The results of numerical analysis of selected phenomena occurring in a rail fastening system were presented in the paper. The study is focused on assessment of the state of displacement and stresses in the rail pad subjected to a moving load. Two finite element models of the considered system were developed. The first one included elementary track segment corresponding to one sleeper. The second FE model consisted of several elementary segments. The number of the track segments was determined independently on the basis of dynamic analysis carried out using LS-DYNA computer code. Essential FE analyses were performed using MSC.Marc/Mentat software. FE model of the elementary segment included 600 mm length rail and a two-side shaped rail pad. The Mooney - Rivlin material model was applied for the polyurethane rail pad. The fastening systems were modelled using spring elements. The vertical and longitudinal spring elements were also applied for the ballast modelling. A case of moving load caused by single vertical force - one axle - was considered in the study. Methodology of moving load simulation in the MSC.Marc software was proposed. The obtained results allowed assessing the total deflection of the rail pad, the state of stress, the load distribution on respective sleepers. Moreover, they gave information about the behaviour of the rail pad under moving load in context of static test described in respective standards.
Numerical analysis of selected type of the polyurethane rail pad is presented in the paper. A shaped pad with cylindrical-shaped elements in its working section was selected as a representative for the computational simulation. Analysis reflected the experimental test according to the valid standard. The test included loading of the vertical force perpendicular to the foot of the rail. Such test allows determining the static stiffness of the pad. The Mooney - Rivlin material model was selected in the current study. Necessary experimental tests including a uniaxial compression and tension were conducted to provide material constants for the hyperelastic material model applied for the FE model. Simplified FE models of the considered rail pad and the rail were developed. Rounded corners and edges of the cylindrical-shaped elements were omitted, since their modelling required a significant density of the FE mesh. Vertical force perpendicular to the foot of the rail was declared as nodal force distributed evenly along the edges of the selected finite element models Non-linear static analysis was performed using MSC.Marc software with large displacements and deformations taken into consideration. The obtained results allowed estimating deformations and the state of stress in a highly deformed rail pad. The static stiffness of the pad was defined as secant stiffness based on the vertical force - deflection curve.
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