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Journal articles on the topic 'Greasers'
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1
Wang, Yanshuang, Pu Zhang, Jianghai Lin, and Xudong Gao. "Rheological and Tribological Properties of Lithium Grease and Polyurea Grease with Different Consistencies." Coatings 12, no. 4 (April 13, 2022): 527. http://dx.doi.org/10.3390/coatings12040527.
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The rheological properties of lithium grease and polyurea grease at different temperatures and consistencies were determined with a rotary rheometer. The plateau moduli of the greases were calculated, and the mechanism of influence of consistency and temperature on the rheological properties of the greases was explained. The tribological and wear properties of the two greases were measured by high-temperature friction and wear tester. The friction and wear mechanisms are probed by the rheological properties of lubricating grease. The results show that the plateau modulus GN can be used to assess the structural strength of different greases, but it can only assess the degree of entanglement of the same grease. The higher the consistency of the grease, the larger the apparent viscosity, structural strength, and yield stress. The rheological properties of PAO-polyurea grease are greatly affected by temperature, but its structural strength is better than that of mineral oil-lithium grease. The consistency of mineral oil-lithium grease is expected to affect the friction coefficient and wear through its influence on the grease’s structural strength and film-forming ability. For PAO-polyurea, the consistency in a certain range has little effect on the friction coefficient and wear resistance.
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Farcas, Flavian, and Mihail Catalin Tiron. "Rolling Bearings Greases Deterioration: Structure, Chemical Composition, Rheology, Service Life Correlations." Applied Mechanics and Materials 658 (October 2014): 311–16. http://dx.doi.org/10.4028/www.scientific.net/amm.658.311.
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Grease lubrication for ball or roller bearings became a daily practice in technical applications (over than 80% of bearings assemblies can be greased lubricated) because of its advantages in avoiding the sophisticated circulation or cooling systems.In the same time, all the researches that were developed in this field are lack in informations regarding the forming and the deterioration of grease lubricated contacts.The global results of the researches on the lubricating greases are presented. The tests were done in different functioning conditions and media and for greases analyses chemical and imagistic methods were performed. The discovered correlations are very useful in obtaining as long as possible greased rolling bearings service life.
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Salmon, Roberto Mario, and Arnoldo De Leon. "They Called Them Greasers: Anglo Attitudes toward Mexicans in Texas, 1821-1900." History Teacher 18, no. 3 (May 1985): 471. http://dx.doi.org/10.2307/493089.
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Sanchez Garrido, Daniel, Samuel Leventini, and Ashlie Martini. "Effect of Temperature and Surface Roughness on the Tribological Behavior of Electric Motor Greases for Hybrid Bearing Materials." Lubricants 9, no. 6 (May 24, 2021): 59. http://dx.doi.org/10.3390/lubricants9060059.
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Greased bearings in electric motors (EMs) are subject to a wide range of operational requirements and corresponding micro-environments. Consequently, greases must function effectively in these conditions. Here, the tribological performance of four market-available EM greases was characterized by measuring friction and wear of silicon nitride sliding on hardened 52100 steel. The EM greases evaluated had similar viscosity grades but different combinations of polyurea or lithium thickener with mineral or synthetic base oil. Measurements were performed at a range of temperature and surface roughness conditions to capture behavior in multiple lubrication regimes. Results enabled direct comparison of market-available products across different application-relevant metrics, and the analysis methods developed can be used as a baseline for future studies of EM grease performance.
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Alexander, Donna Maria. "Greasers, Gringos and Wetbacks: Ventriloquizing the U.S.–Mexico Borderlands in Gloria Anzaldúa’s Dramatic Monologues." Forum for Modern Language Studies 54, no. 4 (October 1, 2018): 379–99. http://dx.doi.org/10.1093/fmls/cqy063.
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Zhang, Pei Lin, Guo Gang Wang, Yue Ju Zhao, Hao Wu, and Yan Qiu Xia. "Study of Conductive and Friction Properties of Grease Containing Carbon Black Additive." Advanced Materials Research 1120-1121 (July 2015): 586–89. http://dx.doi.org/10.4028/www.scientific.net/amr.1120-1121.586.
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The conductive and fiction properties of overbased calcium sulfonate complex grease and lithium grease containing carbon black (CB) additive were investigated in detail. The results indicate that CB can dramatically improve the conductivities of the greases. Also the tribol-test results indicate that the CB can dramatically improve the tribological properties of the greases. The lithium greases containing CB, have better tribological properties than overbased calcium sulfonate complex greases. Among the lithium greases, 5% CB contained grease performs the best friction reduction properties, and among the overbased calcium sulfonate complex greases, 6% CB contained grease performs the best friction reduction properties.
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Senatore, Adolfo, Haiping Hong, Veronica D’Urso, and Hammad Younes. "Tribological Behavior of Novel CNTs-Based Lubricant Grease in Steady-State and Fretting Sliding Conditions." Lubricants 9, no. 11 (October 29, 2021): 107. http://dx.doi.org/10.3390/lubricants9110107.
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The tribological behavior of novel 7.5 wt% carbon nanotube-based lubricant greases in PAO (polyalphaolefin) oil with and without 1.0 wt% MoS2, together with several other commercial greases such as calcium, lithium, were studied. The test results showed a marked reduction of frictional coefficient achieved by the CNTs based grease samples with an average benefit of around 30% compared to conventional greases. The steady state test under 1.00 GPa average contact pressure in a mixed lubrication regime and the fretting test showed the best results in terms of friction reduction obtained by CNTs greases. Steady state tests at higher average contact pressure of 1.67 GPa proved to have a lower friction coefficient for CNTs grease containing MoS2; otherwise CNTs grease without MoS2 showed an average value of CoF comparable to calcium and lithium greases, both in a boundary and a mixed regime. The protection against wear, a considerable decrease (−60%) of reference parameter was measured with CNTs grease with MoS2 (NLGI 2) in comparison with the worst conventional grease and −22% in comparison with the best conventional grease. The data indicated that our novel carbon nanotube greases show superior tribological properties and will have promising applications in the corresponding industry.
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KOWALEWSKI, Piotr, and Maciej PASZKOWSKI. "THE INFLUENCE OF KINEMATIC CONDITION AND LUBRICANT PROPERTIES ON FRICTION IN COMPLEX SLIDE–ROLL MOTION." Tribologia 289, no. 1 (March 31, 2020): 41–48. http://dx.doi.org/10.5604/01.3001.0014.0842.
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The paper presents the results of preliminary studies into the influence of selected lubricants (greases) and the variable temperature of the friction joint on the value of friction during complex slide-roll motion. The experiment was carried out for three different types of lubricants: bentonite grease (Benterm 2), lithium grease (GREASEN ŁT4S2), and calcium grease with the addition of graphite (GREASEN GRAFIT) at different temperatures. Tribological investigations were carried out in a roller-plate system at a wide range of plate dislocation velocities and at a constant slip rate; rheological investigations consisted in determining the changes in shear stress as a function of shear time at constant average shear velocity of 50 mm/s. The results showed a significant influence of kinematic conditions on the value of friction. Four different cases of lubricant flow during friction were identified. The least resistance to motion was found when the lubricant was applied in the same direction along the surface of the roller and plate. It has been shown that the greatest influence of the kinematics of working elements on friction occurs at low temperatures, i.e. at -10°C. This phenomenon is closely related to the rheological properties of the lubricant. It was also found that the lubricant thickened with bentonite is the most susceptible to kinematic changes of the friction joint.
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Padgurskas, Juozas, Raimundas Rukuiža, Arturas Kupcinskas, and Raimondas Kreivaitis. "Lubrication properties of modified lard and rapeseed oil greases with sodium and lithium thickeners." Industrial Lubrication and Tribology 67, no. 6 (September 14, 2015): 557–63. http://dx.doi.org/10.1108/ilt-12-2014-0140.
