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Title: Development of railtrack tuned mass damper module
Authors: Tam, Po Lai
Degree: M.Phil.
Issue Date: 2017
Abstract: Among all six types of railway noise, rolling noise is the dominant noise in most of the speed range. Wheel/rail interaction induces wheel and rail vibrations which makes rolling noise, and such interaction also excites a pinned-pinned mode of vibration which frequency depends on the sleeper spacing. For UIC60 and UIC54 rail track, our on-site measurements, together with finite elements analysis, showed that the pin-pin resonance modes of the rail track in lateral and vertical direction (i.e. the two principal directions perpendicular to the length of rail tracks) are in the frequency ratio of around 1:2. Following our recent development of Tuned Mass Damper(TMD), multiple masses were employed so that they oscillate along the shear direction of the resilient layers to form a multiple spring-mass system in both vertical and lateral directions. As the damping mechanism strongly relies on the stiffness of the resilient layer, thus a resilient composite material with orthogonal shear moduli in orthogonal directions can be used to tackle the issue of different pin-pin resonance modes in both lateral and vertical directions. Since the resonant frequency is proportional to the square root of the modulus, with a frequency ratio of ~ 2 between the vertical and lateral pin-pin resonance modes, a ratio of 4 between the shear moduli of the two respective directions is required. In this study, aligned glass fibres and copper fibres were embedded into silicone matrix to form uniform composite resilient layers with different orthogonal shear moduli. Their shear stiffness were measured by a tensile tester, with the setup for shear modulus measurement based on the International Organization for Standardization ISO-1827. Our results showed that these composites obtained an acceptable orthogonal shear moduli ratio. Vibration tests were performed to verify that two natural frequencies were observed in these TMDs using the orthogonal resilient layers, which is not possible for TMDs using homogeneous resilient layer materials. Hence, resilient layer material of orthogonal shear moduli as applied on the TMD is promising for suppressing the two directions pinned-pinned resonance modes in rail tracks. Meanwhile, a finite element analysis was introduced to investigate the optimal arrangement of the composite.
Subjects: Hong Kong Polytechnic University -- Dissertations
Railroads -- Noise
Noise control
Pages: xiii, 67 pages : color illustrations
Appears in Collections:Thesis

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