With an increasing need for accurate full vehicle models, a sensitivity analysis of the modelling of tyres depending on their age and wear was conducted. This included a sensitivity analysis into the accuracy of acquiring the tyre stiffnesses on a static test setup. An FTire model is developed with the aim to update this model with basic tests to give a more accurate representation of the aged or worn tyre. A well-researched and documented method is used to artificially age the tyres. During the aging process the tyre was statically tested to monitor the potential changes in characteristics. Tyres were also worn on a dynamic test setup and periodically tested to monitor the property changes. These tests included both static and dynamic measurements. The results indicate that the vertical and longitudinal stiffnesses of the tyre have convincing dependencies on the age and wear of the tyre. While the aging process was a trustworthy method, the wear process created irregular wear across and around the tyre subsequently skewing the results. Simple methods of updating the FTire tyre model without re-parameterising the model completely, was found to be effective in accounting for age and wear. / Dissertation (MEng)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

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.

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

An Hand einer Vielzahl von Einzeluntersuchungen an sogenannten Runflat-Reifen, dass sind Notlaufreifen mit verstärkten Seitenwänden, werden folgende Themen in der Dissertation behandelt. ? Wie hoch ist die Erhöhung der Belastung des Fahrwerks und bewirkt der Einsatz von Notlaufreifen auf Fahrzeugen, die für Standardbereifung ausgelegt sind, eine erhöhte Schädigungswahrscheinlichkeit und damit eine verkürzte Bauteillebensdauer? ? In welcher Größenordnung sind Komfortverschlechterungen zu erwarten? ? Wie ist das Notlaufverhalten dieser Reifen? Gibt es Möglichkeiten der Bewertung des defekten Reifens während des Fahrens am Fahrzeug? Auf der Basis von Schlagleistenuntersuchungen an einem Reifen- und einem Radaufhängungsprüfstand wird in einem neu entwickelten Untersuchungs- und Auswerteverfahren dargestellt, wie man durch eine Betriebsfestigkeitsauswertung der Lastkollektive zu einer relativen Aussage bezüglich der zu erwartenden Schädigung eines Fahrwerks gelangen kann. Dazu wird die durch den Reifen indizierte Belastung beim Überrollen einer Schlagleiste in Bezug zu den Festigkeitseigenschaften eines Fahrwerkes gesetzt und die Wahrscheinlichkeit einer Schädigung beurteilt. In einem weiteren auf Basis der Schlagleistenmessungen entwickelten Auswerteverfahren kann der Einfluss des Reifens auf den zu erwartenden Fahrkomfort abgeschätzt werden.

Motorsport has become a multidisciplinary sport in which skilled engineers and strategists play as big a part in the team’s success as the athlete driving the car. In Formula One it is common practice for teams to have dedicated resources on the track that are supported by a second team back at the home base who analyses telemetry data and performs simulations to refine the racing strategy. Optimal control calculations are typically used to optimise vehicle setup parameters (such as ride height and heave spring stiffness) and driver inputs (such as braking and steering) specific to each track. Traditionally this approach has been employed by minimising time over a single lap. Although this is useful in qualifying simulations, there is an unexplored element of optimising a vehicle’s "race pace". Drivers complete qualifying laps using minimal fuel with new tyres to get the best possible lap time but this performance cannot be sustained throughout the whole race. Drivers need to manage their tyres so that they do not wear prematurely and have a detrimental effect on their performance. This work places an emphasis on tyre modelling and in particular how optimal control can be used to optimise a tyre management strategy. A model has been presented that reduces grip as a function of tyre wear. This ensures that the qualifying pace cannot be sustained indefinitely. A thermodynamic model consisting of two states (surface and carcass temperature) is used to calculate tyre wear, which ultimately dictates how much grip can be provided by each tyre. The objective function for the optimal control problem is to minimise time over multiple laps and the absolute tyre wear (in mm tread) is constrained to a predefined limit. This ensures that the consequences of pushing the car to its limits are considered: overheating temperatures and accelerated wear will be detrimental to racing performance. The optimal control solver needs to manage the tyre temperatures carefully over a racing distance. It has been shown that lap times degrade more severely as the tyres reach the end of their life. At some point in the race this drop off in performance will render the car uncompetitive and strategists can use this model to evaluate the performance of different tyre compounds at each track and to strategically plan pit stops during a race. / Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / MEng (Electronic Engineering) / Unrestricted

The complex interface between tyre and terrain is a largely studied topic in terramechanics and vehicle dynamics research. This interface, known as the contact patch, is however hidden from view and cannot easily be measured. Several studies have focused on measuring tyre strain on the inside surface of the tyre to indirectly determine tyre parameters. The inner surface is separated from the contact patch by the tyre thickness however this difference can be considered small in comparison to the bene t gained by a safe environment for measurement systems. Static studies of tyre strain have been successful however lacks the important phenomena occurring in a rolling tyre. Tyre strain measurements in dynamic tyres have been limited to discrete points and/or once per revolution, which is an insufficient sampling rate for vehicle stability controllers such as ABS. This study performs full-fi eld and point strain measurements of the inner tyre surface of a rolling agricultural tyre at low speeds. Stereo cameras mounted on a mechanically stabilised rim will record full-fi eld measurement of the contact patch kept in constant view. Digital Image Correlation techniques are used to determine full-fi eld deformation and strain from successively captured images. Point measurements, such as strain gauges, are included in the study for a comparative measurement. An agricultural tyre hosts large lugs which include large strain concentrations within the contact patch. The complex tyre structure signi ficantly influences the strain measurements, other factors such as inflation pressure, vertical load and slip angle is also studied. Since most vehicle forces are transmitted through the tyre at the tyre-terrain interface, capabilities to measure this area will be a great benefi t for tyre research and leading towards a smart tyre. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2020. / Mechanical and Aeronautical Engineering / MEng (Mechanical Engineering) / Unrestricted