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Purpose – The purpose of this paper is to conduct research on the possibility of improving the tribological and utilization properties of lard and rapeseed oil bio-based greases by mixing it with ethanol and selection of thickener and modification with special biological additives. Design/methodology/approach – Rapeseed oil- and lard-based greases with sodium and lithium soap thickeners were mixed with either water or ethanol and modified with a special biological anti-wear additive. Tribological properties of modified lubricants evaluated on a four-ball machine. Findings – Rapeseed oil- and lard-based greases suspended in ethanol and modified with bio-additive have the same wear resistance as the industrial non-biological lubrication grease and much higher wear resistance as bio-based reference grease. The tribological efficiency of the additives is higher in greases of rapeseed oil and less efficient in lard-based greases. Oxidation and wear tests show that investigated bio-based greases have comparatively stable tribological properties also after their aging. Modified greases have sufficient consistence according penetration measurements and high thermal resistance according drop-point temperature measurements. All produced experimental greases pass within the category of the easily degradable materials. Originality/value – The greases mixed with the ethanol make possible to form more homogeneous and stable grease mixture. Modified bio-based greases have significantly higher wear resistance as bio-based reference grease, their lubrication properties are stable also after the aging and are categorized as easily degradable materials.
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Skibińska, Agnieszka. "Stabilność termooksydacyjna smarów plastycznych." Nafta-Gaz 77, no. 7 (July 2021): 471–79. http://dx.doi.org/10.18668/ng.2021.07.06.
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This review article deals with a particular property of lubricating greases – resistance to oxidation. This property, also referred to as oxidative or thermal oxidation stability, has a decisive influence on the quality and duration of lubricating greases service life in friction nodes, bearings and lubrication systems. Lubricating greases are colloidal systems in which the thickener creates an elastic three-dimensional network, maintaining the liquid phase. The structure of lubricating greases, division of greases into types, depending on the thickener used, is presented. The basic additives in lubricating greases are described, and the group of used antioxidant additives is discussed in detail. Under operating conditions, the grease is subject to factors that cause its destruction – shear stress, pressure, loads, changing operating conditions, especially temperature changes. The types of lubricating greases degradation are presented, as well as methods and techniques of aging processes evaluation. During operation, the grease fulfilling its basic functions in the lubrication system is primarily exposed to high temperatures. The predominant aging process which directly affects the service life of the grease is oxidation. The oxidation process is discussed, with the specification of its four stages: initiation, propagation, chain branching and termination. One of the methods of preventing the oxidation process is the selection of appropriate improvers. Thermal oxidation stability of greases can be modified by introducing appropriate antioxidants, the selection of which depends on the type of grease thickener and the operating temperature of the grease. The published literature review from over the last ten years shows how diverse are the ways of modifying thermal oxidation stability of greases and the methods of assessing this property.
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Frank, Dana. "White Working-Class Women and the Race Question." International Labor and Working-Class History 54 (1998): 80–102. http://dx.doi.org/10.1017/s0147547900006220.
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In Towards the Abolition of Whiteness David Roediger tells the story of Covington Hall, the editor of a newsletter published by the Brotherhood of Timber Workers in Louisiana in 1913 and 1914. Roediger deftly analyzes efforts by Hall and other white writers in the brotherhood to construct cross-racial unity within an otherwise racially torn working class. He shows how Hall redrew the lines of solidarity: On one side were the degraded, of any race.On the other were enlightened workers who eschewed racial divisions, racist language, and stereotypes. “There are white men, Negro men, and Mexican men in this union, but no niggers, greasers or white trash,” proclaimed Ed Lehman, a soapbox speaker for the Brotherhood. A headline in the newsletter similarly asked readers to choose, “SLAVES OR MEN, WHICH?” Still more graphically, a cartoon commanded, “Let all white MEN and Negro MEN get on the same side of this rotten log.”
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Grablander, Travis, Greg Christensen, Craig Bailey, Ding Lou, Haiping Hong, and Hammad Younes. "CPU Performance Improvement Using Novel Thermally Conductive Carbon Nano Grease." Lubricants 10, no. 8 (July 27, 2022): 172. http://dx.doi.org/10.3390/lubricants10080172.
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Electronics depend on their ability to shed operational heat to maintain operating temperature. Inferior grease can create preventable problems in electronics. This is typically achieved through a thermal grease or paste. If this grease fails to dissipate heat or maintain thermal contact, then the equipment will have faults. Greases with less-than-optimal performance create excessive wear, heat, and reduced life expectancy. This can cause equipment failures and malfunctions at the most inopportune moments. Thermal greases are applied to Central Processors (CPU) and Graphics Processors (GPU) in avionics LRUs, computers, Solar panels, HVAC systems, and other electronics. A high-performance novel nano grease will shed excess heat and increase device life expectancy. The fabricated nano greases show improvements of up to 80% in thermal conductivity measurements. CPU testing resulted in a 100% decrease in the standard deviation of temperature variation from commercial greases.
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Miyanaga, Norifumi, Mitsumi Nihei, and Jun Tomioka. "Effects of Flow Properties of Lithium Soap Greases on Bearing Torque." Key Engineering Materials 823 (September 2019): 123–27. http://dx.doi.org/10.4028/www.scientific.net/kem.823.123.
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This study describes the influence of flow properties of lithium soap greases on torque of small ball bearings. Three types of greases with different worked penetration were tested in this study. Their rheological properties are revealed by a cone plate type rheometer. Shear stresses under various shear rates are fitted with the Herschel-Bulkley equation. In addition, viscoelastic behaviors of the greases are measured by small amplitude oscillatory shear. The crossover stress that means the shear stress at G’=G” is obtained for the greases. Then, the bearing torque when three types of greases are used as a lubricant is measured. As the results, the grease with higher crossover stress shows the lower bearing torque regardless of that it has larger apparent viscosity. On the other hand, the grease with lower crossover stress shows the higher bearing torque regardless of that it has lower apparent viscosity. These results imply that the channeling state appears in the grease with higher crossover stress while the churning state appears in the grease with lower crossover stress.
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Jingjing, Mao, Li Jianming, Qiu Jianwei, Liu Lijun, Wang Yue, and Zhang Lijiuan. "The Investigation on Rheology and Microstructure for Lithium Complex Grease." Energy and Earth Science 2, no. 2 (September 4, 2019): p54. http://dx.doi.org/10.22158/ees.v2n2p54.
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The rheological characteristic parameters of five lithium complex lubricating greases were determined. The comparison of rheological characteristic parameters and microstructure of the five greases was made. The results showed that the knowledge of the rheological properties of lubricating greases may contribute to reflect the change of the thickener structure. The flow transition index characterized the breaking behavior of inner structure of grease, the greater this index, the better that soap fiber structure of grease; The damping factor was shifted from a medium range towards a lower value which resulted in brittle character of sample. At a constant shear rate, the soap fiber structure of complex lithium grease is dense and uniform, apparent viscosity decline rate is small. In this sense, it is relevant to understand how the development of the soap fiber structures in the grease contributes to several functional and rheological properties of lubricating greases.
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Farré-Lladós, Josep, Lars G. Westerberg, Jasmina Casals-Terré, Johan Leckner, and René Westbroek. "On the Flow Dynamics of Polymer Greases." Lubricants 10, no. 4 (April 13, 2022): 66. http://dx.doi.org/10.3390/lubricants10040066.
