Este trabalho apresenta um procedimento para a análise dinâmica da frenagem total de emergência de um veículo de dois eixos (4x2), considerando os efeitos do aumento da temperatura no sistema de freios. Um protótipo de ônibus urbano equipado com freios a disco foi utilizado nos ensaios em perímetro urbano e em pista de teste da TRW Automotive em Limeira- SP. O sistema de freios do veículo protótipo foi instrumentado com termopares em diversos de seus componentes, com sensores de velocidade e pressão, percorrendo um perímetro típico urbano com trânsito intenso na cidade de São Paulo. Os pontos críticos de aquecimento foram observados bem como sua tendência de aumento de temperatura no tempo. Paralelamente ao teste em perímetro urbano foi realizado um teste padrão de \"fade\" na pista da TRW Automotive, estendendo o ciclo de frenagens até se observar o aumento e estabilização da temperatura do sistema de freios. Simultaneamente aos testes de pista foi realizado um teste em dinamômetro inercial na Fras-Le, em Caxias do Sul- RS, para se obter a variação do fator de freio com a variação da temperatura do sistema de freios. Parte de um programa computacional em Matlab, que simula computacionalmente o veículo freando, foi desenvolvido, considerando os efeitos da temperatura do sistema de freios, durante frenagens totais de emergência, partindo de diferentes velocidades iniciais de frenagem. O sistema de freios em estudo mostrou-se capaz de simular a frenagem de um veículo em emergência mesmo estando em altas temperaturas, observadas no perímetro urbano. / One procedure for vehicle dynamics analysis during total emergency braking in a two axles vehicle (4x2) was showed. For this procedure the effect of increasing temperature in the brake system was considered. A bus (prototype) equipped with disc brake was used in two practical test when the bus go through: a urban rout (São Paulo city) an a TRW\'s test lane (Limeira-SP). Thermocouples were installed in several parts of the brake system as well as velocity and pressure sensors. Acquisitions of date were made during the intensive traffic of São Paulo city. Critical temperature points were observed as well as the raise temperature tendency with the time. Tests in an inertial dynamometer were also performed in Fras-Le company (Caxias do Sul- RS) to get the brake factor variation related to temperature variation of the brake system. Simulation using MatLab program to study the vehicle performance during braking was developed. In this simulation the effect of brake system temperature was considered. Two main conclusions could be obtained: MatLab model is a useful tool to study emergency braking considering the variation of brake system and the brake system studied was able to stop the vehicle in a emergency braking even under high temperature.

Squeal noise has been an on-going concern with automotive brake systems since their inception. Even after many decades of research no single theory exists that adequately describes the phenomenon, and no general methods for eliminating squeal noise exist. Broadly speaking, three primary methods of analysis have been applied to understanding and eliminating brake squeal: analytical, experimental and numerical. Analytical models provide some insight into the mechanisms involved when a brake squeals, but have limitations in applicability to specific brake systems. Experimental methods provide the backbone of brake squeal investigations, especially in an industrial environment. However, the core focus of this thesis is to use a large scale finite element analysis (FEA) model to investigate brake squeal. Initially the FEA model was developed and the dynamic characteristics were validated against experimental modal analysis results. A complex eigenvalue analysis was performed to identify potential squeal modes which appear as unstable system vibration modes. Further techniques are described that allow the deeper probing of unstable brake system modes. Feed-in energy, which is the conversion of friction work into vibrational energy during the onset of squeal, is used to determine the relative contribution of each brake pad to the overall system vibration. The distribution of the feed-in energy across the face of a brake pad is also calculated. Component strain energy distributions are determined for a brake system as a guide to identifying which components might best be modified in addressing an unstable system mode. Finally modal participation is assessed by calculating the Modal Assurance Criterion (MAC) between component free modes and the component in the assembly during squeal. This allows participating modes to be visualised and aids in the development of countermeasures. The majority of the work in this thesis was performed using the commercial FEA code MSC.Nastran with user defined friction interfaces. An alternative approach using a contact element formulation available in Abaqus was also implemented and compared to the MSC.Nastran results. This analysis showed that considerable differences were noted in the results even though the overall predicted stability correlated relatively well to observed squeal. Abaqus was also used in a case study into the design of a brake rotor in a noisy brake system. The results of this study provided good correlation to observed squeal and facilitated effective rotor countermeasures to be developed. Some success was achieved in the main aims of predicting brake squeal and developing countermeasures. However, while the tools presented do allow a deeper probing of system behaviour during squeal, their use requires good correlation to observed squeal on brake system to be established. As such, their use as up-front design tools is still limited. This shortcoming stems from the complexity of brake squeal itself and the limitations in modelling the true nature of the non-linearities within a brake system.

