Applications relying on a high static friction include various types of fixtures, couplings, bolted joints, torsion joints, etc. The common characteristic of these applications is that they rely on the friction force to maintain the relative position of two mating surfaces. Also applications relying on high dynamic friction are common, the main example being brakes, where a low friction could be devastating. The plateau model for the friction of brakes has been refined. By using advanced electron microscopy, it has been shown that during braking a partly amorphous friction film, comprising nanosized iron oxide agglomerates, dissipates the friction energy. The film is only about 100 nm thick. It is separated from the underlying less mobile material by a thin boundary. The actual braking power is thus localised to this very thin film, leading to remarkably high power densities. In a typical case it was estimated to 40 GW/dm3. Squeal and vibrations are critical problems for brakes. The present work has shown that a textured disc pattern may counteract squeal efficiently. The most successful pattern has spiral shaped arms in which wear resistant ceramic particles are embedded. The different wear characteristics of treated and untreated disc surface lead to an elevation of the patterned area above the rest of the disc. In a related experiment, laser technique was used to inject the particles deeper into the disc surface, and thus prolonging the time of silence. Textured diamond surfaces have been used to study the influence of load, repeated scratching and surface roughness on the static coefficient of friction. It was shown that these surfaces were remarkably stable at high friction levels. A maximum load limit was found above which the coefficient of friction falls. This and a number of other factors were found important for the successful design of high-friction joints.

The main purpose of this study is to simulate and analyze the temperature and contact pressure of the disc brake plate of a motorcycle during braking by the finite element method. By utilizing the software package Mentate and Marc which are signified with drawing and construction of the brake model to do the analysis of thermal and contact problem. In accordance with the result of analysis, the researcher discussed and compared the three-dimensional model and the two dimensional axial symmetrical model for the temperature, pressure and stress distribution of the brake. Finally, the researcher made some suggestions for the improvement of the mechanism of disc brake plate of a motorcycle.

No description available.

The air brake system is one of the critical components in ensuring the safe operation of any commercial vehicle. This work is directed towards the development of a fault-free model of the pneumatic subsystem of the air brake system. This model can be used in brake control and diagnostic applications. Current enforcement inspections are done manually and hence are time consuming and subjective. The long-term objective is to develop a model-based, performance-based diagnostic system that will automate enforcement inspections and help in monitoring the condition of the air brake system. Such a diagnostic system can update the driver on the performance of the brake system during travel and with recent advancements in communication technology, this information can be remotely transferred to the brake inspection teams. Since this system is performance-based, it will eliminate the subjective nature of visual inspections. The first step in the development of such a diagnostic system is to obtain a fault-free model of the air brake system. The model of the pneumatic subsystem correlates the pressure transients in the brake chamber with the brake pedal actuation force and the brake valve plunger displacement. An experimental test bench was set up at Texas A&M University and the experimental data is used to corroborate the results obtained from the model.

Techn. Universiẗat, Diss., 2005--Darmstadt.

Zugl.: Aachen, Techn. Hochsch., Diss., 2008

Passenger vehicle disk brakes produce large amounts of wear debris that needs to be analyzed to verify its environmental and health impact because its effects are amplified by the massive extent of vehicular transportation around the world. An efficient and thorough method for wear debris analysis should be derived from this research to assist brake manufacturers and researchers in understanding the characteristics of wear particulates being released from current brake materials. In addition, a test method allowing inspection of brake formulations in development phase should be provided and several model "environmentally friendly" brake lining materials should be developed. The most hazardous constituents in a known brake lining formula should be replaced with non-hazardous materials that will obtain performance specifications comparable to the original formula. The brake manufacturing industry and general public should be notified of important findings from this research. Model brake linings fabricated on-site with known constituents were run through an AO4D performance dynamometer test to collect airborne and non-airborne wear debris that is comparable to wear debris produced by an average passenger vehicle. Based on previous experience with analysis of brake linings, this wear debris will be analyzed with scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX), transmission electron microscopy with EDX (TEM-EDX), X-ray diffraction (XRD), polarized light microscopy (PLM), X-ray fluorescence (XRF), and laser scattering particle size distribution analyzer (LSPSDA). Research presented in this report indicates clearly that the previous work published by several groups is lacking sufficient information and the findings should be corrected. For instance the particle size distribution detected by particle size analyzers and impactors (recommended by EPA) is not accurate and TEM as well as SEM studies allowing direct observation of wear particles revealed considerable differences between sizes detected by these analyzers and realistic particle size. EDX in combination with XRF and XRD allows for reliable identification of chemical species and crystalline phases present in wear debris. True airborne wear debris should be sampled from brake exhaust from an appropriate distance. Degummed hemp shows promising results as a copper replacement in low-metallic friction material.

