1,721,077 research outputs found
Use of numerical models to determine the effectiveness of anti-vibration systems for railways
No full textVibration from trains can cause annoyance and also concern about possible damage to property. It is a major issue in the environmental impact assessment of new railways and where new traffic is to be added on existing railways. Track designed to control vibration has been implemented on a number of railways. These designs are effective solutions for vibration at frequencies at the low end of the audible range. Such vibration causes re-radiated noise in buildings and is especially associated with trains in tunnels. However, at present there are no proven, effective solutions for vibration from heavy freight trains. This occurs at lower frequencies (down to about 4 Hz) and can be felt.In an attempt to deal with frequency vibration, experimental track has been built containing continuous slabs of concrete. This has shown encouraging results in tests but it is not clear how generally applicable these improvements would be, or even whether the test results were valid. To clarify these matters it is necessary to develop theoretical models.To date, a number of two- and three-dimensional models have been developed at British Rail Research. These are used to investigate the expected performance of different track constructions covering the cases of both re-radiated noise and low-frequency vibration.Experimental work is being carried out in parallel to validate the theoretical approach and to provide data on appropriate material parameters for the ground
Extended validation of a theoretical model for railway rolling noise using novel wheel and track designs
No full textRolling noise generated by railway wheels with visco-elastic layers
No full textThe noise-generating characteristics of two types of railway wheel design have been studied theoretically. These are "resilient wheels" in which a viscoelastic layer is located between the type and the web, and wheels with constrained layer damping treatments applied to the web. A method of predicting the rolling noise of these wheel types using the TWINS rolling noise model has been developed. For this, a modal description of the wheel must be constructed. A finite element model is used to calculate the mode shapes and modal masses. The modal damping is predicted by a complex modal analysis of the finite element model in which a material-specific damping parameter is used. Analyses have been carried out for a number of resilient wheels with different stiffnesses of their resilient layer, including the case where the wheel becomes a conventional one by specifying the resilient element as steel. The sound power radiated by both the wheel and the rail are shown to be dependent on this stiffness. A number of configurations of wheels with constrained layer damping treatments have been analysed taking into account the frequency variation of the properties of real damping materials. Significant reductions in the wheel sound power are shown to be possible
A boundary element model for two-dimensional elastodynamics on a single open or closed domain
No full textSound radiation from a vibrating railway wheel
No full textThe sound radiation characteristics of a railway wheel are investigated by using boundary element calculations. The axisymmetry of the wheel allows an axi-harmonic formulation to be used, in which the wheel is defined by a two-dimensional mesh of its cross-section and the motion is decomposed into harmonics of different numbers of nodal diameters. The radiation ratios of the wheel, vibrating in its various normal modes, are calculated for a range of frequencies. The effects of variation in the wheel radius, web thickness and tyre depth are also investigated. From these results, simple formulae are proposed that allow the radiation ratios to be approximated closely. These are more convenient than the boundary element calculations for calculating the rolling noise from a wheel since they are a function of a few simple geometrical parameters. The directivity of wheel radiation is also considered, with comparisons with measured data indicating that simple monopole and dipole characteristics can be applied
Controlling noise by wheel and track design
No full textRolling noise forms the main source of noise from railways. Effective control at source requires a good understanding of the mechanisms of generation. To this end, detailed theoretical models for rolling noise have been developed. Using these methods, it is possible to evaluate the rolling noise behaviour of different wheel and track designs, allowing new designs to be derived that are inherently quieter. In this paper, an overview is given of the mechanisms involved in noise generation and the parameters that have most influence are identified. Examples are then given of two techniques that have been developed using the model with the aim of reducing the noise at source. A tuned absorber system applied to the rail is found in field measurements to reduce the noise from the track by about 6 dB(A). The wheel component of noise can be reduced by an optimised wheel shape in combination with damping treatments
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