This paper is the first in a series of three that describe an approach to the analysis of disc brake squeal. In this paper, the problem is introduced together with the philosophy that underpins the model. The methodology adopted to permit the prediction of disc brake squeal through an integrated finite element analysis has been outlined. An important step in this process is to predict the varying contact pressure distribution over the frictional interface. The finite element model developed for this task is parametric in nature and has, so far, enabled the efficient quantification of the effect of geometric and loading parameters on the nature of the contact occuring at the disc-pad interface. This has been shown to involve incomplete, unsymmetric contact under the imposition of realistic braking loads. The proposed solution to the contact problem has proven to be robust. A reasonable magnitude of contact stiffness has been determined by numerical trials. These showed that the shape of the contacting areas did not change when a contact stiffness of at least 1.2 GNm-1 was specified. Lowering the contact stiffness leads to the prediction of unrealistically uniform pressure distributions whilst a greater contact stiffness demands more computation time without the benefit of improved accuracy. The introduction of friction necessitates the use of an iterative solution procedure to solve the contact problem. Numerical trials demonstrated that the minimum number of iterations needed to realize a state of equilibrium in the system was 4 and that no practical benefit could be gained by going beyond this figure. The interfacial contact pressure distribution between the pads and the disc is highly non-uniform and is quite different for the piston and paw loaded interfaces. In the case of the former, there is considerable loss of contact near the edges of the pad. The friction coefficient substantially influences the contact force distribution at the disc-pad interface. The effect of circumferential friction, encountered under braking conditions, is to drag the center of contact force towards the leading ends of both the piston and paw loaded interfaces. The contact forces are enhanced near the leading end whilst further separation is promoted at the trailing end. The second paper deals with the linearisation of the disc brake system and the subsequent analysis of its free vibration behaviour. Of importance here is the influence exerted on the system stability by the distribution of the interface contact force which has, in the present paper, been shown to fluctuate considerably with change in common braking parameters. (to be continued)
A predictive tool to evaluate disk brake squeal propensity part 1: the model philosophy and the contact problem
Prognoseverfahren zur Auswertung der Quietsch-Tendenz von Scheibenbremsen, Teil 1: Modell-Philosophie und das Kontakt-Problem
International Journal of Vehicle Design ; 31 , 3 ; 289-308
2003
20 Seiten, 16 Bilder, 1 Tabelle, 21 Quellen
Aufsatz (Zeitschrift)
Englisch
A predictive tool to evaluate disc brake squeal propensity Part 3: Parametric design studies
Online Contents | 2003
|