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In this paper, the flow dynamics of polymer greases was investigated using micro-particle image velocimetry. Polymer greases have a different thickener structure, compared to widely used lithium-based greases, and they have the well-known ability to release oil. How these properties affect grease deformation and its ability to flow is investigated and compared to the corresponding behavior of a lithium complex grease with the same consistency. Two main tests were carried out, where velocity profiles in a straight channel were measured and analyzed, and velocity evolution during the transition period from a no-flow to a fully-established flow was measured, respectively. It was found that the polymer grease flow dynamics is different from that of the lithium grease. This indicates that the internal structure of the grease and the grease ability to bleed oil have a strong influence on the deformation on a global scale, which in turn entails other lubricating abilities for the two grease types.
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CZARNY, Ryszard. "INFLUENCE OF FILLERS ON THE RHEOLOGICAL PROPERTIES OF THEIR COMPOSITIONS WITH LUBRICATING GREASES." Tribologia 273, no. 3 (April 30, 2018): 47–55. http://dx.doi.org/10.5604/01.3001.0010.6120.
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The paper presents the results of studies on the influence of fillers, introduced into lubricating greases, on the rheological properties of resultant grease compositions. These fillers were graphite and PTFE powders. They are added to greases in order to improve their tribological properties. They also affect their rheological properties, and they mainly change the value of the shear stress in grease during its flow in a lubrication system. Knowledge of this value is important in designing automated central lubrication systems in which these compositions may be used. Measurements during experimental tests were performed by means of a rotary rheometer Rheotest 2.1. Tests were performed on pure lithium and bentonite greases, with the addition of oxidation and corrosion inhibitors as well as compositions of these greases with different shares of the above mentioned fillers. These tests were performed by changing the gradient of shearing rate. Test results have shown that both the kind of grease and the kind of filler introduced into this grease affect the rheological properties of produced grease compositions.
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Nizam, Mohd Khairul, Mohamad Shafiq Mohd Razmi, Najmuddin Mohd Ramli, and Mohd Najib Razali. "Formulation of Food-Grade Grease Using Paraffin Oil, Fumed Silica, and Chitosan." Materials Science Forum 1069 (August 31, 2022): 211–18. http://dx.doi.org/10.4028/p-yza5n0.
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Three formulations intended for NSF H1 food-grade grease were prepared in this study comprising paraffin oil as a base oil and fumed silica as a thickener. No additive was added in formulation 1 (F1) and formulation 2 (F2), whereas chitosan was added in formulation 3 (F3) as an additive. A commercial food-grade grease (FGG) was used for comparison purposes. The formulated greases and the commercial FGG were characterised for thermal stability via thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). Fourier-transform infrared (FTIR) spectroscopy, dropping point, oil separation, and consistency tests were also carried out to evaluate the properties of the greases. The FTIR spectra were obtained for the fresh and aged greases for grease characterisation. The results showed that the grease made with chitosan as an additive demonstrated higher oil separation, better consistency, and was less affected by ageing, as indicated by the change of grease colour after the oil separation test. F1, F2, F3, and the commercial FGG recorded dropping points higher than 350 °C, indicating no dropping point properties for the tested greases. The grease formulated with chitosan (F3) achieved the highest oil separation with 1.21%, while the commercial FGG recorded the lowest oil separation with 0.66%, followed by F1 and F3 with the oil separation of 0.99% and 0.98%, respectively. For the consistency test, the NLGI number for each formulation varied but the commercial FGG showed the lowest NLGI number of 2, whereas F3 showed the NLGI number in the range of 2–3, and F1 showed the NLGI number of 3. The aged grease of F3 had unchanged consistency after the oil separation test. Based on the results, the formulated greases have acceptable properties in comparison to the commercial FGG, and the addition of chitosan contributes positively to the grease characteristics.
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Georgiou, Emmanuel P., Dirk Drees, Michel De Bilde, Michael Anderson, Matthias Carlstedt, and Olaf Mollenhauer. "Quantification of Tackiness of a Grease: The Road to a Method." Lubricants 9, no. 3 (March 7, 2021): 32. http://dx.doi.org/10.3390/lubricants9030032.
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In this work, we report on the most recent progress in studying temperature influence on tackiness of greases, as well as the reproducibility of the method. Tackiness and adhesion of greases have been identified as key intrinsic properties that can influence their functionality and performance. During the last eight years, a reliable method to quantify the tackiness and adhesion of greases has evolved from an experimental lab-scale set-up towards a standardised approach, including an ASTM method and a dedicated test tool. The performance of lubricating greases—extensively used in diverse industrial applications—is strongly dependent on their adherence to the substrate, cohesion and thread formation or tackiness of the greases. This issue attracts more and more industrial interest as the complexity in grease formulation evolves and it is harder to differentiate between available greases. With this method, grease formulators will have an efficient measurement tool to support their work.
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Khonsari, Michael M., K. P. Lijesh, Roger A. Miller, and Raj Shah. "Evaluating Grease Degradation through Contact Angle Approach." Lubricants 9, no. 1 (January 18, 2021): 11. http://dx.doi.org/10.3390/lubricants9010011.
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Grease is highly susceptible to degradation due to regular usage and the severity of the operating conditions. Degradation can negatively impact the performance of grease-lubricated machinery, demanding frequent maintenance to avoid premature failure of machine elements. Quantification of grease degradation has proven to be a formidable task, for which no accepted standards are currently available. In this paper, we extend the results of a novel approach developed recently for the evaluation of the water-resistant property in grease to quantify degradation. The methodology is based on measurements of the contact angle of a water droplet on the surface of a sample of grease. We report the results of extensive tests performed on different grades of lithium complex greases to evaluate the variation of contact angle values with the composition of grease. The measurements were compared with penetrometer readings to quantify a relationship between the grease consistency and contact angle. Detailed study results are also presented on three types of greases sheared in a grease worker for a different number of strokes: contact angle and the yield stress values were measured and compared. Finally, the tribological characteristics were determined for two greases that exhibited a low or high change in their contact angles.
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Kaneta, M., T. Ogata, Y. Takubo, and M. Naka. "Effects of a thickener structure on grease elastohydrodynamic lubrication films." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 214, no. 4 (April 1, 2000): 327–36. http://dx.doi.org/10.1243/1350650001543214.
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The effects of the thickener structure and base oil viscosity on the grease film formation in rolling point elastohydrodynamic contacts have been discussed on the basis of direct observation using the optical interferometry technique. Three different types of diurea greases without additives have been used as test greases. As the base oils three kinds of ether-type synthetic oils having similar molecular structures but different viscosities were used. The film behaviour of fresh greases has also been compared with that of the degraded greases. It has been found that the behaviour of grease elastohydrodynamic lubrication films is basically influenced by the thickener structure and base oil viscosity. The adhesion or deposition of the thickener on the contacting surfaces and oil starvation which affect film formation depend on the thickener structure, base oil viscosity and rolling speed. Furthermore, it has been suggested that there is an optimum temperature which gives a maximum film thickness according to the consistency of the grease.
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Gurt, Alan, and Michael Khonsari. "An Overview of Grease Water Resistance." Lubricants 8, no. 9 (August 21, 2020): 86. http://dx.doi.org/10.3390/lubricants8090086.
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Many grease-lubricated components operate in wet environments, making them susceptible to water contamination which degrades their performance, functionality, and useful life. Hence, selecting a grease with appropriate water-resistant properties can have a significant influence on the life of the machine. While industry standards attempt to evaluate a grease’s water resistance, research indicates that a more thorough understanding of water resistance is needed to properly match a grease to an application. This paper provides an overview of the interaction of grease and water, covers existing water-resistance standards, discusses the results of available experiments aiming to describe the effects of water on grease, demonstrates the need for more meaningful standards, and suggests additional measures for characterizing a grease’s water resistance.
