Research On Nonlinear Vibrational At Contact Condition

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 of Hertz 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; The vibration response of pulse,sine,triangular and linear-sweep excitation with different contact gap,and preload including unilateral contact, bilateral contacts as well as different contact stiffness are studied.In the Matlab, the vibration signal, which had been obtained from the experiment and numerical simulation, was processed in the time domain,in order to obtain the required signal and remove the noise component, the vibration signal was processed by means of interception, pre-filtering and smoothing,and in the frequency 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.According to the analysis results in the paper, the following nonlinear vibration characteristics were found. The resonance of system relevant to the forms of exciting. A contact system exists obvious octave resonance phenomenon,in other words sub-harmonic resonance,which is the nature characteristic of a nonlinear system. The contact gap, contact stiffness and the preload have more or less effect to the respond frequency of the system,the most significant one is the contact stiffness. In vibration response of the system is similar to the linear response under certain conditions and an phenomenon of energy transfer from a high-frequency mode to a low-frequency mode, which may lead to instability. The explanation of the relation between restoring force and vibratory response,by non-linear spring system.Finally, based on the above research achievements, taking lathe spindle and saddle as an example to illustrate the reasons of vibratory response.