Despite many research pieces on brake systems, there is still research to be done on brake pad geometry and the dissipation of heat during brake engagements using the finite element analysis method. Brake application is a process in which the kinetic energy of the vehicle is mostly converted into thermal energy and then dissipated in the form of heat. Based on dynamometer test results it was seen that brake pad temperatures could reach up to 600° C [23]. Preliminary research using computer modeling software has shown that heat dissipation in brake pads with wavy geometries and air channels from the top to bottom is much better compared to pads that do not have those specific features. Brake pads that dissipate heat faster are prone to brake fade and other braking issues that may arise due to overheating [15]. For this research, two readily available brake pads and two designs of brake pads with new geometry were modeled using CAE software. Finite element analysis was then performed to test how well each brake pad dissipated heat after reaching brake fade temperatures. The readily available brake pads were from Power Stop and Wagner [26]. ANSYS Space Claim [25] was used to design and model the brake pads, ANSYS 18.2 [24] was used to perform the finite element analysis on the pads. After performing the analysis, results indicate that a brake pad with a design that had zones for turbulent air at ambient conditions and convection slots from the top to the bottom decreased in temperature by about 90° C more in the same time compared to the conventional design. By studying the changing values of the convection heat transfer coefficient with velocity, the placing of the turbulence zones can be more precise in order attain greater airflow to remove heat from the brake pad quicker.

Orientador: Auteliano Antunes dos Santos Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T01:53:22Z (GMT). No. of bitstreams: 1 Santos_ValdecirJosedos_M.pdf: 11167855 bytes, checksum: 4602f2d43f51266597072a259e482e7f (MD5) Previous issue date: 2013 / Resumo: O resumo poderá ser visualizado no texto completo da tese digital / Abstract: The abstract is available with the full electronic document / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Under der senaste år-tiondet har 'X-by-wire' teknologier stadigt introducerats inom kommersiellbiltilverkning. Detta har hänt på grund av de otaliga fördelar dessa teknologier har över derasmekaniska motparter. Huvudskillnaden är att man använder sig av elektro-mekaniska system iställetfor mekaniska förbindelser. I ett 'throttle-by-wire' system till exempel blir positionen av gaspedalenkontrollerad av sensorer och den elektriska aktuatorn föryttar strypan följaktligen. Fördelen är attinformationen som samlas av andra sensorer även kan påverka på hur strypan öppnas. Detta gerextra flexibilitet till mekanismen. Det nästa system bil-manufaktorer vill anpassa till 'by-wire'-systemär bromsarna. Principen här är att flytta bromspedalerna med en elektrisk motor som är placeradi kaliperna och därmed helt byta ut kolvarna och den hydraulkretsen som just nu används för attåstadkomma detta. Att genomföra detta är mödosamt då bromsning ar kritiskt för säkerheten ochdärmed måste fullt följa strikta regulationer. Man måste fortfarande kunna bromsa om strömmen intefungerar i huvudströmkretsen. Biltillverkare har därför undersökt olika backup-system for att kringgådetta problem. Alla möjligheter har sina nackdelar och förvecklar designen en hel del. Detta arbeteutforskar en ny 'brake-by-wire'-design som är härledd från studier av andra undersökta system. Måletav det nya konceptet är att lösa några av de uppmärksammade problem i andra design. Dokumentetbörjar genom att granska redan existerande 'brake-by-wire' teknologier och beskriver deras för-och nackdelar.Vidare kommer det nya konceptet beskrivas med de förbundna fördelarna. Efter det byggsen simulationsmodell for att ta reda på om ideen är möjlig att bygga och skulle fungera. Sedan ritasen CAD-modell av monteringen och ett flertal FEM-studier genomförs för att utvärdera styrkorna avnågra kritiska komponenter. Till slut förfinas modellen och de erhållna resultaten diskuteras. Dessaanvänds för att kritiskt kommentera koncepten och för att ge rekommendationer for möjlig framtidautveckling. / In the last decades or so, \X-by-wire" technologies have been steadily introduced in commercial carsfor the numerous advantages they provide over their mechanical counterparts. The core principleconsists of using electro-mechanical systems instead of mechanical linkages. In a throttle-by-wiresystem for instance, the position of the gas pedal is monitored by a bunch of sensors while an electricactuator moves the throttle accordingly. The advantage is that data gathered by other sensors mayalso inuence the throttle opening, giving extra exibility to the mechanism.The next system automobile manufacturers want to adapt to \by-wire" is the brake. The principleis to move the braking pads with an electric motor located in the calipers and to get completely ridof the pistons and hydraulic circuit currently used to this eect in cars. Nonetheless, the transition isarduous because braking is safety critical and must therefore comply with strict regulations. Indeed,it must still be possible to apply the brakes in case of a power loss on the main electric circuit.Manufacturers have therefore been exploring dierent backup systems to circumvent the issue butthey all present downsides and complicate the design to a great extent.This work studies a new brake-by-wire design whose concept was derived from the study of theother systems presently investigated. The aim of this new concept is to resolve some of the issuesobserved in other designs.This document starts by reviewing the existing brake-by-wire technologies and describing their prosand cons. Next, the new concept is described along with the advantages it may bring. Subsequently,a simulation model is built to assess whether the idea is plausible and can function properly. Later, aCAD model of the assembly is drawn and various FEM studies are conducted to evaluate the strengthof some critical components. Finally, the simulation model is rened and the results obtained arediscussed and used to comment critically the concept and give recommendations for possible futuredevelopments.