Abstract
Squeal noise from brakes is very annoying and it is perceived by customers as sign of poor product quality. The research work presented in this paper attempts to understand the squeal generation mechanism in light of the mode coupling phenomenon. Initially conditions required to recreate squeal noise in drum and disk brakes were identified. The squeal noise was then recorded on road and in lab using data acquisition equipment and chassis dynamometer. Further, tests were done to identify the natural frequencies and mode shape of individual components. Tests have been designed to understand the effect, structural stiffness of brake components have, in generation of squeal noise. The study reveals some interesting insights, test carried out on drum brakes have helped us to understand the source of noise radiation and the required corrective action. The squeal noise from the drum brake were lower frequency squeal below 3k Hz. Whereas squeal noise from disk brakes were at much higher frequency i.e. above 10k Hz usually categorized as high frequency squeal. Changing the pad stiffness has shown certain squeal noise frequencies to shift and some others frequency to more or less vanish. One other important aspect in the squeal generation phenomenon namely the frictional interaction between the sliding surfaces was not studied as a part of these tests. Tests were done in lab conditions on new brakes and effects of amount of wear or the wear pattern were ignored for the study. The study was done on full vehicle and hence is much closer to the actual conditions that lead to the generation of squeal noise from brakes. The outcome from the tests agrees to some extend with the mode coupling theory and provide a first level proof for the same at a vehicle level.