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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Evaluation of energy from waste in the cement industry

Buchanan, James Dickson Alexander January 2003 (has links)
No description available.

Measurement and analysis of dynamic tyre forces generated by lorries

Cole, David James January 1990 (has links)
No description available.

Analýza marketingového mixu a nabídkového portfolia ve společnosti Barum Continental, s.r.o. / Analysis of Marketing Mix Tools in the company Barum Continental, s.r.o.

Anderle, Jiří January 2009 (has links)
This degree work is targeted on the analysis of marketing mix tools in the company Barum Continental. At the end it would be analyse also the the portfolio of the products and their effect on the customers. From this informations the author deduced the conclusion, which could be used by the company Barum Continental to improve their current processes.

Investigation on fatigue failure in tyres

Baumard, Thomas Louis Marie January 2017 (has links)
Tyres are highly engineered complex rubber composite products. They are constructed from a wide range of different materials in addition to the rubber. In different parts of the tyre's construction, the rubber elements are expected to perform different functions and as a consequence many different types of rubber are used, each of which will have its own specific detailed compound formulation. These different regions of a tyre's construction are joined together by different types of molecular bonding. This variety of materials introduces potential sources of failure both in the homogenous regions within the tyre's construction but also at the interfaces between them. This thesis investigates the crack growth resistance of the rubber materials used in different regions of a tyre's construction as well as the interfaces that are found between the different parts of the tyre. A fracture mechanics framework was used to investigate the fatigue behaviour of bulk rubber and some of the interfaces. The loading of a tyre is periodic in nature as a consequence of the wheel's rotation therefore the materials were characterised over a range of loading conditions. The effect of cyclical loading frequency on the fatigue behavior of the bulk rubber was also investigated. This work discovered that the amount of crack growth per cycle was comprised from two different crack growth contributions. The first is related to the steady tear which is related to the length of time the load is applied. The second resulted from additional damage caused by the repeated loading and unloading of the material. Potential reasons for this additional crack growth contribution are discussed. The interfacial fatigue properties between adjoining and potentially dissimilar rubber compounds were examined using a fatigue peeling experiment. A novel test piece geometry was developed to evaluate the fatigue properties of interfaces in tyres and it was also used to investigate how different processing parameters such as the pressure at the interface during vulcanisation alter the interfacial strength. A significant effect was observed and this was related to the different phenomena occurring when two rubbery polymers are brought into contact. Finally, a fracture mechanics approach was also used to derive the value of the tearing energy, the variable governing crack growth propagation in the rubber materials found in tyres, using submodelling technique in finite element analysis. The tearing energy values at different locations within a tyre were calculated and are shown not to exceed the minimum energy criteria for crack propagation under normal service conditions.

