Study On Prediction And Control Of Vibration And Acoustic Radiation Characteristics Of Wheel/Rail System

An important source of vibration and noise in railway transportation is a wheel/rail system. The formation mechanism, prediction and control of them have become important aspects in the study on railway vibration and noise. In order to predict and analyze the vibration and radiated noise of wheel/rail system effectively, as well as the effect of mitigation measures on them, a prediction model characterizing wheel/rail system vibration and sound radiation is developed. Making use of this prediction model, the vibration and acoustic radiation characteristics of high-speed wheel/rail system are predicted, in addition, the control effect of rail vibration absorber is also investigated.First, a prediction model of track dynamics in vertical direction is established in frequency domain. In this prediction model, track is modelled as an infinite Euler-beam on a periodically discrete foundation, the Green’s function of Euler-beam is used to describe the displacement response of rail in vertical direction excited by a wheel/rail loading at a fixed point, or a moving wheel/rail load. This model predicts and analyzes the vibration characteristics of rail in vertical direction that are excited by either a fixed unit harmonic load, or a moving unit harmonic load. The influence of excitation frequency and moving speed of the load on rail’s dynamic response are also investigated.Based on the above model, considering the structures of wheel and track and the wheel-rail interaction, a more detailed prediction model is developed, in which the surface roughness of wheel and rail measured from high-speed railway sites are used as the input of excitation. The vibration characteristics of wheel and rail are predicted when they are excited by the moving wheel/rail contact force are predicted, the influence of the excitation frequency and moving speed of the force on the rail dynamic response are analyzed.Second, using the response of wheel/rail system and theories of acoustic radiation develops a prediction model of noise radiated by wheel/rail system. In the excitation of wheel/rail contact force that is caused by moving relative displacement/roughness, the acoustic characteristics of the wheel/rail excited by the force at different moving speed are simulated.Last, a prediction model of vibration and acoustic characteristics of the whole wheel-rail-absorber system is built on the basis of the above prediction model, in which the rail vibration absorber is modeled as a discrete mass-spring-damper system amounted on the middle section of the rail between the two neighboring sleepers. The dynamical characteristics of the rail vibration absorber to reduce rail vibration and noise are analyzed, which depend mainly on the absorber’s6parameters, the influence of its parameters is also investigated. It is found that rail pinned-pinned resonance can be suppressed effectively by amounting the rail vibration absorbers on the rail, but meanwhile the use of the rail vibration absorber causes a new vibration response peaks and the vibration energy increase beside the its tuned frequency. In addition, the noise radiated by the wheel/rail system can be reduced effectively in the frequency range500～1250Hz, and the maximum noise reduction reaches5.1dBA. Through the optimal selection and grouping of the6parameters the effectiveness of vibration absorption of it is notably increased.