| More and more cities are opening or constructing urban rail transit.Due to its advantages such as fastness,safety,large capacity,high efficiency,and independence from weather,it is the preferred mode of public transportation for many people.It plays an important role in facilitating residents’ travel,but the environmental vibration and noise caused by the operation of rail transit has also received more and more attention.The damping rail is a rubber damping plate laid on the ordinary 60-rail.Compared with other rail vibration and noise reduction measures,the damping rail has the advantages of simple installation,significant effect and low cost.This paper analyzes and studies the wheel-rail vibration characteristics and radiated noise under wheel-rail force before and after laying the damping plate on the rail,and evaluates the damping and noise reduction effects of the damping rail.A 2.5-dimensional method is used to establish a solid model of ordinary rails and damped rails.The three-dimensional wheel model is used to calculate the wheel-rail forces generated by wheel-rail interactions at different speeds are calculated.The vibration response and environmental noise of the rails under wheel-rail interactions are calculated,and relevant tests are added to compare and verify models and methods.The damped rails are evaluated from actual and calculated angles.Vibration and noise reduction performance.The main conclusions of this study are as follows:(1)Compared with ordinary 60 rails,the vertical displacement response at the bottom of the damped rail shows a decline in the entire frequency band;the peak vertical displacement at the bottom of the rail has decreased by 11.2%;and for the mid-to-high frequency band above 450 Hz,the attenuation effect is more obvious.The peak vertical acceleration at the bottom of the rail was reduced by 17.5%.After the frequency of 600 Hz,the reduction of the damping rail relative to the ordinary 60-rail became more significant.The maximum value of ordinary 60 rails and damped rails is 48.22 d B and 47.47 d B respectively.The maximum sound pressure attenuation is 12.7 d B.The attenuation effect of damped rails is obvious.(2)The wheel’s radial displacement admittance has a dense peak at a frequency especially after 1100 Hz,and the admittance changes very sharply,with a minimum value around 800 Hz.At a frequency of 0.3 Hz,the wheel-rail force reaches a maximum value;at a frequency of about 72 Hz,the wheel-rail force fluctuates greatly,which may be because the wheel reaches its first-order natural mode at 72 Hz.(3)Under the action of wheel and rail,the vertical response of the damped steel rail at midhigh frequencies after 400 Hz is more and more obvious.When the vertical displacement response reached its first peak,it was attenuated by 15.3%.The maximum vertical acceleration reached.At four speeds,the damped rails attenuated by 31.78%,33.43%,33.59%,and 32.55% compared to ordinary rails.This shows that under the effect of wheel-rail force,the damped rail has a good damping effect,and the damping effect on acceleration is better than the displacement response.(4)After 50 Hz of wheel noise under wheel and rail,the sound pressure fluctuations of the three positions are basically synchronized;as the distance increases,the sound pressure of the wheels tends to decrease.The sound pressure difference corresponding to the same frequency of the wheels at 7.5m and 30 m is between 4 and 7 d B,which meets the characteristics of doubled distance and reduced noise by about 3 d B.At four speeds,the sound pressure tends to rise first and then fluctuate.In most frequency ranges,a damping plate is installed,which has a good attenuation effect on the radiated noise of the rail.This theoretically combined with the rail-radiated noise of the wheel-rail force under the action of the wheel-rail,confirms that the damped rail has the effect of reducing the bottom-radiated rail’s radiated noise.(5)The z-levels of the six measured vibration points were reduced by 2.2 d B,4.1 d B,1.1 d B,4.7 d B,3.7 d B,and 1.3 d B,respectively.The acceleration peaks at each measurement point are significantly reduced after the damping is installed,and the vibration damping effect on the rail is better than that of the track plate.The frequency is greater than 400 Hz,and the rail laying damping can well absorb the vibration of the rail under the action of the wheel rail.In the measured noise,the continuous equivalent sound level of the train is reduced to varying degrees,and the amplitudes of the reductions are between 1.4 to 8.1 d B and 2.1 to 5.3 d B;the amplitude of the noise reduction of the train passing through the train is reduced by an average of 2.88 d B and 3.86 d B.At distance of 1.2m from the centerline of the line,the damped rail with the damping plate has a significant decrease in wheel-rail noise radiated from ordinary rails;at 7.5m and 30 m,the sound pressure level is significantly reduced,and the reduction amplitude is about 3d BA.As the distance from the line increases,the noise reduction effect of the railmounted damping plate gradually decreases.(6)The measured and simulated values of the rail vibration acceleration are basically the same in the changing trend,showing two main frequency bands as whole.Except for the peaks in the 50.0 ～ 101.5 Hz frequency band,the amplitudes of other frequency bands are basically consistent.Before and after the rails are equipped with damping plates,the measured wheelrail noise is in good agreement with the calculated wheel-rail noise,and the predicted trends are basically the same.This proves that the methods and models used in the article to predict wheel-rail vibration and noise are accurate and feasible.(7)The rail wave number finite element-boundary element vibration acoustic radiation model established in this paper has good calculation efficiency and accuracy. |
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