| Urban rail transit has developed rapidly in China,and the resulting abnormal vibration and noise problems of vehicles and tracks have become increasingly prominent,which seriously affects running safety of vehicles and ride comfort of passengers.In order to achieve the purpose of vibration and noise reduction,a series of reduction measures of vibration and noise for vehicles and tracks are widely used,such as low-noise wheels or resilent wheels,damped rails,and vibration-damping tracks.The resilient wheel has a rubber layer between the rim and the web of it.The rubber layer has the functions of vibration absorption and vibration isolation,and reduces the effect of the unsprung mass of the vehicle significantly,and then reduces the high-frequency dynamic force between the wheel and rail,extends the lifetime of the vehicle and track components.In addition,resilient wheels are also considered to have potential advantages in reducing the wear of wheel and rail.Therefore,the use of resilient wheels is a potential effective solution to the current situation of vibration and noise levels in subways.However in China,resilient wheels are mainly used in trams,and have not yet been adopted in subway trains.Although a lot of research has been done on resilient wheels at home and abroad,and some achievements have been achieved,the three-dimensional rolling contact characteristics of resilent wheel and rail,effect of vehicle/track coupling dynamics by resilent wheels,wheel-rail noise and other issues have not been studied in depth.In order to promote the application and promotion of the resilient wheels in subway,it is necessary to carry out the research on the vibration and noise reduction mechanism,and the running safety of the resilient wheels.In this paper,the mechanism of vibration and noise reduction of resilient wheels is revealed through theoretical simulations and laboratory tests.The main research work is as follows:(1)Briefly introduces the status quo of the development and research of resilient wheel products at home and abroad and the necessity of research in this aspect,and briefly introduces the research ideas of this thesis.(2)A new resilient wheel was designed to reduce wheel/rail vibration and noise of metro lines.The stiffness characteristics of the new resilient wheel rubber block are tested and analyzed.Based on the test results,the resilient wheel static strength analysis model is established.Referring to the UIC510-5 standard,the static strength of the resilient wheel is checked.The fatigue strength of it is evaluated using the Goodman curve.The checking results show that the static strength and fatigue strength of the new designed resilient wheel meet the requirements of the standard.(3)The vibration and sound radiation characteristics of the new resilient wheel are tested in laboratory,and their vibration response and radiated sound power are obtained.The noise prediction model of the resilient wheel is established by using the finite element-boundary element method.The theoretical and experimental results of vibration and sound radiation of the resilient wheel are compared.It is found that the model can predict the vibration and sound radiation characteristics of resilient wheels well.Based on this model,the wheel-rail rolling noise under the excitation of the measured wheel-rail roughness in Metro is investigated.The results show that in the frequency band(500-1250Hz)significant interior noise generates,and the main reason why the resilient wheel can reduce the wheel-rail rolling noise effectively is that it reduces the noise of the rail in the frequency band from 500 to 1000 Hz.In addition,the effects of elastic modulus and damping of rubber on vibration and noise reduction of elastic wheels are discussed.Through laboratory tests and the analysis by using the theoretical models,the mechanism and characteristics of wheel-rail rolling noise reduction for the resilient wheel are preliminarily revealed.(4)A dynamic vehicle/rail coupling dynamics model considering the resilient wheels is established,including vehicle submodel,track submodel and interaction submodel of vehicle and track.In the resilent wheel modeling,the rubber layer between the resilient wheel rim and the web is simulated by a three-direction spring-damper unit,five degrees of freedom of the rim and the wheel hub can be considered.If so,The lateral motion,ups and downs,rolling,rotation,and pitching can be analyzed simultaneously.In the track submodel,the rail is simplified to a Timoshenko beam,and the fastener connected to the slab is simulated by the spring-damper unit.The wheel-rail normal force is obtained by using the Hertz nonlinear elastic contact spring,and the tangential force is obtained by using the Shen's theory.The measured data of the resilient wheels of the tram is used to verify the rationality of the new resilient wheel modeling method in the vehicle/track coupling dynamics model at low frequencies.Firstly,Considering the effect of the new subway resilient wheel,the metro vehicle/track coupling dynamics model is used to compare the dynamic characteristics and dynamic performance of both the rigid and resilient wheels.Then the influences of the radial stiffness and axial stiffness of the resilient wheel(variation range 1~500 kN/mm)on the dynamic characteristics and dynamic performance of the vehicle are investigated systematically,and obtained results can provide the theoretical guidance for the subsequent optimization of the parameters of subway resilient wheels.(5)Using the implicit-explicit finite element method,a three-dimensional transient wheel-rail rolling contact model of the new resilient wheel is established.By introducing the true geometry of the wheel and rail and taking into account the nonlinearity of the wheel-rail contact,the rolling contact characteristics of the resilient wheel and rail are obtained,including wheel-rail force,contact stress,stick-slip zone distribution,axle box acceleration and so on.On this basis,the rail corrugation and the weld joint irregularity excitation are considered on the surface of the rail.The high-frequency dynamic characteristics of the resilient wheel under two kinds of irregular excitation conditions are obtained,and compared with the results of the rigid wheel,which is very useful in the vibration-damping performance evaluation and subsequent optimization of the resilient wheel. |
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