The Study Of Experiment Modal Analysis And Structural Dynamic Modification Of Automobile Frame

All the loads that act on the automobile's parts belong to dynamic loads when the vehicle runs on the road. As one part of the automobile structure, the frame withstands the complex dynamic loads coming from the road surface and the other parts that fixed on it. If the frequency of these dynamic load close with some the natural frequency of the frame, the frame will be caused the intense vibration which will not only affect automobile's comfortableness, but also cause the very high dynamic-load stress, and make the early fatigue failure or the un-allowed distortion happened .In order to prevent the frame' resonating and make sure the safety and the reliableness in the use, its dynamic characteristic need to be studied deeply and the dynamic modification should be carried on if necessary . The modal analysis is an effective method which studies the dynamic characteristic of the component and structure. The modal parameters such as natural frequency and vibration mode, can be obtain through the modal test exactly.One type automobile frame is regarded as the studied object in this paper. Based on the overall evaluation of the influence on the result by the hanging condition, the excitation method and the point arrangement, the first five modal parameters are obtained through the modal test firstly. Then the simulation force response analysis of the frame is carried on under the typical road surface condition. The simulation force signal is obtained through the road testing for some typical road surface. Finally, a structural dynamic modification method which is going to raise the natural frequency of the frame is explored based on the studying of the dynamic characteristic which influenced by the change of its mass and rigidity. It provided one helpful method for frame structure optimization.