Railway noise is activated by irregularities on the running surfaces of rails and wheels, these being more significant for the most part of the wavelength and the frequency range of interest. The rolling noise generation mechanism consists of two major structural components: the wheel and rail. The contribution to the noise of the track can be further separated into noise radiation on the rails and in the sleepers. To mitigate the rolling noise, these components must be analysed. To direct and manage mitigation methods within Faurei Railway Testing Center, the rail surface roughness in accordance with EN 15610 was determined in a line of alignment, this being a direct method of measuring the surface roughness of the rail, in association with the rolling noise introduction. In this paper, it is proposed a fractal analysis of the microgeometry of the rail surface, with the possibility of using it as an acoustic parameter.

For comprehending tribological phenomena such as wear, friction, contact deformation and tightness of contact joints is the essential characterisation of the multiple scale topography of roughness surfaces. Wheel roughness obtained through direct measurement and then a description of wheel roughness has been obtained using the fractal function. The statistical parameters and fractal sizes for drive wheels which ran 2000 km and another ones new wheels have been analysed.By registering the results and programmable automaton of the roughness, the principal statistical characteristics were determined to be stands out the Abbott-Firestone curve and respectively, the fractal character. The appearance of roughness on the surface of the wheel causes the production of vertical vibrations that act on the complex wheel-rail system.In the analysis of the wheel irregularity, the fractal geometry was applied, so that to obtain the fractal parameters Dw, respectively Ltw (opothesy length), the method of the structure function was used [1, 2]. Therefore, the experimental measurement and obtained results processed presented.

One of the essential parameters of the roughness with effects on the vibration of the wheel and the rail is the contact stiffness. This rigidity considers the geometry and material of the wheel and rail, which are considered elastic. Also, the micro-geometry of the roughness and the load on the wheel, with elastic, elastoplastic and plastic deformations, depending on the deterministic or random character of the roughness were considered. The dependence of the stiffness on the deformation state of the roughness may explain the different amplitude of the vertical vibrations at the same force on the wheel and the same height of the roughness, but one roughness with different fractal parameters. For the analysis of the dynamic forces in contact, the continuous and underived analytical function that modelled the roughness measured experimentally on the rail was applied.