| Environmental noise due to the widespread use of high-speed railways has become a public concern. With the fast development of high-speed railway, an in-depth study of the generation mechanism and control technologies of wheel/rail noise, an important source of noise generated by high-speed railways, is an important work to be done. Compared with ordinary railway line, the wheel/rail interaction force in high-speed railway line is much greater; besides, soft pads are commonly applied in order to improve the stationarity of the track, consequently leading to an increase in the radiated noise from rail component. Considering the cost of noise control, the wheel/rail noise of high-speed railway can be greatly reduced by controlling the radiated noise from wheel/rail noise sources. However, the precondition of providing appropriate equipment of noise control is to thoroughly understand the generation mechanism of wheel/rail noise in high-speed railway lines, which should be obviously based on appropriate and precise theoretical models.This dissertation focuses on wheel/rail noise radiation control in high-speed railway. Based on the theories of vehicle-track coupling dynamics, structure vibration and noise radiation, different prediction models for wheel/rail noise from different track constructions in high-speed railway are founded in frequency domain. This dissertation analyzes the wheel/rail noise in high-speed railway generation mechanisms, noise radiation characteristics and the performance of damped wheel and rail absorber on wheel/rail noise control through numerical simulations based on the built models. Meanwhile, the provided models in this dissertation are validated by comparing the simulation results with the existing wheel/rail noise prediction results in references and field test data.The detailed research and main conclusions in this dissertation are summarized as follows:(1) The models of wheel, ballasted track and wheel/rail coupling dynamic system in vertical direction are presented in frequency domain. The calculation precision, the application scope of different wheel/rail models, and the influences of wave reflections due to multiple wheels on wheel/rail interaction are researched through numerical simulations.(2) The ballastless track system of high-speed railway is modeled in frequency domain. The numerical simulations results show that the support structures under the rail pad have little effects on rail vibratory response. The influences of the design parameters of the slab and supportive components are main concern on slab vibratory response. With the differences in amplitude and phase of the wheelset loads taken into consideration, the effects are mainly limited on the response of the slab due to the great stiffness of mortar layer underneath the slab.(3) The wheel/rail noise prediction model is provided based on the mechanical model of wheel/rail dynamic system in frequency domain of high-speed railway. The research shows that the radiated noise of different components of wheel/rail dynamic system causes different levels of noise to that of the system as a whole due to different frequency bands. In addition, a prediction model of slab component radiated noise in slab track is proposed. It is found that the slab radiated noise is mainly from the several slabs adjacent to wheel position. The slab noise can be reduced by increasing the slab thickness and the Young's modulus of mortar layer. However, the slab length has little effects on the radiated noise of the slab.(4) The influences of a constrained layer damping treatment on vibration response and noise radiation of the wheel are investigated. Calculation results show that the track structures have little influence on noise reduction of damped wheel. Such treatments by using steel and aluminum as the restraint layer, can reduce wheel component noise by 8.4 dB (A) and 5.8 dB (A) respectively. The overall A-weighted sound power level of wheel can be reduced by about 1.8 dB (A) for one-fold increase in thickness of the restraint layer. However, the wheel noise does not fall with the increase of the damped layer thickness.(5) Different theoretical models are presented according to the structures of rail absorbers. And the radiation efficiency of the rail absorber is successfully predicted by using FEM (finite element method) and BEM (boundary element method). Compared with the rail without an absorber, the radiation efficiency is remarkably lower for the rail with one from 300?1250 Hz. The decay rate of rail vibration in vertical direction increases significantly in the designed frequencies around 500 Hz and 1000 Hz. The sound power level from rail radiation is reduced by 4.5 dB (A). In addition, it is found that the wheel/rail noise can achieve reductions of 5.7 dB (A) by combining the damped wheel and the rail absorber through numerical simulations.(6) The influences of rail absorbers and wave reflections due to multiple wheels on a rail on wheel/rail interaction and rail radiated noise are investigated by using a compound track-absorber model. The simulation calculation results show that the wave reflections have significant effects on receptance of the rail, the vertical vibration decay rate and the wheel/rail interaction force. However, due to the narrowband vibration energy averaged into one-third octave bands, the effects of wave reflections due to multiple wheels on the rail radiated noise have been weakened. On the contrary, the rail component noise can be reduced by 5.7 dB (A) by using the rail absorber. |
PDF Full Text Request