Percorrer por autor "Cousseau, Tiago"
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- Experimental measuring procedure for the friction torque in rolling bearingsPublication . Cousseau, Tiago; Graça, Beatriz M.; Campos, Armando José Vilaça; Seabra, JorgeThe reduction of the power loss generated in mechanical transmissions and the use of low friction biodegradable lubricants has been attracting considerable attention in recent times. Therefore, it is necessary to develop methods to test and evaluate the performance of such lubricants and compare them with conventional ones. In this sense, a Four-Ball Machine was modified allowing the test of rolling bearings. A 51107 thrust ball bearing was used to test two different greases and the corresponding base oils. Friction torque and operating temperatures were continuously monitored to quantify the power loss and the heat evacuation for each lubricant tested. Copyright © 2010 John Wiley & Sons, Ltd.
- Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oilsPublication . Cousseau, Tiago; Björling, M.; Graça, Beatriz M.; Campos, Armando José Vilaça; Seabra, Jorge; Larsson, R.Three different lubricating greases and their bleed and base oils were compared in terms of film thickness in a ball-on-disc test rig through optical interferometry. The theoretical values calculated according to Hamrock's equation are in close agreement with the base oil film thickness measurements, which validates the selected experimental methodology. The grease and bleed oil film thickness under fully flooded lubrication conditions presented quite similar behaviour and levels. Therefore, the grease film thickness under full film conditions might be predicted using their bleed oil properties, namely the viscosity and pressure-viscosity coefficient. The base and bleed oil lubricant parameter LP are proportional to the measured film thickness. A relationship between grease and the corresponding bleed oil film thickness was evidenced.
- Friction and wear in thrust ball bearings lubricated with biodegradable greasesPublication . Cousseau, Tiago; Graça, Beatriz M.; Campos, Armando José Vilaça; Seabra, JorgeThrust ball bearings lubricated with several different types of grease, including three biodegradable low-toxicity greases, were tested in a modified four-ball machine in order to evaluate the bearing friction torque. At the end of each test, grease samples were obtained and analysed through ferrography, allowing the quantification and evaluation of the bearing wear. In order to compare the grease performance in terms of friction and wear, a correlation between the grease characteristics (base oil, bleed oil, thickener structure, and rheological parameters) and the experimental results was established.
- Friction torque in grease lubricated thrust ball bearingsPublication . Cousseau, Tiago; Graça, Beatriz M.; Campos, Armando José Vilaça; Seabra, JorgeThrust ball bearings lubricated with several different greases were tested on a modified Four-Ball Machine, where the Four-Ball arrangement was replaced by a bearing assembly. The friction torque and operating temperatures in a thrust ball bearing were measured during the tests. At the end of each test a grease sample was analyzed through ferrographic techniques in order to quantify and evaluate bearing wear. A rolling bearing friction torque model was used and the coefficient of friction in full film lubrication was determined for each grease, depending on the operating conditions. The experimental results obtained showed that grease formulation had a very significant influence on friction torque and operating temperature. The friction torque depends on the viscosity of the grease base oil, on its nature (mineral, ester, PAO, etc.), on the coefficient of friction in full film conditions, but also on the interaction between grease thickener and base oil, which affected contact replenishment and contact starvation, and thus influenced the friction torque.
- Influence of grease formulation on thrust bearings power lossPublication . Cousseau, Tiago; Graça, Beatriz M.; Campos, Armando José Vilaça; Seabra, JorgeThe minimization of the power loss and the use of the biodegradable greases have attracting considerable attention. To compare the energetic performance of biodegradable lubricant greases, power loss tests were performed on a modified four-ball machine. A correlation between the grease formulation and rheology was established with its energetic performance
- Influence of grease rheology on thrust ball bearings friction torquePublication . Cousseau, Tiago; Graça, Beatriz M.; Campos, Armando José Vilaça; Seabra, JorgeThe friction torque and the operating temperatures in a thrust ball bearing were measured for seven different types of greases, including three biodegradable greases having low toxicity. These friction torque tests were performed using a modified Four-Ball machine. Rheological evaluations of the lubricating greases were made using a rheometer. Bleed oils were extracted from the greases and the dynamic viscosities were measured. In order to compare the performance of the lubricant greases in terms of friction, the grease characteristics were related to experimental results, showing that the interaction between thickener and base oil have strong influences in the bearing friction torque.