Thesis (Ph.D.)(Electronic Engineering)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Orientador: Kátia Lucchesi Cavalca Dedini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T19:40:17Z (GMT). No. of bitstreams: 1 Hodel_MarceloNogueira_M.pdf: 2409507 bytes, checksum: 2a63cd5603f35b3409c428810dde5cc3 (MD5) Previous issue date: 2010 / Resumo: Com a necessidade do lançamento de novos produtos e a introdução de novas tecnologias, em tempos cada vez mais competitivos, as empresas automobilísticas desenvolvem métodos para homologação de seus produtos, visando reduzir o tempo de desenvolvimento, e continuar atendendo aos requisitos de qualidade. Sendo assim, no setor automobilístico são desenvolvidas pistas de testes, para simular as principais características das aplicações veiculares, visando antecipar e analisar os resultados de confiabilidade dos componentes, antes do lançamento do veículo no mercado. Para avaliar os resultados obtidos durante a simulação é preciso compará-los com os dados de garantia, entretanto há componentes que são considerados itens de desgaste, que não são cobertos em garantia pela montadora, dificultando a comparação entre a simulação e os dados de garantia. Para validar os resultados obtidos por meio de uma simulação, para pastilhas de freio foram selecionadas amostras de usuários do veículo, logo após o seu lançamento. Foram realizados acompanhamentos sobre o desgaste das pastilhas de freio, para se obter os dados de confiabilidade em aplicações reais. Este estudo possui o objetivo de comparar os dados obtidos nos dois testes citados utilizando os conceitos de confiabilidade. A metodologia desenvolvida pode ser aplicada para validar os ensaios realizados para itens de desgaste, durante o desenvolvimento de novos produtos, principalmente veículos / Abstract: Due to the necessity of launching new products and the introduction of new technologies in more and more competitive times, automobile companies develop methods in order to get the approval of its products aiming at reducing the development time and keep meeting the quality requirements. Thus, in the automobile sector test tracks are developed in order to simulate the vehicle applications main features aiming at anticipating and analyzing the reliability results of components before launching the product in the market. In order to check the effectiveness of the results obtained during the simulation test, it is necessary to compare them with warranty data. However, there are components which are considered wear items and which aren't covered by the automaker warranty making it difficult the comparison with the results obtained in the simulation tests. Thus, in order to check the effectiveness of the results obtained through a simulation to brake pads it was selected samples from many vehicle users right after its launch and it was monitored for the wear of brake pads, aiming at obtaining reliability data in real application. The objective of this work is compare information obtained in both tests, using the reliability concepts. The developed methodology can be applied to validate the tests to wear items, during the development of new products, mainly vehicles / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

No / There are several types of disc brake instabilities associated with the brake systems; however, they are usually classified into two main categories depending on the frequency range: brake groan 0–300 Hz and brake squeal 1– 16 kHz. The groan is associated with the stick-slip motion while the squeal is associated with the modal coupling. This paper presents a detailed analysis of low frequency noise (0–300 Hz) in a commercial vehicle trailer disc brake as a result of stick-slip vibration. A range of experimental techniques are used to understand the characteristic behaviour of the caliper and the brake pads during braking events on a laboratory test rig. The analysed brake system comprised a full disc brake assembly and the trailer suspension system with a beam axle. Laser-based optical displacement sensors were used to investigate the deformation of the caliper body and the brake pads during a braking application. The contact pressure distribution at the disc/pad interfaces were also measured to gain more insight into the contact profile of the pad surfaces. Results revealed that the stick-slip phenomenon, in this study, was a result of the combination of the deformation of the caliper and the friction material formulation of the brake pads. In addition, it was observed through the testing of two different sets of pads that a low compression modulus would help to reduce the stick-slip phenomenon.

An important part of automobile safety is the braking system. Disc brakes have been widely used in automobiles for sped retardation for over 30 years. During that time, they have developed from a simple disc to a complex disc with channels, vanes, holes and grooves. The stopping capability of disc brakes is affected by the rate at which heat is dissipated by forced convection and the thermal capacity of the rotor. Catastrophic failure of brake rotors can occur during rapid increases or decreases in rotor temperature where regions of high temperature gradients result in high thermal strains. There is little information in the public domain regarding the relative merits of different disc brake rotor geometries, particularly in terms of airflow patterns, heat transfer rates, and internal thermal gradients. The aim of this research project was to investigate how geometrical variations affect the thermal performance of bi-directional disc brake rotors, particularly for high performance applications. Dynamometer testing showed that respectable increases in braking performance are achievable with relatively simple machining modifications. Tuft and smoke visualization techniques provided a preliminary understanding of the airflow in the passages of three distinct bi-directional rotor designs. Particle Image Velocimetry was used for detailed flow measurements which supported the numerical simulations. Computational Fluid Dynamics was used to predict the airflow and heat transfer associated with eight bi-directional brake rotor designs. The results show that 'pillared' passage designs can achieve higher heat transfer rates than traditional straight radial vane designs and that the heat loss from pillared rotors is generally more uniform than from vaned rotors. Subsequent conjugate heat transfer simulations found that temperature gradients inside pillared rotors are typically lower than inside vaned rotors. Thus failure rates due to excessive thermal strain are expected to be lower for pillared rotors. It was shown that rotor selection based solely on heat transfer rates is inappropriate and different passage designs are suited to different applications. The findings of this research will directly benefit local disc brake manufacturers, who do not have resources to conduct thorough studies comparing the thermal characteristics of different brake rotor designs.

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No description available.

The design of vehicle brake systems involves optimising a large number of competing parameters. In order to find an appropriate balance of properties, it is important to have a good picture of the range of operating conditions the system will operate under. Obtaining such information for a large range of driving conditions requires recording data over a long period from a number of vehicles under a number of different driving conditions. In this thesis, a proposed data acquisition system has been designed, constructed and implemented to measure and store in real-time performance related parameters of brake systems. The system proposed in this thesis to monitor brake performance employs a small embedded PC system along with a number of peripheral cards as its basis [...] / Masters

The design of vehicle brake systems involves optimising a large number of competing parameters. In order to find an appropriate balance of properties, it is important to have a good picture of the range of operating conditions the system will operate under. Obtaining such information for a large range of driving conditions requires recording data over a long period from a number of vehicles under a number of different driving conditions. In this thesis, a proposed data acquisition system has been designed, constructed and implemented to measure and store in real-time performance related parameters of brake systems. The system proposed in this thesis to monitor brake performance employs a small embedded PC system along with a number of peripheral cards as its basis [...] / Masters

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaf 60). Also available on the World Wide Web.

The investigation was involved with the reduction of the lining temperatures of a caliper disc brake by conversion of the standard mass produced wheel into a ventilated fan unit. The prerequisite was a newly designed vehicle wheel, fabricated in the Mechanical Engineering Laboratory of the Virginia Polytechnic Institute. Lining temperature comparison tests of the standard and newly designed Ventilated Fan Wheel were made, giving due consideration to various wheel speeds and particular conditions. The wheels were mounted simulating as nearly as possible the conditions one may find on an actual vehicle. Test speeds over a random spectrum in 10 MPH increments were selected. The cooling or heating rate data was acquired by using a General Electric cradle dynamometer. A manually operated hydraulic device was used to apply the normal braking force to the rotating brake disc. The energy absorption converted into heat and established a temperature gradient in the brake friction pads. The temperature of the pads was recorded with respect to time. The results were conclusive; the newly designed Ventilated Fan Wheel showed substantial reduction in the operating temperatures of the brake friction pads. / M.S.