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Brake squeal has been a chronic customer complaint, often appearing high on the list of items that reduce customers' satisfaction with their vehicles. Brake squeal can emanate from either a drum brake or a disc brake even though the geometry of the two systems is significantly different. A drum brake generates friction within a cylindrical drum interacting with two semi-circular linings. A disc brake consists of a flat disc and two flat pads. The observed squeal behavior in a vehicle differs somewhat between drum and disc brakes. A drum brake may have a loud noise coming from three or more squeal frequencies, whereas a disc brake typically has one or two major squeal frequencies making up the noise. A good understanding of the operational deflection shapes of the brake components during noise events will definitely aid in design to reduce squeal occurrences and improve product quality.

Brake squeal noise is a top warranty concernsmplaints for virtually all automotive companies. How to identify squeal frequencies and mode shapes is typically very challenging. The identification of potential squeal problems still rely heavily on experimental methods using inertia and chassis dynamometers or on-road tests, but these require hardware to run. Good numerical methods have advantages of evaluating up-front designs before the cutting tools ever hit any metal. But for brake squeal, there are still many challenges to overcome to correctly model a complete brake system due to the nature of the complexity of the frictional excitation. In this paper, a disc brake system model was established to simulate brake squeal using nonlinear transient analysis methods provided through LS-DYNA. The model includes rotor, pads, linings, caliper and pistons. From the example analyzed, the squeal frequency is identified using frequency domain analysis of the numerical time-domain output.

Tires are the only load path between the road and the vehicle's suspension and so play a key role in determining vehicle NVH performance. Tire structure and behavior include many nonlinear phenomena, such as rubber material response to load, tire contact patch conformity with road profile, and bulging of side walls. In addition to structural nonlinearities, the tire's rotational motion introduces nonlinear resonances that are dependent on vehicle speed, and also rotationally induced harmonics. When a tire rolls over a cleat, the rolling resonance at the spindle may vary with the vehicle's speed. Since tire behavior couples several nonlinear parameters, a numerical tire model that can consider physical characteristics such as, rolling resonance dependence on speed and the harmonic resonances, will definitely be helpful for improving vehicle NVH quality. This paper presents a study of a finite element tire model rolling over an impact cleat at different speeds.