The role and effects of the third body in the wheel–rail interaction

Y. BERTHIER,C. DESRAYAUD,M. C. BAIETTO‐DUBOURG,E. NICCOLINI,M. BUSQUET,S. DESCARTES,L. BAILLET

doi:10.1111/j.1460-2695.2004.00764.x

Abstract

ABSTRACTThis paper focuses on the presence of the third body, a solid interfacial layer in the wheel–rail contact. This third body is studied from different viewpoints: its presence including composition, thickness and morphology; and its role with respect to its load‐carrying capacity, shearing behaviour, transfer of material and finally global friction coefficient. The general approach is phenomenological and is carried out as closely as possible of the real tribological behaviour of this contact. This paper presents a synthesis of different studies coming from: analysis of specimens taken out periodically from rails and wheels in service, and thus under real contact conditions; and test laboratories, allowing us to impose rolling–sliding conditions with very high precision. From all these studies and results, a better understanding of the role of the third body and its influence on friction, adhesion and damage mechanisms (wear, pits, cracks …) is reached and this is the first step for including its effect in numerical models.

Highlights

Trains have been running for more than a century, the tribological phenomena activated in the wheel– rail contact are still not completely understood and based mainly on assumptions rather than on rational analysis
Composed of particles stemming from wheels and rails, this third body flows into the contact to accommodate the sliding between wheel and rail
The results show the presence of a natural third body ranging in thickness from a few micrometers to several dozen micrometers on the rail and wheel

Summary

Introduction

Trains have been running for more than a century, the tribological phenomena activated in the wheel– rail contact are still not completely understood and based mainly on assumptions rather than on rational analysis. The lack in the knowledge of the local contact conditions and their evolution with time makes it difficult to reach a complete understanding and predict accurately the initiation of headchecking, squats, roaring rail, etc.; their various consequences have been clearly identified and described.[1] This situation stems from the difficulty of instrumenting a wheel–rail contact in situ, and both industrial companies and scientists have had to cope as well as they can. Face to this statement the alternative adopted by wheel and bogie manufacturers, as well as rail manufacturers and networks, is to prevent from a catastrophic growth of cracking. This problem has been addressed independently by many disciplines at different scales, such as r railway dynamics (global scale), r contact mechanics (local scale), r materials, damage (local scale)

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Results

Conclusion