Parametrical analysis of the railways dynamic response at high speed moving loads

Abstract

The paper introduces some findings about a sensitivity analysis conducted on every geometrical and mechanical parameters which characterize the use of a railway superstructure at the high velocity. This analysis was carried out by implementing a forecast model that is derived from the simplified Gazetas and Dobry one. This model turns out to be particularly appropriate in the explication of problems connected to high velocity, since it evaluates both inertial and viscous effects activated by the moving load speed. The model implementation requires the\ud transfer function determination that represents the action occurred by the bed surfaces on the railway and it therefore contains information concerning the geometrical and the mechanical characteristics of the embankment, of the ballast and of the sub-ballast. The transfer function H has been evaluated with the finite elements method and particularly, by resorting the ANSYS code with a harmonic structural analysis in the frequencies field. The authors, from the critic examination of the system’s dynamics response in its entirety, glean a series of observations both of a general and a specific character, finally attaining a propose of a design modification of the standard railway superstructure at the high velocity of train operation adopted today especially in Italy

Modeling the dynamic behavior of railway track taking into account the occurrence of defects in the system wheel-rail

“…For the determination of normal contact stresses for a non-conformal contact one could apply the approximation method of nonlinear geometry by using ellipses or carry out the modelling of contact bodies based on the elastic Winkler foundation, where the deformation of surfaces is proportional to the normal contact stresses. The maximum contact stress obtained in this case is 1.3 times higher than that obtained from the Hertz theory [5,9,11]. The size of the contact area at the normal wheel-rail geometry as well as the type of contact stresses depend on the normal load between a wheel and a rail, the profiles of a wheel and a rail, the transverse and angular position of the wheel pair on rails as well as the angle of the tread surfaces of rails [3,7,15].…”

“…5) The model where the force of interaction is divided into loading and unloading steps [11,12]. For a loading step -(1), for an unloading step -…”

“…In these cases [3,5,7,9,11,12,13] the maximum impact force of a wheel with a flat spot on rail is determined as:…”

Surface Displacement Field of a Coated Elastic Half-Space Under the Influence of a Moving Distributional Load

“…, 3 = −ℎ where 3 and 33 are components of the Cauchy stress tensor, = 1,2, (⋅) is Dirac delta function and is a parameter describing the Gaussian profile of the load. Employing Helmholtz decomposition of a vector field (see, [9]…”

Simulation of the railway under dynamic loading. Part 2. Splicing method of the wave and contact solutions

“…There are also analytical [7] and numerical [8] methods allowing to solve problems of contact interaction of solids, taking into account their movement [9], various geometric and mechanical properties [10]. The real engineering problems [11,12] of structures analyzing and their elements on the dynamic interaction of the vehicles often have a dual nature, and include both the wave and the contact component [13,14]. To accurately determine the kinematic (displacement, sag) and dynamic parameters (forces, stress) in this paper the computer system makes it possible to obtain analytical expressions for the unknown quantities up to the mechanical characteristics of the target material and the parameters of the dynamic interaction of the initial application.…”