Study On Fram Modal Analysis And Modal Parameters Application

With speed increasing and entironment that vehicles run in worsing, the vibration of vehicles is more serious. So the modal parameters which depicting the inherent feature of the vehicle were more valued. And the frame, the crucial part bearing the weight, is also paid more attention to. The problem caused by high speed in the frame is urgent to be solved.This paper was support by the project introduced by China Railway- Ministry. Firstly the best modal parameters were obtained within 200Hz under the FEM model, basing on the principle of optimum of frame frequency when in service. Its result shows that the frequency of the entire first order bend and torsion vibration was 101.73Hz and 32.46Hz individually. It also indicates the local mode vibration will not be stimulated within 200Hz. The node of first order modal will occur at the midpoint of side girder and middle girder, where corresponding to the maximum distortion.. In line with the fact that the number of grid created by FEM analysis is more than that of the device used for the measure of the modal, the freedom used for experiment is different from that used for the FEM analysis. We have studied the modal parameter determined by the points we have selected whether to accurately reflect the expected non-rigid modal of the frame within 200Hz. Based on the condition of our experiment and dynamic- coagulating technology, 40 points have been selected to fix the freedom for FEM analysis.Secondly the devices for experiment were chosen with regard to the result of FEM analysis. And the results manifested the freedom and the points were appropriate to get the modal parameter within 200Hz. The entire first order bend frequency and torsion frequency of the frame was 104.7 and 35.49 respectively. The third order was anti-symmetrically128.9Hz.The fourth order was symmetrically 138.52Hz. Finally, we also studied the rationality of the modal parameter of the frame. The frame could fulfill the demands of the speed below 300km/h. The first order torsion modal was triggered up by the spectrum of JiaoJi track and the structure modal damp was slightly low in the meantime when the speed reached 300km/h. So as the enhancement of the first order modal frequency, the enhancement of structure modal damp was suggested, when speed was heighten above 300km/h.