Nonlinear transient dynamic analysis of disc brake squeal using improved Hilbert-Huang transform

Brake squeal is believed as a friction-induced, self-excited phenomenon. The nonlinear transient analysis is the only appropriate method for the brake system with strong nonlinearities. The braking simulation is conducted based on a finite element model of disc brake, and their time-frequency properties of transient and stationary nonlinear response obtained by the improved Hilbert-Huang Transform are presented to investigate the transient dynamic behavior of brake system. It is demonstrated that the dynamic response of the friction-induced vibration is composed of multiple IMF components. The low-frequency IMF components have relative constant instantaneous frequencies but fluctuated energy with time. On the contrary, the high-frequency components have significant fluctuated frequencies. It is considered that the variations of the high-frequency are attributed to the nonlinearity of the brake system that includes the friction damping and contact nonlinearity in the present work. Some higher frequencies appear in the stationary vibration stage after the transient response. The propensity of system instability and brake squeal rises with an increase in friction coefficient. The simulated processing results have also manifested that the improved HHT can clearly provide the time-frequency property of the brake system compared to the conventional HHT, hence, it is a promising tool for processing the complicated nonlinear and nonstationary signals.