limited, are adopted as the subject of this research. The material properties, especially the rubber and fabric materials, have been investigated. The finite element hyperelastic models have been utilized to represent rubbers and been correlated to experimental data. The 2D and 3D finite element tyre models, along with the finite element wheel models are created in the commercial finite element code, LS-Dyna. The finite element models have been validated with either industrial standardised simulation results or experimental data. Basing on the validated models, simulations that duplicating static test and dynamic operational scenarios have been developed. The researches have provided knowledge in comparing single and double bead tyre designs with respect to wheel loading mechanisms. The computational model also allowed manufacturers to assess the performance and safety criteria of a particular tyre at its design stage. The development of such models would add to the general drive towards the use of more virtual prototypes in an area traditionally reliant on experimental testing.

The current state-of-the-art tyre models tend to be demanding in parameterisation terms, typically requiring extensive and expensive testing, and computational power. Consequently, an alternative parameterisation approach, which also allows for the separation of model fidelity from computational demand, is essential. Based on the above, a tyre model is introduced in this work. Tyre motion is separated into two components, the first being the non-linear global motion of the tyre as a rigid body and the second being the linear local deformation of each node. The resulting system of differential equations of motion consists of a reduced number of equations, depending on the number of rigid and elastic modes considered rather than the degrees of freedom. These equations are populated by the eigenvectors and the eigenvalues of the elastic tyre modes, the eigenvectors corresponding to the rigid tyre modes and the inertia properties of the tyre. The contact sub-model consists of bristles attached to each belt node. Shear forces generated in the contact area are calculated by a distributed LuGre friction model while vertical tread dynamics are obtained by the vertical motion of the contact nodes and the corresponding bristle stiffness and damping characteristics. To populate the abovementioned system of differential equations, the modal properties of the rigid and the elastic belt modes are required. In the context of the present work, rigid belt modes are calculated analytically, while in-plane and out-of-plane elastic belt modes are identified experimentally by performing modal testing on the physical tyre. To this end, the eigenvalue of any particular mode is obtained by fitting a rational fraction polynomial expression to frequency response data surrounding that mode. The eigenvector calculation requires a different approach as typically modes located in the vicinity of the examined mode have an effect on the apparent residue. Consequently, an alternative method has been developed which takes into account the out-of-band modes leading to identified residues representing only the modes of interest. The validation of the proposed modelling approach is performed by comparing simulation results to experimental data and trends found in the literature. In terms of vertical stiffness, correlation with experimental data is achieved for a limited vertical load range, due to the nature of the identified modal properties. Moreover, the tyre model response to transient lateral slip is investigated for a range of longitudinal speeds and vertical loads, and the resulting relaxation length trends are compared with the relevant literature.

Competitive performance of an F1 race car relies upon a well designed and highly developed aerodynamic system. In order to achieve this, total understanding of the downstream wake of exposed rotating wheels is essential. Components such as bargeboards and indeed much of the front wing are developed to provide pressure gradients and vortex structures to influence the wheel wake, ensuring high energy mass-flow to the sensitive leading edge of the underfloor and eventually the rear wing. Wind tunnel testing of model-scale deformable tyres has become a common occurrence in F1 in recent years although there is a significant lack of available literature, academic or otherwise, as to their use. This work has studied in detail the aerodynamic consequences which occur from the varying sidewall bulge and contact patch region making use of several techniques. These include scanning rotating tyre profiles under load, static contact patch size measurements, five-hole pressure probe wake measurements, particle image velocimetry (PIV) and load-cell drag measurements. CFD simulations utilising two industrial codes have also been performed to support the experimental work. Coordinates representing tyre profiles under a range of on-track conditions are available for other researchers to use as a basis for CFD studies. The work presented here includes a full range of representative on-track axle heights which far exceed the more conservative range usually tested in an industrial setting for longevity reasons. The most sensitive parameters for aerodynamic testing of wheels have been identified. For development of a full car, in decreasing order of priority, the following must be correctly matched to the realistic scenario: axle height, yaw condition (without glycerol - often used to reduce friction at the expense of a compromised tyre profile), camber angle, detailed internals, high inflation pressure, through-hub flow rate and least significantly the rotation of the internal brake rotor. The study of through-hub flows revealed that the external aerodynamic effect of the brake scoop inlet varies significantly with the amount of internal restriction. The pumping effect of the brake rotor was measured to be negligible compared to the restrictive effect of its internal passages and that leads to an effect known as inlet spillage with a negative cooling drag trend, whereby the drag of the wheel assembly decreases with increased through-hub flow.