Sufficient heat dissipation is crucial to the effective operation of friction based braking systems. Such cooling is generally provided by ensuring a sufficient supply of cooling air to the heated components, hence the aerodynamics in the region of the brake components is extremely important. The objective of the research was to develop an understanding of how aerodynamics could be used to improve the cooling of automotive disc brakes. Two separate sets of wind tunnel experiments were developed. Tests were performed on a vented disc (rotor) to measure the internal flow through the vents on a rotating vented disc under various conditions, including an isolated disc in still air, the disc in still air with the wheel on, the disc in moving air with the wheel on, and an on-road simulation using a ¼ car. On vehicle tests were also performed in a wind tunnel using a purpose built brake test rig. These tests measured the thermal performance of different brake discs under various operating parameters; including constant load braking, and cooling from high temperature under various speeds, wheels and disc types. It was found that airflow through vented rotors was significantly reduced during simulated on-road driving, compared to when measured in isolation, but not particularly affected by the vehicles speed. In the situations tested, vented discs offered a 40+% improvement in cooling over an equivalent sized solid rotors. However the research indicates that the greatest benefit of vented rotors over solid will be in vehicles where air entering the wheel cavity is limited, such as low drag vehicles. It was also found that the most significant improvements in brake thermal performance could be achieved by maximising the airflow into the region of the brake components; including increasing the open area of the wheel, and increasing the vehicle velocity. Other improvements can be achieved by using a wheel material with good conductive capability, and increasing the mass of the disc. Evidence of vortex shedding was also discovered in the airflow at the exit of an internal vented rotor, any reduction in this flow disturbance should lead to increased airflow with associated improvements in thermal performance.

The heat dissipation and thermal performance of ventilated brake discs strongly depends on the aerodynamic characteristics of the air flow through the rotor passages. In this thesis, the thermal convection is analyzed using an analytical method, and the velocity distribution, temperature contours and Nusselt number are determined. Then numerical models for different rotors, pillar post rotors and vane rotors are generated and numerical simulations are conducted to determine the desired parameters. To analyze more realistic vane and pillar post rotor models, commercial CFD software packages, Fluent and Gambit, are used to simulate the heat flux rate, air flow rate, velocity distributions, temperature contours, and pressure distributions inside the rotors. Furthermore, sensitivity studies have been performed, to determine the effects of a different number of vanes or pillar posts, inner and outer radii and various angles of vanes. To automate the tedious and repetitive design process of the disc rotor, a design synthesis framework, iSIGHT, is used to integrate the geometrical modeling using GAMBIT and numerical simulations based on FLUENT. Through this integrated design synthesis process, the disc rotor geometrical optimization is performed using design of experiment studies. / UOIT

All electric machines have two mechanical operations, motoring and braking. The nature of braking can be regenerative, where the kinetic energy of the rotor is converted into electricity and sent back to the power source or non-regenerative, where the source supplies electric power to provide braking. This thesis investigates several critical issues related to regenerative braking in both DC and AC electric machines, including the determination of boundaries in the torque-speed plane defining the regenerative braking capability region and the evaluation of operating points within that capability region that result in maximum regenerative braking recharge current. Electric machines are used in the powertrains of electric and hybrid-electric vehicles to provide motoring or braking torque in response to the driver's request and power management logic. Since such vehicles carry a limited amount of electrical energy on-board their energy storage systems (such as a battery pack), it is important to conserve as much electrical energy as possible in order to increase the range of travel. Therefore, the concept of regenerative braking is of importance for such vehicles since operating in this mode during a braking event sends power back to the energy storage system thereby replenishing its energy level. Since the electric machine assists the mechanical friction braking system of the vehicle, it results in reduced wear on components within the mechanical friction brake system. As both mechanical friction braking and electric machine braking are used to provide the requested vehicle braking torque, braking strategies which relate to splitting of the braking command between the two braking mechanisms are discussed. The reduction in energy consumption of a test vehicle along different driving schedules while using different braking strategies is also studied.

