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On the Steady-State Flow and Yielding Behaviour of Lubricating Greases

Pro2TecS-Chemical Process and Product Technology Research Center, Universidad de Huelva, Campus El Carmen, 21071 Huelva, Spain
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Received: 6 December 2018 / Revised: 26 December 2018 / Accepted: 4 January 2019 / Published: 9 January 2019
(This article belongs to the Special Issue Advances in Experimental and Computational Rheology)
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Abstract

Practical steady-state flow curves were obtained from different rheological tests and protocols for five lubricating greases, containing thickeners of a rather different nature, i.e., aluminum complex, lithium, lithium complex, and calcium complex soaps and polyurea. The experimental results demonstrated the difficulty to reach “real” steady-state flow conditions for these colloidal suspensions as a consequence of the strong time dependence and marked yielding behavior in a wide range of shear rates, resulting in flow instabilities such as shear banding and fracture. In order to better understand these phenomena, transient flow experiments, at constant shear rates, and creep tests, at constant shear stresses, were also carried out using controlled-strain and controlled-stress rheometers, respectively. The main objective of this work was to study the steady-state flow behaviour of lubricating greases, analyzing how the microstructural characteristics may affect the yielding flow behaviour. View Full-Text
Keywords: lubricating grease; rheology; steady-state and transient flow; microstructure lubricating grease; rheology; steady-state and transient flow; microstructure
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MDPI and ACS Style

Delgado, M.A.; Secouard, S.; Valencia, C.; Franco, J.M. On the Steady-State Flow and Yielding Behaviour of Lubricating Greases. Fluids 2019, 4, 6.

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