Nonlinear transient vibrations and coexistences of multi-instabilities induced by friction in an aircraft braking system

Abstract Friction-induced vibration is still a cause for concern in a wide variety of mechanical systems, because it can lead to structural damage if high vibration levels are reached. Another effect is the noise produced that can be very unpleasant for end-users, thereby making it a major problem in the field of terrestrial transport. In this work the case of an aircraft braking system is examined. An analytical model with polynomial nonlinearity in the contact between rotors and stators is considered. Stability analysis is commonly used to evaluate the capacity of a nonlinear system to generate friction-induced vibrations. With this approach, the effects of variations in the system parameters on stability can be easily estimated. However, this technique does not give the amplitude of the vibrations produced. The integration of the full set of nonlinear dynamic equations allows computing the time-history response of the system when vibration occurs. This technique, which can be time-consuming for a model with a large number of degrees of freedom (dof), is nevertheless necessary in order to calculate the transient-state behavior of the system. The use of a continuous wavelet transform (CWT) is very suitable for the detailed analysis of the transient response. In this paper, the possibilities of coexistence of several instabilities at the same time will be examined. It will be shown that the behavior of the brake can be very complex and cannot be predicted by stability analysis alone.