Abstract Non-additized batches of lubricating greases were subjected to an artificial thermal agi... more Abstract Non-additized batches of lubricating greases were subjected to an artificial thermal aging procedure. The fresh and aged samples were then tribologically characterized through film thickness measurements and Stribeck curves, over a large range of entrainment speeds on a ball-on-disc test rig at different operating temperatures, ensuring fully flooded conditions. The results were analysed at the light of the physical and chemical changes regarding the fresh greases. The film thickness increased for all greases after the thermal aging. The film thickness plateau at low speeds also changed and for certain greases it disappeared under the same range of entrainment speeds. The friction behaviour also changed considerably given the changes to the lubrication regimes for the same speeds.
Abstract Non-additized batches of lubricating greases were tribologically characterized through t... more Abstract Non-additized batches of lubricating greases were tribologically characterized through traction coefficient and Stribeck curves at different operating conditions on a ball-on-disc test rig, ensuring that the contact was fully flooded. The tests were performed at constant load, but different operating temperatures while varying the slide-to roll ratio (SRR) or the rolling entrainment speed. The results were correlated to the greases׳ formulation in terms of base oil viscosity, thickener and/or elastomer content. A relationship between the coefficient of friction (COF) of greases formulated with different thickener content was found and the thickener influence on the COF was addressed.
The film thickness of a ball-on-disc contact lubricated with four greases of different formulatio... more The film thickness of a ball-on-disc contact lubricated with four greases of different formulations was measured under different operating conditions until starvation. Two polymer-thickened greases and two lithium-thickened greases, formulated with base oils of different nature and/or viscosity, were tested. The central film thickness was measured under constant operating conditions (load, temperature, slide-to-roll ratio) varying only the entrainment speed. In a separate test, the film thickness was measured over time with all operating conditions set to constant. Pictures of the film thickness profile across the contact area were also registered. The results were compared with the fully flooded results. The coefficient of friction (COF) was measured in a ball-on-disc contact under equal operating conditions and the results were correlated with the film thickness findings. The different grease formulations and the influence of the operating conditions on the film thickness and COF ...
... é então proposto um algoritmo para a análise numérica de tais contactos. a zona de contacto é... more ... é então proposto um algoritmo para a análise numérica de tais contactos. a zona de contacto é discretizada em elementos de dimensão constante e as equações envolvidas são aplicadas à discretização. no final do capitulo i são apresentados dois exemplos. ...
Taper roller bearings were tested under the same operating conditions, varying the initial amount... more Taper roller bearings were tested under the same operating conditions, varying the initial amount of grease used to lubricate the bearing. Two biodegradable greases and one reference mineral grease were used to study the influence of grease amount on bearing internal friction, wear and grease degradation. The operating bearing temperatures were monitored (grease, raceways, housing and environment) during each test to evaluate the power loss performance of the grease. At the end of each test the used grease was collected for post-testing analysis using oil analysis techniques (Ferrometry and Analytical Ferrography). Optical Microscopy, Scanning Electron Microscopy (SEM) and Energy Dis-persive X-ray (EDX) techniques were used to complement the analysis of the wear particles, to examine the bearing surface morphology and identify their metallurgical composition.
2] Instituto Superior de Engenharia do Instituto Politécnico do Porto-ISEP-IPP-ajc@isep.ipp.pt [3... more 2] Instituto Superior de Engenharia do Instituto Politécnico do Porto-ISEP-IPP-ajc@isep.ipp.pt [3] Faculdade de Engenharia da Universidade do Porto-FEUP-jseabra@fe.up.pt Resumo As crescentes preocupações ambientais vêm conduzindo ao desenvolvimento de uma nova geração de massas lubrificantes, com especial atenção para as biodegradáveis e de baixa toxicidade. Por outro lado, as restrições económi-cas impõem a necessidade de medir a eficiência desta nova geração de massas lubrificantes, das quais o comportamento tribológico ainda está em estudo. Assim, torna-se necessário desenvolver métodos que permitam comparar o desempenho das novas massas lubrificantes com as convencionais. Nesse sentido, modificou-se uma máquina de 4 esferas de modo a ser possível medir o momento de atrito em rolamentos, nomeadamente, rolamentos axiais de esferas, de rolos cónicos e de contacto angular, permitindo velocidades de rotação e cargas axiais até 2500 rpm e 7000 N, respectivamente. Os valores medidos do...
