Damping efect on nonlinear drum brake squeal prediction

In the present study, Complex Eigenvalue Analysis (CEA) was used for predicting squeal noise generation in a commercial drum brake. By using a CEA model, Rayleigh damping properties were added to the computer simulation on ANSYS, and a discussion about its implications and proposed calculations are also shown. The Rayleigh damping coefcients (α and β) were obtained through impact tests carried out in a commercial drum brake. Three diferent cases of damping levels were simulated: (a) Undamped condition, (b) Damped–0 bar, and (c) Damped–2 bar. Results of experimental tests showed that increasing brake pressure from 0 to 2 bar in the damped condition leads to a shift in the resonant frequencies towards higher values, as well as to increase the damping response of the drum brake system. Results of CEA showed a large number of vibration modes occurred within a narrow range of frequencies (0–4500 Hz). This means the drum brake is prone to modal coupling, which may lead to noise generation. The frst model simulated by CEA (undamped case) showed fve instabilities in the frequency range considered, from this point, the second model was built (damped–0 bar case) and only three instabilities were identifed. Thus, the third model (damped–2 bar case) was analyzed and it showed only one unstable frequency, which means over-predictions could be avoided due to the addition of damping. Thus, it was noticed a signifcant negative ofset caused by the damping efect, however, the system instabilities for all fve modes remain. CEA models were validated by comparison of predicted and vehicle noise frequencies, which were very close