A methodology for developing high damping materials with application to noise reduction of railway track

Abstract

A methodology is developed that allows a material to be formulated for a particular damping application where temperature-dependence has to be taken into account. This is applied to a tuned absorber system used for damping the vibration of a railway track. This is required to be effective over a temperature range -20 to 40 deg C. The time-temperature superposition principle is used to convert frequency-dependence to temperature-dependence for a notional material with constant loss factor. This is used in the prediction of decay rates and thereby noise reduction. In addition, a weighted noise reduction is studied by using measured rail temperature distributions. Two types of viscoelastic material, butyl and EPDM rubbers with various amount of fillers and plasticisers, are investigated. The properties of both rubbers have been measured over the range of temperatures for frequencies 300-3000 Hz. For butyl, the best combination of filler and plasticiser gives temperature weighted noise reductions up to 5.9 dB(A). The best EPDM compound gives a temperature-weighted noise reduction up to 6.2 dB(A). Comparing these two rubbers, EPDM is more suitable for low temperatures below 10 deg and butyl is more suitable for higher temperatures above 10 deg.