Mixing rheometry for studying the manufacture of lubricating greases

Franco, J.M.; Delgado, Miguel; Valencia, C.; Sánchez, Manuel Marín; Gallegos, C.

doi:10.1016/j.ces.2004.10.042

Cited by 76 publications

(62 citation statements)

References 29 publications

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“…By comparing these three types of grease, it was found that the aluminum-complex-based grease formed the thickest film, followed by the lithium-based grease, and then the urea-based grease, when the speed was equal to 15 mm/s. It should be noted that these conclusions are valid only for the testing greases considered in this study, since different manufacturing processes can strongly affect the mechanical behavior of lubricating grease [16]. Figure 8 shows the interference images of film thickness at the middle and end areas of the roller lubricated with the aluminum-complex-based grease by using the two profiled rollers.…”

Section: Film Thickness Of Roller's Middle and End Regionsmentioning

confidence: 91%

Experimental investigation of EHD grease lubrication in finite line contacts

et al. 2018

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Abstract:The objective of this study was to investigate the grease-lubricated film-forming mechanisms in the finite line contact and to improve the grease-lubricated finite line contact's film-forming capacity. An elastohydrodynamic lubrication (EHL) test rig with two interferometry microscopes, which could simultaneously monitor two different contact locations in the finite line contact, was constructed in order to study the influences of the grease thickener formulation on the film thickness and lubrication condition. By using the relative light intensity method, the thickness maps of the grease-lubricated film were calculated from the interferometer images captured by the two microscopes. The test results revealed that the grease thickener's formulation had remarkable effects on film formation and the perturbation of film thickness. For the lithium-based grease, the film's thickness near the two ends of the roller was prone to severe perturbation caused by the conglomeration of clumps that were hard to shear. For the aluminum-complex-based grease, the fibers tended to accumulate in the middle of the roller rather than at the two ends. The urea-based grease could be easily sheared into smaller particles. In addition to the straight-line profile rollers, the logarithmic profile rollers were tested and found to effectively enhance the axial grease flow, increase the axial shear stress, and thus shear more fibers into particles within the contact area.

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Section: Film Thickness Of Roller's Middle and End Regionsmentioning

confidence: 91%

Experimental investigation of EHD grease lubrication in finite line contacts

et al. 2018

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“…Afterwards, a controlled cooling ramp was imposed on the grease. Processing details and procedure have been extensively described elsewhere [9,11]. A final homogenisation treatment (rotational speed: 8800 rpm; homogenisation time: 15 min), using a rotor-stator turbine (Ultra Turrax T-50, Ika, Staufen, Germany), was applied at room temperature.…”

Section: Manufacture Of Lithium Lubricating Greasesmentioning

confidence: 99%

Thermorheological behaviour of a lithium lubricating grease

et al. 2006

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Thermal-induced changes in the viscous and viscoelastic responses of lubricating greases have been investigated through different rheological techniques in a temperature range of 0-175°C. Small-amplitude oscillatory shear and viscous flow measurements were carried out on a model conventional lithium lubricating grease prepared by inducing the in situ saponification reaction between 12-hydroxystearic acid and hydrated lithium hydroxide. The linear viscoelasticity functions dramatically decrease above 110°C, but not below this critical temperature, which determines the maximum recommended operating temperature in relation to its durability and resistance under working conditions. Two different regions, below and above this critical temperature, in the plateau modulus versus temperature plot have been detected. From this thermal dependence, a much larger thermal susceptibility of the lubricating grease at temperatures above 110°C is apparent. The thermo-mechanical reversibility of this material has been studied by applying different combined stress-temperature protocols. Regarding the viscous flow, a minimum in the shear stress versus shear rate plots appeared at temperatures above 60°C, more pronounced as temperature increases, resulting from material instabilities. The experimental results obtained have been explained on the basis of the thermo-mechanical degradation of the lubricating grease microstructure.

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“…In general, the design and development of lubricants require ample experience and knowledge to obtain an appropriate behavior for specific applications. In the particular case of lubricating greases, further adequate microstructure and related physical properties must be reached from an appropriate sequence selection of both grease ingredients and manufacturing process [2,3].…”

Section: Introductionmentioning

confidence: 99%

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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Mixing rheometry for studying the manufacture of lubricating greases

Cited by 76 publications

References 29 publications

Experimental investigation of EHD grease lubrication in finite line contacts

Experimental investigation of EHD grease lubrication in finite line contacts

Thermorheological behaviour of a lithium lubricating grease

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

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