Comparative Study of the Impact of Corundum Particle Contaminants Size on Wear and Fatigue Life of Grease Lubricated Ball Bearings

Abstract

Ball bearings' rating life is reduced with the presence of hard particle contaminants in the lubricant. This life reduction is taken into account when calculating the modified rating life by using the contamination factor. The contamination factor is based on a general characterization of the lubrication conditions but the impact of contaminant's variables such as size, hardness and concentration level is not determined in detail. In this work, greases contaminated with hard corundum (alumina, Al 2 O 3) particles of different sizes are tested aiming at finding a pattern in the relationship between particle sizes' and wear's progress. A laboratory rig is utilized for these tests and vibration analysis tools regarding bearings' condition and estimated residual life are being assessed. After the tests, optical inspections using a stereoscope verify the vibration analyses results. The experimental results show that wear is progressing faster when smaller particles are used. The crystalline structure of the corundum and the different degree of brittleness of the contaminants seem to be the reasons for this behavior, whereas severe abrasion and deformation of the raceways have been detected.

Criteria Justification for Assessing the Technical Condition of Gearboxes of Mining Machines Based on Infrared Thermography

“…At the same time as it is shown in the work [11], the greatest damage to the raceways can be caused by small solid particles smaller than 68 microns. During a single sample probation such particles do not always appear, and thus the spectral analysis can't define them.…”

Analysis and prediction of vibrations of ball bearings contaminated by open pit coal mine debris particles

“…However, other authors claim that when particles larger than the oil film thickness enter the contact zone, they cause stress peaks and permanent indentations in the raceway as they are over rolled. These stress peaks lead to a reduced life of the rolling bearing due to fatigue [9].…”

“…Koulocheris et al [9] performed experiments with three types of ball bearings (1207, 2207 and YSA -bore diameter: 35 mm) whose grease was contaminated by hard corundum particles (alumina, Al2O3, hardness 2000HV) with sizes of 62-73 µm and 105-177 µm, where a quantity of 0,75 cm 3 of particles were premixed with 50 g of clean SKF LGMT3 grease. Their goal was to find a pattern in the relationship between contamination particle sizes and wear progress, using vibrations analysis tools.…”

“…Also, the basic dynamic radial C r and axial C a load are used in conjunction with the dynamic equivalent radial P r or axial P a load [9].…”

Data-driven imbalance and hard particle detection in rotating machinery using infrared thermal imaging

“…These particles can consist of steel fragments, sand or any other type of residue and can damage the REB and reduce the rotating machine's operational lifetime significantly. Hence, most of the largest REB manufacturers state that lubricant contamination is the major cause of REB failure before they reach their rated life [4].…”