This thesis is concerned with the characterization of layered contact problems. The research project has been prompted by an investigation into creep, and ultimately, gross sliding, of rubber tyres fitted around steel wheels in earth moving equipment. In general, slippage between tyre and rim is experienced in common engineering applications employing tyred systems. A general and systematic approach for investigating the interfacial behaviour of tyred systems has consequently been proposed. Classical techniques together with novel numerical approaches based on advanced mathematical programming have been implemented to support the investigation. Creep between mating surfaces, frictional shakedown and measuring friction in partial slip condition are the main objects of investigation. The analytical and numerical models developed by the author have been complemented by experimental work, whose detailed description is also included in this thesis. Finally, further studies have been performed to shed light on some of the design issues offered by the threedimensional full-scale engineering application. The numerical approach based on finite element modelling used to tackle these aspects of the project and the experimental work carried out by the author to corroborate the numerical findings are also presented.

Orientador: José Roberto de França Arruda
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-28T12:34:37Z (GMT). No. of bitstreams: 1 Pugliese_DanielPerussi_M.pdf: 5689260 bytes, checksum: fc23e46a7c6b4785faef7e0a5f83078f (MD5) Previous issue date: 2015
Resumo: A não uniformidade em pneus esta associada com o seu processo de fabricação e afeta todos os tipos de pneus, mas é mais relevante em pneus de veículos de passeio, dado que este setor exige elevados níveis de conforto a altas velocidades. As forças dinâmicas devido à rotação dos pneus variam de acordo com a velocidade do veículo. Em certas velocidades podem excitar frequências naturais do sistema pneu-suspensão. Este trabalho explora os efeitos dinâmicos das não uniformidades de um conjunto de pneu-roda de um veiculo de passeio. Seu impacto sobre as forças da roda nas direções radiais, transversais e longitudinais, em baixas e altas velocidades são investigados tanto numérica quanto experimentalmente. A principal contribuição deste trabalho é a geração de um modelo tridimensional dinâmico para o estudo da não uniformidade. O modelo é construído utilizando o método dos elementos finitos. A validação do modelo é realizada utilizando-se o modelo de pneu comercial mais amplamente utilizado, e com uma campanha experimental significativa. Os resultados numéricos preveem os principais efeitos observados experimentalmente da não uniformidade do conjunto pneu-roda no sentido vertical e longitudinal. Este último predominante a elevadas velocidades. O modelo numérico é útil para a análise dinâmica virtual de diferentes tipos de não uniformidade
Abstract: Tire non-uniformity is associated with the production process and affects all types of tires, but is more relevant for passenger tires, as this sector requires high levels of comfort at the high speeds achieved by vehicles in this segment. Dynamic forces due to tire rotation vary with the vehicle speed. At certain speeds they can excite natural frequencies of the tire-suspension system. This work explores the dynamic effects of non-uniformities of a car tire-wheel assembly. Their impact on hub forces at the radial, lateral and longitudinal directions, at low and high speeds are investigated both numerically and experimentally. The main contribution of this work is the generation of a dynamic three-dimensional model for the study of tire non-uniformity. The model is built using the Finite Element Method. The model is validated with the most widely used commercial tire model and with a significant experimental campaign, which is also described in the paper. Numerical results predict the main experimentally observed effects of non-uniformity of the tire-wheel assembly in the vertical and longitudinal directions. The latter predominate at higher speeds. The numerical model is helpful for the virtual dynamic analysis of different types of non-uniformity
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica

This research has investigated the effect of tyre rutting of wheeled construction plant performance traversing in wet and deformable terrain, specifically clay and sand. The purpose was to translate the wheel rutting into performance reduction measured in drawbar-pull. The ultimate goal was to translate the power loss into practical effects on cost, time and other economic variations on construction projects that are characterised by movement of wheeled plant on long haulage deformable roads. In order to achieve this aim, mathematical modelling was deployed based on Newton’s laws of motion, principles of energy conservation and numerical integration. The model is based on a single rigid wheel because construction plant tyres are inflated to high pressure in order to support heavy loads thereby translating the flexible tyres into rigid mode. The results from the mathematical model were verified using a three stage robust verification process which included computational analysis based on two existing semi-empirical methods and real experimental data. Laboratory experiments using Mobility SF- 3713 were also used to check the validity of the results. The results from the mathematical model verify that a flexible tyre can operate in rigid mode if it encounters softer and wet ground. Results further indicate that the soil cohesion, angle of shearing resistance and moisture content play key roles in the subsequent power loss created by motion resistance. All the results from computational analysis and the experiments were found to be consistent with the mathematical model results. The study concludes that there is ample evidence to suggest that there is significant power loss associated with wheeled construction plant traversing in soft terrain which can be assessed. The study further concludes that a combination of economic decisions on variables must be considered with respect to existing ground conditions. This will considerably reduce uncertainty levels in cost and resource management on construction projects.

