Fault Analysis Of The Abnormal Vibration And Structure Optimization For A Pickup Truck

The NVH performance has become the most core indicator when evaluate the quality of modern automotive. Abnormal vibration is one of the main problems, which is seriously affect NVH performance of the automotive during the usually longer use. In the engineering practice, the experienced engineers would make a list of tests according to vibration phenomena to pinpoint the cause and solve the abnormal vibration problems by structural optimization for stagger the resonant frequency. The abnormal vibration not only affect its using performance and service life, also give users additional pressure on the economy an spirit, then damage to the brand image and competitive power on market of the automotive company. It is very important to solve the problem of abnormal vibration in order to improve the NVH performance of the automotive. Based on the technical route combining simulation and test, in this paper, vibration tests of the whole vehicle and simulation optimization of the frame were made for the abnormal vibration problem of the prototype at specific speed.Firstly, analysis was made on vibration principle, transfer path and phenomenon of the main excitation sources based on "source-path-receiver" vibration model of the vehicle. Then, determined the excitation source was the wheel assembly by vehicle vibration tests, and the test date was analyzed from two aspects of time domain and frequency domain. The transfer path was wheel-frame-body, which was determined by partial frequency test on body/wheel and normal modal test on frame/body. In Summary, the cause of the abnormal vibration is rotation frequency of the wheel under fault speed, partial frequency of the wheel assembly and first order bending mode frequency of the frame happened to coupling. Then, from the view point of improving vibration transfer path, the finite element model of the frame was established, static and dynamic simulation were taken by using the software of HyperWorks. The accuracy of finite element model is verified by comparing modal parameters, which are from simulation and tests. On the basis of the modal distribution and modal matching principle, studies on the strategy for modal matching of the frame have been done. On the basis of the Kriging approximate model and MOGA, optimization design of the frame dynamic characteristic is further conducted. The results of optimization show that lower modes of frame not only avoid the resonant frequency, but achieved stiffness optimization and lightweight design frame for the frame. Finally, the author verified the effectiveness of the optimization design by comparatively analyzing the road vibration test results before and after optimization design of the Pick-up truck’s frame.