In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners ...In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners with different surfactant dosages and constituents were synthesized through intercalation reaction between sodium montmorillonite(NaM MT) and quaternary ammonium surfactants in aqueous solvents. The lubricating greases were prepared with the resulting organoclays, while the penetration and oil separation of lubricating greases were evaluated, respectively. The surface modification process of montmorillonite(MMT) was analyzed and the thickening mechanism of OMMT was discussed in this study. The experimental results showed that, with an increasing amount of surfactant, the basal spacing between the clay platelets was increasing and the structure of modifier molecules layer in the interlayer was changing from lateral bilayer to paraffin-type bilayer. The optimal properties of lubricating greases were achieved, when the structure of surfactant molecules loaded in the interlayer was the paraffin-type monolayer, which meant that the dosage of modifier was equal to 120—140 mmol/(100g). Meanwhile, it was found that the thickening performance, colloid stability, anti-wear and friction-reducing performance of lubricating greases were improved, when the surfactants were mixed with octadecyl trimethyl ammonium chloride(OTAC) and hexadecyl trimethyl ammonium chloride(HTAC). And the optimum mole ratio of two surfactants is was 1:1.展开更多
Oxidation induction time(OIT) testing by differential scanning calorimetry(DSC) was used to evaluate the oxidation resistance of lubricating greases. Under the high temperature condition, bearing noise was detected wh...Oxidation induction time(OIT) testing by differential scanning calorimetry(DSC) was used to evaluate the oxidation resistance of lubricating greases. Under the high temperature condition, bearing noise was detected when grease passed the initial stable stage of oxidation. The chemical and physical structure of grease samples before and after high temperature oxidation were also analyzed by FT-IR spectrometry and scanning electron microscopy(SEM), then the effects of oxidation at high temperature on bearing noise were investigated. It is found out that for lithium greases, oxidation of base oil and thickener is the main reason responsible for the increasing bearing noise. As regards the polyurea greases, the change of fiber microstructure at high temperature is the main reason for the increasing bearing noise.展开更多
The wax gel grease (S0) was prepared from a mixture of 2.3:1 base oil blend (base oil grade 260/290, transformer oil), and microcrystalline wax in the presence of 0.1% - 2% of polyoxyethylene sorption nano-palmitate a...The wax gel grease (S0) was prepared from a mixture of 2.3:1 base oil blend (base oil grade 260/290, transformer oil), and microcrystalline wax in the presence of 0.1% - 2% of polyoxyethylene sorption nano-palmitate as antioxidant and 2,2 methylene bis (4-methyle-6-tertiary butyl phenol) as anticorrosion. It was found that the prepared Wax gel grease has inconvenient physico-chemical and dielectric properties, so in order to improve its physico-chemical properties (viscosity, penetration, dropping point and water resistance) and dielectric Properties (dielectric constant, dielectric loss and volume resistivity), Butyl rubber, isoprene rubber and bitumen were added separately as thickening agents to the prepared wax gel in certain proportion at certain frequency range 1 - 1000 KHz at 35°C. The best dielectric properties were achieved by adding butyl rubber to the prepared wax gel.展开更多
Grease life refers to the time it takes for the grease to lose its ability to keep the lubrication due to grease degradation. As grease life is generally shorter than fatigue life of bearing, the service life of greas...Grease life refers to the time it takes for the grease to lose its ability to keep the lubrication due to grease degradation. As grease life is generally shorter than fatigue life of bearing, the service life of grease-lubricated rolling bearings is often dominated by grease life. When designing a bearing systemolecular weightith grease lubrication, it is necessary to define the operating conditions limits of the bearing, for which grease life becomes a determining factor. Prolongation of grease life becomes an especially important challenge when the bearing is to be operated trader high-speed, high-temperature, and other severe conditions. Selecting a number of commercially sold greases composed of varying base oils, the author evaluated their properties and analyzed how each property affected the grease life by performing a multiple regression analysis. The optimum grease composition to best exploit each property was also examined. The results revealed among others that one would need to first determine the base oil type and then maximize ultimate bleeding while minimizing the evaporation rate.展开更多
