Role of additive concentration in slow-speed sliding contact under boundary lubrication conditions

Lee, Bora; Yu, Yonghun; Cho, Dae‐Seung; Cho, Yongjoo

doi:10.1007/s12206-019-1029-z

Cited by 3 publications

(4 citation statements)

References 14 publications

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“…F NC was given as , Besides, the particles were also under the action of friction from the substrate which was expressed as where n̅ is the equivalent number of particles arrayed as a line, f is the friction coefficient taking into account the influence of the liquid layer between nanoparticles and the substrate based on the lubrication theory, , and F a is the total adhesive force including gravity, electrostatic force, van der Waals force, and the normal capillary force . Compared with the normal capillary force, the other three forces could be neglected; thus, F a was approximately equal to F NC .…”

Section: Resultsmentioning

confidence: 99%

Evaporative Deposition of Surfactant-Laden Nanofluid Droplets over a Silicon Surface

Yang

Huang

et al. 2022

Langmuir

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Morphologies of evaporative deposition, which has been widely applied in potential fields, were induced by the competition between internal flows inside evaporating droplets. Controlling the pattern of deposition and suppressing the coffeering effect are essential issues of intense interest in the aspects of industrial technologies and scientific applications. Here, evaporative deposition of surfactant-laden nanofluid droplets over silicon was experimentally investigated. A ring-like deposition was formed after complete evaporation of sodium dodecyl sulfate (SDS)-laden nanofluid droplets with an initial SDS concentration ranging from 0 to 1.5 CMC. In the case of initial SDS concentrations above 1.3 CMC, no cracks were observed in the ring-like deposition, indicating that the deposition patterns of nanofluid droplets could be completely changed and cracks could be eliminated by sufficient addition of SDS. With the increase of the initial concentration of hexadecyl trimethylammonium bromide (CTAB), the width of the deposition ring gradually decreased until no ring-like structure was formed. On the contrary, with the increase of the initial Triton X-100 (TX-100) concentration, the width of the deposition ring gradually increased until a uniform deposition was generated. Moreover, when the initial TX-100 concentration was high, a "tree-ring-like" pattern was discovered. Besides, morphologies of evaporative pattern due to the addition of surfacants were qualitatively analyzed.

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Section: Resultsmentioning

confidence: 99%

Evaporative Deposition of Surfactant-Laden Nanofluid Droplets over a Silicon Surface

Yang

Huang

et al. 2022

Langmuir

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“…Due to the thin fluid layer thickness and minimal separation between the opposing surfaces at low sliding speeds, the high COF was believed to be the cause. 60 This was also the cause of the growing wear rate observed from 0 to 60 min, roughly equivalent to a sliding velocity of 0.5 m/s. However, the engine oil with rGO as an additive beat the other two lubricants due to the mending effect, where the additives deposited in the grooves and reduced the coefficient of friction significantly.…”

Section: Tribological Investigationmentioning

confidence: 94%

Synthesis of chemically exfoliated reduced graphene oxide from as-grated graphite rods recovered from used household batteries for utilization in tribological applications

Manokaran

Manikkavasagan

Nesappan

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part L:

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The research objective of this work is to reuse graphite rods recovered from used batteries and utilize them as an additive in SAE20W40 oil to improve the engine parts’ lubrication ability and wear resistance. The graphite rods are grated to obtain ultra-fine particles and then chemically exfoliated using an Improved Hummer's process that results in graphene oxide. Then, it is thermally reduced at 350 °C to yield reduced graphene oxide. Different ratios (0.25, 0.50, 0.75, and 1.00 wt.%) of as-grated graphite particles and reduced graphene oxide were dispersed in the above oil to form a colloidal solution and then used for tribological studies. The graphite particles and synthesized reduced graphene oxide were characterized using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. X-ray diffraction data confirms the presence of graphite, graphene oxide, and reduced graphene oxide in the prepared powders and matches with the standard files. High-resolution transmission electron microscopy images reveal the presence of multilayer sheets with an interplanar distance of 0.34 nm having wrinkles, folds, and gas holes. The G and D band positions of Raman spectra prove the formation of oxygenated functional groups, and the ID/ IG ratio confirms the defects in graphene oxide and reduced graphene oxide. The viscosity of prepared lubricant increases by 35% and 21% for graphite and reduced graphene oxide, respectively. The results of tribological studies with 0.25 wt.% graphite and 0.5 wt.% reduced graphene oxide lubricants showed improvement in coefficient of friction by 32% and 36%, respectively. At these optimal concentrations, the specific wear rate dropped by 51% for reduced graphene oxide. Scanning electron microscopy/energy dispersive spectroscopy, images show that the nanolubricant's mending effect over the worn surface improves reduced graphene oxide added SAE20W40 oil tribological characteristics. From the results, reduced graphene oxide synthesized from as-grated graphite rods proves to be a low-cost, sustainable, and effective friction modifier for engine oils.

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“…In addition to the contact surface, the surface of the wear particles also functions as the adsorption target area. From the mass conservation equation for the additive in the control volume, it was discovered that the gradient of the additive concentration is shown in below using c, the number of moles of additive per unit control volume (Lee et al, 2019).…”

Section: Additive Concentrationmentioning

confidence: 99%

“…where N s ; A w0 and n are total number of adsorption sites per area, surface area of a wear particle and the number of wear particles per unit volume, respectively. The derivation process and the detailed explanation of this equation are described in the author's previous paper (Lee et al, 2019), so here is a brief introduction. The first term on the right side refers to the change of the additive concentration passing through the control volume by the fluid flow; the second and third terms indicate the change due to the contact surface and the wear particle surface, respectively.…”

Section: Additive Concentrationmentioning

confidence: 99%

A scuffing model considering additive depletion in boundary lubrication

Lee

Cho

2019

ILT

Self Cite

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Purpose This paper aims to propose a new scuffing model caused by the depletion of additives in boundary lubrication condition. Design/methodology/approach The differential equation governing the distribution of additive content in the fluid film was used. This formula was derived from the principle of mass conservation of additives considering the consumption due to surface adsorption of wear particles. The occurrence of scuffing was determined by comparing the wear rate of the oxide layer with the oxidation rate. Findings If the additive becomes depleted while sliding, the scuffing failure occurs even at a low-temperature condition below the critical temperature. The critical sliding distance at which scuffing failure occurred was suggested. The experimental data of the existing literature and the theoretical prediction using the proposed model are shown to be in good agreement. Originality/value It is expected to be used in the design of oil supply grooves for sliding bearings operating under extreme conditions or in selecting the minimum initial additive concentration required to avoid scuffing failure under given contact conditions.

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Role of additive concentration in slow-speed sliding contact under boundary lubrication conditions

Cited by 3 publications

References 14 publications

Evaporative Deposition of Surfactant-Laden Nanofluid Droplets over a Silicon Surface

Evaporative Deposition of Surfactant-Laden Nanofluid Droplets over a Silicon Surface

Synthesis of chemically exfoliated reduced graphene oxide from as-grated graphite rods recovered from used household batteries for utilization in tribological applications

A scuffing model considering additive depletion in boundary lubrication

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