ICSV 14 Cairns • Australia 9-12 July , 2007 1 DISC BRAKE SQUEAL : PROGRESS AND CHALLENGES
Brake squeal noise has been an ongoing concern with automotive brake systems since their inception. It is generated by the vibration of an unstable vibration mode of the brake system, usually with the brake rotor acting as a loudspeaker. The squeal noise that is of concern usually falls into a frequency range from 1 to 16 kHz. Although there is often not any degradation in the braking performance, most customers tend to interpret brake squeal noise as indicative of a defective brake. Furthermore, with improvements made in interior noise and comfort levels in vehicles, brake squeal noise has become an increasing source of customer dissatisfaction and is a major contributor to warranty cost. Research into predicting and controlling brake squeal has been conducted since the 1930s and despite significant research efforts in the past 2 decades, brake squeal still remains a challenging problem that is begging for a better understanding of its generation mechanisms and better methodologies for countermeasures other than empirical approaches. Brake squeal is a transient phenomenon and is highly dependent on geometries of brake components, complex interface conditions between components and material properties that are functions of both temperature and pressure. In this paper, recent developments in understanding and controlling brake squeal noise will be reviewed and challenges that remain to be met are discussed.
The method of feed-in energy on disc brake squeal
Brake squeal is studied in this paper by feed-in energy analysis. Based on the brake closed-loop coupling model, a calculation method of feed-in energy for squeal mode is derived. Result of the feed-in energy indicates squeal tendency of the brake system, while formula for calculating it discloses the relation among brake squeal phenomenon and structural parameters, such as frictional coefficient, geometric shape of brake pads, elastic modulus of frictional material, substructure modal shape, etc. The method also helps to analyze the effectiveness of various structural modification schemes attempted to eliminate the squeal noise. Finally, this method is illustrated by application to a typical squealing disc brake.
Prediction of a representative point for rail temperature measurement by considering longitudinal deformation
Monitoring rail temperature is very important for determining the safe running speed of trains and to prevent buckling. In general, the maximum variation of the internal rail temperature can be >7 ℃ depending on the point of measurement. However, there is as yet no sufficient information about how to predict the measurement point to represent the thermal deformation due to temperature distribution. In this study, the authors report a new point, called the representative measurement point, at which the rail temperature can be measured. This point considers the average deformation of the rail through structural analysis by adopting experimental and actual rail temperature data. The authors designed and installed a measurement system similar to an actual rail environment. Using the system, various data were acquired (internal/surface rail temperature and weather data) for 10 months. On the basis of these data, an analysis was done to calculate the average deformation point through thermal analysis. Finally, the representative measurement point was proposed as the position at which the average deformation point converges regardless of weather or seasons. The authors believe that the method described herein is advantageous in that it could be used in a high-accuracy temperature-monitoring system and for predicting thermal deformation and buckling.