The creative project is an educational film that will be used in vocational auto mechanics classes as an aid to the lecture and demonstration of brake repair.Eight millimeter Kodak color film was used and is supplemented with magnetic taped sound.The film deals with the steps and procedures that are necessary to complete a brake repair job. Each step explains the procedures and outlines the technical knowledge needed to complete the brake repair job.

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.

During braking, both the disc and pads in disc brakes are worn. Since disc brakes are not sealed,some of the wear particles generated can become airborne. Several studies have found anassociation between adverse health effects and the concentration of particles in the atmosphere,so it is of interest to improve our knowledge of the airborne wear particles generated by discbrakes. This thesis deals with experimental and computational methods focusing on airborne wearparticles from disc brakes. The eight appended papers discuss the possibility to both measure andnumerically determine the concentration and size distribution of airborne wear particles thatoriginate from the pad-to-disc contact. The objective is to increase the scientific knowledge ofairborne wear particles generated from disc brakes. Papers A, B and C describe tests of disc brake materials conducted in a modified pin-on-discmachine. The results show that the test set-up can be used to measure and rank disc brakematerials with respect to the concentration of airborne particles generated. Ultrafine (nanosized),fine and coarse airborne wear particles that contain metals such as iron, copper and tin werefound. Papers D and E describe a novel disc brake assembly test stand and tests of disc brake materialsconducted in it. The results show that the test set-up can be used to measure the concentrationand size distribution of airborne wear particles generated from disc brake materials. The resultsalso indicate an ability to rank different pad/disc combinations with respect to the concentrationof airborne wear particles. Furthermore, the results suggest that this test stand can be used tostudy rust layer removal from the disc and that airborne particles are generated even at low brakepressures, such as used to remove dirt from the disc. Paper F compares measurements made in passenger car field tests with measurements made in adisc brake assembly test stand and in a pin-on-disc machine. A promising correlation between thethree different test methods is found. Paper G presents and discusses a simulation methodology that numerically determines theconcentration and size distribution of airborne wear particles generated from the pad-to-disccontact in disc brakes by using general-purpose finite element software. Paper H discusses a cellular automaton model that describes the microscopic contact situationbetween the pad and disc in disc brakes. This model is used to numerically determine the amountof wear that leaves the contact. The results correlate qualitatively with experimental observationsfound in the literature. / QC 20110317

Le taux de couverture vaccinale contre le papillomavirus humain (HPV) reste faible en France autour de 20%. Ce travail porte sur l’attitude adoptée par la population française afin de comprendre les motivations et les freins à la vaccination HPV.Une série d’études, qualitatives et quantitatives, a été réalisée en 2014-2016 sur deux populations, la première de jeunes filles de 15 à 25 ans et la deuxième de mères ayant des filles âgées de 11 à 16 ans. Notre approche méthodologique est essentiellement basée sur le modèle combiné issu de la théorie du comportement planifié (Theory of Planned Behavior, TPB, Ajzen, 1991) et du modèle des croyances relatives à la santé (Health Beliefs Model, HBM, Rosenstock, 1974). Parmi les modérateurs de la décision les deux systèmes de motivation décrits par Carver et White (1994) ont été retenus. En complément, une étude expérimentale a été conduite basée sur la Théorie des perspectives (Prospect Theory) de Kahneman et Tversky (1979). Les analyses statistiques ont été effectuées avec les logiciels R et SPSS. Plusieurs traitements statistiques ont été opérés sur les données : analyse des comparaisons, analyse en composantes principales (ACP), régressions linéaires multiples, ANCOVA etc.Les résultats apportent de nouveaux éclairages quant au processus de décision d’acceptation ou de refus de vaccination. Le modèle mis en évidence par ces études fait apparaître des facteurs caractéristiques tels que l'attitude favorable à la vaccination, la sécurité du vaccin, le contrôle perçu ainsi que le regret anticipé, qui jouent un rôle déterminant dans le processus de décision. L’environnement médical et familial proche jouent également un rôle essentiel. / The immunization coverage against HPV remains around 20%. The attitude of French girls was studied to understand the motivations and breaks to HPV.Several studies, qualitative and quantitative, were conducted in 2014-2016 on two populations, first sample of young women aged 15 to 25 years and second of mothers of girls aged 11 to 16. Our methodological approach is essentially based on the handset model from The Theory of Planned Behavior (TPB, Ajzen, 1991) and the Health Beliefs Model (HBM, Rosenstock, 1974). To find the moderators of making decision we opted for the two motivational systems described by Carver and White (1994). Finally, the experimental study we were inspired by the Prospect Theory of Kahneman and Tversky (1979). Statistical analyzes were performed using the softwares R and SPSS. Four types of treatment were carried out on the data: Analyze of comparisons (1); Principal Component Analysis (PCA) (2); Linear Regression to explain an intention to be vaccinated by some variables that allows us to make a prediction (3), and ANCOVA (4).The results provide new insights about the process of decision on vaccine acceptance. It appears that the favorable attitude to vaccination, the vaccine safety, the perceived control, and the anticipated regret play an important role in this decision process as well the doctor’s advice and family.

