Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.

Für die Entwicklung von Gesamtfahrzeugeigenschaften ist die objektive Beschreibung von Reifencharakteristika unter der Anwendung entsprechenden Bedingungen von wesentlicher Bedeutung. Der hierzu beschriebene, neuartige Prozess zur Reifencharakterisierung gründet sich auf einem definierten Satz objektiver Gesamtfahrzeugkenngrößen, welche mithilfe dedizierter Fahrmanöver identifiziert werden. Der Kern der hybriden Methode besteht in der zweckmäßigen Klassifizierung von Reifencharakteristika nach Struktur- und Reibgrößen. Auf Basis der kinematischen Deformationsmechanismen in der Reifenkontaktfläche und -konstruktion werden analytische Formulierungen für wesentliche Reifencharakteristika hergeleitet. Die Kombination neuer Prüfmethoden auf Flachbahn- und Anhängerprüfständen erlaubt anschließend deren präzise Identifikation. Zur Zusammenführung der autark gemessenen Eigenschaften wird ein analytisches Synthesemodell beschrieben, welches die Parameteridentifikation von empirischen Reifenmodellen erlaubt. Die Validierung der so identifizierten Reifeneigenschaften erfolgt auf der Gesamtfahrzeugebene. Hier bestätigt sich die maßgebliche Verbesserung der Fahrdynamikrechnung im Linear- und Grenzbereich gegenüber dem bisherigen Stand der Technik.

Für die Entwicklung von Gesamtfahrzeugeigenschaften ist die objektive Beschreibung von Reifencharakteristika unter der Anwendung entsprechenden Bedingungen von wesentlicher Bedeutung. Der hierzu beschriebene, neuartige Prozess zur Reifencharakterisierung gründet sich auf einem definierten Satz objektiver Gesamtfahrzeugkenngrößen, welche mithilfe dedizierter Fahrmanöver identifiziert werden. Der Kern der hybriden Methode besteht in der zweckmäßigen Klassifizierung von Reifencharakteristika nach Struktur- und Reibgrößen. Auf Basis der kinematischen Deformationsmechanismen in der Reifenkontaktfläche und -konstruktion werden analytische Formulierungen für wesentliche Reifencharakteristika hergeleitet. Die Kombination neuer Prüfmethoden auf Flachbahn- und Anhängerprüfständen erlaubt anschließend deren präzise Identifikation. Zur Zusammenführung der autark gemessenen Eigenschaften wird ein analytisches Synthesemodell beschrieben, welches die Parameteridentifikation von empirischen Reifenmodellen erlaubt. Die Validierung der so identifizierten Reifeneigenschaften erfolgt auf der Gesamtfahrzeugebene. Hier bestätigt sich die maßgebliche Verbesserung der Fahrdynamikrechnung im Linear- und Grenzbereich gegenüber dem bisherigen Stand der Technik.

Structures acting as waveguides are quite common withexamples being, construction beams, fluid filled pipes, railsand extruded aluminium profiles. Curved structures like cartyres and pipe-bends may also be considered as waveguides. Wavesolutions in such structures may be found by a method calledthe Waveguide Finite Element Method or WFEM. This method uses afinite element approach on the cross-section of a waveguide tomodel the vibro-acoustic response as a set of linear, coupled,one dimensional, wave-equations. In this thesis six novel waveguide finite elements arederived and validated. These elements are, straight and curvedpre-stressed, orthotropic or anisotropic shell elements,straight and curved fluid elements, and straight and curvedfluid-shell coupling elements. Forced response and input power calculations for infiniteand periodic waveguides are presented. The assembled waveguidemodels can also serve as input for the Super Spectral FiniteElement Method, which enables forced response calculations formore complex boundaries. Furthermore, several properties ofdamped and undamped wave solutions are investigated. Finally, a car tyre model, encompassing for the highlyanisotropic material and the air cavity inside the tyre is setforth. A number of forced response calculations for this modelare presented and compared with measurements with goodagreement. Keywords:wave equation, wave solution, waveguide,finite element, spectral finite element, tyre noise, tyrevibration, input power, shells, pre-stress, fluid-shellcoupling axi-symmetric, two-and-half-dimensional

