Avoidance of brake squeal by a separation of the brake ... - tuprints

1 Introduction
The technical progress in the automotive, transport and aircraft industry over
the last decades, increasing safety standards and customer demands have
led to the development of sophisticated, high-performing and comfortable
brake systems. Despite this rapid progress, some problems of brake systems
remain or have even been increased due to the requirement for lightweight
and cost-effective construction. One of those is brake squeal, which is a noise
phenomenon studied at least since the 1930s, as Kinkaid et al. report [60].
There is no precise definition of brake squeal available in the literature, still,
most authors agree that squeal is a high-pitched, friction-induced sound with
frequencies ranging from 1 kHz to approximately 16 kHz for brakes used in
the automotive and motorcycle industry [2,21,60,92] and 100 Hz to 1000 Hz
for aircraft brakes [2]. The frequently made distinction between low frequency
squeal and high frequency squeal [26], however, is not adopted in this thesis. It
is characteristic for most squeal events that the generated noise is dominated
by one distinct frequency independent of the rotational speed. Furthermore,
brake squeal is indicated by amplitudes of the vibrations of the brake disc in
the micrometer range and the created sound pressure level (SPL) can reach
over 100 dB [60,92]. In most cases, brake squeal is a pure comfort problem
leading to passenger complaints and high warranty cost reaching over 100
Million Dollar each year regarding the automotive industry in particular [27].
It does not affect the main function of friction brakes to reduce vehicle speed
by a conversion of kinetic to thermal energy. Squeal can also be highly safety
relevant if squealing brake systems are connected to lightweight rims used
especially for high-performance motorcycles and bicycles, since the friction
induced vibrations can lead to fatigue and material failure of spokes [44,79].
Brake squeal can occur for all types of friction-based brake systems, for disc
brakes used in the aircraft, automotive, transport and motorcycle industry,
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