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 f...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, Al2O3) 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.展开更多
In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate th...In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate the main parameters of the hydraulic system under various loads through the use of leakage-simulating throttle valves. After the completion of modeling, the throttle valves that simulate the internal leakages were calibrated and a number of test runs were performed for the cases of normal operation and the operation with increased internal leakages. The theoretical predictions were compared against the experimental results from an actual hydraulic test platform installed in the laboratory. In all cases, modeling and experimental data curves correlate very well in form, magnitude and response times for all the system’s main parameters. This proves that the present modeling can be used to accurately predict various faults in hydraulic systems, and can thus be used for proactive fault finding in many cases, especially when the defective component is not easily detected and obvious at first sight.展开更多
文摘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, Al2O3) 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.
文摘In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate the main parameters of the hydraulic system under various loads through the use of leakage-simulating throttle valves. After the completion of modeling, the throttle valves that simulate the internal leakages were calibrated and a number of test runs were performed for the cases of normal operation and the operation with increased internal leakages. The theoretical predictions were compared against the experimental results from an actual hydraulic test platform installed in the laboratory. In all cases, modeling and experimental data curves correlate very well in form, magnitude and response times for all the system’s main parameters. This proves that the present modeling can be used to accurately predict various faults in hydraulic systems, and can thus be used for proactive fault finding in many cases, especially when the defective component is not easily detected and obvious at first sight.
