No description available.

Wheeled Mobile Driving Simulators (WMDS) promise a high potential for urban traffic simulation. The tires generate the accelerations of WMDS and therefore are a key component of this simulator type. Hence, the choice of a proper tire concept is of high importance. Solid tires with compact dimensions and a high vertical stiffness are a possible alternative approach to conventional pneumatic tires. To assess the application potential of solid tires their characteristics are identified. The results show that high slip values and slip angles are necessary to reach the maximum friction coefficient of about 0.8 while their correlation is highly nonlinear. With the identified tire properties, the impact of the tires on energy consumption and motion control performance of WMDS is investigated. The solid tires show an increased energy consumption of about 4% compared to pneumatic tires in representative urban driving cycle simulations. Solid tires with their nonlinear characteristics lead to five times higher lateral acceleration errors in relation to pneumatic tires at accelerations of 5 m/s2 during a horizontal eight maneuver. The vertical properties of both tires were identified to be not sufficient for the application of a WMDS solely sprung by tires on uneven grounds of common quality.

No description available.

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.

Submitted in fulfillment of the requirements of the degree of Master of Engineering: Mechanical Engineering, Durban University of Technology, Durban, South Africa, 2016. / Pneumatic tyres are of major importance in the modern life. It is estimated that over one billion tyres are manufactured worldwide annually. The manufacturing process is rather power consuming one, mainly to a curing operation taking place in a press dome. The tyre compression mould warm up process is a powerful heat transfer technique. Saturated steam is fed into a press dome to directly transfer heat energy into the prismatic container through convection and conduction heat transfer. This dissertation concerns the work done at Apollo-Dunlop tyres, the tyre compression mould warm up process was optimised to reduce the high energy cost. A heat transfer numerical analysis was carried out to investigate the steam quantity required to warm up the tyre compression mould from an ambient temperature ( ) to operational temperature ( ). Thereafter, an experimental work was performed to investigate the actual duration required to warm up the tyre compression mould to the operational temperature. This was achieved by establishing a temperature profile of the tyre compression mould during the warm up session. The numerical analysis and the experimental results were correlated to create a new warm up process with reduced steam consumption and warm up duration. The new warm up process was tested and the results are furnished in this study (see Appendix B for the performance results sheet). Apollo-Dunlop tyres (Pty) Ltd reduced a five hour tyre compression mould warm up process to a three hour process. The implementation of the proposed reduced warm up process occurred after the research work in this paper was presented to Apollo-Dunlop tyres (Pty) Ltd board members. This work was acknowledged by the company management and a new technological process has been implemented (Appendix A for the relevant documents, note: the specifications sheet show the warm-up duration as four hours, but the actual operational warm up duration is five hours). A cost saving analysis on energy usage was carried out to indicate that Apollo–Dunlop tyres will currently save approximately around about 0.64 million per year after implementing this study. / M

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Civil Engineering / Master / Master of Philosophy

<p style="text-align: justify;">U disertaciji je prikazan matematički model<br />gasifikacije otpadnih automobilskih pneumatika.<br />Modelom je istražen uticaj količine ubačenog vazduha<br />i vodene pare u gasifikator i temperatura gasifikacije<br />na prinos gasovitih produkata. Numerička procedura<br />je rije&scaron;ena Newton-Raphson metodom a brojne<br />vrijednosti molskih udjela gasovitih komponenata u<br />ravnotežnoj mje&scaron;avini dobijene su kori&scaron;ćenjem<br />programskog jezika C.<br />U drugom dijelu disertacije prikazano je<br />eksperimentalno ispitivanje pirolize otpadnih<br />automobilskih pneumatika. Eksperimentalni rezultati<br />ukazuju da na prinos gasa, odnosno na prinos čvrstog<br />(koksnog) ostatka značajno utiču parametri: veličina<br />čestice otpadne gume, temperatura pirolize i brzina<br />zagrijavanja uzorka.</p> / <p>The dissertation presents a mathematical model of<br />gasification of waste automotive tires. The model<br />examined the impact of the amount of the loaded air and<br />water vapor in the gasifier and gasification temperature<br />to yield gaseous products. The numerical procedure is<br />resolved Newton-Raphson method and the numerical<br />values of mole portions of gaseous components in the<br />equilibrium mixture obtained using the programming<br />language C.<br />In the second part of the thesis is shown<br />experimentally testing pyrolysis of waste automotive<br />tires. Experimental results indicate that the yield of gas,<br />or to yield a solid (coke) significantly affect the rest of the<br />parameters: the size of the particles of waste rubber<br />pyrolysis temperature and heating rate of the sample.</p>

