Effects of debris particles in sliding/rolling elastohydrodynamic contacts

Nikas, George K.; Sayles, R.S.; loannides, E.

doi:10.1243/1350650981542146

Cited by 41 publications

(69 citation statements)

References 7 publications

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“…Dents essentially represent stress concentration sites, which increase the possibilities for the occurrence of spalling, accelerating the failure process [19]. In terms of contaminant particle sizes, Maru et al [20] and Nikas et al [21] state that the critical size of the contaminant particles is in the order of the lubrication film thickness. 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.…”

Section: Theoretical and Experimental Backgroundmentioning

confidence: 99%

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

et al. 2017

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Preliminary communicationAnalysis of the relevant literature has shown that only few researches are dealing with the bearings dynamic behaviour in real environmental conditionswhere high concentration of solid contaminant particles is evident. There is still no established mathematical correlation between bearings vibration characteristics, working time and concentration level of contaminant particles in their grease. Solving this problem was the main goal of research described in this paper. First step was thorough analysis of the chemical composition and structure of contamination particles directly causing the sample bearings failure on open pit coal mines. After that, specific experimental methodology was developed and implemented. Finally, by processing of the experimental results, new mathematical correlation between listed bearings characteristics was determined. Keywords: bearings; conveyor idlers; coal mines; contamination; particles; vibrations Analiza i predviđanje vibracija kotrljajnih kugličnih ležaja kontaminiranih nečistoćama s površinskih kopova ugljaPrethodno priopćenje Analiza relevantne literature pokazuje da se vrlo mali broj istraživača bavi problematikom dinamičkog ponašanja kotrljajnih ležaja u realnim

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Section: Theoretical and Experimental Backgroundmentioning

confidence: 99%

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

et al. 2017

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“…The researches of (Godet, 1984;Nikas et al, 1998) on bearings' wear due to contaminants point to several possible mechanisms of wear. In terms of contaminant sizes (Maru et al, 2007;Dwyer-Joyce, 1999) state that the critical size is in the order of the lubrication film thickness as particles entrapped in the contact zone are causing local oil starvation, increased heating and material melting, while others report 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.…”

Section: Basic Rating Life Of Rolling Element Bearingsmentioning

confidence: 99%

The Adverse Effect of Steel Particle Contaminants on Fatigue Life of Grease Lubricated Ball Bearings

Koulocheris

Raptis

2014

American Journal of Applied Sciences

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The rating life of ball bearings is reduced when hard particle contaminants are present in the lubricant. Usually, this life reduction is taken into account in the calculation of modified rating life by using the contamination factor through a general characterization of the lubrication conditions. However, the impact of contaminant's variables such as size, hardness and concentration level has to be specified in detail. This need is resolved by the present work, where greases contaminated with hard steel particles of different sizes are tested with the purpose of finding a pattern in the relationship between steel particle sizes and the progress of wear inside the bearings. A laboratory rig is utilized for these tests and vibration analysis is performed to estimate the condition and the residual life of the bearings. After the tests, optical inspections performed in a stereoscope verify the predictions of vibration analyses. It was found that large contaminating particles, after their initial deformation, produce high stresses and therefore higher wear of the bearings and that the wear mechanism is closely related to the interruption of the lubricating film in such a way that local overheating caused point melting and adhesion of the particles adhered on the raceways. In case of grease contaminated with steel particles, vibration analysis can indicate the severity of wear and monitor its progress. From the conducted tests of the present work it is proved that the size of the contaminant particles affect strongly the wear process in such a way that the larger steel particle contaminants cause greater damage to the bearing. The vibration levels were higher and the damage was greater as particle size increased. It is difficult to establish an equation that describes and quantifies the wear progress involving all the parameters of size and concentration levels of the steel contaminant particles due to the stochastic nature of the wear mechanisms and therefore presently a statistical approach of the wear and the residual life expectancy seems to be more practical. The collection of a large number of experimental results is underway.

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“…Hard particles plough through and cut away surface material, leading to loss of clearance and rough surfaces accompanied by high friction Accelerated oil oxidation Catalytic surfaces of fresh metal wear debris accelerate oil oxidation, lead to acidity, oil thickening, and sticky fouling deposits The dynamic clearances between moving parts are on the order of 1 lm, which is the same dimension as many hard contaminant particles. Hard particles trapped in rolling contacts indent raceway surfaces creating raised metal shoulders that act as stress risers [85][86][87][88]. The pressure increase around a dent can surpass the normal Hertzian pressure.…”

Section: Contamination-based Tribological Problemsmentioning

confidence: 99%