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Experimental verification is an important approach for understanding the mechanisms of disc brake squeal. One mechanism of disc brake squeal, i.e., coupling of in-plane and out-of-plane vibration modes of disc brake rotor, was found by experiments. Despite the vast amount of experimental data available, little effort has been dedicated to exploring what the time series information can reveal in relevance to squeal. In this paper, a new signal processing tool employing the Empirical Mode Decomposition Method (EMD) and its application to the identification of the characteristics of disc brake squeal will be discussed. The EMD was originally developed for ocean wave mechanics [1] and is particularly useful for the type of non-stationary data found in disc brake squeal. EMD is a time series analysis method that extracts a set of basis functions describing the fundamental characteristics of the response of a system.

The understanding, prediction and prevention of brake squeal is a difficult and challenging problem because of the large number of design variables involved in a complex brake system and many operational and environmental conditions under which squeal may occur. The design variables may have different optimal values and different contribution trends for different brake systems. Since the 1930's, much progress has been made in gaining physical insight into brake squeal mechanisms and causes, and brakes have become quieter. However, the recurring occurrence of disc brake squeal indicates that our understanding of the phenomenon is both insufficient and incomplete, and that brake squeal is still a quality issue in the automotive industry and its prevention is far from reality. Part I of this series of articles first reviews the various hypotheses put forth for brake squeal mechanisms and causes.