Thesis (doctoral)--Technische Universiteit Delft, 1997. / Includes bibliographical references (p. 133-137).

Thesis (doctoral)--Technische Universiteit Delft, 1997. / Includes bibliographical references (p. 133-137).

M.Ing. / Vehicles used in military, agricultural, forestry, or construction applications often encounter different road surfaces during a single journey. In order to optimise the mobility of these vehicles, different tyre pressures are required for different types of terrain (sand, mud, cross country, tar road, etc.). An in-motion tyre pressure control system will enable the vehicle's operator to change the tyre pressures without leaving the vehicle. Such a system will not only allow optimum surface contact between the tyres and the terrain - thus improving vehicletraction, but it can also increase the lifespan of the tyres and reduce fuel consumption. The key design criteria for such a system are: quick reaction times, an effective operator interface, and reliability. In case of system failure, the operator must be able to override the control, and the tyres should be inflated to a pre-set default pressure. When the fault had been corrected, the system can be restarted from within the cabin, to inflate or deflate the tyres as required. The focus of this thesis is on the design criteria of a tyre pressure control system, receiving inputs from the driver and from onboard vehicle sensors; and then adjusting individual tyre pressures if necessary, while the vehicle is on the move. Based on the inputs to the control system, the optimum setting for the tyre pressure is determined from a look-up table stored in memory of an onboard computer. This table contains the pressure-speed and pressure-axle load relationship. A unique relation is programmed into the microprocessor for each different vehicle. To install a tyre pressure control system on a vehicle, a computer program is used to control the following hardware which are necessary to inflate or deflate tyres: An air compressor and storage tank. Pneumatic valve. Rotating seal. Pressure and speed sensing elements. Electronic control unit. An experimental set-up was built, from various components or sub-systems, which were integrated systematically until the system was working as a unit. The functionality of the system was tested, and although the results obtained do not yet justify the commercial manufacturing of such systems, it is trusted that this research has contributed towards the increased emphasis that is placed upon vehicle safety and comfort systems.

Extensive use of steel belted radial tires made it necessary to investigate the rubber-brass adhesion. Surface analysis techniques were used to give a better understanding of this bond, After about a decade of research, investigators have been successful in optimizing many of the parameters to obtain a bond of high strength. However there are still certain areas in which more work has to be done to make better quality tires. One such area is the effect of compound formulation on adhesion. Compound formulations still to a large extent are empirical. The purpose of this work is to give a scientific basis for formulating the rubber compound for best possible adhesion. / Master of Science

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / This investigation considers the influence of a three spring and damper suspension system (SDS) on overall vehicle performance. Three SDS systems are used in high performance winged racing cars to manage the effects of the aerodynamic forces. The aim of the investigation was to quantify and compare the performance of a three SDS system to that of a conventional two SDS system. The investigation was carried out on the Bailey Cars LMP2 race car. Physical track testing was conducted on Zwartkops Raceway to measure the vehicle’s performance, with further testing conducted on the vehicle’s tyres. A software model of the vehicle and tyres was then created in ADAMS/Car, with models for the conventional two SDS system, as well as the three SDS system. The ADAMS/Car model was then validated against the test data. A Design of Experiments approach was used to investigate the influence of the parameters in both the suspension models. The optimal set of suspension parameters, that maximised vehicle performance on Zwartkops Raceway, was then identified. The performance of the optimal suspension systems was then compared to quantify the effect of the three SDS system. It was found that the optimised three SDS system travelled 4.38 m less than the optimal two SDS in a 60 second simulation on Zwartkops Raceway. However, the three SDS was effectively able to isolate the pitch and roll stiffness of the vehicle. The optimal three SDS had a greater pitch stiffness and less roll stiffness than the two SDS. This is significant for winged vehicles where aerodynamic forces are highly sensitive to vehicle pitch, such as the Bailey Cars LMP2 race car, allowing for a soft wheel rate without sacrificing the pitch stiffness of the vehicle. / MT2017

