Research On Operatioanal Modal Analysis Methods For Door In Track Vehicle

In recent years, the high-speed railway developes rapidly in China, and the network of the high speed railway has initially taken shape with large coverage and positive effect. The railway line is updating fast and more attention is paid to the safety and condition improvement in high-speed passenger car. It is significant to conduct structural test of vehicle door for safety and comfort of passengers since the performance of the door has much effects on the sealing and noise control in the running train. Due to excitation of the track irregularity, wheel/rail contact and external environment including passing through tunnel and vehicles meeting, the vibration state of the door is very complicated. Once the serious structural damage even falling down happens in the door, it would threaten the safety of the passenger. Operational modal analysis could estimate the modal parameters when train is running. In this way, it could not only provide the basis for structural design and optimization by getting the vibration characteristics of the door, but also prevent terrible accident caused by the fault of the door by receiving the structural health information extracted from real-time modal parameters. This thesis set up research of the modal parameters estimation method for vehicle door based on the wavelet method. The core content of this thesis is as follows,The fundamental knowledge of the modal analysis is briefly analyzed, and the advantages and disadvantages of experimental modal analysis and operational modal analysis is researched and presented.The basic wavelet theory is described and much emphasis has been put into the time-frequency property of the wavelet. The selection of wavelet base is also taken into consideration systematically. By combination of energy and shannon entropy, the energy-shannon entropy ratio is used to select wavelet base for modal analysis. And this method is verified by Gaussian modulation signal.The principle of the wavelet transform of the free vibration response from linear structures is discussed which supports the modal analysis theoretically. The physical meaning of wavelet ridge and the ridge extraction is presented and verified. Using finite element method, the modal parameters of girder are obtained. Then, the simulation of environment excitation to girder is conducted. All the simulation data is compared to the results from wavelet-based modal analysis.By IDT method and wavelet-based method, the modal natural frequency, modal damping ratio and modal vibration shape are estimated for the door in high-speed train. Based on the comparison of two methods, the result shows that wavelet transform is relatively suitable modal parameters recognition.