C.L. Saw et al. 2011. Int. J. Vehicle Structures & Systems, 3(1), 28-35 International Journal of Vehicle Structures & Systems Available online at www.ijvss.maftree.org ISSN: 0975-3060 (Print), 0975-3540 (Online) doi:10.4273/ijvss.3.1.04 © 2011. MechAero Foundation for Technical Research & Education Excellence 28 Disc Brake Squeal Suppression Through Chamfered and Slotted Pad Saw Chun Lin a,b , Choong Chee Guan a , Abd Rahim Abu Bakar c , Mohd Rahimi Jamaluddin c , Wan Mohd Musyris Wan Harujan c , and Badri Abd Ghani c a Politeknik Premier Ungku Omar, Jalan Raja Musa Mahadi, 31400 Ipoh, Perak, Malaysia. b Corresponding Author, Email: clsaw78@gmail.com c Automotive Engineering Department, Universiti Teknologi Malaysia, 81310 UTM Skudai, Malaysia. ABSTRCT: For decades, it has been a challenging task for brake engineers to reduce or totally eliminate squeal that emanates from brake systems. Despite the large number of proposals that have been implemented in tackling disc brake squeal, very few solutions are totally effective to reduce or suppress it. This paper presents an approach to tackle disc brake squeal through chamfered and slotted pad. A three-dimensional FE model of an actual disc brake system is developed. The baseline FE model is first simulated using complex eigenvalue and transient analysis to predict squeal and compared to the squeal tests data obtained in the brake dynamometer. A reasonable correlation is found between these results. Then, three different pad modifications are proposed, simulated and tested. It is shown that pad with chamfers and diagonal slot can totally suppress squeal both in prediction and squeal test. KEYWORDS: Disc brake; Finite element; Pad modifications; Squeal; Complex eigenvalue; Dynamic transient; Brake dynamometer CITATION: C.L.Saw, C.G. Choong, A.R. Abu Bakar, M.R. Jamaluddin, W.M.M.W. Harujan, and B.A. Ghani. 2011. Disc brake squeal suppression through chamfered and slotted pad, Int. J. Vehicle Structures & Systems, 3(1), 28-35. doi:10.4273/ ijvss.3.1.04 1. Introduction Over decades, brake squeal has been a major issue to vehicle manufacturers due to high warranty payouts. Akay [1] stated that the warranty claims due to the noise, vibration and harshness (NVH) issues including brake squeal in North America alone were up to one billion US dollars a year. Similarly, Abendroth and Wernitz [2] noted that many friction material suppliers had to spend up to 50 percent of their engineering budgets on the NVH issues. It is well accepted that brake squeal is due to friction - induced vibration or self-excited vibration via a rotating disc. Brake squeal frequently occurs at frequency above 1 kHz [3] and is described as sound pressure level (SPL) above 78 dB [4]. Brake squeal has been studied since 1930’s by many investigators through experimental, analytical and numerical methods in an attempt to understand, to predict and to prevent squeal occurrence. In recent years, the finite element (FE) method has become the preferred method in studying brake squeal. The popularity of FE analysis is due to the inadequacy of experimental methods in predicting squeal at the early stage in the design process. Moreover, FE analysis can potentially simulate any changes made on the disc brake components much faster and easier than experimental methods [5]. With advances in computing technology, more complex and complete FE models can be easily generated and analyzed in quick turn-around time. Nowadays the complex eigenvalue analysis has become a preferred method to study brake squeal compared to the dynamic transient analysis. Although complex eigenvalue analysis [6-10] is the standard methodology used in theoretical studies of brake squeal, the transient analysis [10-14] is gradually gaining popularity. Chen [15] provided comprehensive guidelines to suppress and eliminate squeal occurrence which includes optimization of the damping, minimizing the impulsive excitation and reducing the modal coupling. These three guidelines have been implemented by many researchers and thought to be essential for squeal reduction approaches. Structural modifications have been a favored means for achieving improved squeal performance. For instance, Ishihara et al. [16] proposed a method for reducing low-frequency disc brake squeal. The fixed type, four opposed piston, disc brake was used in their experiments. Changing rotor shape and material were confirmed experimentally able to reduce the squeal. Dunlap et al. [17] provided general solutions for every categories of disc brake noise. In order to address low frequency squeal, they proposed to decouple the caliper and the disc modes where the disc material was changed from gray cast iron to dampen iron. For high frequency squeal, they increased the brake rotor stiffness to reduce squeal propensity. They also observed that the brake pad geometry and contact pressure had significant effect on brake squeal.