An Hand einer Vielzahl von Einzeluntersuchungen an sogenannten Runflat-Reifen, dass sind Notlaufreifen mit verstärkten Seitenwänden, werden folgende Themen in der Dissertation behandelt. ? Wie hoch ist die Erhöhung der Belastung des Fahrwerks und bewirkt der Einsatz von Notlaufreifen auf Fahrzeugen, die für Standardbereifung ausgelegt sind, eine erhöhte Schädigungswahrscheinlichkeit und damit eine verkürzte Bauteillebensdauer? ? In welcher Größenordnung sind Komfortverschlechterungen zu erwarten? ? Wie ist das Notlaufverhalten dieser Reifen? Gibt es Möglichkeiten der Bewertung des defekten Reifens während des Fahrens am Fahrzeug? Auf der Basis von Schlagleistenuntersuchungen an einem Reifen- und einem Radaufhängungsprüfstand wird in einem neu entwickelten Untersuchungs- und Auswerteverfahren dargestellt, wie man durch eine Betriebsfestigkeitsauswertung der Lastkollektive zu einer relativen Aussage bezüglich der zu erwartenden Schädigung eines Fahrwerks gelangen kann. Dazu wird die durch den Reifen indizierte Belastung beim Überrollen einer Schlagleiste in Bezug zu den Festigkeitseigenschaften eines Fahrwerkes gesetzt und die Wahrscheinlichkeit einer Schädigung beurteilt. In einem weiteren auf Basis der Schlagleistenmessungen entwickelten Auswerteverfahren kann der Einfluss des Reifens auf den zu erwartenden Fahrkomfort abgeschätzt werden.

Bicycles are becoming always more popular as a cheap and healthy tool for urban travels. The concerns für crowded public transport means are changing the habits after the pandemic situation caused by Covid-19, encomaging people towards the use of bicycle. As stated in literature, tyres play a large role in the handling ofbicycles . This is why it is necessary to characterize tyres so as to derive useful parameters for modeling. To this purpose, proper experimental methods have been implemented for bicycle tyres. A deepen knowledge of the phenomena occurring at tyre/road contact patch is indeed fundamental to ensure proper adherence and safety conditions, especiatly for vehicles as bicycles or motorcycles working with high camber angles. This paper aims at enabling the future development of bicycle tyres, in order to improve the safety and the performances. Specifically, the focus is devoted to understand how the road temperature can impact on tyre performances, and therefore on bicycle handling. After a brief section describing the methods and instruments used für this research activity, the results of an experimental campaign carried out on road racing tyre are presented and discussed. The remarkable variation of temperature oftyre rolling surface can have multiple impacts on the performances. lt can affect the noise emissions as weil as rolling resistance, as noted in, where higher temperature was co.rrelated to lower rolling resistance coefficient. In the temperatu.re influence on car tyre lateral characteristics is investigated on a drum testrig. A They found a decrease in cornering stiffness as temperature increases, while no particular variations on relaxation length were observed. Despite the known influence of the temperature on tyre properties, there is a lack of studies regarding bicycle tyres. In a test on testrig of wintertype tyre revealed remarkable differences with respect to the mechanical characteristics of other tyres tested at room temperature. This may suggest the important role played by temperature on bicycle tyres characteristics, thus affecting the tyre/road interaction.

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.

Driving with tyres not appropriate for the actual conditions can not only lead to accidents related to the tyres, but also cause detrimental effects on the environment via emission of rubber particles if the driving conditions are causing an unexpectedly high amount of tread wear. Estimating tyre performance in an online setting is therefore of interest, and the feasibility to estimate friction performance, velocity performance, and tread wear utilizing available information from the automotive grade sensors is investigated in this thesis. For the friction performance, a trend analysis is performed to investigate the correlation between tyre stiffness and friction potential. Given that there is a correlation, a model is derived based on the trend having a stiffness parameter as an input in order to predict the friction performance. Tendencies for a linear trend is shown, and a linear regression model is fitted to data and is evaluated by calculating a model fit and studying the residuals. Having a model fit of $80\%$, the precision of the expected values stemming from the proposed model is concluded to be fairly low, but still enough to roughly indicate the friction performance in winter conditions. A tread wear model that can estimate the amount of abrasive wear is also derived, and the proposed model only utilizes available information from the automotive grade sensors. Due to the model having a parameter that is assumed to be highly tyre specific, only a relative wear difference can be calculated. The model is evaluated in a simulation environment by its ability to indicate if a tyre is under the influence of a higher wear caused by a higher ambient temperature. The results indicates that the model is insufficient in an online setting and cannot accurately describe the phenomena of softer tyres having a larger amount of wear caused by a high ambient temperature compared to stiffer tyres. Lastly, a double lane change test (ISO 3888-2) is conducted to determine the critical velocity for cornering manoeuvres, which defines the velocity performance. The test was executed for six different sets of tyres, two of each type (winter, all-season, and summer). The approach to estimate the velocity performance in an online setting is analogue to that of the friction performance, and a trend analysis is performed to investigate the correlation between longitudinal tyre stiffness and the critical velocity. The results are rather unexpected and shows no substantial differences in velocity performance, even though the tyre-road grip felt distinctively worse for the softer tyres according to the driver. It is concluded that the bias stemming from the professional driver's skills might have distorted the results, and that another approach might need to be considered in order to estimate this performance.