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He, Qiang, Zhigang Wang, Anling Li, Yachen Guo, and Songfeng Liu. "Tribological properties of nanometer Al2O3 and nanometer ZnO as additives in lithium-based grease." Industrial Lubrication and Tribology 70, no. 6 (August 13, 2018): 953–60. http://dx.doi.org/10.1108/ilt-10-2016-0241.
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Purpose Nanoparticles as the grease additives play an important role in anti-wear and friction-reducing property during the mechanical operation. To improve the lubrication action of grease, the tribological behavior of lithium-based greases with single (nanometer Al2O3 or nanometer ZnO) and composite additives (Al2O3–ZnO nanoparticles) were investigated in this paper. Design/methodology/approach The morphology and microstructure of nanoparticles were characterized by means of transmission electron microscope and X-ray diffraction. Tribological properties of different nanoparticles as additives in lithium-based greases were evaluated using a universal friction and wear testing machine. In addition, the friction coefficient (COF) and wear scar diameter were analyzed. The surface morphology and element overlay of the worn steel surface were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. Findings The results show that the greases with nanometer Al2O3 or nanometer ZnO and the composite nanoparticles additives both exhibit lower COFs and wear scar diameters than those of base grease. And the grease with Al2O3–ZnO composite nanoparticles possesses much lower COF and shows much better wear resistance than greases with single additives. When the additives contents are 0.4 Wt.% Al2O3 and 0.6 Wt.% ZnO, the composite nanoparticles-based grease exhibits the lowest mean COF (0.04) and wear scar diameter (0.65 mm), which is about 160% and 28% lower than those of base grease, respectively. Originality/value The main innovative thought of this work lies in dealing with the grease using single or composite nanoparticles. And through a serial contrast experiments, the anti-wear and friction-reducing property with different nanoparticles additives in lithium grease are evaluated.
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Williamson, B. P. "An Optical Study Of Grease Rheology in an Elastohydrodynamic Point Contact Under Fully Flooded and Starvation Conditions." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 209, no. 1 (March 1995): 63–74. http://dx.doi.org/10.1243/pime_proc_1995_209_406_02.
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An interferometric study of grease rheology in a fully flooded and deliberately starved elastohydrodynamic (EHD) point contact has been carried out under isothermal conditions at 30 °C and various rolling speeeds up to 1 m/s for a viscous liquid lubricant and greases made with lithium, calcium and polyurea thickeners. The measured grease film thickness (GFT) is always greater than that generated by their base oils under fully flooded conditions. The enhanced GFT generated by the lithium and calcium thickened greases can be described by Newtonian flow behaviour using an effective grease viscosity. The results are consistent with the thickener for these greases being fully degraded in passage through the EHD inlet region. The polyurea grease exhibited non-Newtonian fluid flow behaviour (shear thinning) and gave the greatest GFT enhancement (over that exhibited by the base oil). A model to predict the degree of grease starvation in a rolling EHD contact is proposed which is based on determining the inlet meniscus position. Comparison of the results predicted by this model with experiment indicate that the heavily worked grease in the contact inlet exhibits Newtonian behaviour under constant speed conditions. This suggests that the role of the degraded thickener is to increase the effective viscosity of the grease base oil.
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Padgurskas, Juozas, Raimundas Rukuiža, Ihor Mandziuk, Arturas Kupcinskas, Katerina Prisyazhna, Andrei Grigoriev, Inna Kavaliova, and Sergej Revo. "Tribological properties of beef tallow as lubricating grease." Industrial Lubrication and Tribology 69, no. 5 (September 4, 2017): 645–54. http://dx.doi.org/10.1108/ilt-01-2016-0014.
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Purpose The purpose of this paper is to report on the tribological properties of beef tallow grease and improvements therein through modification with special processing, polymeric compounds and additives. Design/methodology/approach Pure original beef tallow grease was used as a biological lubricating grease reference material for the tribological research. Beef tallow was modified and synthesized by adding special biological anti-oxidant additives, LZ anti-wear additives, waste polyethylene terephthalate (PET) polymer compounds and thermally processed graphite. Findings Rheometric measurements indicate that the beef tallow grease modification technology used in this study enables control of the synthesis process to produce lubricants with the required microstructure. Investigation results of the tribological properties of differently modified greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The grease compound with thermally processed graphite has good tribological properties at 300 N load levels. The critical load level of lubricating greases could be significantly increased through the use of anti-wear additives and thermally processed graphite. Originality/value Investigation results of the tribological properties of differently modified beef tallow greases show that beef tallow synthesized with polymer additives efficiently operates together with anti-wear additives to reduce friction and wear. The critical load level of lubricating beef tallow greases could be significantly increased using anti-wear additives and thermally processed graphite.
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Vafaei, Seyedmohammad, Dennis Fischer, Max Jopen, Georg Jacobs, Florian König, and Ralf Weberskirch. "Investigation of Tribological Behavior of Lubricating Greases Composed of Different Bio-Based Polymer Thickeners." Lubricants 9, no. 8 (August 17, 2021): 80. http://dx.doi.org/10.3390/lubricants9080080.
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One commonly used lubricant in rolling bearings is grease, which consists of base oil, thickener and small amounts of additives. Commercial greases are mostly produced from petrochemical base oil and thickener. Recently, the development of base oils from renewable resources have been significantly focused on in the lubricant industry. However, to produce an entirely bio-based grease, the thickener must also be produced from renewable materials. Therefore, this work presents the design and evaluation of three different bio-based polymer thickener systems. Tribological tests are performed to characterize lubrication properties of developed bio-based greases. The effect of thickener type on film thickness and friction behavior of the produced bio-based greases is evaluated on a ball-on-disc tribometer. Moreover, the results are compared to a commercial petrochemical grease chosen as benchmark.
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Wang, Jiabei, Hong Zhang, Wenjing Hu, and Jiusheng Li. "Modified Ni Nanoparticles as Additives in Various Greases: Assessment of Comparative Performance Potential." Lubricants 10, no. 12 (December 17, 2022): 367. http://dx.doi.org/10.3390/lubricants10120367.
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China’s rapid industrial development requires more energy consumption based on non-renewable energy resources. The energy consumption caused by unnecessary friction accounts for about 4.5% of the GDP in China. Although grease effectively lubricates machines, lubrication failure may occur under severe conditions. Nanomaterials exhibit intriguing tribological performances and have received much attention regarding lubrication. In this study, oleylamine-modified Ni nanoparticles (OA-Ni) were synthesized and used as lubricant additive in four kinds of commonly used greases: lithium, calcium, composite calcium, and polyurea grease. The OA-Ni were uniformly dispersed in the greases through electromagnetic stirring, ultrasonic vibration, and three-roll grinding. The physicochemical properties and the structure of OA-Ni-doped grease were investigated, while the feasibility of OA-Ni as various grease additives at different contact modes was evaluated by a four-ball friction tester and a UMT-tribolab tester. Tribological tests results revealed that the friction-reducing and anti-wear properties of point-to-point contact were increased by 56.7% and 70.3% in lithium grease, respectively, while those of the point-to-face contact were increased by 59.5% and 68.9% in polyurea grease, respectively. The present work provides not only theoretical guidance of nano nickel modification but also a practical reference for the application of modified nanomaterials to various greases.
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Ren, Guanlin, Pengfei Zhang, Xiangyuan Ye, Wen Li, Xiaoqiang Fan, and Minhao Zhu. "Comparative study on corrosion resistance and lubrication function of lithium complex grease and polyurea grease." Friction 9, no. 1 (December 13, 2019): 75–91. http://dx.doi.org/10.1007/s40544-019-0325-z.