In response to increased demand for fuel efficiency and sustainability, companies are seeking advancements in tire technologies to reduce fuel consumption and greenhouse gas emissions. There are several factors that affect fuel efficiency in tires. The tire tread is of most interest and relevance today, as it is responsible for the grip and wear issues, thereby requiring the highest performance. Silica is added as a reinforcing filler to the tread compounds to achieve a lower rolling resistance, while maintaining high grip and wear resistance. Due to the polarity difference between hydrophilic silica and hydrophobic rubber, industries mostly use silane agents to aid the dispersion. Such dispersion methods involve surface modification of silica in situ but provide very little control over the dispersion states achieved. Polymer grafted nanoparticles have recently attracted attention due to their ability to control and optimize dispersion. Tuning parameters like grafting density and ratio of matrix to graft chain length results in various dispersion states, which in turn have a direct correlation with reinforcement. However, most of their applications have been restricted to plastics, especially in the melt state. In this dissertation, we extended the use of grafted nanoparticles to polyisoprene rubber composites, where the grafted polymer and elastomer matrix don’t have the same chemical microstructure. We explored wide range of morphologies, ranging from well dispersed, connected networks, strings, sheets and small clusters. After studying the relative importance of entropic vs enthalpic effects on the self-assembly of nanoparticles, we observed how the morphologies evolved on crosslinking. The different morphologies studied were independent of the state of crosslinking and the chemical composition of the matrix, with minor changes occurring in samples where the nanoparticles were well dispersed. We next investigated the mechanical properties of the composites in two critical areas: linear regime and nonlinear regime. In each area, we performed systematic studies on the different morphologies in order to isolate the morphology that shows the optimal properties under different conditions. We demonstrated that nanoparticle dispersion states play a very important role in mechanical properties and are sensitive to the state of the polymer. While the connected network morphology shows the maximum reinforcement in the melt state, it is the aggregated sheets morphology at a lower grafting density that shows the highest reinforcement in the crosslinked state. This morphology at intermediate grafting density also shows the highest strain dependence in the Payne effect measurements. To understand the reinforcement mechanism in the linear and nonlinear measurements, we attempted to explore the underlying dynamics through NMR and XPCS. The evaluation crosslink density of the rubber matrix using NMR suggests that we do not have a fully developed immobilized layer and there is no variation in crosslink density in the polymer phase across the composites. This eliminates the popular theory that immobilized polymer layer in the vicinity of nanoparticles is responsible for reinforcement in rubber composites. Our research shows that filler network plays a crucial role in determining the dynamic properties of filled elastomers. At the intermediate grafting density region where sheets morphology form, the particles are aggregated with particle-particle contacts while having enough graft chains to entangle and crosslink. We believe that the crosslinked grafts connect the different sheets in the composite and aid in an improved stress transfer. This causes the filler network to percolate at much lower NP loadings. This lower percolation threshold for sheets morphologies explains the high reinforcement in the linear regime and large modulus drop in Payne effect measurements at lower nanoparticle loadings as compared to the other morphologies. Furthermore, the macroscale mechanical properties and results of XPCS derived microscopic dynamics align well. We observed that when the particles are dispersed they show faster dynamics as compared to the aggregated morphologies above the percolation threshold. At lower nanoparticle loadings, all the morphologies show similar dynamics, emphasizing the importance of percolation. In summary, we have used a combination of different techniques to understand the underlying mechanism of rubber reinforcement. We have identified which dispersion states affect reinforcement in the linear and nonlinear regime under different conditions. We combined macroscale mechanical testing with nanoscale dynamic measurements to draw a holistic picture on the dependence of reinforcement on nanoparticle dispersion states.

To minimize devastation and maximize opportunities provided during a corporate crisis, public relations professionals should collaborate with lawyers on crisis response strategies. The purpose of this study was to examine coverage of the Ford Motor Co. and Bridgestone/ Firestone, Inc. tire recall from May 2000 through May 2001 to determine whether there was a difference between the strategies used by each company and whether Ford Motor Co. and Bridgestone/Firestone, Inc. used more traditional public relations than traditional legal strategies during each crisis stage.A content analysis was conducted of articles covering the crisis from The Wall Street Journal and The Washington Post containing sentences attributed to each company's spokespeople. The search yielded 234 usable articles with 2,192 sentences.Coders identified strategies as traditional public relations, traditional legal, mixed, diversionary, or other. A chi-square was used to test the hypotheses.The first hypothesis, which said there would be no significant difference between strategies used by each company, was rejected. The second and third hypotheses, which said Ford Motor Co. and Bridgestone/Firestone, Inc. used significantly more traditional public relations than traditional legal strategies during each time period, were accepted. / Department of Journalism

Orientador: Franco Giuseppe Dedini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-17T17:46:09Z (GMT). No. of bitstreams: 1 Silva_LudmilaCorreaAlkmine_D.pdf: 6413492 bytes, checksum: 8a07a3a7a3d0737b4eb13c9f02f909e2 (MD5) Previous issue date: 2011 / Resumo: Neste trabalho foi estudada a modelagem do contato roda-piso e a teoria de controle de uma cadeira de rodas. Logo, para complementar os testes e estudos, foi desenvolvido um laboratório virtual objetivando o estudo da dinâmica veicular e da modelagem do contato roda-piso. Esse laboratório, criado em programas multicorpos como o Working Model 2D ® e o MSC Adams?, foi usado para a visualização do comportamento dinâmico de uma cadeira de rodas em diversas situações. Nesta aplicação, observa-se que as características dos pneus são alguns dos parâmetros mais importantes da modelagem do contato roda-piso de um veículo. Deste modo, para a obtenção desses parâmetros foi construída uma bancada experimental. Esta bancada experimental é constituída basicamente de uma mesa fixada por células de cargas e uma estrutura onde a roda é presa. Vários testes experimentais foram propostos e os parâmetros, ou seja, as características do pneu foram levantados, implementados e comparados entre si, através de imagens e gráficos. Para o estudo da teoria de controle, foi construído um protótipo funcional de uma cadeira de rodas motorizada no qual o principal objetivo é seguir uma linha desenhada no chão. A utilização de sensores, microcontroladores e estratégias de controle foram necessárias a fim de atingir este alvo. Diferentes tipos de controle robusto foram simulados levando em consideração as características do pneu e o controlador PID foi implementado no protótipo funcional apresentando resultado satisfatórios ao seguir uma trilha desenhada no chão / Abstract: In this work was studied the model of the contact between the tire and the ground and the control theory of a wheelchair. Thus, for the tests and studies was developed a virtual laboratory for the dynamic vehicle and the contact between tire and ground model. This laboratory was created in a multibody program as Working Model 2D® and MSC Adams®, also was used to visualize the dynamic behavior of a wheelchair in various situations. The characteristics of tires are the most important parameters of the contact between ground and tire, so for that an experimental device was built. This test rig consists basically of a table fixed by the load cells and a structure where the wheel is attached. Several experimental tests have been proposed and the parameters or the characteristics of a tire were investigated, compared and implemented with each other by images and graphs. For the control theory was built a prototype of a electric wheelchair in which the main objective is to follow a path drawn on the floor. For this goal was necessary to use sensors, microcontrollers and control strategies as a PID / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica