Self-replenishing powder transfer film lubrication in textured and untextured tribosystems: Experiments and modeling.

摘要

Thin transfer film powder lubrication is a relatively new subject and has only been studied extensively in the past two decades. Initially, "pellet-on-disk" tests were performed to investigate the performance of molybdenum disulfide (MoS2) in bearings by using a modified pin-on-disk tribometer, and since then, thin film powder lubrication has been incorporated in bearings technology by embedding powder lubricants inside solid lubricant reservoirs (SLRs). A tribosystem is comprised of two surfaces in sliding contact with a lubricant in between them. Though its relevance can be observed in many industrial applications today, modeling the frictional behavior or lifetime prediction of SLR tribosystems is still a challenge.;A new modeling approach is proposed to describe transfer film lubrication from powder compacts in protruding or confined configurations. Based on the conservation of mass, the model assumes that the friction coefficient is a function of the volume fraction of powder lubricant occupying the asperity domain. The volumetric fractional coverage (VFC) model developed in this work introduced a more rigorous methodology for calculating the wear coefficients from powder compacts in sliding contacts. Additionally, the distribution processes of the transfer film on the surface asperities can be described mathematically more easily due to the fact the VFC model accounts for the volume of lubricant in situ. An investigation of SLR tribosystems is conducted by employing slider-on-disk experiments which have been used to validate the VFC model and predict the frictional performance. The random distribution process is used to determine the threshold volume fraction at which a tribosystem reaches its effective lubricated friction coefficient value.;In this thesis proposal, the flexibility and fidelity of the new VFC model are demonstrated through comparisons with experimental results. The reasonable agreement between experiments and modeling suggest the framework holds promise for being able to predict the frictional performance and lifetime of transfer film tribosystems. This work presents a volume-based fractional coverage model which can predict the tribological performance of textured and untextured sliding surfaces lubricated by transfer films. Data from pellet-on-disk with slider experiments have been used to assess the accuracy of the model.