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AbstractIn this study, lithium complex grease (LCG) and polyurea grease (PUG) were synthesized using mineral oil (500SN) and polyalphaolefin (PAO40) as base oil, adsorbed onto lithium complex soap and polyurea as thickeners, respectively. The effects of grease formulation (thickener and base oil with different amounts (80, 85, and 90 wt%) on the corrosion resistance and lubrication function were investigated in detail. The results have verified that the as-prepared greases have good anti-corrosion ability, ascribed to good salt-spray resistance and sealing function. Furthermore, the increase in the amount of base oil reduces the friction of the contact interface to some extent, whereas the wear resistance of these greases is not consistent with the friction reduction, because the thickener has a significant influence on the tribological property of greases, especially load-carrying capacity. PUG displays better physicochemical performance and lubrication function than LCG under the same conditions, mainly depending on the component/structure of polyurea thickener. The polyurea grease with 90 wt% PAO displays the best wear resistance owing to the synergistic lubrication of grease-film and tribochemical film, composed of Fe2O3, FeO(OH), and nitrogen oxide.
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Xhemajli, Ariana. "TRANSITION ECONOMIES PROBLEMS WITH SPECIFIC FOCUS ON DEALING WITH SCALE OF CORRUPTION CASE STUDY – KOSOVO." Knowledge International Journal 28, no. 1 (December 10, 2018): 329–34. http://dx.doi.org/10.35120/kij2801329x.
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Theoretical and empirical debate on the impact of corruption on the economy remains unclear. Many studies on corruption seem that the world is occupied by two kinds of people, "sanders" and "greasers”. It depends on what the meaning of "corruption" is for them. Some scholars argue that corruption is an obstacle to economic growth, whereas others believe that corruption can (in some circumstances) endorse growth. Corruption also has a negative impact on investment, Foreign Direct Investment, and economic development as a whole. Measuring corruption is still an issue for most economists due to the difficulties of defining it, and also different forms of corruption require different objective measures. Nevertheless, recently, some measures of corruption have been widely accepted and recognized by researchers. This paper is a critical review at these positions by reviewing the theoretical literature on the impact of corruption on an economy as a whole. In this paper we will treat the corruption level in Kosovo, and its presence in forms and ways how the bribe is been given. Instead, this document reviews different measurements of corruption to reveal that corruption is harmful for the economy.
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Prashad, Har. "The Effects of Current Leakage on Electroadhesion Forces in Rolling Friction and Magnetic Flux Density Distribution on the Surface of Rolling Element Bearings." Journal of Tribology 110, no. 3 (July 1, 1988): 448–55. http://dx.doi.org/10.1115/1.3261649.
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The present work deals with the investigations carried out on the various rolling element bearings after being operated under the influence of electric fields, and pure rolling friction on the roller bearing test machine. The significant magnetic flux density was detected on surfaces of the bearings lubricated with low-resistivity grease under the influence of electrical fields. No such phenomenon was observed either on bearings using high or low-resistivity greases under pure rolling friction or on bearings lubricated with high-resistivity grease under the influence of electrical fields. New bearing surfaces do not show significant magnetic flux density but it has been detected after long operation on different motor bearings, lubricated with low resistivity greases. The electroadhesion forces in the bearings using low-resistivity greases increase under the influence of electrical fields in contrast to those with high resistivity greases. Under pure rolling friction resistivity of greases do not affect the electroadhesion forces. The investigations reported in this paper along with the study of damaged/corrugated surfaces, and deterioration of the used greases [1, 2, 3], the leakage of current leading to failure of the noninsulated motor bearings can be established.
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Matzke, Markus, Susanne Beyer-Faiß, Markus Grebe, and Olav Höger. "Thermo-oxidative grease service life evaluation – laboratory study with the catalytically accelerated method using the RapidOxy." Tribologie und Schmierungstechnik 69, no. 1 (March 8, 2022): 41–49. http://dx.doi.org/10.24053/tus-2022-0005.
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With increasing product lifetime requirements including reduced failure rates and higher loads greases are challenged and appropriate methods for grease service life estimation are necessary. Thermo-oxidation is one dominant degradation mechanism in many automotive applications at elevated operating temperatures. At 60th German Tribology Conference 2019, the Bosch method for quantitatively accelerated testing of thermo-oxidative stability of greases with the RapidOxy test apparatus was presented. This method differs from ASTM D8206 and DIN 51830-1 because it measures the grease in contact with the oxidation catalysts steel or brass and it is additionally used to calculate the Arrhenius activation energy of the grease. The oxidation induction time which is indicated by a significant decrease of the autoclave pressure gradient is applied as criterion for grease service life. The method was introduced to the DIN working group “grease ageing” and a laboratory study with participation of seven member laboratories was carried out. The objective of this study was to evaluate repeatability and reproducibility of this method and to verify the application of Arrhenius law for this mechanism. The study was carried out with a commercially available lubricating grease of NLGI-class 2 which consists of a lithium 12-hydroxystearate thickener, mineral oil and an additive package. The grease was spread in thin layers on either steel or brass plates and the activation energy was measured at 130 °C, 145 °C and 160 °C. The oxidation induction times at different temperatures were used to derive the activation energies of the Arrhenius equation on both plate materials. The applicability of Arrhenius law was verified by R2-values above 0,998 for a linear regression in the Arrhenius plot. Results indicated remarkably low scattering of values. The values of activation energies of this specific grease were in the range of 126 - 134 kJ/mol on steel and 99 - 113 kJ/mol on brass. The pressure curve as evaluation criterion was correlated with visual inspection and rheological flow curves. Based on the results of this collaborative study and on internal experiences at Bosch, this method was proposed to DIN in 2020 for definition as a new industry standard. The draft “mDIN 51830-2 Testing of greases – Determination of oxidation resistance of greases – Part 2: Determination of the Arrhenius activation energy of thermo-oxidative degradation” is currently in review of the DIN working group and an official round robin test with several greases and more laboratories is currently in preparation.
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KRAWIEC, Michał. "EVALUATION OF THE LUBRICATION EFFICIENCY OF GREASES ACCORDING TO CRITERION OF WEAR EXPERIMENTALLY DETERMINED AT VARIABLE VALUES OF MOTION PARAMETERS." Tribologia 273, no. 3 (June 30, 2018): 77–83. http://dx.doi.org/10.5604/01.3001.0010.6135.
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The results of tribological investigations into the lubrication efficiency of greases in steel sliding pairs working in mixed friction conditions are presented. The lubrication efficiency was evaluated according to the criterion of wear determined by tribological tests conducted at variable values of motion parameters: load F and sliding velocity v. Wear volume VF(d), calculated from wear regression equations (wear d = f(p,v), was adopted as the lubrication efficiency criterion. Five different commercial greases currently available on the market and one in-house grease (a compound of grease 1S and two solid greases (6% PTFE and 5% Cu)) were tested. The experiment was conducted in a four-ball tester at five levels in accordance with the rotatable experiment design. A regression function with interrelated ball wear d, sliding velocity v, and applied load F, was formulated for each of the tested greases. Wear volumes VF(d) were calculated and conclusions were drawn.
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Mas, Re´my, and Albert Magnin. "Rheological and Physical Studies of Lubricating Greases Before and After Use in Bearings." Journal of Tribology 118, no. 3 (July 1, 1996): 681–86. http://dx.doi.org/10.1115/1.2831592.
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Lithium soap and calcium complex soap-based lubricating greases are studied when fresh and after use in roller and ball bearings. Examination of the rheological properties of these greases using rotating rheometers reveals changes that have occurred during use in the bearings. These modifications are not uniform throughout the hearing. Physical and chemical analyses enable these modifications in rheological properties to be linked to variations in composition or structure, depending on the type of grease and bearing. Several mechanisms involved in lubricating a bearing with a lubricating grease are confirmed or clarified.