Three different lubricating greases and their bleed-oils and base oils were compared in terms of ... more Three different lubricating greases and their bleed-oils and base oils were compared in terms of film thickness in a ball-on-disc test rig through optical interferometry. Film thickness measurements of all lubricants, under fully flooded conditions,followed EHL equations and showed that lubricating greases and the corresponding bleed-oils had similar film thickness values.Therefore bleed oil properties might be used to predict film thickness in grease lubricated thrust ball bearings. Friction torque measurements of thrust ball bearings were performed in a modified 4-Ball machine under a large range of entrainment speed. The friction torque measurements were used as input in the latest SKF friction torque model in order to predict the rolling and sliding friction torque components. It was assumed, based on the film thickness measurements, that grease lubrication is similar to oil-spot lubrication and it depends on the bleed-oil properties. The results showed that grease formulation h...
ABSTRACT Taper roller bearings were tested under the same operating conditions, varying the initi... more ABSTRACT Taper roller bearings were tested under the same operating conditions, varying the initial amount of grease used to lubricate the bearing. Two biodegradable greases and one reference mineral grease were used to study the influence of grease amount on bearing internal friction, wear and grease degradation. The operating bearing temperatures were monitored (grease, raceways, housing and environment) during each test to evaluate the power loss performance of the grease. At the end of each test the used grease was collected for post-testing analysis using oil analysis techniques (Ferrometry and Analytical Ferrography). Optical Microscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) techniques were used to complement the analysis of the wear particles, to examine the bearing surface morphology and identify their metallurgical composition.
Abstract Non-additized batches of lubricating greases were subjected to an artificial thermal agi... more Abstract Non-additized batches of lubricating greases were subjected to an artificial thermal aging procedure. The fresh and aged samples were then tribologically characterized through film thickness measurements and Stribeck curves, over a large range of entrainment speeds on a ball-on-disc test rig at different operating temperatures, ensuring fully flooded conditions. The results were analysed at the light of the physical and chemical changes regarding the fresh greases. The film thickness increased for all greases after the thermal aging. The film thickness plateau at low speeds also changed and for certain greases it disappeared under the same range of entrainment speeds. The friction behaviour also changed considerably given the changes to the lubrication regimes for the same speeds.
Abstract Non-additized batches of lubricating greases were tribologically characterized through t... more Abstract Non-additized batches of lubricating greases were tribologically characterized through traction coefficient and Stribeck curves at different operating conditions on a ball-on-disc test rig, ensuring that the contact was fully flooded. The tests were performed at constant load, but different operating temperatures while varying the slide-to roll ratio (SRR) or the rolling entrainment speed. The results were correlated to the greases׳ formulation in terms of base oil viscosity, thickener and/or elastomer content. A relationship between the coefficient of friction (COF) of greases formulated with different thickener content was found and the thickener influence on the COF was addressed.
The film thickness of a ball-on-disc contact lubricated with four greases of different formulatio... more The film thickness of a ball-on-disc contact lubricated with four greases of different formulations was measured under different operating conditions until starvation. Two polymer-thickened greases and two lithium-thickened greases, formulated with base oils of different nature and/or viscosity, were tested. The central film thickness was measured under constant operating conditions (load, temperature, slide-to-roll ratio) varying only the entrainment speed. In a separate test, the film thickness was measured over time with all operating conditions set to constant. Pictures of the film thickness profile across the contact area were also registered. The results were compared with the fully flooded results. The coefficient of friction (COF) was measured in a ball-on-disc contact under equal operating conditions and the results were correlated with the film thickness findings. The different grease formulations and the influence of the operating conditions on the film thickness and COF ...
