An energy-based approach to understand the effect of fretting displacement amplitude on grease-lubricated interface

Grease lubricants are extensively used in contacts, usually to reduce friction and wear. Under small amplitude sliding, however, as in rolling systems subject to vibration, there is significant lubricant decay. The present study analyses the fretting sliding response of two grease lubricants subjected to small (i.e. partial slip) and large displacement amplitude (i.e. gross slip fretting). Tribological behavior and associated wear volume were investigated as a function of displacement amplitude. The investigation confirmed that, below a threshold displacement amplitude, scarce lubrication induced significant wear activation, while, above threshold, low friction and a low wear response were observed. A new effective friction energy wear concept is introduced to quantify wear rate whatever the fretting sliding condition.