This research has investigated the effect of tyre rutting of wheeled construction plant performance traversing in wet and deformable terrain, specifically clay and sand. The purpose was to translate the wheel rutting into performance reduction measured in drawbar-pull. The ultimate goal was to translate the power loss into practical effects on cost, time and other economic variations on construction projects that are characterised by movement of wheeled plant on long haulage deformable roads. In order to achieve this aim, mathematical modelling was deployed based on Newton’s laws of motion, principles of energy conservation and numerical integration. The model is based on a single rigid wheel because construction plant tyres are inflated to high pressure in order to support heavy loads thereby translating the flexible tyres into rigid mode. The results from the mathematical model were verified using a three stage robust verification process which included computational analysis based on two existing semi-empirical methods and real experimental data. Laboratory experiments using Mobility SF- 3713 were also used to check the validity of the results. The results from the mathematical model verify that a flexible tyre can operate in rigid mode if it encounters softer and wet ground. Results further indicate that the soil cohesion, angle of shearing resistance and moisture content play key roles in the subsequent power loss created by motion resistance. All the results from computational analysis and the experiments were found to be consistent with the mathematical model results. The study concludes that there is ample evidence to suggest that there is significant power loss associated with wheeled construction plant traversing in soft terrain which can be assessed. The study further concludes that a combination of economic decisions on variables must be considered with respect to existing ground conditions. This will considerably reduce uncertainty levels in cost and resource management on construction projects.

