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Thermoelastic instabilities in the contact of brake friction material cause hotbands and hotspots on the surface of brake disc. These phenomena generate thermal stresses that result in generation of cracks, which limit the lifetime of the discs. In the present work, the influence of the chemical composition of brake discs on the thermoelastic behavior of the system and on the lifetime of the discs was investigated. The experimental evaluation was carried out in an inertial dynamometer using the SAE J3080 standard procedure applied on a brake system. Two discs (namely A and B) with different chemical compositions were subjected to the tests. The brake pad composition was kept fixed. The thermoelastic effects on the inner surface of the disc were observed by contact (thermocouple) and noncontact measurement techniques (thermography), as well as through photographic images of the disc’s surfaces. Disc A showed negligible amount of Nb while disc B exhibited 0.360%.

Pedal feeling for race cars is a subject of great uncertainties, due to singularities of this type of system and the large amount of components that may influence it. High performance friction materials are developed considering different requirements, aiming to establish a commitment relationship, among different characteristics - for example, compressibility, friction and wear - for critical conditions of use, such as high temperatures and pressure applications. The purpose of this study is to analyze the brake system strain through the fluid displacement measurements and analysis, during brake events, applying different brake pressures for static tests performed on an inertial dynamometer. Test procedures applied aim to simulate automobile race laps, according measurements previously done. Two high performance friction materials, specifically developed for this application, with similar compositions - around 5% different and some physical properties improved - were analyzed.

The current study presents some testing procedures which have been designed for friction and noise measurements of brake friction materials using a laboratory-scale tribometer. The uncertainties (errors) and precision of the measurements are also described in this paper. Some case studies related to friction, wear and noise related issues in brake friction materials were chosen to show the respective testing procedures. Through the error study, it was shown that the uncertainties of the lab. test bench are mainly associated with 3 variables: torque, force and sliding radius. The combined uncertainty of the friction measurements is less than or equal to ±1%, considering the typical operating range of the machine. The possibility of using two samples from a single brake pad also contributes to the reliability of the machine test and procedures.