Rapid Failure of Lubricated Contacts with Grease Under ZEV Condition

Abstract

Abstract In response to the rapid failure of grease lubrication under low surface speed with zero entraining velocity (ZEV), a common occurrence in ball screws or retainerless rolling element bearings, detailed observations were conducted through optical interferometric experiments. It was observed that despite a constant surface speed and load, the motion remained transient due to the transition between outlet cavitation and inlet starvation. The reciprocating motion of the cavitation zone rapidly depleted the contact area, leading to severe surface peeling. However, as the surface speed increased, this phenomenon was alleviated and eventually disappeared. To enhance lubrication performance, bilateral grooves were created using laser technology, proving to be advantageous for grease lubrication life under low surface speed conditions. Despite the occurrence of rapid surface failure, grease lubrication demonstrated clear benefits over oil lubrication when operating at low surface speeds.