Tillage operations in farming often require high traction forces applied by tractor wheels. These interact with topsoil via a stress system along the contact surface, this interaction resulting in soil and tyre deformation. Topsoil is subject to normal and tangential stresses at the contact surface. The tangential stress rises sharply with increasing traction force and may cause topsoil among tyre lugs to fail, with the consequent formation of a strengthless layer strongly exposed to erosion and an underlying layer where shear deformations contribute to the alteration of soil structure functionalities. This work aimed to investigate mechanical conditions along the soil-tyre contact surface which lead to topsoil damage. These conditions are analysed in the light of simulations with a soil-tyre interaction model and discussed on the basis of results of specific experimental tests. A semi-empirical model of interaction between the soil and a pneumatic wheel was adapted to simulate the traction performance of mechanical front-wheel drive MFWD vehicles, taking into account the load transfer effect, the multi-pass effect, and the theoretical speed ratio between the front and the rear axles. This model was employed to simulate (i) the traction performance of tractors in terms of drawbar pull, motion resistance due to soil compaction, traction coefficient and traction efficiency as a function of slip, wheel load and tyre inflation pressure; (ii) soil stress paths along the contact surface with tyres; and (iii) the risk of soil failure corresponding to a defined slip level. Several traction tests were performed on four agricultural soils of different texture (clay, clay loam, silty loam, and loamy sand). Four tractors of wide ranging power (40.4 kW, 65 kW, 110 kW, and 123 kW) and weight (25.3 kN, 40 kN, 66.7 kN, and 68 kN) were used. Tractor configurations were varied by changing tyre inflation pressure and tractor weight, and by using dual tyres. Slip normally ranged between 0% and 35%, only in some cases higher values, up to 58%, were reached. The shearing effect on the topsoil due to slip of tractor tyres was investigated on the silty loam agricultural field by measuring longitudinal topsoil displacements along the driving corridors during traction tests. A system of strips orthogonal to the tractor track was spray-painted on the soil surface to enable easy visualisation of the topsoil displacements. The changes in soil hydraulic properties owing to deformation caused by the passage of the 40 kN tractor, both in a self-propelled condition without wheel slip, and with high drawbar pull (21.8 kN) and high wheel slip (27%), were compared in the clay loam agricultural field. The mechanical properties of the topsoil were determined in situ on the basis of vertical plate-penetration tests and horizontal plate-shear deformation tests with a tractor-mounted bevameter. Soil stress-strain conditions at contact with a traction tyre were reproduced in the laboratory by means of a direct simple shear box. A Geonor shear box was modified in order to carry out hydraulic conductivity measurements in saturated conditions while shearing the soil sample. Simulations with the soil-tractor interaction model matched measured traction performance with general good agreement (overall mean error of 12% and overall mean residual of 3.30 kN). As soon as the soil failure condition, as simulated by the model, was approached along the soil-tyre contact surface, longitudinal topsoil displacements measured in the silty loam agricultural field clearly increased. The slip values at which soil failure was reached were identified for three configurations of the 40 kN tractor. These slip values should be regarded as indicative limits not to be exceeded in tillage operations in order to avoid topsoil damage in the conditions under consideration. The stress state at the soil-tyre contact surface increased significantly, mostly in terms of shear stress, when the tractor moved with slip rather than without slip. As a consequence, the severity of tractor-traffic-induced soil degradation increased appreciably. The change in soil structure and hydraulic properties measured in the clay loam agricultural field was more pronounced in the first 0.15 m where the total porosity decreases by 11% without slip and 29% with slip, with a reduction in macropores of about 60% and 100%, respectively. The saturated hydraulic conductivity of the shallow topsoil (0 - 0.04 m) turned out to be reduced by about 66% without slip and about 98% with 27% slip. The results of the simple shear tests confirmed that shear deformations may contribute to damage topsoil structure functionalities, decreasing, in most cases, hydraulic conductivity. However, in the samples of clay, clay loam and silty loam, the major decrease in hydraulic conductivity was caused by the deformation during compression. Moreover, it emerged that the effects of shearing on the saturated hydraulic conductivity are mainly controlled by the volumetric strain coupled to the shear strain, and the variation in voids volume of the pore system affects the hydraulic conductivity more than a pure distortional deformation which may alter the water pathways in the sample. The validated approach for modelling tractor traction performance and predicting topsoil damage from the shearing effect due to tyre slip was used as a framework for developing a new Excel module for the third edition of the TASC V3.0.xlsm software: www.agrartechnik-agroscope.ch. This module also provides the power-wheel slip relationship. Four practical tests were set up for the user to enable a fast, simple and reliable mechanical characterisation of topsoil behaviour. Different tractor configurations, soil textures and conditions can be confronted. The limit beyond which topsoil damage is expected to occur is reported in terms of net traction and wheel slip. TASC V3.0 offers a valuable support tool for identifying tractor configurations and soil conditions which optimise traction, resulting in increased fuel saving, reduced tyre wear and limited topsoil damage.
