| With the increase of train speed, the wheel/rail interaction becomes very fierce and the railway noise pollution increases dramatically. The research of railway noise is a hot topic that the international academia, the governments and the public are very concerned about. The analysis on the exterior noise characteristics of high-speed trains and damping control measures for low noise wheels are the key technologies in developing high-speed trains. According to the international standard ISO3095-2005, the existing noise theory researches and testing experiences of foreign high-speed trains, the noise source localization of high-speed trains operating on Jingjin and Wuguang high-speed railways is in detail identified by using a modern high-speed train noise source localization system. The exterior noise distribution characteristic is studied based on the test data, the principle of noise source localization and exterior noise propagation characteristics of high-speed trains. Aimed at the wheel noise reduction, the optimal constrained damping structure is considered to further research the vibration and sound radiation control of the wheel. The main research work in the present thesis involves:(1) According to the field test data from Jingjin and Wuguang high-speed lines, the distribution and spectrum characteristics of the exterior noises of the high-speed trains are analyzed in detail. The noise characteristics distributed in the vertical-longitudinal plane are researched to get its distribution.According to the obtained distribution of the sources, the typical region division of the sources is made, and the energy contribution of each main sound source and the dependence of sound source intensity on train speed are analyzed.(2) Using the field test data on Jingjin and Wuguang lines anslyzes the noise spectrum characteristics at the standard points specified by the ISO. The dependence of the noise level on the operation speed is obtained according to the standard point noise level under different speeds. Meanwhile, the standard point noise under 500 km/h operation speed is forecasted.(3) A preliminary exterior noise prediction model of high-speed trains is established. The model uses the surface noises of high-speed trains as sound input and the noises at ISO standard points as evaluation index. The prediction model also consideres the Doppler Effect when trains are running at high speeds, noise propagation paths, and the noise propagation attenuation (e.g. geometrical divergent, ground effect, surface reflection, etc.), respectively. The prediction model is verified on the basis of the results measured at the sites.(4) In order to further reduce the acoustic radiation of damping wheels, a dumping wheel is simply modified by a full-sized disc on which circumference and radial constrained damping ridgers are used. Based on a hybrid FEM-BEM method, the paper puts forward a vibro-acoustic radiation model. The calculated and compared in detail are the vibro-acoustic radiation characteristics of the damping wheel with different damping ridges. According to the distribution of the system modal strain energy, the best place on the plate is found to distribute the circle ridges and radial ridges to effectively reduce the plate vibro-acoustic radiation. The present analysis provides an important reference for railway damping wheel design to reduce the vibration and noise of the wheel. |
