Tyrimo tikslas – nustatyti stabdžių skysčio eksploatacinių rodiklių kitimą automobiliuose su senu ir automobiliuose su naujai užpiltu stabdžių skysčiu, atsižvelgiant į Lietuvos sąlygas ir automobilių eksploatavimą. Tyrimai atlikti su keturiais automobiliais, dviejuose automobiliuose skystis buvo nežinomas, o likusiuose pakeistas nauju. Atsižvelgiant į eksploatacijos ir oro sąlygas, bei automobilių amžių, gavome tokius teiginius.Aplinkos temperatūrai nukritus žemiau 0 °C, vandens kiekis stabdžių skystyje didėja, o skysčio virimo temperatūra mažėja.Nustatyta, didesnis vandens kiekis susikaupė tokioje automobilio sistemoje, kuri buvo eksploatuojama mažiau.Galima teigti, kad automobilis, kuris yra tankiau stabdomas, dėl įkaitusios sistemos, stabdžių skystyje susidaręs vanduo palaipsniui garuoja.Galima teigti, kad oro temperatūrai esant apie + 20 °C, vandens kiekis stabdžių sistemose pradeda garuoti, arba išlieka nekitęs ir būna mažesnis.Remiantis surinktais duomenimis ne visus pokyčius galime paremti tiksliomis išvadomis, todėl būtų tikslinga tęsti matavimus įvertinant faktorius. / The purpose - to set the brake fluid dynamics performance indicators with the old cars, and cars with the newly brewed brake fluid, according to Lithuanian conditions and vehicle. Investigations were carried out with four cars, two cars liquid was unknown, and the remaining replacement. Given the operational and weather conditions, and car's age, received such claims. Ambient temperature falls below 0°C, water brake fluid increases and the boiling point of the liquid drop. Found greater amount of water accumulated in a car system, which has been operated less. It can be said that the car, which is densely stopped for hot systems, brake fluid resulting from water gradually evaporates. It can be argued that the air temperature of +20 °C, water starts to evaporate, brake systems, and remains unchanged is lower. Based on data collected at all the changes we can support precise conclusions, it would be appropriate to continue the measurements evaluating factors.

L’occurrence en service commercial de fissures macroscopiques dans certains disques de frein TGV a pu être reliée au type de garniture utilisé. L’objectif de cette thèse est de comprendre cette relation, d’identifier les paramètres d’influence et de proposer des voies d’amélioration pour la conception de garnitures à risque de fissuration réduit. Le comportement thermique de quatre couples disque-garnitures est d’abord analysé par le biais d’une campagne expérimentale de freinage originale. Elle met en évidence différents types de localisations thermiques et permet d’identifier des signatures thermiques caractéristiques des garnitures. Le lien entre localisations thermiques et risques de fissuration est ensuite établi à l’aide d’une modélisation thermomécanique. Des indicateurs tenant compte des caractéristiques spatiales et temporelles des localisations thermiques ainsi que des niveaux de température atteints sont proposés. Ils permettent de classer les garnitures testées dans un graphe de « criticité ». Enfin, une étude d’influence des caractéristiques mécaniques et thermiques des garnitures sur les localisations engendrées permet de dégager des préconisations et des voies d’amélioration pour la conception de nouvelles garnitures. La caractérisation expérimentale du comportement de deux nouvelles garnitures, l’une s’approchant le plus des préconisations faites, l’autre s’en éloignant fortement, montre la pertinence de l’approche développée et la validité des préconisations / The occurrence of macroscopic cracks in some TGV brake discs in commercial service has been linked to the pad type used. The objective of this thesis is to understand this relationship, to identify sensitive parameters and to propose guidelines to the design of pads reducing the risk of cracking.The thermal behavior of four disc-pad couples is first analyzed through an original experimental campaign of braking. It highlights various types of thermal localisations and enables to identify thermal signatures characteristic of the various pads. The relationship between thermal localisation and risk of cracking is then determined using thermomechanical modeling. Some indicators taking into account spatial and temporal characteristics of thermal localisations and temperature levels achieved are proposed. They enable to classify the tested pads in a graph of "criticity". Finally, a study of the influence of mechanical and thermal properties of pads on the thermal localisations occurrence enables to propose guidelines and improving ways for the design of new pads. An experimental characterization of the behavior of two new pads, one very close to the given recommendations, the other strongly away from them, shows the relevance of the approach and the validity of the present recommendations

