Some Aspects of Grease Flow in Lubrication Systems and Friction Nodes

Paszkowski, Maciej

doi:10.5772/55929

Cited by 9 publications

(8 citation statements)

References 48 publications

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“…the soap thickener can be observed in both AFM and SEM analysis. Thus, the microstructure of samples C1 and C4 consist of fine, small and slightly entangled and twisted fibres as previously described [13,32], whereas a granular and/or sponge-like thickener microstructure was detected in both AFM and SEM micrographs for samples C2 and C3, when the thickener was dispersed in vegetable-derived oils. However, a certain degree of crosslinked structures can be distinguished for sample C2 in the SEM image taken at the highest magnification (Figure 2).…”

Section: Comparison Between Afm and Sem Imaging Of Lubricating Greasementioning

confidence: 74%

AFM and SEM Assessment of Lubricating Grease Microstructures: Influence of Sample Preparation Protocol, Frictional Working Conditions and Composition

2016

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The microstructure of lubricating greases greatly conditions their in-service performance. In that sense, optimal testing protocols are required in order to accomplish their correct morphological characterization. This study explores and compares the suitability of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) techniques for imaging six different commercial metallic soap-based greases and two novel biopolymer-based formulations. Pros and cons of both techniques as well as the effect of sample preparation protocol were analyzed. The results revealed a wide variety of morphological characteristics depending on composition. Thus, the four anhydrous calcium-based greases demonstrated two clearly distinct microstructures (fibrous and granular) determined by the type of base oil employed. With regard to the lithium complex greases, the typically reported microstructure characterized by welldefined entangled and fibrous network was observed in both AFM and SEM techniques.As for the two biopolymer-based greases, fiber networks were also encountered.Besides this, selected greases were subjected to different tribological tests, and the effect of high-shear frictional working treatments on their microstructure was also analyzed. As a result of the friction and internal wear, the AFM results evidenced microstructural changes which depended on grease composition. Overall, the combined use of AFM and SEM techniques was demonstrated to be a powerful approach to microstructurally characterize lubricating greases.

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Section: Comparison Between Afm and Sem Imaging Of Lubricating Greasementioning

confidence: 74%

AFM and SEM Assessment of Lubricating Grease Microstructures: Influence of Sample Preparation Protocol, Frictional Working Conditions and Composition

2016

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“…At this point, the microstructure begins to break apart. This releases, or 'bleeds', the base liquid onto the interface causing the viscosity to reduce rapidly until a minimum viscosity is reached [41]. This process is effectively showcased in Figure 4.…”

Section: Viscous Response To Shearmentioning

confidence: 97%

“…These results suggest that besides simple adhesions between base liquids and particles, other factors, such as base liquid chemical structure, have on these viscoelastic properties. Greases with higher moduli intersection generally have a stronger microstructure [41]. Table 2 therefore indicates that [BMIM][TFSI] based greases have the strongest microstructure, followed by mineral oil based greases, and [P 6,6,6,14 ][TFSI] based greases the weakest microstructure.…”

Section: Strain Sweepmentioning

confidence: 98%

“…The intersection of the steeply decreasing storage modulus with the loss modulus as strain increases is determined to be the point at which the grease microstructure has broken down. Physically, this represents the transition from a solid-like to a liquid-like state [41]. The critical strain, the average tan(δ) in the LVR region and the moduli intersection for each of the greases are presented in Table 2.…”

Section: Strain Sweepmentioning

confidence: 99%

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Ionic Liquids as Grease Base Liquids

Mozes

Cooper

2017

Lubricants

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Abstract:The rheological characteristics of one mineral oil and two ionic liquid (IL) based lubricating greases were explored as a function of thickener concentration. The ILs used are 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P 6,6,6,14 ][TFSI]), with polytetrafluoroethylene (PTFE) particles used as thickeners. Greases with different base liquid concentrations (60-80 wt %) were investigated using small-amplitude oscillatory shear and viscous flow measurements, and contact angle measurements probed adhesion at base liquid-PTFE interfaces. Rheological properties are influenced by base liquid-PTFE adhesion and the chemical structure of the grease base liquids. With the addition of thickener, the greases generally have higher elasticity, strain resistance, and frequency independent properties. Viscometric rheological tests illustrate non-Newtonian shear-thinning behaviour for all greases. [BMIM][TFSI] based greases show the most elastic properties and strain resistance, as well as the highest initial and lowest final viscosities of the greases tested.

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“…The research results reported by many researchers show that greases form a boundary layer which is from ten nanometers to ten micrometers thick. An extensive survey of the literature on the subject can be found in, for example, [1][2][3][4][5][6]. The boundary layer is the result of the grouping of the grease's ensembles of thickener particles on the surface of the material being lubricated.…”

Section: Introductionmentioning

confidence: 99%

Studies of the Influence of Temperature and the Energy State of the Surface Layer of Adsorbents on Wall Effects in Soap-Based Greases

2016

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This paper presents the results of studies of wall effects in commercial soap-based greases LT4-S2 and HUTPLEX EP-2, thickened with, respectively, lithium 12-hydroxystearate and overbased calcium sulfonate. The studies were conducted in the presence of five different materials: copper alloy C11000, bronze B476, EPDM rubber and PTFE and PU thermoplastics. The influence of the energy state of the surface layer of the adsorbents and temperature (ranging from -20 to 60°C) on the intensity of wall effects was investigated. Changes in the structural viscosity and shear stress in the boundary layer area in the greases and the soap-based thickener's ability to adsorb on the surfaces of the adsorbents were determined by evaluating the rheological parameter plateau modulus.

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Some Aspects of Grease Flow in Lubrication Systems and Friction Nodes

Cited by 9 publications

References 48 publications

AFM and SEM Assessment of Lubricating Grease Microstructures: Influence of Sample Preparation Protocol, Frictional Working Conditions and Composition

AFM and SEM Assessment of Lubricating Grease Microstructures: Influence of Sample Preparation Protocol, Frictional Working Conditions and Composition

Ionic Liquids as Grease Base Liquids

Studies of the Influence of Temperature and the Energy State of the Surface Layer of Adsorbents on Wall Effects in Soap-Based Greases

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