Abstract :
One of the important problems in tribology is the evaluation of contact and wear modes under different contact conditions. A deformation predicted by contact models should correspond to an actual wear mode. The aim of this work is to compare the deformation of metallic materials in a steady friction state using contact models and a description of the dislocation structure. In order to analyze the behavior of materials under repeated sliding, the steady friction state was characterized. It was shown that the steady friction state is characterized by reaching a saturated state where a balance between hardening and relaxation of dislocations in high-deformed layers and by an equilibrium between deformation and fracture due to wear particle detachment, is exhibited. Based on an analysis of the dislocation structure of high-deformed layers in steady friction state, it was found out that the asperity contacts enable elastic deformation in macroscopic scale, whereas plastic deformation of wall-cell structure and the accommodation of substrate grain layers is reached in microscopic and mesoscopic scales. It is suggested that the hardness or yield strength and the radius of hemispherical asperity of soft metallic materials before the sliding test used in the contact models, do not reflect the deformation of asperity contact in the steady friction state. It was concluded that the development of the dislocation dynamics of surface layers under repeated sliding while taking into account the real asperity contact in steady friction state, can advance the analysis of the transition from one contact/wear mode to another.
