Investigation of the effect of relative humidity on lateral force in rolling contact and curve squeal

Abstract

Curve squeal is the result of the lateral force in rolling contact of rail and wheels along curves. Recently, field measurements of wheel squeal occurrences at a site in Australia showed an increasing possibility for a squeal event to occur as the relative humidity increases. To verify these results, a new method to measure the lateral and normal force simultaneously was developed on a test rig, so as to determine the friction-creep curves. To investigate the effect of relative humidity on squeal and friction creep curves, the relative humidity inside the acoustic enclosure of test rig was adjusted under controlled conditions of 50%, 70% and 90%. The test rig results show that the lateral adhesion ratio decreases slightly with the increase of relative humidity and that squeal is more likely in high relative humidity. The modelling analysis shows that the critical creepage decreases with the increase of the relative humidity, which means negative damping occurs for lower angle of attack.