On the Steady-State Flow and Yielding Behaviour of Lubricating Greases
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
2.2. Rheological Characterization
2.2.1. Stepped Shear Rate and Shear Stress Ramps
2.2.2. Transient Experiments at Constant Shear Rate
2.2.3. Creep Tests
2.2.4. SAOS Experiments
2.3. Atomic Force Microscopy
3. Results
3.1. Linear Viscoelastic Response and Microstructure
3.2. Stepped-Shear Rate and Stress Ramps: The “Practical” Steady-State Flow Curve
3.3. Transient Flow
3.4. Correction of the “Practical” Steady-State Flow Curve
4. Concluding Remarks
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Soap | Oil Viscosity at 40 °C (cP) | NLGI Grade | Drop Point (°C) |
---|---|---|---|
Aluminum Complex | 130 | 2 | >250 |
Lithium | 150 | 2 | >150 |
Lithium Complex | 160 | 2 | >250 |
Calcium Complex | 150 | 1 | >250 |
Polyurea | 110 | 2 | >240 |
Lubricating Greases | 0.0125 s−1 | 0.1 s−1 | 1 s−1 | |||
---|---|---|---|---|---|---|
S+ | tmax (s) | S+ | tmax (s) | S+ | tmax (s) | |
Aluminum Complex | 0.282 | 74 | 0.321 | 16.8 | 0.439 | 1.91 |
Lithium | 0.172 | 128 | 0.157 | 22.1 | 0.238 | 3.08 |
Lithium complex | 0.392 | 85 | 0.397 | 15.7 | 0.351 | 1.67 |
Calcium complex | 2.946 | 26 | 1.635 | 2.6 | 3.043 | 0.24 |
Polyurea | 0.708 | 52 | 0.890 | 6.8 | 1.477 | 0.65 |
Lubricating Greases | τ0 (Pa) | kH (Pa·sn) | n |
---|---|---|---|
Aluminum Complex | 654 | 232 | 0.28 |
Lithium | 448 | 301 | 0.35 |
Lithium Complex | 626 | 105 | 0.72 |
Calcium Complex | 543 | 40 | 0.15 |
Polyurea | 859 | 47 | 0.20 |
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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. https://doi.org/10.3390/fluids4010006
Delgado MA, Secouard S, Valencia C, Franco JM. On the Steady-State Flow and Yielding Behaviour of Lubricating Greases. Fluids. 2019; 4(1):6. https://doi.org/10.3390/fluids4010006
Chicago/Turabian StyleDelgado, Miguel A., Sebastien Secouard, Concepción Valencia, and José M. Franco. 2019. "On the Steady-State Flow and Yielding Behaviour of Lubricating Greases" Fluids 4, no. 1: 6. https://doi.org/10.3390/fluids4010006
APA StyleDelgado, M. A., Secouard, S., Valencia, C., & Franco, J. M. (2019). On the Steady-State Flow and Yielding Behaviour of Lubricating Greases. Fluids, 4(1), 6. https://doi.org/10.3390/fluids4010006