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

2.2 Splitting of the brake rotor’s eigenfrequencies by asymmetry
I
P
B
C
Figure 2.4: Comparison of the minimal necessary separation of eigenfrequencies
∆f for the four considered types of brake discs. Prototype brake disc (P), ceramic
disc (C), cast iron disc (I), bicycle disc (B).
brake disc requires a much higher separation of eigenfrequencies for squeal
avoidance and also shows affinity for brake squeal up to much higher frequencies.
This partially originates from a stiffer brake pad and a higher friction
coefficient between brake pad and disc, partially from a different geometry.
In contrast, the much thinner cast iron brake disc, which is in contact with a
brake pad of lower stiffness and has a higher damping, shows reduced affinity
to squeal. This corresponds to the practical experience that less stiff brake
pads and higher damping frequently lead to brake systems less susceptible to
squeal. In contrast to first intuition, the bicycle brake disc, which is a totally
different kind of brake disc as is shown in Fig. 4.18, lies in the same range of
frequency split and squeal limit frequency as the other three types of brake
discs. The necessary separation of eigenfrequencies ∆f and the limit frequencies
f lim for the four types of analyzed brake discs are given in Tab. 2.2. Some
important conclusions can be drawn for the structural optimization of brake
discs that will be presented in the following chapters. The first is that it is
not necessary to optimize in the whole audible frequency range up to 20 kHz
but only up to a smaller limit frequency that can be estimated in advance if
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