چكيده به لاتين
Abstract:
Railway modeling is one of the most important parts of designing and analyzing in railway engineering. A modern railway track is included a rail which is fastened on sleepers and the sleepers are located on ballast. In dynamic modeling, the model of rail and the foundation subjected to an external force is very important. This modeling is used for analysis of noise and vibration, fatigue designing, comfort for passenger, stability, and safety. Rail is modeled with Euler Bernoulli or Timoshenko beam. In modeling the foundation which is under rail, the accurate model of railpad is a significant problem. Railpad is one of the most important part of track which effects on the stiffness and damping of whole track. Therefore, the accurate modeling of railpad is essential. Different models have been suggested in the literature for modeling the railpad. Among the suggested models, the viscoelastic fractional model has the best fitting with experimental data – especially in high frequencies- and this study is focused on this type of railpad. In this regard, simulation of railway track is accomplished and the governing equation is extracted. The Newmark method is applied for solving the governing equation. In order to the railway track behave more accurate – especially in heavy loading - a nonlinear element is added to foundation and the nonlinear fractional differential equation is solve by combining Newmark method and Adomian decomposition method for the first time. Then, the acoustical pressure field above the rail is obtained by Rayleigh integral. After that, the effect of fractional parameters, frequency, velocity, and loading condition on the response of system are investigated. It is found that the stresses of the system can be control by fractional parameters. Additionally, displacement and stress are more affected from loading condition; while, acoustical pressure is remarkably influenced from frequency and velocity.
Keywords: railway track modeling, acoustical and vibration analysis, viscoelastic fractional railpad, fractional calculus, Numerical methods.
