Research on vibration and noise reduction of the h

Research on vibration and noise reduction of high-speed rail transit and prospects for its key technologies

0 introduction

high speed rail transit can not only effectively improve the traffic environment and facilitate people's travel, but also help drive urban and rural construction and economic development, with significant economic and social benefits. However, it should also be recognized that the rail transit system will inevitably bring problems such as noise, vibration, electromagnetic radiation to the urban and rural environment and affect the landscape, especially the noise and vibration during train operation. Excessive noise and vibration will seriously affect the normal life of passengers and people along the track; On the other hand, noise and vibration may also cause fatigue damage to relevant equipment and structures and surrounding buildings, shortening the service life. Therefore, controlling the noise and vibration of rail transit is an important topic to improve passenger comfort and environmental protection. Reducing the vibration and noise level of the train and taking corresponding vibration and noise reduction measures in the rail transit section have become a key in the construction of the rail transit system

a large number of studies have been carried out at home and abroad on the vibration and noise control of rail transit. It mainly focuses on three aspects: vibration source and sound source control, vibration and sound propagation control, and material and structure control. Theoretically speaking, controlling the vibration source and sound source is the most fundamental method, but at present, according to the actual situation of our country, there are still some difficulties in carrying out this work. For the rail transit system that has been built, the control of vibration and noise transmission, the use of new vibration and noise reduction materials and acoustic structure design have become a very important means

(1) the main vibration source

dynamic interaction between train and structure

Vehicle Powertrain vibration

track structure vibration

wheel rail irregularity

(2) main noise sources

wheel rail noise, including rolling noise, impact noise, friction noise

structural noise (the vibration generated by the interaction between wheel and rail surface is transmitted through the track, bridge and foundation, resulting in the corresponding structural vibration and radiated noise)

vehicle power equipment noise, including traction motor, ventilator, compressor pantograph and other equipment noise

aerodynamic noise during vehicle operation

rail transit noise usually has broadband characteristics, and the frequency range is 0.0~6.0khz, among which the frequency with great impact on the environment is 0.1~1.0khz

at present, the research on vibration and noise reduction of rail transit at home and abroad mainly focuses on the following aspects:

1.1 vibration and noise reduction of vehicles

using technologies such as elastic wheels, inflatable rubber wheels, damping wheels and elastic tread wheels, which can usually reduce vibration and noise by 2~10dba. For example, inflatable rubber wheels are used in vehicles in Paris subway and straddle unicycle vehicles in Japan. Compared with ordinary steel wheels, this kind of wheel can reduce noise by 10dba

changing the noise emission performance by changing the wheel structure can reduce the wheel rail noise. For example, in Germany, by placing the brake disc on the wheel center to reduce the noise, the test results show that the noise above 1000Hz can be reduced by about 5dB. Adopt vibration and noise reduction power drive system. Such as Vancouver, Detroit, Osaka and other rail transit systems in the 1980s, the vehicles used linear motor technology. Due to the adoption of linear motor, a series of transmission mechanisms such as gearbox are omitted, and many noise sources are reduced. Therefore, the noise level is about 10dba lower than that of ordinary vehicles. In addition, due to the radial bogie, the vehicle can pass the curve smoothly, reduce the wheel rail wear and eliminate the scream when the conventional bogie passes the curve, so the noise is reduced by nearly 20dBA compared with the general vehicle

1.2 vibration and noise control of track structure

track structure is mainly composed of rails, fasteners and foundation under the rail. According to the vibration theory, the vibration noise between wheel and rail is closely related to the mass, stiffness and structural damping of each track component. The vibration and noise reduction of track structure is mainly achieved by changing the structural parameters

compared with ballasted track, ballastless track has the advantages of good overall stability and less maintenance, but its disadvantage is that the vibration and noise are large, especially when used in elevated track. Therefore, effective vibration and noise reduction measures should be taken

from the perspective of track structure, the vibration and noise reduction measures that have been tried abroad mainly include: ① using welded long rails; ② Adopt vibration damping steel rail; ③ Adopt vibration damping fasteners (such as double iron pad, shear type, compression type, low stiffness type, etc.); ④ Adopt vibration damping foundation under rail (for example, ballasted track adopts elastic sleeper and elastic rubber pad of track bed, ballastless track adopts elastic support block, vibration proof track slab, etc.); ⑤ Rail grinding technology is adopted. These measures have been proved to have different degrees of vibration and noise reduction effects and meet the requirements of environmental protection. For example, the effect of vibration and noise reduction of the elastic support block track structure composed of elastic support blocks, track bed plates, concrete bases and supporting fasteners is obvious. Therefore, for sections sensitive to vibration and noise, especially elevated structures, the elastic support block ballastless track structure is an ideal scheme

the research of vibration damping foundation under the track is also very valuable. For example, on the basis of gravel track bed, add elastic sleeper track bed and ballast cushion track bed, and increase the production of track bed ammunition is carried out according to the special high-quality requirements of low-grade packaging materials for drugs corresponding to GMP, which can effectively reduce the vibration of ballast. Compared with general gravel track bed, its vibration damping effect can reach 5~15db. The floating plate structure is used in the special vibration reduction sections of Singapore and Hong Kong Metro, and the vibration reduction effect is very significant. In addition, controlling the track irregularity can also achieve good vibration and noise reduction results. For example, after the rail is polished, the vibration noise decreases by 4~8dba within the vibration frequency range of 8~100hz, and the vibration noise on the platform decreases by 5~15dba

