Tribology International 40 (2007) 973–981 Modelling third body flows with a discrete element method—a tool for understanding wear with adhesive particles N. Fillot à , I. Iordanoff, Y. Berthier LaMCoS, INSA de Lyon 20, Avenue Albert Einstein 69621 Villeurbanne Cedex, France Available online 18 April 2006 Abstract This work presents a fundamental approach to the study of the wear process by considering the detachment of particles, their flow in the contact and their ejection. A numerical model is constructed in order to visualize and to accurately measure these phenomena. Moreover, the adhesion between the detached particles and with the rubbing surfaces can be simulated and controlled. This physicochemical parameter plays an antagonistic role on the wear process. The greater the particle adhesion the thicker the interfacial layer will be, though with a corresponding reduction in the ejection of particles. Finally, emphasis is placed on the influence of the interfacial layer on the wear process. r 2006 Elsevier Ltd. All rights reserved. Keywords: Wear; Third body; Discrete element method; Adhesion 1. Introduction According to the literature, wear has been studied extensively over the past fifty years, undoubtedly due to its primordial role in many industrial problems. Surprisingly, Meng and Ludema [1] made a dramatic assessment in 1995, concerning wear modelling, concluding that many aspects of wear still remain far from being well understood. In fact, wear has often been investigated via the way materials degrade, by the loss of mass when rubbed together. This method stemmed from a Scottish study on the wear of coins, performed in the 17th century, which linked a loss of mass with a loss of function [2]. Since wear has no legal unit, identifying wear with a mass was a practical means of quantifying it, and constituted the first step towards modelling. A major contribution in wear modelling was made by Archard in 1953 [3]. The worn volume or mass (detached from the materials rubbing together) is proportional to the pressure applied to the contact multiplied by the sliding distance. The problem with this famous wear law is that the coefficient of proportionality should vary by several orders of magnitude to be applicable to practical applications. On the other hand, different aspects of wear are studied separately with abrasive, adhesive, corrosive, etc. wear mechanism concepts. In particular, ‘‘adhesion’’ is often mentioned in the literature as a wear mechanism that involves adhesive surfaces [4]. When bonds establish between the surfaces, one solid is able to remove material from the other solid. Classically, a ‘‘transfer film’’ is formed on one surface, constituted by the matter detached from the antagonistic material. By repeating the operation, a mixture of the two materials is formed at the interface. Following on from Archard, many researchers have developed their own law, involving new parameters depending on their needs and cultures. Unfortunately, ‘‘the available equations are so confusing that few designers can use any of them to predict product life with confidence’’ [1]. In the 1970s, Godet proposed the concept of the third body in order to unify the problems of friction and wear in dry contacts with the theory of lubrication. In the case of a bearing, one can easily imagine the fluid at the interface that supports the load, separates the materials in contact and accommodates the sliding speed. Even without an interfacial fluid, Godet [5,6] and finally Berthier [7] showed ARTICLE IN PRESS www.elsevier.com/locate/triboint 0301-679X/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.triboint.2006.02.056 à Corresponding author.