Grease Lubrication in Fretting

Abstract

This paper concerns an experimental investigation of fretting behavior using grease lubrication for ball (ball bearing steel) -flat (low alloyed steel) contact. The influences of the imposed displacement amplitude, contact geometry, pressure, and frequency are emphasized. In order to better understand the effect of grease lubrication at the interface, a glass counterface was used to visualize the contact; sliding tests were used to identify the effect of a large displacement amplitude. Dynamic loading analysis, in combination with subsequent metallographic examinations, have shown that fretting damage depends strongly upon fretting conditions and upon grease durability. Lubrication conditions and palliative effect in fretting are discussed. Results have shown an important effect of normal force, displacement amplitude, and frequency of motion on the lubricating effect of grease. The separation of grease into two phases in the contact during friction, creating bubbles, appears to be an important phenomenon.