<p>Structures acting as waveguides are quite common withexamples being, construction beams, fluid filled pipes, railsand extruded aluminium profiles. Curved structures like cartyres and pipe-bends may also be considered as waveguides. Wavesolutions in such structures may be found by a method calledthe Waveguide Finite Element Method or WFEM. This method uses afinite element approach on the cross-section of a waveguide tomodel the vibro-acoustic response as a set of linear, coupled,one dimensional, wave-equations.</p><p>In this thesis six novel waveguide finite elements arederived and validated. These elements are, straight and curvedpre-stressed, orthotropic or anisotropic shell elements,straight and curved fluid elements, and straight and curvedfluid-shell coupling elements.</p><p>Forced response and input power calculations for infiniteand periodic waveguides are presented. The assembled waveguidemodels can also serve as input for the Super Spectral FiniteElement Method, which enables forced response calculations formore complex boundaries. Furthermore, several properties ofdamped and undamped wave solutions are investigated.</p><p>Finally, a car tyre model, encompassing for the highlyanisotropic material and the air cavity inside the tyre is setforth. A number of forced response calculations for this modelare presented and compared with measurements with goodagreement.</p><p><b>Keywords:</b>wave equation, wave solution, waveguide,finite element, spectral finite element, tyre noise, tyrevibration, input power, shells, pre-stress, fluid-shellcoupling axi-symmetric, two-and-half-dimensional</p>

The Old English Apollonius of Tyre survives as only a fragment of a popular medieval romance which is recorded in numerous Latin manuscripts. Approximately half the story is missing; therefore, studies of this prose romance are usually restricted to linguistic and stylistic analyses. Hence this study focuses on the word order of phrases and clauses and on features of style apparent in the Old English version, with comparison to the Latin source where significant divergences occur.

