Reduction Methods Applied to Aircraft Brake Squeal Prediction and Simulation

Abstract

Aircraft braking systems may be subjected to friction-induced vibrations, during which the brake is unstable and behaves as a source of mechanical vibrations. This is an issue for aircraft brake manufacturers because it may jeopardize structural integrity due to accelerated fatigue life or generate discomfort for the aircraft crew and passengers. Hence, there is a need for instability simulation and prediction methods that can be used as early as the design stage. At this stage, finite element models are available, but their sizes are prohibitive as far as vibration-level prediction is concerned, thus requiring model reduction. This paper presents a comparative study between several modal reduction methods, among them the well-known Craig–Bampton method. The reference model to be reduced is a full brake system finite element model. The system stability is assessed by means of the classical complex eigenvalue analysis. Convergence of the implemented reduction strategies is studied. Double modal synthesis is implemented, and an improved version is introduced. They appear to be efficient model reduction strategies for application to squeal prediction. By reducing all the system’s degrees of freedom on several sets of generalized coordinates, an excellent compromise between system size and precision can be found.