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MOLENDA, Jarosław, Zbigniew PAWELEC, Ewa PAWELEC, and Bernadetta KAŹMIERCZAK. "THE INFLUENCE OF BIOCARBON ADDITIVES ON GREASE FUNCTIONALITY." Tribologia 290, no. 2 (June 30, 2020): 47–53. http://dx.doi.org/10.5604/01.3001.0014.3739.
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The article presents the results of tests on tribological and physicochemical properties of plastic greases, in which the dispersing phase was highly refined mineral oil and the dispersed phase (thickener) lithium stearate. The functional additives were biocarbon, which were obtained in the pyrolysis process of waste of natural origin, i.e. stems with corn leaves, wheat straw, flax straw, and cherry stones. The compositions containing 5% m/m biocarbon were prepared. Their evaluated on the functional properties of plastic greases was assessed. Tribological characteristics of the greases compositions were determined using the T-02 tester in accordance with the requirements of the subject standards. The effect of biocarbon used on anti-wear (Goz) and anti-seizing (Pt, poz) plastic greases was determined. An assessment was also made of the effect of plant biocarbon on changes in basic physicochemical properties of the composition of plastic greases, i.e. penetration, dropping temperature, and thermo-oxidative stability. It was found that some of the biocarbon significantly improve the tribological properties of plastic greases without significantly affecting the change of key physicochemical parameters. The most beneficial impact of the tested additives on the operational properties of plastic greases was observed when using biocarbon from wheat straw. In some cases, a lower oxidative resistance of biocarbon grease is observed compared to grease without the addition of biocarbon.
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Suhaila A Japar, N., M. Aizudin A. Aziz, Mohd Najib Razali, Nurul Waheeda Abdu Rahman, and . "Grease and its Application on Electrical Equipment: a Review." International Journal of Engineering & Technology 7, no. 3.26 (August 14, 2018): 23. http://dx.doi.org/10.14419/ijet.v7i3.26.17455.
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Grease hardening and dry-out have been part of the major challenges in grease usage in electrical industry. The findings obtained over the years related to the study of synthetic, specialty, and new grease have found that the usage of these greases are costly; hence, it is very necessary to find an alternative method to reduce the cost as much as possible. Increasing petroleum demands, depletion of petroleum reserves, and the environmental awareness have influenced a huge interest in the use of waste oil as the alternative of base oil for grease formulation. The waste oils are considered as a promising candidate due the fact that the re-refining process of base oil is relatively cheap with high yield and the recovery of good quality oil. Optimum grease formulation is necessary in solving the aforementioned issues as well as overcoming complication specifically in the electrical industry where these greases are mainly utilized.
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Yao, Lidan, Lixin Wang, Haining Yang, Chuan Li, Hui Song, and Xianguo Hu. "Comparative analysis of stearates as grease lubricant thickeners." Industrial Lubrication and Tribology 71, no. 9 (November 4, 2019): 1093–98. http://dx.doi.org/10.1108/ilt-01-2019-0008.
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Purpose This paper aims to investigate the influence of stearate types on the thickening ability, dropping point and fiber structure of greases. Design/methodology/approach Several greases were prepared from polyolefins and various stearates. The melting point of the stearates and the dropping point of the resultant greases were measured, and the intermolecular binding energies of the thickener and the radial distribution function of the metal–oxygen in the thickener were determined with the aid of molecular simulation. The microstructures of the greases were also analyzed via scanning electron microscopy. Findings A higher stearate binding energy was found to correlate to a higher dropping point of the resultant greases. The thickening ability of the stearate is related to the group and period of the constituent metal ion. Within a group, greater atomic numbers of the metal were correlated to lower thickening ability. In a period, as the atomic number of the metal increased, the thickening ability was enhanced. The radial distribution functions of metal and oxygen can explain the aggregation of the stearate thickeners in the grease. Originality/value This work compared the thickening capacity of several stearates. Guidelines for preparing stearates to tailor the resultant grease are presented.
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Gurt, Alan, and Michael M. Khonsari. "Testing Grease Consistency." Lubricants 9, no. 2 (February 2, 2021): 14. http://dx.doi.org/10.3390/lubricants9020014.
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Because of the influential role of consistency in selecting a grease for a given application, accurate and meaningful methodologies for its measurements are vitally important. A new method, recently introduced, uses a rheometer to compress a grease sample to evaluate a relative consistency between a fresh and degraded grease; however, the results of this approach compared to a standard penetrometer and other methods of assessing consistency have not been studied. This paper takes a closer look at the relevant parameters involved in the rheometer penetration test and establishes a recommended procedure for its use. The consistency of various greases is then tested using this method and compared to results obtained from yield stress, crossover stress, and cone penetration tests. The results indicate that rheometer penetration may be used to assess the change in consistency for a given grease but should not be used to compare different greases. For this purpose, the crossover stress method is recommended, which is shown to correlate very well with cone penetration while using a simple procedure and allowing the use of a substantially smaller sample. A strong power law correlation between crossover stress and cone penetration was found for all greases tested and is presented in Figure 12.
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Slabka, Iryna, Sören Henniger, David Kücükkaya, Michael Dawoud, and Hubert Schwarze. "Influence of Rheological Properties of Lithium Greases on Operating Behavior in Oscillating Rolling Bearings at a Small Swivel Angle." Lubricants 10, no. 7 (July 19, 2022): 163. http://dx.doi.org/10.3390/lubricants10070163.
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In this study, the behavior of greases during oscillating bearing operation with a small oscillation angle and high frequency was investigated. This mode of operation entails demands on the lubrication system that differ significantly from those for continuously rotating bearings. In order to determine the variables influencing the suitability of a lubricating grease for small angle oscillating operation, the grease samples were examined with particular regard to their rheological properties. The focus of this investigation was to find a relationship between the rheological parameters and the real behavior in the bearing. Therefore, rheological and physical parameters, which influence the long-term structural changes and lubrication conditions, were identified. For this purpose, the viscosity was measured over a wide shear-rate range. The storage and loss modulus, the work of deformation, and the adhesion force jump are also determined. Afterward, rotational transient flow measurements were performed. These allowed us to analyze the development of the shear stress over time, at a constant shear rate, and to examine the internal friction behavior by evaluating the energy density. Subsequently, grease-lubricated four-point bearings were used in component tests, while the frictional torque was measured. These bearings operated in oscillating motion. Moreover, the yield point of mechanically aged greases was measured and compared with that of fresh greases to examine the influence of the oscillating operation on the lubricant condition. Finally, correlations between grease composition, rheological measurements, and component tests were investigated. Thereby, parameters influencing the frictional behavior of greases in rolling bearings during oscillating operation at small swivel angles were identified.
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Xu, Yun Gen, Ze Yu Weng, Hong Wu You, Yan Qin Zheng, and Xiao Ping Huang. "Study on the Test Method for High Temperature and Heavy Loaded Grease Bearing Life." Applied Mechanics and Materials 141 (November 2011): 529–33. http://dx.doi.org/10.4028/www.scientific.net/amm.141.529.
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Temperature, load and rotate speed are the main factors which influence grease bearing life are presented by means of study on failure mechanism of grease. According to the test demands of high temperature and heavy loaded grease bearing life, test temperature, load and rotate speed of grease bearing life test are analyzed and discussed, presented that different greases should apply different test temperature. In addition, the filling amount of grease and test running mode of the grease bearing life test are discussed.