Considerando o nível de competitividade do mercado automobilístico atual, a satisfação do cliente tem se tornado uma vantagem competitiva a ser considerada, devido ao aumento da expectativa dos clientes em relação à percepção da qualidade. Neste aspecto, uma das maiores dificuldades existentes no projeto de sistemas de freio reside no fato de transformar informações e/ou opiniões subjetivas em informações e/ou dados objetivos, tais como parâmetros de projeto. O presente trabalho investiga a análise objetiva do conforto de frenagem de automóveis de passeio, estabelecendo indicadores que auxiliem e/ou complementem as análises subjetivas normalmente utilizadas pela empresa, para um estudo de caso envolvendo a mudança de material de atrito da pastilha do freio a disco de um automóvel de passeio. Foram utilizados para a análise objetiva, programas de simulação computacional para analisar o desempenho do sistema de freio com relação aos indicadores estabelecidos. Os dados obtidos através desta simulação foram comparados, tanto com os resultados da avaliação subjetiva, quanto aos resultados de medições experimentais do veículo analisado, buscando analisar a correlação dos resultados. Ao final do trabalho, da comparação realizada entre a avaliação subjetiva e a avaliação objetiva observou-se uma melhoria no conforto de frenagem aos usuários, apesar de ser imperceptível na avaliação subjetiva. Esta ferramenta será muito importante no estabelecimento da curva de conforto de frenagem ótima para os novos desenvolvimentos de sistemas de freio eletrohidráulicos, denominados “brake-by-wire” (BBW). / Considering today’s competitive automotive market, the customer satisfaction has become a competitive advantage to be considered, due to the customer expectation increasing regarding the quality perception. In this aspect, one of biggest existing difficulties in the brake system design is to transform subjective information and/or opinions into objective information and/or data, such as design parameters. The present study investigates the objective analysis of the brake pedal feeling for passenger cars, establishing index that can support and/or complement the subjective analysis, usually used by our company, for a study case involving the friction material change of passenger car’s caliper brake pad. The computational simulation program has been used for the objective analysis, to analyze the brake system performance based on established index. The obtained data through this simulation was compared with the subjective evaluation results as much as with experimental measurements results of the analyzed vehicle, analyzing the correlation of results. To the end of this study, based on the comparison between subjective evaluation and objective evaluation, it observed a brake comfort improvement for drivers, instead of this characteristic would be imperceptive in subjective evaluation. This tool will be very important in the optimum comfort curve establishment for the new developments of electro-hydraulic brake systems, called "brake-by-wire" (BBW).

Foram medidas as perdas de ernergia de íons 14N e 16O em sólidos (Si,Ti,V,Cu,Zn, Zr e Pd) na faixa de energias de 1 MeV/uma. A técnica utilizada constitui-se na medida de energia de projéteis espalhados a 25° por um alvo delgado de Au, antes e depois de atravessar a folha do element freador. Os resultados experimentais são comparados com as previsões semi-empíricas de Northcliffe & Schilling (N&S), Ziegler e uma nova versão de N&S feita por Hubert e colaboradores, sendo observada uma razoável concordância entre os valores medidos e as curvas semi-empíricas. / Energy loss has been measured 14N and 16O at energies of 1 MeV/amu to 4 MeV/amu in Si, Ti, V, Cu, Zn, Zr and Pd foils. The technique consists in the measurement of the energies of ions scattered through 25 ° by a goldfoil before and after passing through the stopping foil. Our data compared to the semiempirical tabulations of Northcliffe and Schilling (N&S), Ziegler and new version of N&S by Hubert et al.. The predictions of these semiempirical compilations are in reasonable agreement with our experimental data.

