Book chapter: Review of studies on the detrimental effects of solid contaminants in lubricated machine element contacts.

Author: George K. Nikas

Published in: chapter 1 (pp. 1-44) of the book "Reliability Engineering Advances" (Ed.: G. I. Hayworth). Nova Science Publishers, New York, USA, 2009. ISBN: 978-1-60692-329-0.

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Maximizing the life expectancy of machine elements in relative motion is the ultimate challenge faced by tribology researchers in industry and academia. However, despite the progress in materials science and lubrication methods, a great obstacle remains in achieving this goal, and that is the presence of solid contaminants in lubricants. The entrainment of 1-100 micron debris particles in concentrated contacts such as in bearings, gears, cam-followers or seals, is associated with various damage modes such as surface indentation and abrasion, lubricant starvation and scuffing, high frictional heating etc. All of these refer to plastic deformations and are detrimental to the life of the machine elements involved and, obviously, to the machine itself.

    This chapter contains a review of theoretical and experimental studies in the literature on the effects of debris particles in lubricated contacts, exploring the progress made in the last few decades. The studies cover the entrainment, entrapment and passage of debris particles through the contacts, and how this is affected by the operating conditions. Analytical, numerical and experimental studies are discussed in view of understanding the damage mechanisms involved in this process. This helps to improve the designs, depending on application requirements, aiming at minimizing the risks, maximizing life expectancy and, thus, improving engineering reliability in industrial, automotive and aerospace applications.

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