Thesis (MBA)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: As Continental Tyre SA strives to carve a path towards high performance, it is critical that the nine (9) factors of workplace practices, suggested by David Maister, are embraced fully and become integral part of its strategic direction. To be able to achieve as a world-class low cost producer of quality tyres, Continental Tyre SA will not only upgrade its technology and improve processes, but also the development of its employees to their best ability is imperative. As the study findings have shown, there is an unwavering commitment and enthusiasm from employees at Continental Tyre. Senior management must capitalize on these positive results in building and instilling more pride, by ensuring that employees are empowered and capacitated to fulfill their personal ambitions and the goals of the organisation at large. For Continental to deliver high quality and maintain supreme standards of service as expected by its customers, they have to ensure that all employees, as people who are in the front line of customer service, are equipped with appropriate knowledge to understand all their products and the unique needs of customers. Quality Systems have to be strengthened and updated regularly through audits, so as to align with global best performers. Another critical consideration of people management are coaching and mentorship programs, that serve as a guide and support to employees development processes. Employees must be encouraged to discuss the issues that affect their performance within this relationship. This management practice helps to exploit the full potential of individual employees as they strive to contribute by the achievement of high performance within the organisation. The culture of high performance is enhanced by well managed and effective protege - mentor relationships that are practiced throughout the organisation. With coaching, complex and highly intimidating change interventions are handled with great confidence by employees. Fair compensation and incentive schemes have become a critical part of reward systems, and Continental Tyre SA is no exception. However, for this business practice to achieve its intended objective, reward and motivation, it has to be implemented in an equitable and fair manner, consistent with the efforts and contributions of employees, When fair, compensation will tend to have a postive influence on the other factors. High levels of satisfaction will not be guaranteed by fair compensation only, but employees will enjoy their work more when allowed to be creative and when given the freedom to make decisions that determine how they will do their job best. Continental Tyre can derive satisfaction and encouragement from the outcome of the survey. Real satisfaction will come from financial and market performances that confinm the positive results of the high achievement research study. Lastly, the culture survey must be developed as an organisation practice that will ensure regular, reliable feedback of employee opinions. Not only will Continental Tyre SA be able to maintain and gain loyalty from its present employees with progressive high achievement practices, they will gradually attain the status of employer of choice, thereby attracting ta lented high potential employees. / AFRIKAANSE OPSOMMING: In Continental Tyre SA se strewe na hoë werkverrigting is dit essensieel dat die nege faktore aangaande werkplek-praktyke soos deur David Maisler voorgestel, ten volle aanvaar word om 'n integrale deel van die organisasie se strategie te vorm. Om hul beeld as verskaffers van wereldklas, lae-koste, gehalte bande uit te leef, poog Continental SA nie alleen om tegnologie te verbeter en sodoende prosesse te verhoog nie, maar is die ontwikkeling van die organisasie se werknemers se vermoens van kardinale belang. Bevindinge uit die studie toon 'n intense toewyding en belangstelling onder werknemers by Continental Tyre SA. Dit is dus noodsaaklik dat senior bestuur voortbou op die bevinding deur geleenthede te skep vir die bemagtinging van werknemers om hul persoonlike ambisies en doelwitte uit te leef, wat op die lange duur tot voordeel van die maatskappy kan strek. Om te verseker dat Continental Tyre SA diens van hoë gehalte en net die hoogste standaarde lewer, soos deur hul klienle verwag word, moet daar toegesien word dat alle werknemers, wat gewoonlik in die voorste linies is as dit kom by klientediens, toegerus word met die nodige kennis oor produkte asook oor die unieke behoeftes van kliente. Die voortdurende versterking en opgradering van kwaliteitstelsels deur middel van ouditte sal verseker dat in pas gebly word met globale presteerders. In mensebestuur moet daar ook krities gekyk word na afrigting- en mentorskapprogramme, wat kan dien as gids en wat ondersteuning kan verleen aan die ontwikkelingsproses van werknemers. Werknemers behoort aangemoedig te word om kwessies rakende hul prestasies binne hierdie verband te bespreek. Sodanige bestuurspraktyk moedig werknemers aan om individueel tot volle potensiaal te ontwikkel in hul strewe om deur die lewering van kwaliteit werk ook 'n bydrae tot die organisasie te maak. Effektiewe en goedbestuurde protege/mentor verhoudinge wat toegepas word in die hele organisasie verhoog die kultuur van hoë werkverrigting en prestasie. Gekompliseerde en hoogs intimiderende veranderingsintervensies kan met die hulp van afrigting, met groot selfvertroue deur werknemers hanteer word. Billike kompensasie en aansporingskemas het al 'n kritieke deel van besoldiging geword in organisasies en Continental Tyre SA is geen uitsondering nie. As besigheidspraktyk met motivering en vergoeding as doelwit, moet hierdie doelwit in pas met die bydraes en pogings van werknemers, op 'n billike wyse ge'implimenteer word. Indien vergoeding billik is, sal dit neig om ander faktore positief te be'invloed. Billike vergoeding lei nie noodwendig tot hoë tevredenheidsvlakke by werknemers nie, maar werknemers sal hul werk meer genotvol vind indien hulle toegelaat word om meer kreatief te wees en die vryheid gegun word om besluite te neem oor hoe om optimaal te funksioneer in hul werk. Die uitslag van die opname kan dien as aanmoediging vir Continental Tyre SA, wat met reg tevrede daarmee kan wees. Werklike bevrediging sal uitvloei uit die finansiele- en markaanwysings wat die positiewe resultate van die hoogstaande studie-navorsing weerspieel. Ten slotte moet die kultuuropname ontwikkel word tot 'n gereelde, betroubare terugvoering van die opinies van werknemers. In die lig hiervan sal Continental SA nie slegs die lojaliteit en hoë werkverrigtingspeil van sy huidige werknemers handhaaf en behou nie, maar sal die status van werkgewer volgens keuse behaal gaandeweg bereik word en sodoende talentvolle, hoë profiel werknemers gelok word.