The influence of snow microstructure and properties on the grip of winter tyres

Cuthill, Fergus January 2017 (has links)
The friction of tyres on roads has been of practical importance for many years with nearly 80% of terrestrial traffic making use of rubber tyres. Tyres provide the grip required for vehicle acceleration, braking and cornering. In order for a tyre to grip on a snow covered surface friction mechanisms such as “ploughing”, (where sharp tread block edges dig into and break bonds between the snow grains) and fluid film lubrication must be considered. These are not present when a tyre interacts with tarmac. In addition metamorphism of the snow over time can result in variations of the structure and mechanical properties, this can occur rapidly especially when dealing with temperatures close to snows melting point. When full car-scale outdoor testing is carried out the snow conditions cannot be controlled and vary daily. This means the snow properties must be measured every day so that any observed variations in friction can be attributed to the tyres rather than the snow. At present the simple measurements being carried out on the snow tracks have not proved sufficient to pick up on the variations in the snow. This leads to inconsistent results: one tyre behaves differently on two different days, even though the snow was measured to be the same. This has resulted in the need for further study of the way snow variations influence the grip of winter tyres. The primary aim of this study is to identify which snow properties contribute to the friction of tyres on snow and be able to estimate the friction from measurements of snow properties. This work is the first comprehensive study to combine: multiple snow properties, microstructure characterisation, measurement of friction behaviour and different snow (both artificial and natural). In order to study the way snow affects the grip of winter tyres, methods of manufacturing artificial snow with consistent mechanical properties and microstructure are used. A method of blending ice chips (a solid state fracturing process) and compressing the resulting snow to form a test track was developed during a previous PhD carried out in our group. An alternate snow microstructure was created by using an established process of creating snow by vapour deposition. The process was simplified and downscaled, the resulting snow consisted of large dendritic grains, very different to the blended ice chips. Both snows were pressed in identical manners to create snow testing tracks. In addition, natural snow collected from the field was tested to compare with the artificial snow. In order to investigate how the variations in the snow affected the friction of tyres extensive testing was carried out in a cold room using a linear tribometer, using procedures established in previous studies. Two analytical rubber samples were used to investigate the friction, a rounded edge sample and a siped sample. Testing was carried out at -10°C at speeds of 0.01m/s, 0.1m/s and 1m/s. A significant part of this PhD involved the development of new methods and equipment which have not been used to study snow in this way before. In order to characterise mechanical properties, shear testing, compression testing and cohesion testing were carried out. To investigate snow microstructure, surface profilometry, microscopy and X-ray microtomography were used. Correlating the changes observed in snow characteristics with the changes recorded in the coefficient of friction has allowed the development of an empirical equation. This can be used to predict the coefficient of friction of a given snow based on three relatively simple snow measurements: a compression test to calculate the effective modulus, a roughness measurement to calculate the peak count density and a snow penetration test. For the first time this study allows us to use the empirical equation to estimate the relative contributions of the ploughing and surface friction mechanisms to the total friction. This allows the comparison of full car-scale test data as it is now possible to account for variations in the snow test tracks.

Thermo-mechanical analysis of non-pneumatic rubber tyres.

Harwood, Stephen January 1999 (has links)
This thesis is concerned with the design, analysis and optimisation of semi-solid or non- pneumatic tyres. More specifically, the thesis is intended to show how the FEA software package Abaqus can be used to determine whether or not an AirBoss tyre meets performance criteria in regards load/deformation criteria and if there is a likelihood of failure through overheating of the tyre during service.The work is intended to clearly explain the nature of natural rubber from a molecular description through to phenomenological descriptions used to solve for stresses, strains, creep and relaxation phenomena and temperature generation through hysteresis losses within the structure of the rubber compound.The thesis examines practical ways to obtain data for use in the analysis and describes test equipment (both "off-the-shelf" and purpose built) to obtain the required information.The objective is to progress, step by step, through the stages of analysis beginning with information to predict static loading conditions for the tyre. Viscoelastic behaviour, such as creep and relaxation are predicted and then tested to determine the correlation and refine test data before proceeding to the next stage of analysis.Ultimately, a prediction is made as to the temperature distribution throughout a section of the non-pneumatic tyre. A testing rig is described which has been built to test the analysis and enable a comparison to be made between FEA prediction and "real life".

Inverkan av hjullast och ringtryck på tryck och deformation i jordprofilen, främst i matjorden /

Anselmsson, Matts Ola. January 2003 (has links) (PDF)

Não uniformidades de pneus e sua influência em baixas e altas velocidades / Tire non-uniformity and its impact at low and high speeds

Pugliese, Daniel Perussi, 1983- 28 August 2018 (has links)
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

Zkušební komora pro ozónovou degradaci pneumatik / Test cell for ozone degradation of tires

Píza, Tomáš January 2008 (has links)
This diploma thesis is occupy by assesment optimum method straining of tyres and then constructional concept of test cell for ozone degradation of rubber tyres with sizes from 13” to 15”. The final aim of this diploma thesis is construction of test cell which is based on choice of optimum method straining of tyres. The next output of this diploma thesis is concept of unit for ozone degaradation of tyres.

An investigation into the finite element modelling of an aircraft tyre and wheel assembly

Guo, H. January 2014 (has links)
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.

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