| The rapid development of rail transit has greatly facilitated people’s lives,but at the same time,the vibration and noise control of rail structures has always been an urgent problem to be studied and solved in related fields.Since the track itself belongs to a typical periodic structure and has bandgap characteristics similar to the phonon crystal structure,when the elastic wave caused by wheel-rail vibration propagates in the direction of the line,some elastic waves in the band gap frequency range will appear obvious attenuation phenomenon,so the vibration and noise reduction measures applied to the track can be developed and improved based on the band gap theory of phonon crystal.According to the periodic law in the corresponding position of the rail to deploy the vibration absorber is essentially a means of using band gap regulation to achieve track vibration reduction and noise reduction,this paper based on the band gap theory to explore the method for increasing the effect of rail vibration absorber,proposed a new amplitude magnification rail vibration absorber,using the energy method to establish a track theoretical model of the amplitude magnification vibration absorber arranged according to the periodic law to analyze its band gap and response characteristics.Through the track acoustic radiation prediction model,the control effect of this type of vibration absorber on wheel and rail radiated noise is evaluated,and it is compared with the commonly used combined vibration absorber,and finally a hybrid vibration absorber is further optimized by combining two broadband vibration reduction mechanisms,and its vibration and noise reduction effect is analyzed.(1)The design principle and working mechanism of amplitude magnification rail vibration absorber are introduced,its feasibility and safety in practical engineering applications are analyzed,and a method is proposed to analyze the track bandgap characteristics of amplitude magnification vibration absorber arranged according to periodic law by energy method.(2)Taking the rail attached with the periodically arranged amplitude magnification vibration absorber as an example,from the perspective of band gap,the energy band structure and vibration transmission characteristics were analyzed by energy method,a finite element simulation model was established to verify the band structure,and the vibration damping effect was analyzed by combining the calculation results of displacement admittance and vibration acceleration stage,and then the mechanism of amplitude magnification and the influence of magnification times on vibration damping performance were further analyzed.It is found that when the relevant parameters are consistent,the equivalent mass,stiffness and damping of the amplitude magnification vibration absorber are amplified year-on-year,which not only broadens the range of the band gap,but also enhances the attenuation effect of the vibration wave in the band gap,and can further improve the vibration damping performance by increasing the leverage ratio(that is,the magnification).(3)Taking the continuous plate type ballastless track as the research object,the prediction model of track acoustic radiation when considering different kinds of vibration absorbers was established,the control effect of amplitude magnification vibration absorber on wheel and rail radiated noise,the influence of different magnification times and different train running speed on the noise reduction effect of vibration absorber was analyzed,The influence of the arranged vibration absorber on the radiated noise of the wheel is also explored,and the attenuation effect of the vibration absorber on the radiated noise of the rail when considering the load of multiple wheels is also analyzed.It is found that when the relevant parameters are consistent,the amplitude magnification vibration absorber has better noise reduction performance than the conventional vibration absorber near the design frequency,but it may also lead to new vibration and noise peaks near the design frequency,and also increase the wheel noise in the local frequency band,but the change of wheel noise does not have a significant impact on the total radiated noise of wheel and rail.(4)The mechanism of a combined vibration absorber that is widely used at present is introduced,the band gap and vibration response calculation model proposed based on the energy method is used to analyze its vibration damping effect,and then the noise control effect is analyzed by the track acoustic radiation calculation model,and the amplitude magnification vibration absorber proposed above is compared,the advantages and disadvantages of the two damping band widening methods are analyzed,and then a modified hybrid vibration absorber is proposed by combining these two mechanisms,and its vibration and noise reduction performance is evaluated.It is found that when the relevant parameters are consistent,Although the combined vibration absorber is obviously inferior to the amplitude magnification vibration absorber in the widening effect of the band gap,but it also avoids excessive peak near the design frequency of the vibration absorber,and the improved hybrid vibration absorber combines the advantages of the two,has obvious broadband vibration reduction and noise reduction effect,and does not cause excessive vibration and noise peak in the local frequency band,and the amount of vibration and noise attenuation in each frequency band is also relatively uniform. |