1.3 vibration and noise reduction of viaduct lines and bridges

(1) research on viaduct structure. At present, most viaduct structures in foreign countries use box girders, such as the newly-built Paris express railway viaduct and Singapore viaduct. Most of the elevated tracks in China also use box girder bridge decks. Scholars at home and abroad agree that because there are acoustic modes in the internal cavity of the box girder in the main frequency band of rail transit noise, the sound field resonance in the cavity may increase the radiation sound of the upper and lower surfaces of the bridge. Moreover, the bottom surface of the box girder bridge is a large area of plane, and the sound radiation efficiency is relatively high. Therefore, it is necessary to study the vibration and noise reduction measures of the box girder. At present, the noise reduction treatment of box girder has the following types of technologies: installing sound-absorbing ceiling under the bridge; The diaphragm is designed and installed in the box girder cavity; Install bridge vibration absorbers, etc

(2) sound absorbing bridge deck and pavement research. The bridge deck of elevated rail transit line is an acoustic reflecting surface. Reducing the acoustic reflection of the bridge deck can greatly reduce the noise when the train passes. All kinds of porous concrete developed in recent years can effectively reduce the sound reflection of the bridge deck, that is, a certain thickness of porous concrete is paved on the bridge deck, which not only does not affect the walking of maintenance personnel, but also has a certain sound absorption coefficient. However, the sound absorption effect of porous concrete on medium and low frequency noise below 1000Hz is not ideal. The preliminary research results show that the medium and low frequency noise centered on 500Hz is the main component of the noise of elevated rail transit, so it is very important to develop a lightweight sound-absorbing pavement on the bridge deck that can absorb the low-frequency noise

(3) research on sound absorption structure. Among the noise sources of elevated rail transit, the radiation noise of bridge vibration has a great impact on the surrounding environment, especially on the low floors. At home and abroad, there are examples of installing sound-absorbing ceilings or suspended space absorbers on the opposite side of viaducts, and some noise reduction effects have been achieved. High sound absorption, safety, beauty and easy cleaning and maintenance are the key points of designing this kind of sound absorption structure. At present, there is no commonly recognized form of viaduct sound-absorbing ceiling

1.4 sound barrier setting

sound barrier is an effective measure to reduce the running noise of rail transit. In foreign countries, noise barriers are built on the main traffic lines to control noise

the existing sound-absorbing barriers are of plate structure, and the sound-absorbing materials used include porous materials (such as foam glass, etc.), perforated plates plus fiber sound-absorbing materials, micro perforated plates, etc. However, the narrow frequency band, especially the low-frequency sound absorption coefficient, is usually only about 0.5, which is the common disadvantage of the existing sound absorption barriers

in addition, there are other problems with the existing sound-absorbing sound barriers. For example, at present, almost all the urban traffic sound barriers use the form of sound-absorbing materials covering the perforated plate. Not only the sound-absorbing effect in the low-frequency region is poor, but also the sound-absorbing performance of the sound barrier decreases or even fails due to the rain and dust invading the sound-absorbing materials through the perforated plate during use

common microperforated plates and other resistant sound absorption structures are more effective for low-frequency noise, but the sound absorption coefficient is often very low in the medium and high frequency band

in a word, because the main components of traffic noise are distributed in 100Hz ~ 5KHz, it is difficult for simple resistive sound absorption or resistant materials to achieve satisfactory sound absorption effect in such a wide frequency range. Therefore, both at home and abroad have studied the impedance composite sound barrier as the main direction to broaden the sound absorption band and improve the noise reduction effect. Reducing cost, thickness, size and weight and improving service life are the pursuit of new sound barrier developers

1.5 shock absorber

metal rubber composite shock absorber. Metal rubber composite shock absorber is the most widely used vibration and noise reduction device at home and abroad, accounting for more than 90% of the total in rail transit (calculated by output value). Because rubber has unique viscoelastic behavior in a wide temperature range, it can not only absorb and store impact energy through elastic deformation like steel springs, but also consume energy greatly through the relative movement of molecular chains. This ability is not possessed by any other material

at present, the research focus of metal rubber composite shock absorber at home and abroad is elastic material. From the perspective of vibration and noise reduction, the most ideal goal is to change all the transmission and connections on the rail vehicle into elastic devices. If so, the whole carriage will be "supported" on the bogie with high-performance elastic materials. This requires not only the elastic material to have excellent damping and drying capacity, but also to have strong strength, which can be used as a structural material

the rubber part is not only the main working part of the shock absorber, but also the key factor affecting the service life. The failure reason of metal rubber shock absorber is mainly the fatigue damage, permanent deformation and aging of the rubber part. Under the same service conditions, the life of metal is much longer than that of rubber. Therefore, the significant improvement of the high performance of rubber, an elastic structural material, especially the comprehensive performance of strength, creep resistance, fatigue resistance and aging resistance, will make a qualitative leap in the shock absorber and greatly improve the comfort and safety of high-speed trains

at present, the research on elastic structural materials for vibration reduction of rail transit at home and abroad mainly focuses on improving mechanical strength and service life. In terms of mechanical strength, China has basically reached the advanced level abroad, but there is still a certain gap from the ideal requirements of rail vehicles (all elastic transmission and elastic connection); Compared with developed countries, there is still a big difference in service life