Greases are composed by lubricating oil dispersed in a thickener that can be a metal soap, polymers or clays. Grease production using vegetable oils is increasing due to biodegradability requirements. Since vegetable ...Greases are composed by lubricating oil dispersed in a thickener that can be a metal soap, polymers or clays. Grease production using vegetable oils is increasing due to biodegradability requirements. Since vegetable oils present a worse oxidation and hydrolysis stability than mineral oils, it is usually difficult to produce a neutral grease using them. Four greases were produced using soybean oil as lubricating oil and lithium 12-hydroxy- stearate as thickener. The maximum temperature of reaction ranged from 230°C to 120°C in a bench process and a reduction in the final product acidity was observed (from 8.2% acid to 0.05% alkaline). Traditional tests to evaluate thickener structure resistance like 10,000-time worked penetration, roll stability and dropping point were performed and results compared. In addition, rheological tests were performed and the results were also compared. Results indicate that it is possible to produce a quite neutral grease using vegetable oils with good thickener structure properties.展开更多
This study employs a stacking ensemble learning framework to establish a regression model for predicting the tribological properties of amide-based lubricating grease and determining the optimal additive ratios.Melami...This study employs a stacking ensemble learning framework to establish a regression model for predicting the tribological properties of amide-based lubricating grease and determining the optimal additive ratios.Melamine cyanuric acid(MCA)was selected as the thickener,and three extreme-pressure anti-wear additives were used to prepare the lubricating grease.The tribological performance was tested using an MFT-R4000 reciprocating friction and wear machine.Based on the tribological experimental data,the synthetic minority oversampling technique(SMOTE)was utilized for data augmentation,and a stacking ensemble algorithm with Bayesian optimization of hyperparameters was used to construct a predictive model for tribological performance.Subsequently,within this model framework,single and multi-objective optimization models were developed,and the fruit fly algorithm was employed to find the optimal additive combination ratios,which were experimentally validated.The results demonstrated that the learning framework based on the stacking ensemble model could effectively predict the tribological properties of amide-based lubricating grease in small sample datasets,with the R2 for the average friction coefficient prediction reaching 0.9939 and for the wear scar width prediction reaching 0.9535.In the experimental validation of the optimal additive ratios,the relative error of the friction coefficient ratio scheme was 0.51%,and the relative error of the wear scar width was 1.10%.This finding suggests that the learning framework provides a novel approach for predicting the performance of amide-based lubricating grease and studying additive combinations.展开更多
In modern high-tech industries,such as aerospace,nuclear energy,and electric power,there is increasing demand for materials with high-temperature adaptability and superior lubrication properties.Grease is an essential...In modern high-tech industries,such as aerospace,nuclear energy,and electric power,there is increasing demand for materials with high-temperature adaptability and superior lubrication properties.Grease is an essential mechanical component that is widely used to reduce mechanical friction,wear,and vibration.This paper comprehensively reviews recent progress in high-temperature grease,including design,performance indices,lubrication characteristics,development,and applications.This paper starts by outlining novel insights into the relationship between the composition and physicochemical properties of high-temperature greases,as well as other factors,emphasizing typical strategies for matrix reinforcement and high-temperature performance enhancement.The gravity analysis focuses on the intrinsic properties of high-temperature grease and the influence of working conditions on its tribological properties,leading to a detailed discussion of the lubrication mechanism.The innovative fusion of high-temperature grease with new materials such as nanomaterials and ionic liquids(ILs)and interdisciplinary research involving modern emerging fields such as artificial intelligence have led to further progress in the development of high-temperature grease,which has a wide range of applications in aerospace components,automotive parts,and turbines.Finally,this review concludes briefly with prospects for the challenges and future directions in high-temperature grease.展开更多