Durante o desenvolvimento de um novo pneu, um dos maiores desafios enfrentados pelo engenheiro é assegurar sua integridade estrutural, pois o envelhecimento dos compostos de borracha é inevitável. Ele leva a mudanças na estrutura molecular e nas propriedades mecânicas dos materiais, resultando em mudanças indesejáveis no desempenho do pneu. Este trabalho apresenta uma metodologia para determinar o comportamento estrutural do pneu envelhecido a partir de análises de elementos finitos (FEA- Finite Element Analysis). É apresentada também uma investigação das condições de contorno, como temperatura, composição do ar e tempo de exposição, para reproduzir em laboratório o envelhecimento observado no mercado. Durante sua vida útil, o pneu sofre deformações cíclicas gerando calor devido ao fenômeno de histerese. A região mais crítica é a extremidade das cinturas, onde as temperaturas atingem valores de 70ºC para pneus de carros e 100ºC para caminhões. O ar permeia através dos componentes do pneu criando uma condição oxidativa propícia à fadiga e propagação de trincas. O envelhecimento está associado às condições operacionais do pneu, porém os engenheiros buscam acelerar os testes laboratoriais aumentando a temperatura, segundo a lei de Arrhenius. O trabalho de Ahagon é reproduzido aqui para interpretar os mecanismos de envelhecimento, o que é possível a partir da análise da relação entre o alongamento à ruptura e o módulo a 100% de deformação. O modelo de pneu proposto é capaz de avaliar concentrações de tensão e prever o comportamento dinâmico dos pneus envelhecidos. A correta caracterização dos compostos mostrou-se essencial para garantir uma correta modelagem e análise, o que leva a um melhor desenvolvimento do pneu e a uma vida útil maior. / During the development of a new tire one of the challenges the engineer must face is to assure tire structural integrity. Rubber compound aging is unavoidable and it changes material molecular structure and mechanical properties resulting in undesirable changes in tire performance. This work presents a methodology to assess the structural behavior of aged tires using the finite element analysis (FEA) with an aged rubber compound characterization. It also presents an investigation regarding the boundary conditions, such as temperature, air composition and time of exposure, to reproduce in laboratory the aging observed in the market. During service life, the tire undergoes repeated and complex stress cycles resulting in heat generation by hysteresis. It is critical in regions like belt edges where temperature measurements show values up to 70ºC for passenger car tires and more than 100ºC for trucks. The inflated air permeates through the tire components leading to oxidative conditions propitious to fatigue and crack propagation. Aging is related to the tire operational conditions but engineers usually accelerate the process in lab tests by increasing the temperature, following the Arrhenius law. Ahagon\'s previous work was reproduced here and used to interpret the aging mechanisms, by analyzing the relation between elongation to brake and the modulus at a hundred percent elongation for different aging conditions. The proposed tire model is able to analyze structural stress concentrations and predict the dynamic behavior of aged tires. The correct compound characterization showed to be essential to assure a good modeling and analysis, which leads to a better tire development and a longer service life.

O objetivo deste trabalho foi utilizar a radiação ionizante na reciclagem de pneus inservíveis de automóvel. As amostras de borracha de pneus inservíveis foram irradiadas com doses de radiação de 200, 400 e 600kGy, em um acelerador de elétrons. Posteriormente, elas foram caracterizadas por termogravimetria (TG), calorimetria exploratória diferencial (DSC), ensaios mecânicos de tração, espectrofotometria de infravermelho por transformada de Fourier (FTIR) e microscopia eletrônica de varredura (MEV). Por TG foi possível observar os efeitos da radiação na perda de massa do material. Por DSC observou-se as curvas exotérmicas associadas à decomposição e valores de variação de entalpia (&Delta;H). Foram estudadas as propriedades mecânicas das amostras da matriz elastomérica com o pó de pneu inservível e verificado o seu comportamento frente à radiação ionizante. Os espectros FTIR foram obtidos na região de 4000 650cm-1. Observou-se que não foi possível observar alteração nos picos devido à irradiação. Nos ensaios por MEV as micrografias foram ampliadas de 32 vezes até 1000 vezes e observadas nos tamanhos de 1mm até 20&mu;m. Observou-se nas doses de 200 e 400kGy, rugosidades correspondentes a quebras ou rupturas, possivelmente causadas pela radiação. Na dose de 600kGy, foi possível observar cavidades causadas pela radiação. Observou-se que para todas as doses houve degradação. Para as amostras dos corpos de prova sem pó e com pó de pneus inservíveis com 10%, 30% e 50% de pó as micrografias foram observadas nas ampliações de 100&mu;m e 200&mu;m. Também foi possível observar a incorporação do pó de pneus inservíveis de automóvel na matriz elastomérica das amostras não irradiadas e irradiadas. / The aim of this study was to use ionizing radiation in the recycling of scrap tires of automotive. Samples of rubber unserviceable tires were irradiated with radiation doses 200, 400 and 600kGy in an electron accelerator. Subsequently, they were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), tensile strenght mechanical test, spectrophotometry Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). By thermogravimetry was possible to observe the effects of radiation in the mass loss of material. In the DSC curves were observed exothermic decomposition peaks and associated values of enthalpy variation (&Delta;H). The mechanical properties of the elastomeric matrix with unserviceable tires powder were studied and its behavior to ionizing radiation was analyzed. FTIR spectra were obtained in the 4000 - 650cm-1 region. It was observed that there was no change in the peaks due irradiation. For SEM the micrographs were enlarged from 32 times up to 1000 times and observed in sizes from 1mm up to 20&mu;m. It was observed at doses of 200 and 400kGy, roughness corresponding to breaks or ruptures possibly caused by radiation. In 600kGy radiation dose was observed cavities caused by radiation. It was observed that at all doses occurred degradation. For samples without powder and with 10, 30 and 50% of unserviceable tires powder it was obtained micrographs of 100&mu;m and 200&mu;m amplification. Also it was possible to observe the incorporation of unserviceable tires powder of automotive in the elastomeric matrix of non-irradiated and irradiated samples.