| As one of the main elastic parts in railway track structure,the dynamic characteristics of rail pad have influence on the lateral vibration characteristics of the rail,and it can not be ignored.In order to provide the theoretical guidance through simulation before the lateral dynamic test of fastener,the 3D solid finite element model of key parts of DZⅢ fastener system of urban rail transit was first established.After the model is verified,the lateral force transmission behavior of fastener system under the condition of no vertical load and vertical load is studied from the static analysis.The results show that the lateral force transmission process of fastener system can be divided into two stages.The first stage gauge is that block has not contacted the rail bottom,and the lateral support of fastener is mainly provided by the shear stiffness of the rail pad.The second stage is that gauge block contacts the rail bottom,the lateral support of fastener will be mainly provided by the compression stiffness of gauge block.The vertical load of fastener will enhance the ability of the elastic pad under rail to resist transverse shear deformation.In the subsequent lateral dynamic test of fastener,the lateral loading range of 0～5k N can ensure that the lateral support of fastener is mainly provided by the shear stiffness of the elastic pad.Then,taking DZⅢ fastener rail pad as the test object,the test for its transverse amplitude-dependent and frequency-dependent dynamic characteristics is designed.Combining the constitutive model of elastic pad and time-temperature superposition(TTS)of polymer materials,the change rule of lateral dynamic viscoelastic and plastic mechanical properties of elastic pad with temperature and frequency is obtained,and the identification results of model parameters are obtained.The results show that the glass transition temperature of DZⅢ fastener elastic pad is about 45 ℃.The lateral dynamic parameters(the storage stiffness and the loss factor)of the pad in logarithmic coordinate system are approximately proportional to the frequency within 1～10000 Hz.The parallel model of nonlinear friction model and fractional Zener model can theoretically represent the real dynamic characteristics of elastic pad of fastener.Finally,the lateral vibration analysis model of Timoshenko beam element rail is established,and the dynamic parameters and loading conditions of the model are determined.After the reliability of the model is verified by the method of indoor test and theoretical formula calculation,the influence of the frequency-dependent dynamic characteristics of the elastic pad on the transverse vibration and the transmission attenuation of the rail is studied by harmonic response analysis.The results show that the lateral vibration displacement admittance of the elastic pad between 20 Hz and 265 Hz will increase significantly due to the change of the transverse damping frequency,and the transverse vibration of the rail will be intensified near the pined-pined resonance and its later frequency range,and there are left and right oscillations.Under this premise,the first-order transverse resonance frequency of rail can be predicted more accurately(93Hz)by considering the frequency-dependent transverse stiffness,which increases 14 Hz compared with constant condition.Under the condition that the lateral dynamic parameters of the elastic plate of fastener are all constant,the frequency band of the curve is stable at a higher level except the adjacent pinned-pined resonance.Under the condition of the frequency-dependent damping,the frequency-dependent stiffness will cause the attenuation amplitude near the first-order resonance frequency(79Hz)of the rail to increase slightly,and the corresponding frequency range will be wider. |
PDF Full Text Request