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Propagation of surface initiated rolling contact fatigue cracks in bearing Steel

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Title: Propagation of surface initiated rolling contact fatigue cracks in bearing Steel
Authors: Rycerz, P
Olver, A
Kadiric, A
Item Type: Journal Article
Abstract: Surface initiated rolling contact fatigue, leading to a surface failure known as pitting, is a life limiting failure mode in many modern machine elements, particularly rolling element bearings. Most research on rolling contact fatigue considers total life to pitting. Instead, this work studies the growth of rolling contact fatigue cracks before they develop into surface pits in an attempt to better understand crack propagation mechanisms. A triple-contact disc machine was used to perform pitting experiments on bearing steel samples under closely controlled contact conditions in mixed lubrication regime. Crack growth across the specimen surface is monitored and crack propagation rates extracted. The morphology of the generated cracks is observed by preparing sections of cracked specimens at the end of the test. It was found that crack initiation occurred very early in total life, which was attributed to high asperity stresses due to mixed lubrication regime. Total life to pitting was dominated by crack propagation. Results provide direct evidence of two distinct stages of crack growth in rolling contact fatigue: stage 1, within which cracks grow at a slow and relatively steady rate, consumed most of the total life; and stage 2, reached at a critical crack length, within which the propagation rate rapidly increases. Contact pressure and crack size were shown to be the main parameters controlling the propagation rate. Results show that crack propagation under rolling contact fatigue follows similar trends to those known to occur in classical fatigue. A log-log plot of measured crack growth rates against the product of maximum contact pressure and the square root of crack length, a parameter describing the applied stress intensity, produces a straight line for stage 2 propagation. This provides the first evidence that growth of hereby-identified stage 2 rolling contact fatigue cracks can be described by a Paris-type power law, where the rate of crack growth across the surface is proportional to the contact pressure raised to a power of approximately 7.5.
Issue Date: Apr-2017
Date of Acceptance: 2-Dec-2016
URI: http://hdl.handle.net/10044/1/42966
DOI: 10.1016/j.ijfatigue.2016.12.004
ISSN: 1879-3452
Publisher: Elsevier
Start Page: 29
End Page: 38
Journal / Book Title: International Journal of Fatigue
Volume: 97
Copyright Statement: © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Sponsor/Funder: SKF (UK) Ltd
Funder's Grant Number: n/a
Keywords: Science & Technology
Engineering, Mechanical
Materials Science, Multidisciplinary
Materials Science
Rolling contact fatigue
Crack propagation
Rolling bearings
Mechanical Engineering & Transports
0905 Civil Engineering
0913 Mechanical Engineering
Publication Status: Published
Open Access location: http://ac.els-cdn.com/S014211231630411X/1-s2.0-S014211231630411X-main.pdf?_tid=1030c158-e7d5-11e6-a04b-00000aab0f6c&acdnat=1485881476_003abf8e5f3bdb5b7a1e9421f206fd2c
Online Publication Date: 2016-12-05
Appears in Collections:Mechanical Engineering
Faculty of Engineering