Effect of grease on bearing vibration performance caused by short-time high-temperature exposure

A short-time high-temperature environment is a common working condition in the use of bearings; it can occur as rapid heating before interference assembly of a bearing, or in a quick shutdown due to failure and heating of other parts of equipment. However, the current research mainly focuses on the influence of long-term high temperatures on bearing lubrication. In this paper, the 6204DDU ball bearing with lithium soap/mineral oil (paraffin base type) grease and fatty acid soap/mineral oil (refined white oil) grease (white grease) is investigated. The recovery performance of the two greases after a short-time high temperature is studied. It is found that a large number of fractures occur in the soap fibre of the white grease after 20 min exposure in 140 degrees C temperature environments, while lithium grease remains in a good working condition. The vibration velocity with white grease decreases during a temperature falls from 110 degrees C to the heated balanced temperature, while the vibration velocities with lithium grease is without significant fluctuations. Before and after heating, the vibration velocities in middle frequency band of rolling bearings with lithium grease and white grease increase with the increase in preload, but it is the opposite in the high frequency band except for white grease after heating condition. Infiltration with a small amount of water or oil can greatly affect the performance of white grease. Water can emulsify the white oil and accelerates the oxidation of white grease. The structure of the L-AN32 oil contaminant is different from that of white oil, resulting in uneven dispersion of saponified crystals and obvious flocculent agglomeration is presented.