Le lavorazioni dei terreni agricoli in molti casi richiedono elevate forze di trazione sviluppate dalle ruote dei trattori. Uno pneumatico da trazione interagisce con il terreno attraverso un sistema di tensioni lungo la superficie di contatto tra lo pneumatico e il terreno, tale interazione genera deformazioni sia nel terreno che nello pneumatico. Il terreno viene assoggettato a tensioni normali e tangenziali alla superficie di contatto con lo pneumatico. Le tensioni tangenziali aumentano repentinamente all’aumentare della forza di trazione e possono portare il terreno compresso tra le costolature del battistrada dello pneumatico in condizioni di rottura (effetto di taglio del terreno). Ciò determina la formazione di uno strato superficiale di terreno privo di resistenza meccanica e, quindi, fortemente esposto ai fenomeni erosivi, e uno strato sottostante in cui l’effetto delle deformazioni di taglio contribuisce ad alterare le funzionalità della struttura del terreno. Obiettivo di questo lavoro è l’indagine delle condizioni meccaniche all’interfaccia di contatto tra il terreno e lo pneumatico che generano suddetto danneggiamento del terreno. Tali condizioni meccaniche sono state analizzate e discusse sulla base di simulazioni con un modello di interazione terreno-pneumatico e secondo i risultati di specifiche prove sperimentali. Un modello semiempirico di interazione tra il terreno e una ruota pneumatica è stato adattato per simulare le prestazioni di trazione di trattori MFWD, considerando l’effetto di trasferimento del carico sulla ruota, l’effetto del passaggio multiplo sul terreno e il rapporto delle velocità teoriche tra gli assi anteriore e posteriore. Il modello è stato utilizzato per simulare (i) le prestazioni di trazione di trattori MFWD in termini di trazione netta, resistenza al movimento dovuta al compattamento del terreno, coefficiente di trazione ed efficienza di trazione, in funzione dello slittamento degli pneumatici, del carico sulla ruota e della pressione di gonfiaggio degli pneumatici; (ii) i percorsi di tensione del terreno lungo la superficie di contatto con lo pneumatico e (iii) il rischio di raggiungimento delle condizioni di rottura del terreno in corrispondenza di un definito slittamento. Numerose prove di trazione sono state eseguite su quattro terreni agricoli di differente tessitura (terreno argilloso, franco argilloso, franco limoso e sabbioso franco), utilizzando quattro trattori aventi potenza di 40.4 kW, 65 kW, 110 kW e 123 kW e peso di 25.3 kN, 40 kN, 66.7 kN e 68 kN. La configurazione dei trattori è stata variata modificando la pressione di gonfiaggio degli pneumatici, il peso del trattore e utilizzando doppi pneumatici. Lo slittamento è stato controllato in un intervallo di valori generalmente compresi tra 0% e 35%, in alcuni casi sono stati raggiunti valori più elevati fino a un massimo del 58%. L’effetto di taglio del terreno, dovuto allo slittamento degli pneumatici da trazione, è stato studiato sul terreno agricolo franco limoso attraverso la misura degli spostamenti longitudinali del terreno lungo i corridoi di esecuzione delle prove di trazione. Un sistema di strisce ortogonali al corridoio di avanzamento del trattore è stato tracciato con una vernice spray sulla superficie del suolo, al fine di visualizzare in modo semplice gli spostamenti del terreno. Le alterazioni delle proprietà idrauliche del terreno causate dalle deformazioni indotte dal passaggio del trattore di 40 kN sono state confrontate in un terreno franco argilloso in assenza di slittamento e con elevato slittamento (27%) e forza di trazione netta (21.8 kN). Le proprietà meccaniche del terreno sono state determinate in situ sulla base di prove di compressione verticale e prove di deformazione di taglio in direzione orizzontale eseguite con un bevameter installato su di un trattore. Le condizioni di tensione e deformazione del terreno al contatto con lo pneumatico sono state riprodotte in laboratorio per mezzo di una scatola di taglio semplice diretto della Geonor. Essa è stata modificata al fine di eseguire delle misure di conducibilità idraulica in condizioni di saturazione durante la fase di taglio del provino di terreno. Le simulazioni con il modello di interazione terreno-trattore hanno riprodotto le misure delle prestazioni di trazione con elevata fedeltà (errore medio del 12% e scarto medio di 3.3 kN). Quando la condizione di rottura del terreno (simulata dal modello) è stata raggiunta lungo la superficie di contatto terreno-pneumatico, gli spostamenti longitudinali misurati sulla superficie del terreno franco limoso sono aumentati in maniera evidente. I valori di slittamento corrispondenti al raggiungimento della condizione di rottura del terreno sono stati definiti per tre configurazioni del trattore di 40 kN. Tali valori, che possono essere considerati come limiti indicativi nelle condizioni analizzate, non dovrebbero essere superati nelle operazioni di lavorazione del terreno, al fine di evitarne il danneggiamento. Lo stato di stress al contatto terreno-pneumatico è aumentato significativamente in presenza di slittamento, principalmente in termini di tensioni di taglio, con un conseguente aumento apprezzabile del danneggiamento del terreno indotto dal traffico del trattore. Le alterazioni della struttura e delle proprietà idrauliche misurate nel terreno franco argilloso sono risultate più evidenti nei primi 0.15 m di profondità dove è stata misurata una riduzione di porosità totale dell’11% in assenza di slittamento e del 29% in presenza di slittamento, con una corrispondente diminuzione della macroporosità rispettivamente del 60% e del 100%. Le deformazioni indotte dalle ruote del trattore hanno ridotto la conducibilità idraulica in condizioni di saturazione dello strato più superficiale di terreno (0 - 0.04 m) di circa il 66% in assenza di slittamento e di circa il 98% in presenza di uno slittamento del 27%. I risultati delle prove eseguite con la scatola di taglio semplice hanno confermato che le deformazioni di taglio possono contribuire al danneggiamento delle funzionalità della struttura del terreno, riducendo, in molti casi, la conducibilità idraulica. Tuttavia, nei terreni argilloso, franco argilloso e franco limoso la riduzione complessiva di conducibilità idraulica è stata quasi esclusivamente causata dal processo di compressione. La variazione della conducibilità idraulica durante il processo di taglio è stata principalmente controllata dalle deformazioni volumetriche abbinate a quelle di taglio. La variazione di porosità ha influenzato la conducibilità idraulica più della deformazione distorsionale che può alterare i percorsi idraulici all’interno del provino. L’approccio proposto per la modellazione delle prestazioni di trazione e l’identificazione delle condizioni di danneggiamento del terreno dovute all’effetto di taglio causato dallo slittamento degli pneumatici da trazione è stato convalidato sperimentalmente e utilizzato per lo sviluppo di un nuovo modulo Excel per la terza edizione del software TASC V3.0.xlsm: www.agrartechnik-agroscope.ch. Questo modulo simula anche la relazione tra potenza erogata dal motore e slittamento delle ruote. Per permettere agli utilizzatori una semplice e affidabile caratterizzazione meccanica del terreno, sono state messe a punto quattro pratiche prove di campo. L’applicazione consente di confrontare numerose configurazioni del trattore, su vari terreni con differenti condizioni. Il limite oltre il quale è previsto un danneggiamento del terreno è riportato in termini di trazione netta e slittamento. Il TASC V3.0 rappresenta un valido supporto per identificare le configurazioni del trattore e le condizioni del terreno che ottimizzano le prestazioni di trazione, con conseguente riduzione dei consumi di carburante e limitazione dell’usura degli pneumatici e del danneggiamento del terreno.

