Generation of Acoustic Emission from the running-in and subsequent micropitting of a mixed-elastohydrodynamic contact

This paper presents the use of Acoustic Emission to study the running-in and subsequent micropitting of a pair of hardened steel surfaces under mixed lubrication conditions. These surfaces were loaded together under rolling/sliding conditions typical of heavily loaded gearing. Relocation profilometry was used to measure the rapid running-in process and the development of micropits. Acoustic emission (AE) was found to be highly sensitive to both the initial changes in surface topography during the running-in process, and to subsequent changes caused by micropit formation. However, AE appears to be sensitive to changes in asperity interaction rather than the underlying mechanisms of plastic deformation, crack growth and fracture. It is concluded that AE can provide considerable insight into conditions in mixed-elastohydrodynamic contacts.