Research On Nonlinear Vibrational Characteristic Of Contact System

In this paper, the nonlinear vibration characteristic of contact system was studied, by using the experimental method and the finite element method. With contact theory and finite element numerical method guiding, the numerical model of contact problem was been established in ANSYS software, and experiments proved this model to be reliable. In the Matlab, the vibration signal, which had been obtained from the experiment and numerical simulation, was processed in the time domain, frequency domain, time-frequency domain and the phase space, and the results were showed by using different graphics such as the frequency spectrum, time-frequency distribution, marginal spectrum, phase portraits , etc...In order to obtain the required signal and remove the noise component, the vibration signal was processed by means of interception, pre-filtering, removing zero-mean and differential transform in the time domain. According to the frequency spectrum, the variety regulation of the system resonance frequency were analysed and deduced, which had been obtained by using Fourier transform. Using short-time Fourier transform and Hilbert-Huang transform to obtain the time-frequency distribution and marginal spectrum, whether the system resonance frequency was time-varying in the contact and separation process. In order to analyse the motion state of contact system, the phase portraits were plotted by means of the phase space method, under harmonic excitation.According to the analysis results in the paper, the following nonlinear vibration characteristics were found. The resonance frequency of contact system increased with increasing of contact area—the contact stiffness increased. Under the external excitations, there was obvious resonance phenomenon of double frequency. When the excitation frequency was less than the first-order self-vibration frequency, the system might resonate. Under the harmonic excitations, the main state of contact system was quasi-periodic motion, and which varied with excitation frequency.