... é então proposto um algoritmo para a análise numérica de tais contactos. a zona de contacto é... more ... é então proposto um algoritmo para a análise numérica de tais contactos. a zona de contacto é discretizada em elementos de dimensão constante e as equações envolvidas são aplicadas à discretização. no final do capitulo i são apresentados dois exemplos. ...
Taper roller bearings were tested under the same operating conditions, varying the initial amount... more Taper roller bearings were tested under the same operating conditions, varying the initial amount of grease used to lubricate the bearing. Two biodegradable greases and one reference mineral grease were used to study the influence of grease amount on bearing internal friction, wear and grease degradation. The operating bearing temperatures were monitored (grease, raceways, housing and environment) during each test to evaluate the power loss performance of the grease. At the end of each test the used grease was collected for post-testing analysis using oil analysis techniques (Ferrometry and Analytical Ferrography). Optical Microscopy, Scanning Electron Microscopy (SEM) and Energy Dis-persive X-ray (EDX) techniques were used to complement the analysis of the wear particles, to examine the bearing surface morphology and identify their metallurgical composition.
2] Instituto Superior de Engenharia do Instituto Politécnico do Porto-ISEP-IPP-ajc@isep.ipp.pt [3... more 2] Instituto Superior de Engenharia do Instituto Politécnico do Porto-ISEP-IPP-ajc@isep.ipp.pt [3] Faculdade de Engenharia da Universidade do Porto-FEUP-jseabra@fe.up.pt Resumo As crescentes preocupações ambientais vêm conduzindo ao desenvolvimento de uma nova geração de massas lubrificantes, com especial atenção para as biodegradáveis e de baixa toxicidade. Por outro lado, as restrições económi-cas impõem a necessidade de medir a eficiência desta nova geração de massas lubrificantes, das quais o comportamento tribológico ainda está em estudo. Assim, torna-se necessário desenvolver métodos que permitam comparar o desempenho das novas massas lubrificantes com as convencionais. Nesse sentido, modificou-se uma máquina de 4 esferas de modo a ser possível medir o momento de atrito em rolamentos, nomeadamente, rolamentos axiais de esferas, de rolos cónicos e de contacto angular, permitindo velocidades de rotação e cargas axiais até 2500 rpm e 7000 N, respectivamente. Os valores medidos do...
Three different lubricating greases and their bleed-oils and base oils were compared in terms of ... more Three different lubricating greases and their bleed-oils and base oils were compared in terms of film thickness in a ball-on-disc test rig through optical interferometry. Film thickness measurements of all lubricants, under fully flooded conditions,followed EHL equations and showed that lubricating greases and the corresponding bleed-oils had similar film thickness values.Therefore bleed oil properties might be used to predict film thickness in grease lubricated thrust ball bearings. Friction torque measurements of thrust ball bearings were performed in a modified 4-Ball machine under a large range of entrainment speed. The friction torque measurements were used as input in the latest SKF friction torque model in order to predict the rolling and sliding friction torque components. It was assumed, based on the film thickness measurements, that grease lubrication is similar to oil-spot lubrication and it depends on the bleed-oil properties. The results showed that grease formulation h...
ABSTRACT Taper roller bearings were tested under the same operating conditions, varying the initi... more ABSTRACT Taper roller bearings were tested under the same operating conditions, varying the initial amount of grease used to lubricate the bearing. Two biodegradable greases and one reference mineral grease were used to study the influence of grease amount on bearing internal friction, wear and grease degradation. The operating bearing temperatures were monitored (grease, raceways, housing and environment) during each test to evaluate the power loss performance of the grease. At the end of each test the used grease was collected for post-testing analysis using oil analysis techniques (Ferrometry and Analytical Ferrography). Optical Microscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) techniques were used to complement the analysis of the wear particles, to examine the bearing surface morphology and identify their metallurgical composition.
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