It is the tyre that ensures the interaction between a wheel and road surface and it is the the tyre which also acts as a primary cushioning. Its construction, features and condition highly influence driving properties of a car and thus passenger safety as well. In motorsports the tyre is a key part of the vehicle and therefore it is necessary to make use of its complete potential for reaching the best results. The aim of this thesis is a device construction suitable for tyre parameter and their characteristics measurement. The next task is to design a measuring system for tyre pressure and temperature monitoring. With using of these devices a few real-tyre measurements and subsequent result evaluation will be done. The output of the thesis is an overview of construction details, overview of selected tyre parameters, design and drawing documentation of multipurpose measuring device and the results of my measurements.

Baigiamajame magistro darbe atlikta mokslo darbų, skirtų automobilio rato sąveikai su skirtingos būklės ir savybių kelio danga tyrimams analizė. Atlikti eksperimentiniai tyrimai, kurių metu ištirti temperatūros pokyčiai ratui sąveikaujant su kelio danga ir jų įtaka sankybio rodikliams. Surinkti, susisteminti, statistiškai apdoroti ir išanalizuoti 2011 ir 2012 metais išmatuoto valstybinės reikšmės kelių naujos asfalto dangos ir rato sukibimo koeficiento duomenys. Pateikiamos baigiamojo darbo išvados. Darbą sudaro 6 dalys: įvadas, mokslo darbų analizė, eksperimentiniai automobilio rato sukibimo su kelio danga parametrų tyrimai, valstybinės reikšmės kelių naujos asfalto dangos ir rato sukibimo koeficiento tyrimas ir vertinimas, išvados, literatūros sąrašas. Darbo apimtis – 65 p. teksto be priedų, 46 iliustr., 10 lent., 32 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai.
In this master thesis is performed a research studies analysis about car wheel and road interaction . Car wheel interaction with road pavement tests were performed and temperature changes which affect grip is examined. Collected, structured and statistically analyzed 2011 and 2012 year wheel traction data. The conclusions is presented. The paper consists of six parts: introduction, analysis of scientific articles and studies, experimental study of car wheel grip with road surface parameters, new asphalt pavement grip research and evaluation, conclusions, references. Pages - 65 p. text, 46 pictures., 10 tables., 32 bibliographic sources. Appendixes.

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.

QC 20130503

Cette thèse, collaboration entre Michelin et l’ONERA, propose de mettre en œuvre des simulations instationnaires URANS grâce au code Navier-Stokes elsA de l’ONERA en vue d’analyser l’écoulement complexe 3D instationnaire se développant au voisinage des roues d'un véhicule et d’identifier les mécanismes à l’origine de la production de traînée.En effet, les roues (jantes et pneumatiques) constituent un nouvel axe de recherche prometteur en aérodynamique automobile car on estime de 20% à 40% la contribution des roues et passages de roues à la traînée totale. Cependant, leur optimisation nécessite en premier lieu une compréhension complète des phénomènes aérodynamiques mis en jeu. Les analyses spatio-temporelles menées sur roue isolée et sur véhicule pour trois types de pneumatiques (lisse, rugueux, avec sillons) apportent de nouveaux éléments de compréhension sur la physique de l’écoulement. Ce travail répond notamment aux limites principales des études précédentes grâce à la description de l'écoulement sur des géométries de référence incluant des pneumatiques déformés lisses et grâce à l’étude de l’instationnarité. Les analyses spatiales permettent de décrire l’organisation des structures tourbillonnaires sur roue isolée puis autour des roues avant et arrière d’un véhicule simplifié. Les analyses temporelles facilitent quant à elles la compréhension de la dynamique de l’écoulement par la mise en évidence de la génération des tourbillons et des mécanismes d’interaction avec la carrosserie. Des validations expérimentales sont effectuées à la fois sur roue isolée et sur véhicule en soufflerie. Enfin, l’utilisation de plusieurs types de pneumatiques démontre leur capacité à modifier les caractéristiques spatio-temporelles de l’ensemble de l’écoulement et à jouer ainsi sur la puissance dissipée par le véhicule via la traînée et le moment de rotation des roues
As a collaborative task between Michelin and ONERA, this thesis aims to investigate the complex unsteady 3D flow around car wheels and to identify the mechanisms of drag production linked to this part of the car thanks to URANS unsteady numerical simulations using ONERA’s Navier-Stokes code elsA. The wheels (i.e. rims and tyres) are indeed a promising research topic in the field of car aerodynamics. The part of the total drag due to the wheels and wheelhouses is indeed estimated between 20% and 40%. The first step towards wheel optimisation is to achieve full understanding of the aerodynamic phenomena produced around them. The analysis of the flow for three types of tyres (smooth, rough, grooved), both around isolated wheels and around a simplified vehicle, brings further understanding of the flow physics. This work completes previous studies in this field thanks to the description of basic flows around smooth wheels and the study of unsteady effects. It describes the arrangement of vortical structures around an isolated wheel and around the front and rear wheels of a simplified vehicle. Moreover, the analysis of the flow unsteadiness facilitates understanding of the flow dynamics by highlighting the generation of the main vortices and the interaction phenomena with the car body. The validation of numerical models is performed with specific experiments by Michelin on both an isolated wheel and a vehicle configuration. Finally, the use of different tyres shows their ability to modify both space and time characteristics of the whole flow, thus modifying the power dissipated by the car drag and the rotation moment of the wheels

This diploma thesis deals with modeling and CFD calculation of aerodynamic characteristics of vehicle, influenced by loaded or unloaded tires and boundary conditions applied on this tires. These calculations are combined with three types of variable rear body shape of DrivAer vehicle. There is a complete analysis and evaluation of the effects of these factors.

