Pastilhas de freio para sistemas de freios automotivos correspondem a um dos materiais compósitos mais complexos já que eles contêm muitos componentes, cada qual com uma grande variedade de propriedades físicas e químicas. Esta natureza multi-fase é necessária para satisfazer a grande variedade de demandas relativas à performance. As condições de processamento também possuem grande influência nas propriedades deste complexo compósito. As pastilhas de freio usadas neste trabalho foram sem amianto do tipo semi-metálica contendo muitos elementos, incluindo resina fenólica, fibra de reforço, lubrificantes sólidos, abrasivos e cargas. Este trabalho tem como objetivo principal esclarecer a influência entre as variáveis de processo e de composição nas propriedades de compressibilidade a frio, densidade, dureza, flexão e coeficiente de atrito. Para isso foram utilizados planejamentos de experimentos fracionados e completos. O planejamento de experimentos fracionado, 25-1, indicou que a quantidade de resina fenólica e a temperatura do molde são os fatores mais significativos para a compressibilidade. O planejamento de experimentos completo, 24, mostrou mais uma vez, que a quantidade de resina e a temperatura do molde, bem como as suas interações, são fatores significativos na determinação da compressibilidade. O terceiro planejamento de experimentos, 2³, concentrou-se nas propriedades da resina, já que a mesma mostrou-se muito influente na determinação das propriedades dos materiais de atrito. Os resultados mostraram que é possível controlar as propriedades tribológicas e a compressibilidade das pastilhas de freio dentro de certa escala de valores. Assim, este trabalho mostra que é possível aplicar técnicas estatísticas para racionalizar o projeto de materiais de atrito. / Brake pads for automotive brake systems represent one of the most complex composite materials since they contain many components with widely varying physical and chemical properties. This multiphase nature is necessary to satisfy a wide variety of performance related demands. Processing conditions also have a major influence on the properties of these complex composites. Brake pads used in these studies were semi-metallic non-asbestos friction materials containing many different ingredients, including phenolic resin, reinforcing fibers, solid lubricants, abrasives and fillers. In this work, the influence of composition and process parameters on the compressibility, density, hardness, flexure strength and coefficient of friction were investigated. The designs of experiments selected for this study were fractional and full varieties. In the initial fractional design of experiments, we found both the quantity of resin and the mold temperature to be dominant influences on the compressibility. A full design of experiments again indicated that the quantity of resin and mold temperature, as well as their interaction, are the dominant players in determining the compressibility. A third design of experiments concentrated on the resin properties since this factor was the most influential in determining the properties of friction materials. The results show that it is possible to control both the tribological properties and the compressibility of the pads within a rather large range of values. Thus, the work shows that it is possible to use statistical methods to rationalize brake pad design.

This diploma thesis is engaged in analysis of braking process of vehicles, especially heavy utility vehicles, with regard to their instantaneous weight. This thesis features survey and division of braking systems and function of brakes including schemes and descriptions. Also there is introduce of some systems improving vehicle properties. Furthermore this work puts mind to possibilities of examination of brakes, measurement of braking distance and braking retardation namely in brake test rooms or by outdoor driving tests including descriptions of particular methods and equipment. There is also mention about legislative requirements for braking distance and braking retardation. The conclusion of this thesis compares numerically predicted braking distance and real braking distance measured for factual vehicle during outdoor driving test

