In this article, hypotheses on brake squeal mechanisms, based on refined thoughts, new results from recently developed test/analysis methods, and literature survey are proposed. The squeal mechanisms are categorized into excitation or triggering sources, system characteristics including modal coupling and mode lock-in, and sound radiation processes. Main conclusions on squeal generating mechanisms and causes are as follows: Instantaneous attach-detach or a non-smooth friction/sliding process between contact surfaces can generate impulsive excitation. The friction process at contact surfaces introduces an instant dynamic loading condition that alters resonant frequencies/modes of the friction system to form an instantaneous mode when it squeals. It may be generated based on either weaker impulsive excitation with stronger mode coupling or stronger impulsive excitation with weaker mode coupling. At low frequency (below the first in-plane mode of the rotor), squeal of a disc brake system is usually caused by modal coupling between rotor and other brake components such as knuckle, caliper, anchor bracket, pad or even the wheel besides excitation. Damping can help to stabilise the brake system to reduce or eliminate squeal. There is a particular value or range of stiffness for each brake component which stabilises the system. From analytical and complex eigenvalue analysis, it is certain that a higher friction coefficient will have higher squeal propensity. For any two contact surfaces, there is a fundamental vibration or excitation frequency that is determined mainly by contact stiffness. There are four frequency bands in which squeals most likely occur, the resonant frequency at rotor 3ND mode at which the caliper/pad size is close to the half of the wavelength of the mode, and at the three pairs of rotor in-plane (tangential) and out-of-plane modes. In all, periodic impulsive excitation combined with system modal coupling, synchronising and accumu!ating all vibration energy to the threshold level that creates an unstable instantaneous mode, is the fundamental squeal generation mechanism.
On automotive disc brake squeal part I: Mechanisms and causes
Über das Kreischen von Autobremsscheiben, Teil I: Mechanismen und Ursachen
2003
20 Seiten, 26 Bilder, 109 Quellen
Conference paper
English
Auslösen , Berührungsfläche , Bremsbelag , Bremsdruck , Dämpfung , dynamische Reibung , ebenflächige Belastung , Eigenschwingung , Erregung , Fahrzeugbremse , Feuchtigkeit , Geräuschanalyse , Geräuschdämpfung , Geräuschemission , Geräuschminderung , Geräuschquelle , Gleitreibung , Haftgleitreibung , Kriechen (Werkstoff) , Modenkopplung , Reibung , Reibungskoeffizient , Ruckgleiten , Schallausbreitung , Scheibenbremse , Schieflast , Schwingungsanalyse , Schwingungsfrequenz , Temperatur
On Automotive Disc Brake Squeal Part I: Mechanisms and Causes
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