Reciprocating Sliding Characteristics of Steel Disc / Bearing Steel Ball in Boundary and Mixed Lubrication

Abstract

Reciprocating tests were performed to clarify effects of frequency and stroke on friction in boundary and mixed lubrication. With increase in stroke under constant frequency in boundary lubrication, coefficient of friction was observed to increase, which, however, turned to decrease with promotion of oxidation. Specific wear rate varied in accordance with changes in friction. In the next stage, to specify respective effects of frequency and stroke on friction, reciprocating tests were continued by changing frequency and stroke under a constant sliding velocity in boundary and mixed lubrication. There were two regimes of changes in friction in boundary lubrication, depending on whether oxidation was promoted or not. In severe sliding conditions where little oxidation was observed, a combination of higher frequency and smaller stroke produced rougher surfaces, resulting in higher friction. With improved lubricating conditions, however, higher frequency promoted oxidation, lowering friction, whereas in mixed lubrication, a combination of lower frequency and larger stroke contributed to oil film formation, which showed lower friction than that at a combination of higher frequency and smaller stroke.