Vibrational dynamics of modern lightrail modules

Sie sind hier: Homepage > Suche

Vibrational dynamics of modern lightrail modules

Dekker, H.

The vibrational frequency response of a modern lightrail module is considered in a simple model including dynamical features of the (typically aluminum) body with finite flexural rigidity, which inter alia reveals additional wheel-rail resonances. The model also allows to calculate the systems acoustic noise emission spectra, and to study the differences between aluminum and steel coaches. The mechanical model of modern lightrail modules generalizes the standard suspension models of rigid vehicles to allow for the vibrational dynamics of a nonrigid coach construction (and for rubber wheel tyres). In this manner a comparison can be made between trams with steel or aluminium bodies. The latter are important in view of recent developments in modular low-floor systems. The model is claimed to clarify certain novel dynamical instabilities in the wheel-rail contact, as well as related characteristic acoustical features. Special attention is also given to the problem of critical damping. Inter alia, two pitfalls in the design of modern lightrail modules have been identified. Firstly, undercritical damping not only leads to unstable response characteristics (in particular for free-running modules), but also to significantly higher noise levels (typically 7 dB) over a wide frequence range. Secondly, a near coincidence of the truck resonance with the fundamental flexural body mode strongly enhances both the dynamical response (e.g., a factor four in the wheel spectrum) and the noise levels (up to an extra 10 dB at low but audible frequencies).