Tribological behavior and thermoelastic instability demonstrated in ball-bearing -like specimens operating in dry contacts and with grease lubrication

Abstract Ball-bearing-like specimens are prepared with different groove factors ( GF ) to simulate a ball screw operating in dry contact and grease lubrication. The fluctuations of frictional coefficient μ are identified as instabilities in the running-in process and in the tribo contacts through the model developed for the threshold value μ threshold . The thermoelastic instability in the running-in is dominated by the surface roughness ( R a ) and the GF , and is thus governed by the slip ratio ( SR ). The inception of running-in instability is the earliest when SR is the highest. With a fixed GF , an increase in R a results in a SR rise. Wear coefficient increases by raising SR . The time for instability inception of base material is shortened by increasing SR .