Effects of Lining Thickness on Squeal in Drum Brake Assembly:Experimental Investigations

This paper presents the effects of brake lining thickness due to wear on drum brake squeal. Brake lining will be worn out and subsequently its thickness will be reduced after a few number of braking applications. Hence dynamic properties of the lining, such as its natural frequency, might be changed. In this work, two different sets of brake lining, i.e., new and worn lining are used to investigate its effect on squeal generation. First, modal testing is performed to determine natural frequencies of those brake linings at free-free boundary condition. Later, squeal tests are carried out using brake dynamometer and squeal frequency is measured up to 10 kHz. Several squeal results are plotted over brake operating conditions to observe the influence of different lining thickness. In addition to these, squeal mechanisms, i.e., modal coupling due to closeness of the natural frequency between drum brake components and negative damping due to negative friction-velocity slope that contribute to the squeal generation are also investigated and discussed.