Evolution characteristics and failure mechanism of aero-engine main shaft bearings under oil cut-off conditions

The oil cut-off resistance of aero-engine main shaft bearings is a critical factor influencing overall aero-engine performance. In this study, we investigated the frictional behaviour and failure mechanisms at the bearing surface interface. During the oil cut-off period, lubrication rapidly shifts from elastohydrodynamic lubrication to boundary lubrication and ultimately dry friction. This promotes differential thermal expansion among components, which initiates three-point contact. Rolling elements shift from micro-sliding to forced sliding, generating extreme temperatures and thermal stresses within raceway contact zones and thereby promoting grain refinement in the raceway surface. Exposure to air accelerates oxidation, increasing surface brittleness and susceptibility to crack initiation. Cracks further propagate into spalling, with small-scale spalling being rolled into the raceway surface, whilst large-scale spalling constitutes the primary mechanism leading to bearing failure. This study elucidated the underlying failure mechanism of aero-engine main shaft bearings under extreme oil deprivation, providing scientific insights for future aero-engine development.