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Conrad, Andreas, Annika Hodapp, Bernhard Hochstein, Norbert Willenbacher, and Karl-Heinz Jacob. "Low-Temperature Rheology and Thermoanalytical Investigation of Lubricating Greases: Influence of Thickener Type and Concentration on Melting, Crystallization and Glass Transition." Lubricants 10, no. 1 (December 22, 2021): 1. http://dx.doi.org/10.3390/lubricants10010001.
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This study investigates crystallization, melting and glass transition of Li- and Ca-12-hydroxystearate greases in relation to the pour point of the corresponding oils. The base oils for the greases are mineral oil, polyalphaolefin, alkylated naphthalene, propylene glycol, and trimellitate. For the mineral oil-based greases the crystallization temperature Tc increases and the melting temperature Tm decreases upon addition of thickener. The pour point of the mineral oil then is 3 K below Tc and does not properly define the lowest application temperature for mineral oil (MO) based greases. Both thickeners induce a small increase of the glass transition temperature (1–3 K) of the synthetic oils polyalphaolefin, alkylated naphthalene, propylene glycol. The pour point of the base oils correlates well with the onset of the glass transition in the corresponding grease indicated by a sharp increase in grease viscosity. Pure trimellitate with unbranched alkyl chains does not crystallize upon cooling but shows noticeable supercooling and cold crystallization. As the percentage of thickener in corresponding greases increases, more oil crystallizes upon cooling 20 K above the crystallization temperature of the trimellitate without thickener (−44 °C). Here, the thickener changes the crystallization behavior from homogeneous to heterogeneous and thus acts as a crystallization nucleus. The pour point of the base oil does not provide information on the temperature below which the greases stiffen significantly due to crystallization.
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Prater, Walter, John Burns, Garvin Stone, and Tom Ting. "Evaluation of Perfluorinated Polyalkylether Grease Rheology on Disk Drive Bearing Performance." Journal of Tribology 120, no. 1 (January 1, 1998): 21–27. http://dx.doi.org/10.1115/1.2834182.
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A matrix of specially formulated greases composed of perfluorinated polyalkylether (PFPE) oil and telomers of polytetrafluoroethylene (PTFE) particulate thickener were tested. The PFPE greases were chosen for this evaluation because their oils have a very low vapor pressure and they will not volatilize in the disk drive. Base oil viscosity, PTFE particle size and percentage of oil content were varied. The rheological properties of complex viscosity, storage and loss moduli, and loss factor were measured. Percent oil was determined using thermal gravimetric analysis. The thickener’s PTFE particle sizes were measured and their shapes were imaged using scanning electron microscopy. Bearing low speed torque and bearing noise tests were performed to evaluate the effect of the grease on bearing performance. The head settle track misregistration (TMR) was measured on disk drives to measure the effect of bearing lubrication on the servo performance. Generally, greases with high base oil viscosity had the lowest complex viscosity. Greases with highest viscosity PFPE oils had the highest torque and lowest noise. Greases with large PTFE particles had high loss factors and exhibited high torque and noise levels. High PTFE thickener to PFPE oil ratio (thicker grease) causes the bearings to have fluctuations in torque and noise levels. Actuator bearings lubricated with greases having higher viscosity oil had lower head settle TMR.
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Singh, Tarunendr. "Tribochemistry and EP Activity Assessment of Mo-S Complexes in Lithium-Base Greases." Advances in Tribology 2008 (2008): 1–6. http://dx.doi.org/10.1155/2008/947543.
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The blends of bis(1,5-diaryl-2,4-dithiomalonamido)dioxomolybdenum(VI) complexes in lithium-base grease are evaluated for their extreme pressure activity in a “four-ball test” using 12.7 mm diameter alloy steel ball specimen. The additive, bis(1,5-di-p-methoxyphenyl-2,4-dithiomalonamido)dioxomolybdenum(VI) and bis(1,5-di-p-chloro-phenyl-2,4-dithiomalonamido)dioxomolybdenum(VI) exhibited lower values of wear-scar diameter at higher load and higher values of weld load, flash temperature parameter, and pressure wear index as compared with lithium-base grease without additives. The greases fortified with the developed additives prevent rusting and corrosion of bearings while grease containing no additives did not pass these tests as per the standard tests. These greases have also better oxidation protection as compared to the grease that has no additive. The topography and tribochemistry of the wear-scar surface are carried out by means of scanning electron microscopy and Auger electron spectroscopy techniques, respectively.
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Cao, Zhengfeng, Yanqiu Xia, and Xiangyu Ge. "Conductive capacity and tribological properties of several carbon materials in conductive greases." Industrial Lubrication and Tribology 68, no. 5 (August 8, 2016): 577–85. http://dx.doi.org/10.1108/ilt-07-2015-0113.
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Purpose The purpose of this paper is to synthesize a new kind of conductive grease which possesses a prominent conductive capacity and good tribological properties. Design/methodology/approach A two-step method was used to prepare complex lithium-based grease. Ketjen black (KB), acetylene black (AB) and carbon black (CB) were characterized by transmission electron microscope and used as lubricant additives to prepare conductive greases. Conductive capacity was evaluated by a conductivity meter, a surface volume resistivity meter and a circuit resistance meter. Tribological properties were investigated by a reciprocating friction and wear tester (MFT-R4000). The worn surfaces were analyzed by a scanning electron microscope, Raman spectroscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscope. Findings The conductive grease prepared with KB has a prominent conductive capacity at room temperature, 100°C and 150°C. Further, this conductive grease also possesses better tribological properties than AB and KB greases. When the concentration of KB is 1.8 Wt.%, the coefficient of friction and wear width reduced by 11 and 14 per cent, respectively. Originality/value This work is a new application of nanometer KB as a lubricant additive in grease, which provides a direction for preparing conductive grease. The conductivity and tribology experiments have been carried out though the variation of experiment conductions.
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Castaños, Brenda, Cecilia Fernández, Laura Peña-Parás, Demófilo Maldonado-Cortés, and Juan Rodríguez-Salinas. "Enhancement of tribological properties of greases for circuit breakers." MRS Advances 3, no. 64 (2018): 3979–85. http://dx.doi.org/10.1557/adv.2018.610.
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ABSTRACTGreases are essential in the electrical industry for the purpose of minimizing wear and coefficient of friction (COF) between the components of circuit breakers. Nowadays some researchers have explored the addition of nanoparticles to enhance their tribological properties. In this study, tribological tests were performed on different greases employed for the electrical industry. CuO and ZnO nanoparticles were homogeneously dispersed into the greases, varying their concentration (0.01 wt.%, 0.05 wt.%, and 0.10 wt.%). A four-ball tribotest, according to ASTM D-2266, and a ball-on-disk tribotest, according to ASTM G-99, were performed in order to analyze the wear scar diameter (WSD), COF, wear mass loss and worn area. The worn materials were characterized with an optical 3D profilometer measurement system. Anti-wear properties were enhanced up to 29.30% for the lithium complex grease (LG) with no nanoparticles added, in comparison with the aluminum complex grease (AG), providing a much better tribological performance; in the ball-on-disk tribotests, a 72.80% and a 15.74% reduction in the mass loss and COF were achieved, respectively. The addition of nanoparticles was found to provide improvements of 5.31% in WSD for the AG grease and 34.49% in COF for the LG grease. A pilot test was performed following the security test UL489, achieving a reduction of 45.17% in the worn area achieved by LG grease compared to AG grease.
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Oikawa, Eri, Noriyuki Inami, Michita Hokao, Atsushi Yokouchi, and Joichi Sugimura. "Bearing torque characteristics of lithium soap greases with some synthetic base oils." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 226, no. 6 (March 29, 2012): 575–83. http://dx.doi.org/10.1177/1350650112442780.