Brake materials represent an important source of air pollution, especially in urban areas, where they can contribute to approx. 21 % of the traffic-related particulate matter emission. For this reason, the design of new brake materials with low emissions is a topical issue. In addition to low emissions, the design of new friction materials has to ensure excellent performance with stable coefficients of friction and low wear rate. Due to the several requirements that these materials need to fulfill, their development and testing are complex and intercorrelated. Good performance and low emission strongly depend on the mechanisms acting at the disc-pad interfaces. In this thesis, a brake dynamometer testing protocol is developed to better understand the relationships of the braking parameters with the brake performance and emission behavior, correlating them with the surface characteristics. The surface characteristics were investigated with a-posteriori analysis, in terms of extension of the contact area, degree of compaction of the wear particles and relevant composition. The work is focused on the bedding process and the influence of the braking parameters on the frictional, wear and emission behaviors. Regarding the bedding process, run-in, transition stage and steady states were identified as concerns the frictional, wear and emission behaviors. The frictional behavior gets stabilized by the extension of the secondary plateaus, whereas the wear and emission behaviors are stabilized as their degree of compaction increases. The influence of pressure and velocity under mild sliding conditions were studied for a low-met and NAO material, the two most common types of friction materials. The low-met material featured a more stable and higher friction coefficient and lower wear and emissions than the NAO material. The wear behavior is strongly affected by pressure for the NAO material, and for the low-met material, velocity is very influential. Emissions follow a cube relationship with velocity for both materials. The significant differences in the observed behaviors are explained in terms of the different features of the surfaces. The NAO material featured a smooth and uniform surface, with higher coverage than the low-met material, on which steel fibers play important adhesive and abrasive actions. From tests under mild sliding conditions of several friction materials sliding against cast-iron discs, a linear relationship is found between the specific wear rate and the emission factor. This relationship identifies a wear rate below 2.5 10-14 m2/N complying with the Euro 7 limitation of 3 mg/km/vehicle after 2034. Among the friction materials sliding against cast iron discs, the NAO material and only one friction material displayed an emission factor below the limit of 3 mg/km/vehicle. In addition, the emission factor of low-met material sliding against a cermet-coated disc was lower than this limit. These observations confirm that the NAO materials and coated discs are effective systems to mitigate emissions, whereas further efforts are required to improve the emission behavior of low-met materials. Interestingly, the low-met materials with a reduced presence of secondary plateaus featured higher wear and emissions. Regarding the brake performance, under severe sliding conditions, the NAO material displayed worse frictional and wear behaviors than the reference low-met material. For high-pressure ranges, the effect of pressure is to cause a monotonic decrease in the friction coefficient. The effect of temperature on the friction coefficient causes an increase in the friction coefficient when the tribo-oxidative processes are contained up to 300 °C. For combinations of high velocity and temperature, the tribo-oxidative processes are high enough to form a thick glaze layer on the surfaces. The glaze layers were correlated to a lubricating effect, or fade effect, at disc temperatures above 400 °C, especially when their extension covered the steel fibers. The cermet-coated disc displayed the same fade behavior at high velocity-temperature values, although at low velocities and high temperatures, friction instability was observed and related to larger but fewer patches originating to a significant extent from material transfer from the disc. The friction instability in the coated disc was ascribed to the different tribo-oxidative behavior in the formation of ‘glazes’ due to the low source of iron in the disc material.

This thesis project is a comprehensive practice to improve a research concept vehicle in both hardware and software aspects. The hardware of the friction brake system is improved to have higher stability and accuracy. The brake force distribution function is implemented to optimize the brake control system. A fault tolerant function based on the Pseudo-inverse control allocation strategy is designed, implemented, and tested to compensate for sudden fault in wheels when driving. / Detta examensarbete är ett omfattande arbete att förbättra ett forskningsfordon som heter Research Concept Vehicle (RCV) gällande både hårdvara och mjukvara. Hårdvaran i bromssystemet har förbättrats för bättre stabilitet och noggranhet. Bromskraftsfördelningsfuktionen har implementerats för att optimera bromssystemets reglering. En feltolerant funktion baserad på pseudo-invers reglering har också implementerats och testats för att kunna kompensera plötsliga felfall i hjul under körning.

This master’s thesis focused on the issue of the possible conversion of liquid brake systems, in the form of replacement of wheel brakes. The first part focused on the function and description of the construction of different types of brakes. The second part is focused on description the types of brake system testing and the regulations regarding brake systems. The last part focused on the measurement of both vehicles and comparison of the results with the calculations.

