Brake squeal is a phenomenon, where the whole braking system vibrates within the frequency range between 1 – 16 kHz. From customer’s point of view, squealing of vehicle brakes is a quality flaw and, in some cases, even entitle for reclamation of the car. In general, design of silent brakes is a non-trivial task. Commonly, the squealing tendency of newly developed vehicle disk brakes may only be determined through complex testing of prototypes. The formulation of suitable corrective measures is currently only possible in combination with experimental investigations, as well. For cost and time considerations, it would be expedient to have valid simulation results concerning brake squeal in early stages of the brake development process. In addition, the expenditure of time for finding corrective measures could be considerably reduced. The complex eigenvalue analysis (CEA) is the state of the art method in the industry for the simulation of brake squeal. Due to insufficient compliance of the results using this method and the actual performance regarding squealing of a brake on a test rig, it is currently not possible to shorten the experimental investigations significantly. Improving brake squeal simulation in regards to predictive properties is the aim of the present thesis. This is achieved through a detailed cause analysis of the non-satisfactory informative value of the established method and development of proposals for improvement. First of all, it is examined to what extend brake squeal relevant effects are covered within the CEA performing theoretical and experimental analyses. It is carried out on the basis of a FE brake model corresponding to the industrial standard and academic minimal models. The experimental analyses shall indicate, if additional effects relevant for brake squeal exist, which are not included within the CEA up to now. In the following course of this work, the relevance of nonlinearities for the simulation of brake squeal is investigated. By means of experimental studies, it is shown that a supercritical bifurcation can exist in brake squeal. Hence, considering only the stability of the trivial solution is insufficient in order to decide whether or not a brake will squeal. Consequentially, nonlinearities have to be taken into account for a prediction of brake squeal, its amplitude and the frequency. Therefore, it is discussed in the following, which nonlinearities in a brake system are relevant and how they can be determined. Eventually, it is shown how the high dimensional, nonlinear system of differential equations, which derives from including the relevant nonlinearities in the FE brake model, can be solved using feasible model reduction methods. Thus, it is possible to reproduce brake squeal by means of bifurcation and limit cycle oscillation of nonlinear FE brake models with several million degrees of freedom and improve the predictive character of the simulation in the end.
|Advisor:||Wagner, Utz vonHetzler, Hartmut|
|School:||Technische Universitaet Berlin (Germany)|
|Source:||DAI-C 81/4(E), Dissertation Abstracts International|
|Keywords:||CEA, FE brake model , Nonlinear system|
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