Dans les contacts fortement dissipatifs, la dissipation d'énergie par frottement conduit à des sollicitations thermiques très sévères qui peuvent avoir des répercussions conséquentes sur les performances, la durabilité des organes de friction, l'environnement ou la santé humaine. La connaissance des champs thermiques des surfaces de frottement est un enjeu de premier ordre. Dans le cas de mesures sans contact du rayonnement calorifique, elle s'avère difficile du fait de l'émissivité inconnue de ces surfaces, qui varie spatialement et temporellement lors du frottement. Les travaux ont concerné le développement d'une mesure de champs thermiques par thermographie bichromatique dont l'intérêt est d'accéder simultanément à la température et à l'émissivité de surface. Les difficultés résident dans le recalage spatial et temporel de deux imageurs infrarouges, la calibration en flux des caméras et la variation spectrale de l'émissivité. La technique développée a été appliquée à la mesure in situ des champs de température et d'émissivité d'un disque de frein pendant le freinage, et exploitée pour l'analyse des localisations thermiques induites par le frottement et de leurs interactions avec le circuit tribologique, tirant parti de la connaissance de l'évolution spatiale et temporelle de l'émissivité. / In highly dissipative contacts, the energy dissipated by friction leads to severe thermal loads which could have bad consequences on performances, on friction parts durability, on the environment or on human health. Therefore, knowledge of sliding surfaces thermal fields is a first-rate issue. Due to the lack of knowledge about the emissivity of those surfaces, which change both spatially and temporally during friction, measuring thermal fields is difficult. The work done concerned the development of thermal fields measurement by bispectral thermography, which allows to get simultaneously surface emissivity and temperature. The difficulties reside in the spatial and temporal images registration of two infrared cameras, in the camera flows calibration and in the spectral emissivity variation. The technique developed was applied to the in situ fields measurement of temperature and emissivity of a brake disc during braking. It was then used for analysis of thermal locations induced by friction and their interactions with the tribological circus, leveraging the knowledge of the spatial and temporal evolution of the emissivity.

Maintenance cost is one of the important issues in railway heavy-haul operations. In most of the cases, these costs are majorly referring to reprofiling and changing the wheels of the locomotives and the wagons. The main reason of the wheel damages is usually severe wear and/or surface initiated rolling contact fatigue (RCF).This work tries to enhance and improve the knowledge of the wheel wear and RCF prediction models using dynamic simulations. While most of the contents of this study can be generalised to other operational networks, this study is focused on the locomotives and wagons of the Swedish iron-ore company LKAB. The trains are operating on the approximately 500 km long IORE line from Luleå to Narvik in the north of Sweden and Norway respectively.Firstly, a literature survey of dynamic modelling of the wagons with various three-piece bogie types is presented. Then, with concentrating on the standard three-piece bogies, parameter studies are carried out to find out what the most important reasons of wheel damages are. Moreover, the long-term stability of wheel profiles of the IORE wagons is analysed. This is done by visualising the wear and RCF evolution on the wheel profiles over 150,000km of simulated running distance.Most of the calculations for the wagons are repeated for the locomotives. However, traction and braking are also considered in the simulation model and their effects on wheel damages are briefly studied. To improve the accuracy of the wheel damage analysis, a newly developed algorithm called FaStrip is used to solve the tangential contact problem instead of FASTSIM. The damage prediction model developed in the thesis is used to study the effects of increasing axle load, correcting the track gauge, limiting the electro-dynamic braking and using a harder wheel material on the wheel life. Furthermore, a new method is developed to predict the running distance between two consecutive reprofilings due to severe surface initiated fatigue. The method is based on shakedown analysis and laboratory tests.Most of the research works in wear calculation are limited to two approaches known as wear number and Archard methods. The correlation between these two methods is studied. The possibility of using the relation between the two methods for the wear calculation process is investigated mainly to reduce the calculation time for wheel profile optimisation models. / <p>QC 20171219</p>

The diploma thesis describes the measurement and evaluation of braking traces in cars equipped by system ABS. The result of the work should contribute to improving the quality of photodocumentation of braking traces. To creating a procedure to eliminate as much as possible the loss of information during tracking documentation.

Subject of this diploma work is to complete preliminary report of possibilities and problems with brake disks monitoring on moving vehicle. A vital condition is to choose appropriate temperature sensor as well as assembling complete measuring set and it’s fastening to the vehicle. Temperature readings from driving tests, after specific brake maneuvers, will be evaluate and according to them a sensor will be determined as appropriate or inappropriate for this kind of tests.

This thesis draws up a basic overview of the current groups pedal cars. It focuses on creating a computer model of the pedal group with the help of the mathematical model and simulation stress of individual components and proposed relief.

This thesis deals with Quadbike (ATV) driving behaviour. This work describes the construction of ATVs, driving behavior and specifications ride them. In this work was performed measurements of braking, acceleration tests, measurements of transverse movement ATVs and subsequent analyse of obtained data. The measured values can be used for working forensic experts and analysts accidents.