The aim of my thesis is the design of centrifugal brakes to prevent twisting of the combustion engine with pneumatic compactor. In the first part of my thesis I deal with existing and similar systems that prevent over speeding. In the second part I deal with the design of its own centrifugal brake. This includes basic functional, strength, thermal calculation, design of components and fabrication drawings according to the assignment.

A novel electromechanical brake (EMB) based on the eddy current principle is proposed for application in electrical vehicles. The proposed solution is a feasible replacement for the current conventional hydraulic brake (CHB) systems. Unlike CHBs eddy current brakes (ECBs) use eddy currents and their interaction with an externally applied magnetic field to generate braking torque. Due to their pure electrically controllable and contact free nature, ECBs have multiple advantages over the current CHB systems, such as faster response, reduced weight and number of components, ease of implementing various controllers (e.g., anti-lock braking), and reduced noise levels. However, the torque generated by a typical ECB at low speeds is insufficient to effectively and completely stop a moving vehicle. Therefore, an ECB is commonly used as an assistive brake to the CHB system in heavy vehicles, i.e. trains and trucks In order to overcome this shortcoming, the use of AC magnetic fields is proposed to realize a stand-alone ECB system in which sufficient braking torque can be generated at low speeds. To this end, eddy currents are modeled analytically using the governing Maxwell’s equations with the consideration of time varying field application. The analytical model was validated using finite element analysis. Results show that the braking torque increases with the application of a time varying field. Various forms of time varying fields have been studied. It was found that the frequency-modulated applied field in triangular waveform results in the highest braking torque. Next, the design was optimized to maximize the braking torque and an optimum configuration was obtained using multiple pole projection areas (PPAs). Optimization results show that the braking torque significantly increases with the introduction of additional PPAs to the configuration, and the braking torque generation for an optimum four-PPA ECB configuration exceeds the braking requirements for current passenger vehicles. For control purposes, a dynamic model for a novel stand-alone ECB system using AC fields for automotive applications has been successfully designed and evaluated. Also, a model-based predictive controller has been developed for the optimum ECB configuration. Finally an experimental test-bed has been designed for experimentation of both DC and AC field application on ECB. / Graduate

Brake squeal is an old and well-known problem in the vehicle industry and is a frequent source for customer complain. Although, brake squeal is not usually affecting the performance of the brakes, it is still important to address the problem and to predict the brakes tendency to squeal on an early stage in the design process. Brake squeal is usually defined as a sustained, high-frequency vibration of the brake components, due to the braking action. By using simulation in finite element (FE) method it should be possible to predict at what frequencies the brakes tend to emit sound. The method chosen for the analysis was the complex eigenvalues analysis (CEA) method, since it is a well-known tool to predict unstable modes in FE analysis. The results from the CEA were evaluated against measured data from an earlier study. Even though there are four main mechanism formulated in order to explain the up come of squeal, the main focus in this project was modal coupling, since it is the main mechanism in the CEA. A validation of the key components in model was performed before the analysis, in order to achieve better correlation between the FE model and reality. A parametric study was conducted with the CEA, to investigate how material properties and operating parameters effected the brakes tendency to squeal. The following parameters was included in the analysis; coefficient of friction, brake force, damping, rotational velocity, and Young’s modulus for different components. The result from the CEA did not exactly reproduce the noise frequencies captured in experimental tests. The discrepancy is believed to mainly be due to problems in the calibration process of the components in the model. The result did however show that the most effective way to reduce the brakes tendency for squeal was to lower the coefficient of friction. The effect of varying the Young’s modulus different components showed inconsistent results on the tendency to squeal. By adding damping one of the main disadvantages for the CEA, which the over-prediction of the number of unstable modes, where minimized.