O conforto acústico é um fator que, ultimamente, tem ganhado importância na indústria automobilística, especialmente porque o ruído de freio tem se apresentado como uma das principais causas de desconforto acústico para os usuários. Com isso, o material de atrito é alvo de contínuas pesquisas, com intenção de reduzir os ruídos, mas o sistema de freio também tem responsabilidade no ruído. O ruído de freio tipo squeal ocorre em altas frequências e destaca-se por ser o ruído de freio mais economicamente importante, pois gera elevados custos de acionamento da garantia do veículo. O squeal é induzido pelo efeito do atrito, existindo técnicas de simulação numérica para avaliar esse fenômeno, que se baseiam na análise de autovalores complexos (CEA) do sistema de freio. Os trabalhos encontrados na literatura tratam quase exclusivamente sobre sistemas de freio a disco. Diante disso, esse trabalho visa apresentar uma metodologia de análise de instabilidade dinâmica em sistemas de freio a tambor, considerando os efeitos de amortecimento. É utilizado o programa ANSYS e o Método dos Elementos Finitos para realizar esse estudo. Ao longo do trabalho são apresentadas discussões sobre fatores de influência nas frequências auto excitadas, como amortecimento, coeficiente de atrito e pressão de acionamento. A técnica de CEA é aplicada a dois sistemas de freio a tambor, com geometrias diferentes, sendo os dois casos validados através da comparação com resultados veiculares. Os modelos numéricos são ferramentas muito úteis, e a referida análise fornece grande vantagem no desenvolvimento de um sistema de freio acusticamente confortável. No entanto, os parâmetros de entrada no modelo numérico precisam ser coerentes e cuidadosamente definidos. A metodologia se mostrou adequada para avaliar o fenômeno de acoplamento modal induzido por atrito. / Acoustic comfort has become increasingly important nowadays, especially because brake noise is one of the major causes of acoustic discomfort to the users. Thus, the friction material is a continuous research target, intended to reduce noise, but bearing in mind that the brake system also has responsibility in noise. The squeal noise occurs at high frequencies and stands out for being the most economically important type of brake noise, because it generates high costs of the activation of the vehicle warranty. Squeal noise is induced by friction, and there are numerical simulation techniques to assess this phenomenon, which are based on the complex eigenvalues analysis (CEA). Studies in the literature deal almost exclusively on disc brake systems. Therefore, the present work addresses the dynamic instability analysis methodology applied to drum brake systems, where the damping effect is considered. It is used ANSYS and the Finite Element Method program to perform this study. The influence of damping, friction coefficient and working pressure on the self-excited frequencies of the brake system are discussed throughout this work. CEA technique is applied to two drum brake systems, which have different geometries. These two cases are validated by comparison with results obtained in vehicle tests. The numerical models are very useful tools, and this analysis provides great advantage in developing an acoustically comfortable brake system. However, the input parameters in the numerical model must be carefully defined and consistent. The methodology proved to be adequate to evaluate the modal coupling phenomenon induced by friction in drum brake systems.