A theoretical simulation of the behaviour of debris particles in elastohydrodynamic (EHD) contacts is an effective means for obtaining information regarding the life and performance of lubricated machine elements compared with costly experimentation. The present work indicates that debris particles are often responsible for two failure modes: (a) scuffing caused by particle agglomeration in the inlet zone of an EHD contact and (b) local melting due to high heat produced by the friction of debris in sliding contacts. The present predictions are in agreement with experimental evidence in two ways: firstly, in that EHD contacts may fail because of scuffing if the lubricant becomes contaminated, where the failure due to inlet blockage by debris and eventually fluid starvation, and, secondly, in that sliding asperity contacts encounter high flash temperatures which may cause local melting and thus plastic deformations.
The damage caused by debris particles in concentrated contacts has been studied extensively in the past, both theoretically and experimentally. Most of the theoretical studies, in which the damage on the surfaces was calculated in the form of dents, were performed isothermally. It is known that sliding asperity contacts, which resemble third body contacts, reach high local temperatures that can affect local material properties which, in turn, will affect the way damage is generated on the surfaces of machine elements. In the present work the heat transfer of lubricated, rolling/sliding line contacts in the presence of a ductile spherical particle is modeled. The particle is assumed to be significantly softer than the counterfaces that squash it. The local flash temperatures due to the combined sliding and squashing of a debris particle are calculated. It is found that high temperatures caused from small and soft particles are rather the rule than the exception.
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