Self Excited Multi-Mode Vibrations of Aircraft Brakes With Nonlinear Negative Damping

Abstract

Abstract This paper shows how vibratory modes of a brake/landing gear system can interact strongly when there is nonlinear negative damping being generated at the brake’s friction interface. The approach first considers the normal modes of the linearized system. The nonlinear frictional interface force is then added to the modal equations of motion. The energy added to each of the modes, per cycle of the lowest frequency mode, is then determined. From these functions an amplitude path map and limit cycle amplitudes are determined. Multiple limit cycles are found to exist for certain combinations of damping. Amplitude modulation of the higher-frequency mode at multiples of the lower frequency mode is explained. Time solutions of the motion are obtained and compared to computer simulation results. Results compare closely. The method yields a global view of the stability and modal interactions caused by nonlinear negative damping at the brake’s friction interface.