| The enviroment is deteriorated by the increasing railway-net density, traffic volume and train speed. One of these problems is railway noise which is an important matter of public concern. Now wheel/rail noise is a main component of railway noise. It will become one of the core issues of railway technique, which restricts the further development of railway transportation. There is, therefore, a growing awareness in the railway community that effective methods to reduce the noise from its sources. For effective solutions to find the noise, there is a requirement for enhancing fundamental understanding of how the noise is generated. So far, many related issues to wheel/rail noise have not yet reached full consensus around the world. In order to meet demand of rapid railway transportation development and the great traffic potential in China, the current study is focused on the mechanism of noise generated by the wheel-track system due to their vibration. The main research work in the present thesis involves:(1) Based on 3D solid finite element model (FEM), the nature vibration and frequency responses of the wheel used in China railway are investigated. The dynamic response is used as a velocity boundary condition in acoustic boundary element model (BEM) for noise radiation analysis. In the numerical simulation, three types of web shapes (s-type, straight-type, and corrugated-type) and excitations at three contact positions (flange contact, nominal contact, and field side contact) are considered. The numerical results indicate that the web shape and contact position have a significant effect on the sound radiations of the wheel. Moreover, the sound radiations from different web shapes of wheels are different under an excitation at the same contact position.(2) A linear 3D finite element model for the railway track structure is considered, accounting for the elastic properties of rail, railpad, sleeper and ballast. Comparing the numerical results of this model with the track models in the past studies, it reveals that this model is more rational in the high-frequency range. Using this model, the vibration characteriscs of railway track are studied, and the influence of track structure parameters on the vibration characteriscs of railway track is dicussed in details. (3) Considering the wheel/rail surface roughness excitation and the impact of wheel/rail interaction, a hybrid FEM-BEM wheel/rail noise prediction model is developed. By comparing the predicting values of noise level with the results by other famous software, there is a good agreement between this paper model and existing theories.(4) Based on 3D wheel/rail noise prediction model, the present work discusses the effect of track structure parameters, wheel/rail surface roughness, wheel/rail contact stiffness and speed on track sound radiation. The investigation can help to search methods of reducing noise generated from its sources.
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