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

Abstract

For application in damping treatments, elastomeric materials should have a high damping loss factor, but this is inevitably linked to a strong temperature-dependence of the dynamic properties. 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. The methodology is applied to the case of 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 .To investigate the effect of the temperature on the performance of a rail damper, a simple Timoshenko beam model of the track vibration is used, to which are added single-frequency and dual-frequency tuned absorbers. The results show that a high noise reduction can be achieved for the optimum stiffness, provided that the loss factor is between about 0.25 and 0.4.In order to study the generic effects of high damping versus constant stiffness, 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. This temperatureweighted noise reduction allows a single number measure of performance to be obtained which can be used to assess various elastomeric materials in order to determine the optimum material for a given situation.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 this a test rig had to be modified. For butyl, the best combination of filler and plasticiser gives temperature weighted noise reductions up to 5.9 dB(A). Butyl rubber is suitable for use in the rail absorber giving high noise reductions between 0 and 40 . 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 and butyl is more suitable for higher temperatures above 10 .

Estimation of Rail Axial Force in High‐Speed Railway Ballastless Track Based on Wave Modes

“…Figure 13 shows the sensitivity of mode G to the rail temperature, and the change of the frequency with the temperature is nonlinear. According to the existing research findings [24,25], the stiffness of elastic pad increases nonlinearly with the decrease of the temperature. Meanwhile, the deformation of wave mode G occurs mainly at the rail foot, which will be greatly affected by the temperature-dependent characteristic of the fastening.…”

“…Temperature-Dependent Experiment. Many research findings show that the fastening system parameters are closely related to the temperature [23][24][25][26]. The temperaturedependent experiment is conducted for rail pad and elastic pad of the ballastless track.…”

The effect of temperature on railway rolling noise

“…A series of experiments was performed to determine the effect of temperature on the stiffness of the two railpad materials. 15 For this, a test rig described by Ahmad 17 (see Figure 1) was used to measure the shear stiffness of small samples of the material. Four separate samples (approximately 20 mm  15 mm  5 mm) of each material were cut from the corners of the railpad.…”

“…For this, a test rig described in 17 (see Figure 1) has been used to measure the shear stiffness of small samples of the material. Four separate samples (approximately 20×15×5 mm) of each material were cut from the corners of the railpad.…”

“…A measurement grid was marked up from a reference point 10 sleeper spans (5.96 m) from the rail end. Measurements were made at one-quarter sleeper intervals from this point up to the 16th sleeper span from the end, then at mid-span positions17,18,20, 22, 26, 30, 34, 38, 42 and 46. The total length covered by the grid was 23 m and this set the minimum meas-…”