Braking noise characteristics and a simulation analysis method based on a multiscale braking test

Currently, iron or steel brake disks generally be selected to research braking noise. This research focuses mainly on the influence of the structural characteristics of the brake pads and brake disks on the braking noise, and few studies addresse how braking conditions or braking modes affect the noise characteristics. To clarify the causes of the abnormal noise in the braking process of different friction pairs, through a noise test of the multiscale bench braking test and the simulation method of complex eigenvalue analysis, this paper studys the braking noise characteristics and the generating mechanism of different friction pairs under different braking conditions and braking modes.

According to the scaled test scheme, a scaled test of three types of friction pairs is performed on the MM-1000/IV scaled test machine, and the braking noise characteristics of the friction pairs are compared and analyzed. For the selected friction pair of the SiCp/A356 composite brake disk and synthetic pad, a more realistic 1∶1 bench brake test is performed. On the basis of HyperMesh and Abaqus software, a finite element simulation model of the wheel-mounted disk foundation braking device with a wheel, disks, pads, pad holders, brake levers, etc. is constructed.

Under the same working conditions, the sound pressure levels (SPL) of the two SiCp/A356 composite friction pairs were lower than those of FE-928W friction pair. The maximum value of maximum sound pressure level (Max SPL) was 96 dB for the FE-928W friction pair and 87 dB for the BJTU-928W friction pair. The braking noise type of the FE-928W friction pair was mainly a multifrequency squeal, and the braking squealing phenomenon occured in most working conditions. The noise types of the BJTU-928W friction pair and the KNORR-928W friction pair were mainly wide area noise and single frequency squeal. The friction surfaces of different friction pairs had different degrees of surface scratching, material transfer, and peeling, which led to differences in the braking noise. The main frequency of the squealing noise of the friction pair between the SiCp/A356 composite brake disk and the synthetic brake pad was concentrated near 2.20 kHz, and the Max SPL could reach 110 dB. Brake pads were the main source of braking noise. The greater the energy inputed, the more times of high-temperature continuous braking, the greater the squealing sound pressure level, and the more severe the squeal. In contrast, when braking at a lower energy input level, the disk state would be restored, and quiet braking could be achieved during subsequent braking.

Through the experiments and simulations, the simulation method of complex eigenvalue analysis can better predict the tendency of braking noise, and the braking noise characteristics and causes of different friction pairs under different braking conditions and braking modes are clarified. This research provides a scientific basis for noise reduction strategies such as friction matching, structural design optimization, and braking mode improvement of the friction pair between the SiCp/A356 composite brake disk and the synthetic brake pad.