Function of Drum Brake

2003-01-3348

Drum Brake Contact Analysis and its Influence on Squeal Noise Prediction
P. Ioannidis, P.C Brooks, D.C Barton
University of Leeds
Copyright © 2003 SAE International

ABSTRACT
A non-linear contact analysis of a leading-trailing shoe drum brake, using the finite element method, is presented. The FE model accurately captures both the static and pseudo-dynamic behaviour at the friction interface. Flexible–to-flexible contact surfaces with elastic friction capabilities are used to determine the pressure distribution. Static contact conditions are established by initially pressing the shoes against the drum. This first load step is followed by a gradual increase of applied rotation to the drum in order to define the maximum reacted braking torque and pseudodynamic pressure distribution at the transition point between sticking and sliding motion. The method clearly illustrates the changes in contact force that take place as a function of the applied pressure, coefficient of friction and initial gap between lining and rotor. These changes in contact area are shown to influence the overall stability and therefore squeal propensity of the brake assembly. Dynamometer tests and experimental modal analysis on individual brake components are used to validate the analytical results.

parameters cause changes to the pressure distribution either directly such as changing the applied pressure or indirectly such as the thermal loading. A drum brake operating temperature of 400ºC for example can cause a typical passenger drum brake diameter to increase by 1 to 1.5 mm [2]. This non uniform thermal expansion of the brake components can lead to alternative contact configurations which will result in variation of the brake factor and may also contribute to squeal generation. Hence, the characterisation of the nature of squeal noise as “fugitive” as documented by many researchers is well justified. The parametric studies reported in this paper concentrate on the

References: 1. N.A. Millner, “A Theory of Drum Brake Squeal”. Proc. of the IMechE Conference on Braking of Road Vehicles, 1976, Paper C39/76,pp 177-185 2. P. Limpert, “Brake Design and Safety”,SAE,1999,2nd Edition. 3. Lee,Y.S., Brooks, P.C., Barton, D.C. and Crolla, D.A. (2003) “ A predictive tool to evaluate disc brake squeal propensity Part2:System Linearisation and modal analysis”, Int. J. of Vehicle Design, Vol.31, No.3, pp.309-329 4. A.J. Day, “Drum brake Interface Pressure Distribution”, Proc. Inst. Mech. Engrs, Vol.205, pp.127-136 5. Lee,Y.S., Brooks, P.C., Barton, D.C. and Crolla, D.A. (2003) “ A predictive tool to evaluate disc brake squeal propensity Part1: The model philosophy and the contact problem”, Int. J. of Vehicle Design, Vol.31, No.3, pp.289-308 6. J.Fieldhouse, C. Talbot, C.Beveridge, W. Steel, “Holographic interferometry used to investigate noise from a drum brake mounted on a half vehicle test rig”, Int. Conf. Braking 2002, From the Driver to the Road,pp.25-42 CONCLUSIONS A non-linear finite element contact analysis in conjuction with a complex eigenvalue analysis has been utilized to predict the noise and vibration behavior of a drum brake assembly. The combination of flexible surface to flexible surface contact algorithms and the new process of torque application enabled the model to capture the changes in contact conditions that occur during actuation. The obtained results suggested that the distribution of contact pressure is sensitive to the initial conditions. In addition the complex eigenvalue analysis showed how certain instabilities appear and disappear as a function of actuation pressure. The FE model therefore captures the fugitive nature of the problem. Good agreement with experimental squeal behaviour is also observed. Currently the authors are investigating the effect of the backplate on squeal noise generation when incorporated in the FE assembly. Also efforts are concentrated in analyzing the influence that a dynamic contact stiffness may have on the squeal propensity. A thorough examination of the relationship between shoe fall off and installation gap is underway and current efforts are directed towards modeling the effect of a sliding shoebackplate abutment. Finally, the effect of using a more accurate mathematical approximation of the hydraulic actuation model on the pressure distribution and squeal propensity is being investigated. The method proposed here can also be utilized for brake shoe factor prediction, providing an integrated design tool for the braking industry CONTACT Corresponding author: P.Ioannidis Affiliation: The School of Mechanical Engineering The University of Leeds Leeds LS2 9JT United Kingdom [e-mail]