Effect of the Sliding Velocity on the Size and Amount of Airborne Wear Particles Generated from Dry Sliding Wheel–Rail Contacts

Hailong Liu,Pär Göran Jönsson,Yingying Cha,Lage Tord Ingemar Jonsson,Ulf Olofsson

doi:10.1007/s11249-016-0716-5

Abstract

A set of frictional experiments have been conducted on a pin-on-disk apparatus to investigate the effect of the sliding velocity on airborne wear particles generated from dry sliding wheel–rail contacts. The size and the amount of generated particles were acquired by using particle counter instruments during the whole test period. After the completion of tests, the morphology and chemical compositions of pin worn surfaces and collected particles were analyzed by using scanning electron microscopy combined with an energy-dispersive X-ray analysis system. The results show that the total particle number concentration increases dramatically with an increased sliding velocity from 0.1 to 3.4 m/s. Moreover, the fine and ultrafine particles (<1 µm) dominates the particle generation mode in the case of a high sliding velocity (1.2 and 3.4 m/s). The contact temperature variation is observed to be closely related to the size mode of the particle generation. In addition, the sliding velocity is found to influence the active wear. Correspondingly, an oxidative wear is identified as the predominant wear mechanisms for cases with high sliding velocities (1.2 and 3.4 m/s). This produces a substantial number of iron oxide-containing particles (<1 µm) and reduces the wear rate to a relative low level (the wear rate for a 3.4 m/s sliding velocity is 4.5 % of that for a 0.4 m/s sliding velocity).

Highlights

A large variety of loading conditions and contact geometries exist between railway wheels and rails due to many different rail and wheel profiles, rail cant and curve radii and railway vehicles running on specific networks
The results show that the total particle number concentration increases dramatically with an increased sliding velocity from 0.1 to 3.4 m/s
A study by Lewis and Olofsson [1] based on GENSYS simulations and laboratory tests to create a wear map of wheel–rail contact conditions indicates that the rail gauge–wheel flange contact will experience a severe to a catastrophic wear

Summary

Introduction

A large variety of loading conditions and contact geometries exist between railway wheels and rails due to many different rail and wheel profiles, rail cant and curve radii and railway vehicles running on specific networks. Contact mainly occurs at a wheel tread–rail head in tangent tracks and a wheel flange–rail gauge corner contact in curves. The latter one is usually more severe which leads to greater wear being seen. The wheel–rail contact is a rolling contact with sliding, and the sliding takes place on both tangent and curved track. It increases in curves with a relative sliding velocity peak when braking in a narrow curve. The severe and catastrophic wear of a wheel–rail sliding contact have been speculated to contribute to the high particulate matter levels detected in subway environments [2,3,4]

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