This Master´s thesis deals with construction design of break system of the tractor Zetor Forterra HSX. At the beginning, there is an overview of different possibilities breaking system from other world´s producers of tractors. Afterwards there is constructional working from selection variant of suspension to final project. In this case the thesis contains required calculations of the whole device. Thesis also contains the stress and strain analysis of selected components of construction using a numerical approach of finite element method and drawing documentation of the selected components.

In today’s fast moving world, automobiles are facing challenges in terms of having to survive road accidents, increasing traffic, bad road-conditions and high/express ways. Brake systems play a vital role in controlling the vehicle speed while avoiding road accidents. The conventional brake systems consist of basically an actuator, transmission and frictional parts. This system is difficult for manipulated control by the driver during emergency and panic braking situations. In particular road and environmental conditions, it requires certain skill to have safe and effective brake control, which is always not possible from all drivers. Wheel locking is a predominant phenomenon during panic braking and this will cause vehicle skidding resulting in injuries and road accidents. In the case of a two-wheeler, being a single-track vehicle, skidding is one of the major causes for fatal road accidents due to loss in lateral balance. As the road safety regulations are becoming more stringent, the anti-lock brake systems (ABS) will replace the conventional brake systems in all road vehicles to avoid accidents and to improve vehicle safety. Early ABS systems, developed in the last 100-years, use intermittent and cyclic brake pressure control by sensing the wheel speed or wheel-slip as one of the major control inputs. Regulating the brake pressure with a preset threshold value is another method. These ABS systems have used electronics, or hydraulics or pure mechanical control. However, such ABS are not widely used in two-wheelers and other low cost vehicles till now, because of several limitations identified as follows: High cost, power supply needed for its operation in the case of intermittent and cyclic brake control, susceptibility to failure in the electronics system, interference from RF signals (from cell-phones for example), uneasiness to drivers from pedal pulsations with pedal noise, heavier weight, increased vehicle vibrations and failure modes of wheels due to torsional vibrations. The present research work is carried out to develop a new mechanical ABS concept, which will address most of the above problems. During braking, the change in rider-input force will change wheel reactions. This change is made proportional to the change in rider input force only upto wheel locking. Such a principle is used to develop the new mechanical ABS. The new concept regulates the output force from the ABS, by sensing the dynamic wheel reactions with increase in rider-response. The ABS output force is regulated by one of the following ways: (a) Slipping-down the lever-ratio or (b) preventing the excessive brake input force. Based on the parameters like less number of parts, least weight, simplicity, reliability, efficiency, durability, time-response, etc., the second method (of preventing the excessive brake input force) has been chosen. Further a new concept of ABS interconnecting system is proposed for usage between the front and rear wheels of the vehicle. This interconnecting system will ensure that the two mechanical ABS systems function at any kind of braking-balance between the front and rear applications. An analytical vehicle model has been developed with several input parameters like mass, geometry, inertia, aerodynamic properties, frictions of road and bearing-supports, road gradients, etc. From this analytical model, the dynamic wheel reactions and limiting adhesion of each tyre for various braking conditions are determined and the results are used to design the mechanical ABS. The same analytical model is used to predict the brake performance like stopping distance, vehicle deceleration and the vehicle speed variation for ideal braking conditions. The new ABS is modelled in Pro-E using the inputs from the analytical model. To evaluate the concept, a functional proto-type is built and fitted on a motorcycle. The ABS is evaluated for its functionality and performance at different road (level surface, up-gradients and down gradients) and environmental conditions (dry and wet road conditions). Using the VBOX II, proximate sensors and load-cells fitted on the vehicle, the vehicle stopping distance, wheel slip and pedal force are measured. The results show that wheel locking does not occur under panic driving conditions, which is the primary objective. In addition, the results show a good agreement with the predicted stopping distance and vehicle deceleration from the analytical model. As there is good scope for this new mechanical ABS for use in two-wheelers and other low cost vehicles, further research is needed to make this system work in curvilinear motion & banked surfaces.