9 documents found, page 1 of 1
Film thickness and friction behaviour of thermally aged lubricating greases
Gonçalves, David; Graça, Beatriz; Campos, Armando José Vilaça; Seabra, J.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 physic...
Friction torque in thrust ball bearings lubricated with polymer greases of diff...
Gonçalves, David; Pinho, Samuel; Graça, Beatriz; Campos, Armando José Vilaça; Seabra, Jorge H.O.In this work a series of experimental tests were performed in thrust ball bearings lubricated with polymer greases. The tested greases were formulated with the same base oil but different thickener content. A multi-purpose lithium thickened grease was also tested as reference. The friction torque was measured at constant temperature and load, while varying the rotational speed. The coefficients of friction under...
On the friction behaviour of polymer greases
Gonçalves, David; Graça, Beatriz; Campos, Armando José Vilaça; Seabra, J.Non-additized batches of lubricating greases were tribologically characterized through traction coeffi-cient 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 tempera-tures while varying the slide-to roll ratio (SRR) or the rolling entrainment speed. The results were corr...
Film thickness in a ball-on-disc contact lubricated with greases, bleed oils an...
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 flood...
Influence of grease rheology on thrust ball bearings friction torque
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 viscositi...
Friction torque in grease lubricated thrust ball bearings
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...
Experimental measuring procedure for the friction torque in rolling bearings
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...
Friction and wear in thrust ball bearings lubricated with biodegradable greases
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 i...
Influence of grease formulation on thrust bearings power loss
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