An Experimental Study on Starved Grease Lubricated Contacts

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 were discussed. The polymer thickened the greases, promoting lower COF and higher film thickness, especially when there is thickener material crossing the contact which happens quite often for these greases.

[1]  Pieter Martin Lugt,et al.  Modern advancements in lubricating grease technology , 2016 .

[3]  Jorge H.O. Seabra,et al.  Formulation, rheology and thermal aging of polymer greases—Part II: Influence of the co-thickener content , 2015 .

[4]  J. Tripp,et al.  On the Chaotic Behavior of Grease Lubrication in Rolling Bearings , 2009 .

[5]  Y. Chiu.  An Analysis and Prediction of Lubricant Film Starvation in Rolling Contact Systems , 1974 .

[6]  A. Lubrecht,et al.  Bearing performance limits with grease lubrication: the interaction of bearing design, operating conditions and grease properties , 2007 .

[7]  Jorge H.O. Seabra,et al.  On the film thickness behaviour of polymer greases at low and high speeds , 2015 .

[8]  Jorge H.O. Seabra,et al.  Friction torque in thrust roller bearings lubricated with greases, their base oils and bleed-oils , 2017 .

[9]  Marcus Björling,et al.  Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils , 2012 .

[10]  Hugh Spikes,et al.  The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts , 1996 .

[11]  Guillermo E. Morales-Espejel,et al.  On the Film Thickness of Grease-Lubricated Contacts at Low Speeds , 2014 .

[12]  Jorge H.O. Seabra,et al.  Friction torque in thrust ball bearings lubricated with polymer greases of different thickener content , 2016 .

[13]  N. Technical.  OPTICAL ANALYSIS OF BALL BEARING STARVATION , 1970 .

[14]  P. Lugt,et al.  Film Thickness of Mechanically Worked Lubricating Grease at Very Low Speeds , 2014 .

[15]  P. Lugt.  A Review on Grease Lubrication in Rolling Bearings , 2009 .

[16]  A. Cameron,et al.  A mechanism of fluid replenishment in elastohydrodynamic contacts , 1976 .

[17]  Hiroyoshi Tanaka,et al.  Experimental study of starvation and flow behavior in grease-lubricated EHD contact , 2015 .

[18]  P. M. Cann,et al.  Thin-film grease lubrication , 1999 .

[19]  Antonius Lubrecht,et al.  Shear-degradation of grease and base oil availability in starved EHL lubrication , 2000 .

[20]  J. Seabra,et al.  Film thickness and friction behaviour of thermally aged lubricating greases , 2016 .

[21]  M Kaneta,et al.  Effects of a thickener structure on grease elastohydrodynamic lubrication films , 2000 .

[22]  Pieter Martin Lugt,et al.  The influence of bearing grease composition on friction in rolling/sliding concentrated contacts , 2016 .

[23]  Fabrice Ville,et al.  Comparative overview of five gear oils in mixed and boundary film lubrication , 2012 .

[24]  Philippa Cann,et al.  Starvation and Reflow in a Grease-Lubricated Elastohydrodynamic Contact , 1996 .

[25]  Jorge H.O. Seabra,et al.  On the friction behaviour of polymer greases , 2016 .

[26]  P. Lugt,et al.  Prediction of film thickness decay in starved elasto-hydrodynamically lubricated contacts using a thin layer flow model , 2009 .

[27]  Jorge H.O. Seabra,et al.  Formulation, rheology and thermal ageing of polymer greases—Part I: Influence of the thickener content , 2015 .

[28]  P. Cann.  Grease lubrication of rolling element bearings — role of the grease thickener , 2007 .

[29]  Henrik Åström,et al.  Lubricating Grease Replenishment in an Elastohydrodynamic Point Contact , 1993 .

[30]  Pieter Martin Lugt,et al.  Grease Lubrication in Rolling Bearings , 2013 .

[31]  J. A. Greenwood,et al.  Elastohydrodynamic Lubrication With Herschel-Bulkley Model Greases , 1972 .