Modelamento de vibrações de baixa frequência utilizando curvas de coeficiente de atrito em função da velocidade

Abstract

For the automobile industry, comfort while driving became indispensable, and peculiarities such as noise and vibration have become relevant for consumers, and even determinants for the purchase among vehicles. Considering all noises of a vehicle, brake noises have a special attention of costumers. Among various types of brake noises, a very common one is groan or chatter, characterized for being a low frequency and high vibration energy type of noise, usually occurring at low velocities. Thus, brake noise complaints are constantly headed to friction material producers, even though, friction material is not always the only cause of this phenomena. Mainly for low frequency noise, the axle and suspension assembly?s stiffness are very relevant. This study, consists primarily of characterizing experimentally the friction coefficient as a function of sliding velocity representative for groan noise, 30 km/h to 0 km/h, for different friction materials. For that, tests were performed on a pin-on-disc tribometer, where the disc was made of the same material as the brake disc, while the pin was made of the different friction materials. Subsequently, the experimental curves of COF as a function of the sliding velocity were used as input data in analytical, numerical and multi-body analysis of one or more degrees of freedom, reaching a simplified disc brake model. The main goal of this stage is to understand the influence of the friction coefficient variation according to the sliding velocity, on the system vibrational response of these simplified systems. For this, acceleration amplitudes of the caliper were compared, on each of the proposed models. It was also performed a sensibility analysis for the main parameters of the friction coefficient curves in function the sliding velocity, enabling to understand the best parameters combination which provide lower system vibration. [resumo fornecido pelo autor]