Numerical simulation of non-colloidal suspension flows in a parallel-plate geometry

Rosso, Nezia de; Negrão, Cezar Otaviano Ribeiro

doi:10.1007/s00397-021-01314-z

Cited by 3 publications

(3 citation statements)

References 71 publications

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“…In the present study (Figure 3a), the pseudoplastic behavior was observed at deformation rates < 1 s −1 , which is of limited relevance since the main engine and crankshaft elements operate at rates of 10 4 s −1 . This shear thinning behavior (Figure 3a) may be associated with the findings of De Rosso and Negrão [29] regarding non-colloidal suspensions studied via parallel plate rheometry. According to the authors [29], non-Newtonian behaviors result from a combination of inertial and gravitational effects that affect the particle distribution on the rheometer plates, leading to reduced shear resistance.…”

Section: Rheological Propertiessupporting

confidence: 83%

“…This shear thinning behavior (Figure 3a) may be associated with the findings of De Rosso and Negrão [29] regarding non-colloidal suspensions studied via parallel plate rheometry. According to the authors [29], non-Newtonian behaviors result from a combination of inertial and gravitational effects that affect the particle distribution on the rheometer plates, leading to reduced shear resistance. Another hypothesis relates to the alignment or disentanglement of long polymer chains during rheological measurements at low shear rates [27].…”

Section: Rheological Propertiessupporting

confidence: 83%

“…It is worth noting that viscosity values for low shear rates are of lesser interest since the lubricated elements in the engine operate at very high shear rates [26][27][28]. Moreover, undesired outputs due to wall slip are common in the low shear zone [26,29]. Therefore, the average of the viscosity values obtained from both geometries in the Newtonian regime was calculated, and the results are summarized in Figure 3b.…”

Section: Rheological Propertiesmentioning

confidence: 99%

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Metal conditioners (MC) are added to lubricants to enhance their friction and wear in friction pairs, mainly in engines, gearboxes, and rolling bearings. Its growth in the Brazilian market is primarily focused on internal combustion engines. The effect of mixing MC with commercial engine oil (SAE 5W-30 API SN) was studied regarding the rheological and thermal properties. Also, the tribological performance of steel–steel contact was investigated. The rheological and thermal properties were determined by flow curves (at 20, 40, and 100 °C) and differential scanning calorimetry (DSC), respectively. Reciprocating fully-lubricated tests were performed at 40 °C and 80 °C (Po = 1.7 GPa, 5 Hz). Differences in the chemical composition between SAE 5W-30 and its mixture with MC were identified by infrared spectroscopy and related to their tribological performance. The coefficient of friction remained within the range of 0.09–0.1 for all conditions, typical of lubricated steel–steel contacts under boundary and mixed lubrication regimes. However, the mixture improved the wear resistance by around 33% when lubricated at 80 °C compared to the wear resistance offered by 5W-30. The formation of tribofilms with different chemical compositions was confirmed by SEM-EDS for all conditions. At both temperatures, the tribological performance reveals beneficial synergy between the metal conditioner and fully formulated oil additives. The tests lubricated with the mixture at 40 °C showed a less severe wear mechanism when compared to the tests lubricated with neat 5W-30. The study demonstrated that the mixture maintained the physicochemical properties of the commercial oil with a substantial anti-wear action at 80 °C.

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Section: Rheological Propertiessupporting

confidence: 83%

Section: Rheological Propertiessupporting

confidence: 83%

Section: Rheological Propertiesmentioning

confidence: 99%

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Limits for safe viscosity measurement of non-colloidal suspensions in rotational rheometry—a numerical simulation-based approach

de Rosso,

Negrão

2024

Rheol Acta

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Discrepancies in dynamic yield stress measurements of cement pastes

Dhar,

Liberto,

Barentin

et al. 2024

Rheol Acta

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The dynamic yield stress associated with the flow cessation of cement pastes is measured using a rheometer equipped with various shear geometries such as vane, helical, sandblasted co-axial cylinders, and serrated parallel plates, as well as with the mini-cone spread test. Discrepancies in yield stress values are observed for cement pastes at various volume fractions, with one to two orders of magnitude difference between vane, helical and mini-cone spread measurements on the one hand, and co-axial cylinder and parallel plate measurements on the other hand. To understand this discrepancy, the flow profile of a cement paste in the parallel-plate geometry is investigated with a high-speed camera, revealing the rapid formation of an un-sheared band near the static bottom plate. The width of this band depends upon the rotational velocity of the top plate, and upon the shear time. Recalculation of shear stress shows that the reduced sheared gap alone cannot explain the low measured yield stress. Further exploration suggests the formation of zones with lower particle content, possibly linked to cement particle sedimentation. Here, we argue that the complex nature of cement pastes, composed of negatively buoyant non-Brownian particles with attractive interactions due to highly charged nano-size hydration products, accounts for their complex rheological behavior. Graphical abstract

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Numerical simulation of non-colloidal suspension flows in a parallel-plate geometry

Cited by 3 publications

References 71 publications

Effect of a Metal Conditioner on the Physicochemical Properties and Tribological Performance of the Engine Oil SAE 5W-30 API SN

Effect of a Metal Conditioner on the Physicochemical Properties and Tribological Performance of the Engine Oil SAE 5W-30 API SN

Limits for safe viscosity measurement of non-colloidal suspensions in rotational rheometry—a numerical simulation-based approach

Discrepancies in dynamic yield stress measurements of cement pastes

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