Road vehicle tyres, railway wheels and ball bearings all generate rolling contact forces which are transferred within a finite area of contact between the rolling element and the substrate. Either it is visible or not for the human eye, a certain degree of roughness is always present on the contacting surfaces and it influences the generation of both vertical and lateral contactforces. The purpose of this investigation is to enhance the understanding and modelling of the influence from small-scale surface roughness on the generation of rolling contact forces. To this end, a computationally efficient method to include roughness-induced contact nonlinearities in the dynamic modelling of rolling contacts is proposed. The method is implemented in a time domain model for vertical wheel–track interaction to model rolling-induced rail vibrations, showing good agreement with measurements. Furthermore, a test rig is developed and used for the investigation of tyre–road rolling contact forces. Detailed studies are performed on the influence of substrate roughness on the resulting contact forces for a tyre tread block which is rolling at different operating conditions. The choice of substrate as well as the rolling velocity and the slip ratio is observed to have significant influence on the resulting friction coefficient. For high slip ratios, stick–slip oscillations appear, exhibiting frequency content which is largely dependent on the choice of substrate. The outcomes of this study can potentially be used to improve future tyre–road contacts with respect to wear, traction and noise generation.

QC 20161013

Centre for Eco2 Vehicle Design

This article describes the Dana intelligent Twin Steering System designed for mobile vehicles with two steering axles (i.e. with four steering wheels). Current vehicles with four-wheel steering function are typically equipped with a hydraulic configuration where the two steering cylinders are connected in series. This type of connection highlights some limitations on available power, steering comfort and enabling advanced working functions. Dana evolved this type of hydraulic configuration introducing the possibility to disconnect the rear axle from the front one. In this way the rear axle, through the electronic control of its valve block, allows to improve the steering system performance and introduces advanced steering functions compared to the conventional steering systems.

Transport regulators consider that, with respect to pavement damage, heavy vehicles (HVs) are the riskiest vehicles on the road network. That HV suspension design contributes to road and bridge damage has been recognised for some decades. This thesis deals with some aspects of HV suspension characteristics, particularly (but not exclusively) air suspensions. This is in the areas of developing low-cost in-service heavy vehicle (HV) suspension testing, the effects of larger-than-industry-standard longitudinal air lines and the characteristics of on-board mass (OBM) systems for HVs. All these areas, whilst seemingly disparate, seek to inform the management of HVs, reduce of their impact on the network asset and/or provide a measurement mechanism for worn HV suspensions. A number of project management groups at the State and National level in Australia have been, and will be, presented with the results of the project that resulted in this thesis. This should serve to inform their activities applicable to this research. A number of HVs were tested for various characteristics. These tests were used to form a number of conclusions about HV suspension behaviours. Wheel forces from road test data were analysed. A “novel roughness” measure was developed and applied to the road test data to determine dynamic load sharing, amongst other research outcomes. Further, it was proposed that this approach could inform future development of pavement models incorporating roughness and peak wheel forces. Left/right variations in wheel forces and wheel force variations for different speeds were also presented. This led on to some conclusions regarding suspension and wheel force frequencies, their transmission to the pavement and repetitive wheel loads in the spatial domain. An improved method of determining dynamic load sharing was developed and presented. It used the correlation coefficient between two elements of a HV to determine dynamic load sharing. This was validated against a mature dynamic loadsharing metric, the dynamic load sharing coefficient (de Pont, 1997). This was the first time that the technique of measuring correlation between elements on a HV has been used for a test case vs. a control case for two different sized air lines. That dynamic load sharing was improved at the air springs was shown for the test case of the large longitudinal air lines. The statistically significant improvement in dynamic load sharing at the air springs from larger longitudinal air lines varied from approximately 30 percent to 80 percent. Dynamic load sharing at the wheels was improved only for low air line flow events for the test case of larger longitudinal air lines. Statistically significant improvements to some suspension metrics across the range of test speeds and “novel roughness” values were evident from the use of larger longitudinal air lines, but these were not uniform. Of note were improvements to suspension metrics involving peak dynamic forces ranging from below the error margin to approximately 24 percent. Abstract models of HV suspensions were developed from the results of some of the tests. Those models were used to propose further development of, and future directions of research into, further gains in HV dynamic load sharing. This was from alterations to currently available damping characteristics combined with implementation of large longitudinal air lines. In-service testing of HV suspensions was found to be possible within a documented range from below the error margin to an error of approximately 16 percent. These results were in comparison with either the manufacturer’s certified data or test results replicating the Australian standard for “road-friendly” HV suspensions, Vehicle Standards Bulletin 11. OBM accuracy testing and development of tamper evidence from OBM data were detailed for over 2000 individual data points across twelve test and control OBM systems from eight suppliers installed on eleven HVs. The results indicated that 95 percent of contemporary OBM systems available in Australia are accurate to +/- 500 kg. The total variation in OBM linearity, after three outliers in the data were removed, was 0.5 percent. A tamper indicator and other OBM metrics that could be used by jurisdictions to determine tamper events were developed and documented. That OBM systems could be used as one vector for in-service testing of HV suspensions was one of a number of synergies between the seemingly disparate streams of this project.

