The prevention of brake squeal is a significant task in brake development, because brake squeal is bothersome to users and consequently reduces a vehicle's commercial value. Due to the progress made by researchers in their efforts to gain insight into the mechanisms and causes of brake squeal, the number of brake squeal complaints has declined. However, brake squeal can appear long after the vehicle is produced, without any early sign. In order to maintain long-term high satisfaction among the vehicle owners, it is important to find the factors that create a gradual increase in the occurrence of brake squeal. In this study, we focus on the stiffness factor of brake pads. Also, brake-pad wear due to braking is virtually impossible to completely eliminate. Here, we examine the correlation between pad stiffness and squeal occurrence.
This study presents experimental and analytical results of the influence of pad surface texture on disc brake squeal. Pads with different surface texture were prepared by changing the sliding distances. Surface texture measurements were taken under various thrust pressure conditions using an ultrasonic measuring device. In addition to measuring the pad stiffness, we evaluated the results by pad excitation at frequencies and vibration amplitudes that would cause brake squealing. The results showed that stiffness increased as the surface texture became smoother. Namely, the pad surface texture affected the pad stiffness. Finally, we used a numerical model to analyze the mechanism behind the generation of brake squeal caused by pad surface texture. Our analytical results showed that the squeal frequency increased along with the increase in pad stiffness.