Orientador: Sérgio Tosi Rodrigues / Resumo: O envelhecimento populacional está associado a profundas mudanças sociais, econômicas e culturais. O comprometimento perceptual e cognitivo resultante do envelhecimento pode provocar falhas durante o desempenho da condução de automóvel. Os fatores humanos desempenham um papel fundamental nos riscos de acidentes de trânsito. O objetivo do presente estudo foi determinar os efeitos do envelhecimento do motorista e da luminosidade do ambiente sobre o tempo de reação da frenagem, durante a condução simulada de automóveis. Quinze motoristas adultos jovens e quinze motoristas idosos realizaram uma tarefa de condução na qual foram mensurados os tempos de reação envolvidos na frenagem (retirada do pé do pedal do acelerador e acionamento do pedal de freio) em um simulador de direção de um automóvel. A tarefa dos participantes foi seguir por um percurso de 5 km um carro à frente, que freava bruscamente acendendo a luz vermelha traseiro do carro, em duas condições: uma com luminosidade diurna e outra com luminosidade noturna. Um pré-teste de tempo de reação simples utilizando os pedais de acelerador e freio, fora do cenário simulado da condução, foi realizado como situação controle. Os dados da condução simulada foram submetidos à análise de variância do grupo (adultos, idosos) por luminosidade (diurna, noturna), com medidas repetidas no segundo fator. Nas condições de condução do veículo, os idosos mostraram tempo de reação maior tanto para retirar o pé do acelerador quando para acionar... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Population aging is associated with profound social, economic and cultural changes. The perceptual and cognitive impairment resulting from aging can cause failures during car driving performance. Human factors play a key role in the risks of traffic accidents. The aim of this study was to determine the effects of driver’s aging and ambient luminosity on the braking reaction time during simulated car driving. Fifteen young adult drivers and fifteen elderly drivers performed a driving task in which the reaction times involved in braking (removing the foot from gas pedal and pressing brake pedal) were measured in a car driving simulator. Participants’ task was to follow a car in front of them during a 5 km path, which braked abruptly with the rear red light turning on, in two conditions: day and night light conditions. A simple reaction time pre-test utilizing gas and brake pedals, out of the simulated driving scenario, was conducted as a control situation. Data from driving conditions were submitted to a group (adults, elderly) by luminosity (day, night) analysis of variance, with repeated measures in the second factor. During driving conditions, the elderly group showed greater reaction time to release the gas pedal and to press the brake pedal; the same occurred to the total reaction time in the total reaction time. Interestingly, reaction times during day light luminosity were greater than those during night luminosity for gas pedal and total reaction times. Results are disc... (Complete abstract click electronic access below) / Mestre

This Diploma Thesis is dedicated to solve the source of noise, observed during braking processes on tested vehicle, called Gouki noise and has been worked out in corporation with Federal Mogul company. The aim of this work to create test methology, which allows to experimentally detect the source of undesirable noise and eventually suggest next steps in its prevention.

Objective of this thesis is design of brake system of new car Formula Student class – Dragon 3. This car was built by students of faculty of mechanical engineering on Brno university of technology. Brake parts selection is described as well as designing hydraulic brake line circuits optimized for stable braking behavior on tracks of Formula Student competitions. One of main parts of this thesis is design of front and rear custom brake discs with related parts. These parts are FEM analyzed. In the end the whole brake system fitted on Dragon 3 car is tested on track and its performance is analyzed too.

Low-back pain and injury claims account for a large number of occupational illnesses each year. In the railroad industry, many maintenance and operation activities require a high degree of manual labor, often resulting in increased stress on the lowback. One of the most common functions of railroad yardmen is the setting and releasing of railcar hand brakes. A static three-dimensional low-back biomechanical model was developed to estimate the levels of compressive force on the L3/L4 spinal joint that existed in subjects during an experiment that simulated the hand brake setting task. We recorded three-dimensional body posture and resultant forces at the hands for analysis by the model. The model resolved the external forces acting on the body to a resultant moment about L3/L4 and then employed an optimization algorithm to estimate the internal lumbar muscle forces generated to resist the external forces. The muscle forces and external forces were added to arrive at a prediction of compressive force at L3/L4. The experiment investigated the effects of general body posture, left hand grip, subject anthropometry, and hand brake torque level upon predicted compressive force at L3/L4. An analysis of variance revealed that compressive force was significantly affected by each of the experimental variables. Additional analyses at subjects' maximum voluntary torque levels indicated that compressive force would exceed NIOSH guidelines for low-back compressive force, especially in males. Predicted L3/L4 compressive force at maximum torque ranged from an average of 2350N in small females to an average of 7485N for large males. We then used regression analysis to predict brake torque levels that would cause compressive force to exceed the NIOSH (1981) recommended maximum of 3400N. Based on the prediction methods used, hand brake torques of 40 to 80 Nm would be likely to cause compressive force to exceed this maximum. / Master of Science

No / Braking system characteristics, brake system performance and brake system component design parameters that influence brake pedal ‘feel’ in a passenger car have been studied using the simulation modelling package AMESim, in particular to model the linear and nonlinear characteristics of internal components. A passenger car hydraulic brake system simulation model incorporating the brake pedal, booster, master cylinder, brake lines and calipers has been developed to predict brake system response to assist in the design of braking systems with the desired brake pedal force / travel characteristic characteristics to create good brake pedal ‘feel’. This has highlighted the importance of system components, in particular the master cylinder and caliper seal deformation, and the operating characteristics of the booster in determining the brake pedal force / travel characteristic. The potential contribution of these 3 components to brake pedal ‘feel’ improvement has been investigated, and the results of the AMESim model have been verified using experimental measurement data. The model can be used in the future to provide an accurate prediction of brake system response at the design stage thereby saving time and cost.