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This article describes the influence of rheological properties on the bearing torque characteristics of the lithium soap greases with five types of base oils. The greases used had different yield stress depending on the base oils even with the same thickener concentration. Measurement of bearing torque was conducted for a deep-groove radial ball bearing by using a bearing test apparatus. The bearings filled with greases initially exhibited high torque but showed gradual decrease in the torque with prolonged rotation, where the greases with higher yield stress showed larger normalized torque decrease. Observation of bearing after the rotation revealed a tendency that the greases with larger normalized torque decrease had been pushed aside in the raceway by channeling. This implied that the greases with higher yield stress tended to show channeling. On the other hand, the greases with lower yield stress circulated within the bearing by churning and showed smaller normalized torque decrease. These behaviors were explained in terms of the yield stress of the greases and the shear stress to entrain the greases into the contacts. Observation of grease structure was made with atomic force microscopy showed that the greases whose thickener network structure was distributed more densely had higher yield stress.
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Czarny, Ryszard. "THE EFFECT OF THE TYPE OF WALL MATERIAL AND GREASE COMPOSITION PAIRING ON SHEAR STRESSES IN BOUNDARY LAYER." Tribologia 284, no. 2 (April 30, 2019): 27–36. http://dx.doi.org/10.5604/01.3001.0013.4146.
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The paper presents the results of research on the influence of fillers introduced into plastic greases on the rheological properties of the boundary layer of the resultant lubricant compositions. The fillers were PTFE and MoS2 powders. They are added to lubricants to improve their tribological properties; however, these fillers also affect the rheological properties of the composition. This affects the change of the shear stress value in the lubricant during its flow in the lubrication system. Knowledge of this value, especially during the flow of the lubricant composition in the boundary layer, has a significant impact on the operation of automated central lubrication systems in which these compositions can be used. Measurements were carried out by means of a rotary rheometer (Rheotest 2.1). Tests were performed on lithium and bentonite greases (without additives) as well as compositions of these greases containing various percentage of the fillers mentioned above. Test results showed that both the type of grease and the type of filler introduced into this grease affect the rheological properties in the boundary layer of the produced lubricating compositions.
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Petrashev, A. I., L. G. Knyazeva, V. V. Klepikov, and M. A. Pluzhnikov. "Mobile device for anticorrosive protection of agricultural machinery with sluggish greases." Traktory i sel hozmashiny 81, no. 2 (February 15, 2014): 11–13. http://dx.doi.org/10.17816/0321-4443-65608.
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Parameters of apparatus equipped with local chamber for sluggish rust-preventing grease heating are substantiated. Mobile device for heating and application of sluggish greases on parts of agricultural machines was developed.
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Joysula, Sravan K., Anshuman Dube, Debdutt Patro, and Deepak Halenahally Veeregowda. "On the Fictitious Grease Lubrication Performance in a Four-Ball Tester." Lubricants 9, no. 3 (March 12, 2021): 33. http://dx.doi.org/10.3390/lubricants9030033.
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The extreme pressure (EP) behavior of grease is related to its additives that can prevent seizure. However, in this study following ASTM D2596 four-ball test method, the EP behavior of greases was modified without any changes to its additive package. A four-ball tester with position encoders and variable frequency drive system was used to control the speed ramp up time or delay in motor speed to demonstrate higher grease weld load and lower grease friction that were fictitious. A tenth of a second delay in speed ramp up time had showed an increase in the weld load from 7848 N to 9810 N for grease X and 6082 N to 9810 N for grease Y. Further increase in the speed ramp up time to 0.95 s showed that the greases passed the maximum load of 9810 N that was possible in the four-ball tester without seizure. The mechanism can be related to the delay in rise of local temperature to reach the melting point of steel required for full seizure or welding, that was theoretically attributed to an increase in heat loss as the speed ramp-up time was increased. Furthermore, the speed ramp up time increased the corrected load for grease X and Y. This resulted in lower friction for grease X and Y. This fictitious low friction can be attributed to decrease in surface roughness at higher extreme pressure or higher corrected load. This study suggests that speed ramp up time is a critical factor that should be further investigated by ASTM and grease manufacturers, to prevent the use of grease with fictitious EP behavior.
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Dai, Yingjing, Hong Xu, and Jinxiang Dong. "Lubrication Performance of α-Zirconium Phosphates as an Anti-Wear Additive in Vegetable Oil-Based Anhydrous Calcium Grease." Lubricants 6, no. 3 (July 18, 2018): 63. http://dx.doi.org/10.3390/lubricants6030063.
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Vegetable oil has significant potential as a base oil, and substitute for mineral oil in grease formulation due to its biodegradability, low toxicity and excellent lubrication. This paper studied the development of vegetable oil-based greases with α-Zr(HPO4)2·H2O (α-ZrP) as an additive, exploring base oil influence in tribological behavior. The results demonstrated that the addition of α-ZrP in vegetable-based greases is beneficial to anti-wear property. α-ZrP particles exhibit good performance in anti-wear, friction-reduction and load-carrying capacity, and its tribological performances are better than the normally used molybdenum disulfide and graphite additives. Owing to its superior tribological properties as a vegetable oil-based grease additive, α-ZrP holds great potential for use in environmentally friendly applications in the future.
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Tonkonogov, Boris P., Anastasiya Yu Kilyakova, Sabina Z. Shumakaeva, Vladimir A. Vinokurov, Ravilya Z. Safieva, Olga V. Popova, and Oleg P. Parenago. "USING OF ESTERS AS DISPERSION MEDIUM OF POLYUREA PLASTIC GREASES." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, no. 9 (August 31, 2019): 73–78. http://dx.doi.org/10.6060/ivkkt.20196209.5909.
Full textAbstract:
This article presents first results of the investigated physico-chemical and operational parameters of composition greases obtained with the use of esters of different nature as a dispersion medium and the polyurea as a thickening agent, including the addition of nanocellulose. The choice of the ester base for the production of greases is possible due, on the one hand, to good combination of the physico-chemical properties (high viscosity index, low volatility, high flash and ignition temperature, low pour point, good anti-wear properties). On the other hand, in the production of greases with good ecological characteristics biodegradability of its components is of great importance, which in this case is provided by the use of esters as an oil base and an organic thickener, nanocellulose, as a component of the polyurea dispersed phase. It has been shown that from the dicarboxylic acid esters studied, the polyurea greases based on dioctyl adipate are superior to the dropping point and better colloidal stability as compared to dioctyl sebacate and dibutyl sebacate. The smaller size of the ether molecule provides the stronger structure of the polyurea grease. Similarly, for branched ethers, the grease based on tri-basic alcohols is more effective than the four-basic alcohols. The possibility of using nanocellulose as a thickener component was demonstrated. An increase in the content of nanocellulose to 3.5% increases the colloidal stability and the dropping temperature of the synthesized greases. The obtained samples have a wider range of operating temperatures, better rheological indicators than imported and domestic analogues.
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Wang, Shanshan, Jing Wang, Yiming Han, and Weimin Li. "Variation of zero entraining velocity dimple in grease-lubricated reciprocating motion." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, no. 11 (May 3, 2019): 1661–87. http://dx.doi.org/10.1177/1350650119842683.
Full textAbstract:
In this study, experiments were conducted on a ball-on-disk test rig using optical interferometry to explore the variation in grease film thickness under zero entraining velocity reciprocating motion. The steel ball and the sapphire disk move at equal speeds but in opposite directions within a triangle wave. Three types of commercially available bearing greases with different consistencies, Centoplex 2EP, Centoplex 3, and MP-3, were used in these experiments. The variations in the surface dimple phenomenon with decreasing maximum surface velocity, differing grease consistency, and grease starvation conditions were studied. Results showed that the grease consistency exerts a significant influence on the surface dimple and the starvation severity.