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

Abstract

A B S T R A C T This paper focuses on the presence of the third body, a solid interfacial layer in the wheelrail 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.

Laboratory study of the tribological properties of friction modifier thin films for friction control at the wheel/rail interface

“…Previous work has focused on the study of the "natural" third body between the wheel and rail to explain the interfacial friction and adhesion behavior based on the composition of the third body layer [12]. However, more recently, researchers have begun to investigate the creation of an "engineered" third body layer as a means of controlling friction at the wheel/rail interface, especially between the wheel tread and rail head [13].…”

Rolling–sliding laboratory tests of friction modifiers in dry and wet wheel–rail contacts

“…In the tests with FMs, it may be possible that the firm adherence of the third body layer on the wheel disk (rather than on both disks) could also have influenced the different work-hardening between wheel and rail. Berthier et al [20] showed that a third body layer present between wheel and rail surfaces can accommodate their relative displacement (or slip) so that the shearing of the near-surface grains of wheel and rail surfaces is decreased, thus reducing the work-hardening effect.…”

Inelastic analysis of granular interfaces via computational contact homogenization

“…Although the concept of a TB is sometimes employed in a rather general context that also includes liquids or layers of deformable media (see, e.g. Berthier et al [1]), in this work a TB explicitly refers to solid continua of a granular nature without interstitial fluid layers (i.e. dry granular media).…”

“…For instance, in biomechanical applications where knee and hip implant surface degradation is of concern, the analysis may include both wear debris within the joint [10] and cement particle contaminants from the implant-bone interface [11]. Similarly, wheel-rail traction investigations involve both a wear process that generates intrinsic TBs [12] and a layer of contaminant material on the rail [1]. Extrinsic TBs are almost always undesirable.…”