One of the benefits of electric vehicles (EVs) and hybrid vehicles (HVs) is their potential to recuperate braking energy. Regenerative braking (RB) will minimize duty levels on the brakes, giving advantages including extended brake rotor and friction material life and, more significantly, reduced brake mass and minimised brake pad wear. In this thesis, a mathematical analysis (MATLAB) has been used to analyse the accessibility of regenerative braking energy during a single-stop braking event. The results have indicated that a friction brake could be downsized while maintaining the same functional requirements of the vehicle braking in the standard brakes, including thermomechanical performance (heat transfer coefficient estimation, temperature distribution, cooling and stress deformation). This would allow lighter brakes to be designed and fitted with confidence in a normal passenger car alongside a hybrid electric drive. An approach has been established and a lightweight brake disc design analysed FEA and experimentally verified is presented in this research. Thermal performance was a key factor which was studied using the 3D model in FEA simulations. Ultimately, a design approach for lightweight brake discs suitable for use in any car-sized hybrid vehicle has been developed and tested. The results from experiments on a prototype lightweight brake disc were shown to illustrate the effects of RBS/friction combination in terms of weight reduction. The design requirement, including reducing the thickness, would affect the temperature distribution and increase stress at the critical area. Based on the relationship obtained between rotor weight, thickness and each performance requirement, criteria have been established for designing lightweight brake discs in a vehicle with regenerative braking. / Ministry of Higher Education of Malaysia

The fundamental theories of heat generation and transfer at the friction interface of a brake assume either matching or not matching surface temperatures by having a varying or uniform heat partition ratio respectively. In the research presented the behaviour of heat partition has been investigated in a fundamental study based on experimental measurements of temperature and the associated modelling and simulation of heat transfer in a brake friction pair. For a disc brake, an important parameter that was identified from the literature study is the interface tribo-layer (ITL), which has been modelled as an equivalent thermal resistance value based on its thickness and thermal conductivity. The interface real contact area was also an important parameter in this investigation, and it has been found to affect heat partitioning by adding its own thermal resistance. A 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model is presented, based on which a novel relationship which characterises the total thermal resistance (or conductance) at the friction interface has been characterised based on the ITL thermal properties, the contact area, and the contact pressure at the interface. Using the model the effect of friction material wear on the total thermal resistance (or conductance) at the friction interface was predicted and a comparison of the Archard and Arrhenius wear laws in predicting the wear of a resin bonded composite friction material operating against a cast iron mating surface is presented. A 3-dimensional (3D) model is also presented. This model has represented a small scale disc brake test rig which has been used in parallel with the simulation for validation in a drag braking scenario. Two simulation conditions with different pad surface states were investigated, the first having a nominally flat surface, and the second an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wear model was applied to significance of including wear on the total thermal resistance at the friction interface over a short brake application. A sensitivity analysis on the interface thermal conductance, the location of heat generation, and the magnitude of contact pressure has identified the importance of each factor in determining the total thermal resistance (or conductance) at the friction interface during any friction brake application. It is concluded that the heat partitioning is insensitive on the location of heat generation, and that the most sensitive parameter is the contact pressure. / Institution of Mechanical Engineers (IMechE)

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An attempt was made to construct an ABS system that would both lock the wheel and release the brakes. The system would be mounted on a bicycle with v-brakes. It would then be tested if it could decrease the braking distance and if the system would respond fast enough. A literature study was made to learn what was needed for such a project. After many attempts of using re-purposed components an ABS system would eventually be built with a new stepper motor, and it was strong enough to lock the back wheels. Unfortunately the system could not be as thoroughly tested as expected, where only the reaction time of the system could be tested and not the braking distance due to a motor driver failure prior to the tests taking place. Due to shipping times and our budget and time constraints, further testing could not be done. / Ett försök att bygga ett ABS system som både låser hjulet samt släpper på bromsen gjordes. Systemet skulle kunna monteras på en cykel med fälgbromsar. Systemet skulle testas genom att mäta skillnaden i bromssträcka samt om reaktionstiden var snabb nog. En litteraturstudie gjordes för att få tillräcklig kunskap om vad som krävdes för ett sådant projekt. Efter många försök med att använda olika återanvända komponenter kunde ett ABS system till slut konstrueras med hjälp av en ny stegmotor, som var stark nog för att låsa bakhjulet. Tyvärr kunde bara systemets reaktionstid testas och inte bromssträckans förändring. Detta berodde på en motordrivare slutade fungera. På grund av frakttider och en fast budget samt en tidsbegränsning, kunde inte ytterligare tester genomföras.