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 work presented in this thesis is dedicated to the study of transient tyre dynamics and how these influence the dynamic behaviour of the vehicle and its driveline, with the main focus being on low-to-zero speed manoeuvres such as pull-away events. The bulk of the work focuses on the amalgamation of the hitherto disparate fields of driveline modelling and detailed tyre modelling. Several tyre models are employed and their relative advantages and disadvantages analysed. The observed dynamic behaviour is correlated to the inherent structure of each tyre model in order for the most appropriate for driveline studies to be identified. The main simulation studies are split into two parts: the first comprises a study into isolated driveline dynamics; where the yaw, pitch and roll behaviours of the vehicle body are neglected. A relatively detailed driveline model with an open differential is used with tyre models of increasing complexity with the aim of determining when increased model detail fails to increase the accuracy of the results. The second part is concerned with the study of how the dynamics of the vehicle body and suspension affect tyre model performance and associated effects on the driveline behaviour. For this, the driveline and tyre models are incorporated into a full six degree-of-freedom vehicle model with full suspension effects. Frequency migration on low-μ surfaces is successfully explained via the decoupling of the vehicle and driveline inertias. Frequencies observed in FFT analyses of the simulation results correspond to those obtained through eigen-analysis of appropriately modified state-space models with varying degrees of coupling that reflect the vehicle travelling on uniform low- or split-μ surfaces. The main finding of the thesis is that this decoupling theory can also be applied to high-speed take-off manoeuvres, as it is the position along the tyre slip-force curve that dictates decoupling; i.e. if the curve has saturated. This leads to the effective traction stiffness being zero, which modifies the equations of motion and subsequently the system eigenvalues. A series of measurements are taken in order to verify the findings from the simulation work. Manoeuvres analogous to those simulated are carried out. It is found that only the simulation of split-μ conditions is necessary, as the results from the low-μ test show a similar pattern to those seen on the split-μ surface.

The work presented in this thesis is dedicated to the study of vehicle rollover and the tyre and suspension characteristics influencing it. Recent data shows that 35.4% of recorded fatal crashes in Sports Utility Vehicles (SUVs) included vehicle rollover. The effect of rollover on an SUV tends to be more severe than for other types of passenger vehicle. Additionally, the number of SUVs on the roads is rising. Therefore, a thorough understanding of factors affecting the rollover resistance of SUVs is needed. The majority of previous research work on rollover dynamics has been based on low fidelity models. However, vehicle rollover is a highly non-linear event due to the large angles in vehicle body motion, extreme suspension travel, tyre non-linearities and large forces acting on the wheel, resulting in suspension spring-aids, rebound stops and bushings operating in the non-linear region. This work investigates vehicle rollover using a complex and highly non-linear multi-body validated model with 165 degrees of freedom. The vehicle model is complemented by a Magic Formula tyre model. Design of experiment methodology is used to identify tyre properties affecting vehicle rollover. A novel, statistical approach is used to systematically identify the sensitivity of rollover propensity to suspension kinematic and compliance characteristics. In this process, several rollover metrics are examined together with stability considerations and an appropriate rollover metric is devised. Research so far reveals that the tyre properties having the greatest influence on vehicle rollover are friction coefficient, friction variation with load, camber stiffness, and tyre vertical stiffness. Key kinematic and compliance characteristics affecting rollover propensity are front and rear suspension rate, front roll stiffness, front camber gain, front and rear camber compliance and rear jacking force. The study of suspension and tyre parameters affecting rollover is supplemented by an investigation of a novel anti-rollover control scheme based on a reaction wheel actuator. The simulations performed so far show promising results. Even with a very simple and conservative control scheme the reaction wheel, with actuator torque limited to 100Nm, power limited to 5kW and total energy consumption of less than 3kJ, increases the critical manoeuvre velocity by over 9%. The main advantage of the proposed control scheme, as opposed to other known anti-rollover control schemes, is that it prevents rollover whilst allowing the driver to maintain the desired vehicle path.