Laboratory Measurement of the Vibration Attenuation Performance of the Rail Fastening System
Tuesday 2 june, 2015, 15:20 - 15:40
0.1 London (90)
Ground-borne vibration is the cause of complaints from people who live near railway tracks. In response, rail fastening systems with improved performance regarding vibration attenuation are sought. The vibration attenuation performance of the rail fastening system can normally only be measured after the track has been built, at which stage there is great difficulty in making significant changes to the track structure. Pandrol France has built a test rig that allows measurement of the vibration attenuation provided by a given fastening system in advance of building the track. The rig consists of an upper block, which can be chosen to replicate the unsprung mass of the rolling stock, and a 6 tonne lower block that is mounted on soft supports. The resilient element of the fastening system is mounted between the blocks. A static load is applied to the resilient element in order to represent the preload due to the rail clips and the wheel load. A dynamic load of smaller amplitude is applied to the upper block using an instrumented hammer, representing the excitation due to wheel-rail roughness. An appropriate unsprung mass and preload level are chosen by reference to the low-frequency dynamic stiffness of the fastening system measured to the CEN 13146-9 standard and the use of a simple beam finite element model of the track. Force measurement made with the hammer and accelerations of the two blocks allow transfer functions to be obtained between the dynamic force input, the acceleration of the upper block and the acceleration of the lower block. These transfer functions are used to calculate the attenuation provided by a given fastening system, an insertion loss between two different fastening systems, the dynamic stiffness and the damping loss factor of the resilient element. The measurements can be made for different temperatures.
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