1,721,402 research outputs found
Book review: Fundamentals of rail vehicle dynamics: stability and guidance by A.H. Wickens
No full textA continuous damped vibration absorber to reduce broad-band wave propagation in beams
No full textIn order to attenuate structural waves in beams, a damped mass–spring absorber system is considered that is attached continuously along the beam length. Compared with other measures, such as impedance changes or tuned neutralisers applied at a single point, it is effective for excitation at any location along the beam. Although it is a tuned system, it can also be designed to be effective over a broad frequency range by the use of a high damping loss factor and multiple tuning frequencies. It has the advantage over constrained layer damping treatments that it can be effective even when the structural wavelength is long. The parameters controlling its behaviour are investigated and simple formulae developed, allowing optimisation of its performance. The effective frequency bandwidth increases as the mass ratio of the absorber and the beam is increased and, for moderate-to-high damping, it also increases as the damping loss factor is increased. The maximum decay rate is independent of mass and damping for light damping, but for higher damping it reduces as loss factor increases and increases as the mass ratio increase. A particular application is the reduction of noise from a railway track, which requires the attenuation of structural waves along the rail to be increased over a frequency band of two or more octaves
The theory of a continuous damped vibration absorber to reduce broad-band wave propagation in beams
No full textIn order to attenuate structural waves in beams, a damped mass-spring absorber system is considered that is attached continuously along the beam length. Compared with other measures, such as impedance changes or tuned neutralisers applied at a single point, it is effective for excitation at any location along the beam. Although it is a tuned system, it can also be designed to be effective over a broad frequency range by the use of a high damping loss factor and multiple tuning frequencies. It has the advantage over constrained layer damping treatments that it can be effective even when the structural wavelength is long. The parameters controlling its behaviour are investigated and simple formulae developed, allowing optimisation of its performance. A particular application is the reduction of noise from a railway track, which requires the attenuation of structural waves along the rail to be increased typically in the frequency range 500 to 2000 H
The Influence of the Contact Zone on the Excitation of Wheel/Rail Noise
No full textRolling noise is excited by surface roughness at the wheel/rail contact. The contact patch is known to attenuate the excitation at wavelengths that are short in comparison with its length. A distributed point-reacting spring (DPRS) model is used with measured roughness data to determine the contact filter effect, and this result is compared with analytical predictions. It is found that the analytical model gives an attenuation that is too large at short wavelengths but is usable for wavelengths down to somewhat smaller than the length of the contact patch. Additionally, variations in the detailed geometry of the profile can cause the contact point on the wheel and rail to oscillate laterally. This introduces an oscillating moment that can induce additional vibration and noise. The DPRS model and rolling noise prediction model are both extended and used together to allow an estimate of the contribution to the radiated noise. It is found that, while the direct roughness excitation is still more important, the moment excitation can be significant, particularly for conforming profiles
- …
