Browsing by Author "Seabra, Jorge H.O."
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- Friction torque in thrust ball bearings lubricated with polymer greases of different thickener contentPublication . 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 boundary and full film lubrication were numerically calculated through the optimization of a rolling bearing friction torque model to the experimental measurements. The results show that the higher the thickener content, the smaller is the friction torque generated by the lubricating greases, phenomenon which was found to be especially important at low speeds and low specific film thickness.
- Measurement of mean wear coefficient during gear tests under various operating conditionsPublication . Brandão, José A.; Cerqueira, Pedro; Seabra, Jorge H.O.; Castro, ManuelSeven weartestswereconductedonanFZGgeartestingmachineinordertoascertaintheinfluence of basestock(PAOandmineral),specific film thicknessandcontactloadonthewearofspurgears,parti- cularlyonthewearcoefficient κ that isusedinArchard'slaw.Theresultsshowedthatloadmayhave some influence onthewearcoefficient. Theyalsoshowedthattheinfluence ofspecific film thicknesson wear isverynon-linear.Theinfluence ofbasestock,evenwithoilsofsimilarviscosity,isverysignificant, as muchasanyotherparameterinisolation.
- Surface fitting of an involute spur gear tooth flank roughness measurement to its nominal shapePublication . Brandão, José A.; Seabra, Jorge H.O.; Castro, ManuelA method for fitting a topography measured on an involute spur gear tooth flank to its nominal shape is proposed, so that the exact position along the length of the tooth from which the measured surface originates can be determined, and so that the nominal shape of the surface can be subtracted prior to roughness parameters calculation.