Abstract Summary
When considering industrial models for aircraft braking systems, the number of degrees of freedom (DoF) limits the type of analysis that can be performed. It is therefore sometimes necessary to simplify the model by introducing some hypotheses ; this allows to have satisfactory simulation times. However, these operations can affect the accuracy of the model, in particular its capacity to appropriately represent instabilities due to friction-induced vibrations. This paper investigates and discusses the hypothesis of non-deformation of the disks (i.e. rotors and stators in frictional contact) on the stability of an aircraft braking system at low frequencies. In order to conduct such a study, both finite element models (by considering rigid rotor and stator disks and non-rigid disks respectively) are developed. The non-rigid disk model is introduced and its performance is analysed in order to assess the improvement of the instability prediction. Besides, the convergence with regards to the number of points per surface contact of the non-rigid disks model will be verified. Regarding the non-rigid disk model, the study also presents an efficient strategy to reduce the number of DoF through a model based on a Double Modal Synthesis. This numerical strategy is developed to perform relevance prediction of unstable vibration modes for an aircraft braking system subjected to friction- induced vibration. Particular attention is brought to validating the convergence of the reduced model, specifically on the prediction of the appearance of instabilities as well as its characteristics (i.e. the prediction of both the real and imaginary parts, as well as eigenvectors of the unstable modes generated). It is finally verified that the numerical results via the Double Modal Synthesis are in good agreement with the experiments.
