Abstract
The combined effect of boundary layer formation and surface smoothing on friction and wear rate of metallic surfaces under lubricated point contact condition was investigated. The double trend of friction coefficient variations was revealed during running-in and sub-running-in processes. The evolution of surface topography was measured on-site using white-light interference profilometer and analyzed using bearing area curves. Comprehensive theoretical equations that explicitly express the contributions of boundary friction, adhesive friction and wear have been derived, and results obtained by these equations were compared with experimental observations. It is concluded that the theoretical models are quantitatively adequate to describe the combined effect of surface smoothing due to mechanical wear and formation of boundary films on the changes in friction and wear rate during normal running-in processes.
Highlights
Changes in friction and wear during most machine operations typically occur immediately after the onset of sliding in the interface between contacting fresh dry or lubricated solid surfaces
Based on the common knowledge regarding the running-in process, such gradual decrease in coefficient of friction (COF) values is attributed to the extensive mechanical wear and/or plastic deformation of asperities that leads to http://friction.tsinghuajournals.com∣www.Springer.com/journal/40544 | Friction a gradual increase of real contact area and decrease of asperity contact pressure to generate adsorbed boundary layer at asperity contact regions
The COF peak values in the start-stop test are caused by the destruction of adsorbed boundary layer owing to the frequent cleaning at every stop between tests, and the sub-running-in leads to re-formation of the adsorption boundary lubrication layer
Summary
Changes in friction and wear during most machine operations typically occur immediately after the onset of sliding in the interface between contacting fresh dry or lubricated solid surfaces. The change is apparently associated with the transitions of microscopic contact and lubrication states arisen during sliding process. The initial transition is known as “running-in” or “break-in” process that occurs under nonzero normal force and relative sliding [1]. Most of the previous studies conducted on the friction and wear behavior of materials overlooked the initial transitional stage in machine operations while focused on the steady phase that follows the running-in process. Blau [2] highlighted that owing to ignoring the running-in aspects of sliding, researchers overlooked important clues associated to the evolution of conjoint process that later affects the long-term machine operation. Better understanding of the running-in process is essential for efficient machine operations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
