Abstract
KEYWORDS – Self-excited vibration, Squeal, Disc brake, Dry friction, Coulomb friction
ABSTRACT - The present paper examines disc brake-generated in-plane squeal. The vibration modes of a brake unit during squeal were investigated, and the relationship between the rate of occurrence of squeal and the effect of adding mass to the pads was investigated. The characteristics of in-plane squeal were also analytically investigated using a concentrated mass model formed by connected massless beams. The results are summarized below.
Based on the experiments conducted in the present study, the frequency of in-plane squeal was determined to be approximately 10 kHz. In-plane squeal is caused primarily by the inplane vibration of the disc. The disc vibrates in a coupled mode comprising the (8, 0) mode in the out-of-plane direction and the second mode in the in-plane direction. The characteristics of in-plane squeal are completely different from those of out-of-plane squeal. Adding mass to the pad was found to reduce the natural frequencies of the pad vibration. To lose the balance of natural frequencies of pads and disc, the generation probability of in-plane squeal changes according to the amount of added mass of pads. Analysis revealed that the out-of-plane pad vibration and the two-diametrical-node disc vibration coupled by the second mode in the inplane direction were excited by Coulomb friction and can become more unstable if the inplane vibration of the second mode is excited by dry friction.
The generation mechanism of in-plane squeal generated in car disc brakes was clarified in this study. Adding mass to the pad, which affects the natural frequencies of the out-of-plane pad vibration, was found to have a significant influence on the generation of in-plane squeal. This is a characteristic of high-frequency squeal, which is generated by the coupled vibration of the disc and the brake pads. The characteristics of in-plane squeal were also confirmed analytically, and the analytical results agreed well with those of the in-plane squeal generated in an actual brake.