Aplicação da tribologia ao estudo e desenvolvimento de materiais para embreagem automotiva

Abstract

During the clutch engagement manoeuvre, sliding contact occurs between the pair of clutch facings mounted on the friction disk and the counter faces belonging to the flywheel and the pressure plate. The materials used in the clutch have to ensure a smooth performance and friction coefficient that is sufficiently high and stable, thus providing regular and efficient rotation transmission. The development of friction materials requires a large number of tests to understand their tribological behaviour. Such development is highly empirical and involves a large number of repetitions between the tests. Durability tests using dynamometers are traditionally used to measure the wear life of the friction material used in automotive clutchs. However, these tests are long, relatively expensive and complex, because they require the construction of prototypes. This paper aims to find a correlation between wear mechanism and wear rates for the friction materials used in dry automotive clutches measured using both durability tests and a pin-on-disk sliding tribometer. Pin-on-disk sliding tests are shorter, simpler and cheaper. After the optimization of the tribological parameters, pin-on-disk sliding tests under constant normal load using a pin diameter of 13 mm reproduced with remarkable accuracy the traditional durability tests, although in the durability tests the load was cyclic and the diameter of the component was 200 mm.