Analysis of grease lubrication of a ball bearing using acoustic emission measurement

Abstract

The behaviour of grease lubrication in a rolling bearing is less known than that of oil in the same type of tribological system. In recent years the research of grease lubrication has shown several features of the grease lubrication that differ from the classical elastohydrodynamic lubrication theory of oil lubrication, notably that starvation is more prominent under grease-lubricated conditions. The goal of the present investigation was to clarify, by using a real bearing installation and realistic running conditions, how the fundamental properties of the lubricating grease influence the lubrication in a rolling bearing. The fundamental properties of the greases considered in the study were thickener concentration, base oil viscosity, base oil bleeding rate and consistency. Results obtained with grease lubrication were verified with pure oil lubrication. The analysis of grease lubrication in the present investigation is based on the relative differences in the pulse count rate of the acoustic emission (AE) generated by the running of the bearing. In order to make the correct decisions about the lubrication situation of a bearing, the fundamentals of the behaviour of grease lubrication in rolling bearings and its influence on the AE signal have to be known. Moreover, AE has proven to be a good tool to study grease lubrication in situ in a bearing. The results show that starvation of the lubrication situation increases with increasing thickener content and decreases with lowered base oil viscosity. This is in agreement with film thickness measurements made in ball-and-disc type equipment.

Microbubble Phenomenon in the Grease Lubricating Film Induced by Micro-Oscillation

“…A significant body of experimental and theoretical work has so far been conducted on understanding the underlying mechanisms and exploring the relevant applications of grease lubrication [1][2][3][4]. The results of such studies have led to many different views on grease lubricant [5][6][7][8][9][10][11][12][13][14]. Cann and colleagues [5,6] investigated grease lubrication under fully flooded and lubricant-starved conditions under a rolling contact using a ball-on-plate optical interferometry.…”

“…Larsson et al [10] traced individual grease thickener particles (lumps) as they passed through the elastohydrodynamics lubrication contact using a ballon-plate optical interferometry under pure rolling motion. Miettinen et al clarified how contaminants in the grease [11] and running parts [12] influence the acoustic emission (AE) of the rolling bearing based on measurements of the AE. Mota and Ferreira [13] investigated the influence of grease composition on wear using a twin-disc machine under pure rolling conditions, and Cousseau et al [14] compared three different lubricating greases and their bleed and base oils using ball-on-plate optical interferometry.…”

Monitoring of Lubricant Film Failure in a Ball Bearing Using Ultrasound

“…Recent years have seen a number of workers utilise a range of novel non-destructive techniques to aid the early measurement of bearing failure and diagnose its cause. For example, Miettinen et al [4,5] used acoustic emissions to monitor rolling bearings. The concept being that any ball-raceway contact and production of wear debris produce high frequency sound.…”

Condition monitoring studies on spindle bearing of a lathe

“…Earlier work by other manufacturing researchers has been reported for condition monitoring of cutting tools using acoustic emission signals [17,18]. Modem techniques for bearing diagnosis [19][20][21][22][23], although usually developed for other sytems, are directly applicable to machine tools.…”