In this thesis, a state of the art of the structural components of railway vehicles and the material used for their manufacturing is analyzed in order to find possible new applications for ADI (Austemperd Ductile Iron). The main scope of the research is therefore to demonstrate that high stressed steel components of railway vehicles can be replaced by casted ADI components. After a survey of the possible components to be produce in ADI, three possible applications were found: wheel centre for tyred wheels, bogie frame, couplers for heavy haul operation. A feasibility analysis was performed and after a preliminary design the project has been focused in the development of an optimized tyred wheel as replacement of the current wheel for an existing Diesel Multiple Unit (DMU). Prototypes of this wheel have been finally manufactured and tested in order to demonstrate the feasibility of the application of ADI to the structural components of railway vehicles.

碩士
國立政治大學
國際經營管理英語碩士學位學程(IMBA)
106
The future prospects for growth in the global tire market is robust, according to the latest in-depth analysis from Smithers Rapra. Exclusive provisional data from its forthcoming report, “The Future of Global Tires to 2022,” shows that the market will experience a steady annual growth rate of 3.4% over the next five years, pushing a total of 2.24 billion units by 2017 to a total of 2.65 billion units in 2022. In Swaziland, the industry is still at its growing stage since few companies who have been dominated by a monopolistic company seem to have paddled behind in terms of competitiveness. Whilst consumers are buying into the idea of “safe driving”, concept, there seems to be great opportunity for companies to exploit more and more places in an endeavor to gain market share and creating a competitive market that will help fight road accidents through eradication of unroadworthy vehicles in the Kingdom of Eswatini. Whilst the demand and supply for tyres, wheel alignment and balancing services is fueled by the growing number of vehicles worlwide, this document provides information on the tyre industry, globally and in the Kingdom of Eswatini and through a feasibility study, it also analyses the future prospects of a company venturing into the industry. The study introduces Qina Wheels and Tyres Services Company’s business model which emanates from its business strategy and marketing strategy. Both strategies are developed in order eliminate possible threats and alleviate weaknesses by focusing more on the company’s strengths and opportunities. Key market penetration strategies and key success factors of the company are presented through the marketing strategy and business model of Qina Wheels and Tyres Company respectively.

Thesis (DTech. degree in Mathematics and Statistics) Tshwane University of Technology
For decades, the development of rhythmic corrugations on untarred roads has fascinated road engineers and technicians and even travellers. Numerous researchers have proposed theories about the formation and movement of these corrugations. Automobile tyres are essentially designed for use on tarred or concrete road surfaces. However, these tyres are also used on dirt roads, which often develop corrugations as a result of the interaction between the vehicle and dry road surfaces. Designing a tyre suited to corrugated dirt road conditions would be advantageous for rural inhabitants as well as the economy of a country. The aim of this research is to investigate the tangential oscillation of the vehicle tyre’s tread surface when the tyre strikes an obstacle in the road and the effect of this tangential oscillation on the formation of corrugations. A theoretical analysis of the nature and frequency of the tangential oscillation of the tread surface of the rubber tyre was done. A mathematical model (torsional oscillator model) of the tangential oscillations of the rubber tyre’s tread surface was proposed, in the form of an ordinary differential equation with constant coefficients. To verify this model, static experiments were performed on a wheel with a rigid, stationary axle. Dynamic experiments were then carried out on the tyre of a vehicle. It was found that, when a vehicle is travelling a corrugated dirt road and an obstacle (such as a corrugation) is struck in the road, the tread surface of the rubber tyre will oscillate tangentially. A second theoretical model, the forced telegraph equation model, in the form of a partial differential equation, was also proposed. Correlation between the graphs of the two models was evident. The experiments and observations in this research are consistent with the hypothesis that corrugations are formed, at least partially by the tangential oscillation of the vehicle tyre’s tread surface. It is suggested that, to minimize the formation of dirt road corrugations, the design of tyres must take into account the tangential oscillation of the rubber tyre’s tread surface. If the tangential oscillation of the tyres’ tread surface can be effectively damped, their tendency to generate corrugations might be reduced.