This work investigated the temperature changes inside the bulk of lubricating greases under controlled high-shear stress conditions(250-500 s-1).For this purpose,a newly developed temperature-measuring cell called Cal...This work investigated the temperature changes inside the bulk of lubricating greases under controlled high-shear stress conditions(250-500 s-1).For this purpose,a newly developed temperature-measuring cell called Calidus was successfully tested.The temperature changes(ΔT)have been related to the greases'components(thickener,base oil-type,and composition)and the structural degradation of the lubricating greases.Furthermore,a theoretical approach was proposed for calculating the internal temperature change of lubricating greases during shear stress.All greases showed an internal temperature profile characterised by a sudden rise inΔT within the first 4 h from starting the test and subsequentΔT decay until it reaches the steady state value.Furthermore,it was found that greases C1 and C5,formulated with lithium and calcium soap,respectively,with different soap content(16.1 wt%and 9.7 wt%,respectively),but the same base castor oil,showed the highest value of the maximumΔT,c.a.3.2 K,and the most drastic drop ofΔT.These greases showed both the highest specific densities and heat capacities.In addition,they showed the lowest ratio of expended energies(Rtee),which means more structural degradation in the stressed grease.On the contrary,the grease C3,with 13 wt%of Li-soap but the lowest base oil's viscosity,showed the lowest maximumΔT and the temperature profile was characterised by a moderate variation ofΔT along the test.The biogenic grease B3 developed a low-temperature change in the group of pure bio-genic greases close to grease C3.展开更多
This study investigates the development of novel montmorillonite/castor oil blends to formulate sustainable lubricating greases to promote the replacement of petrochemicals industry-derived materials by substances obt...This study investigates the development of novel montmorillonite/castor oil blends to formulate sustainable lubricating greases to promote the replacement of petrochemicals industry-derived materials by substances obtained from renewable sources.Specifically,the effect of the thickener concentration on the rheological,chemical,thermal,tribological properties,and atomic force microscopy(AFM)microstructure of these systems were studied.The results showed that the C20A nanoclay content could be used to modulate the viscosity values,the linear viscoelastic functions,and tribological properties of these montmorillonite dispersions.In general,these gel-like dispersions exhibited remarkable lubricant properties;the samples showed values of the friction coefficient and wear scars similar or lower than those obtained with model bentonite grease.展开更多
In this study,we synthesized two types of calcium sulfonate complex greases(barium soap and calcium soap)and investigated their physical,rheological,and tribological properties in detail.The test results showed that t...In this study,we synthesized two types of calcium sulfonate complex greases(barium soap and calcium soap)and investigated their physical,rheological,and tribological properties in detail.The test results showed that the evolution of their linear viscoelasticity functions with frequency were quite similar to those of traditional lubricating greases.Moreover,these two calcium sulfonate complex greases had good friction-reducing and antiwear properties at room temperature and at 150°C.In addition,by adding an organic molybdenum compound(MoDTC)to the base greases,we obtained a very low friction coefficient(0.065)for one of the greases(calcium soap)at 400 N and 500 N(maximum Hertzian pressures of 3.47 GPa and 3.74 GPa,respectively)at 150°C.X-ray photoelectron spectroscopy(XPS)analysis showed that the tribofilm was composed of some complex oxide species and CaCO3 that had formed on the worn surface.展开更多
Grease is extensively used in rolling bearings due to its inherent sealing properties.However,mechanical degradation typically occurs,resulting in a significantly shorter lifespan for the grease compared to the bearin...Grease is extensively used in rolling bearings due to its inherent sealing properties.However,mechanical degradation typically occurs,resulting in a significantly shorter lifespan for the grease compared to the bearing.Investigating aging mechanisms is essential.This study utilized rolling bearings to obtain mechanically aged greases.The aged samples were then subjected to do rheological test,FTIR test and friction test to examine the effects of aging time,radial load,and rotational speed.An innovative disk-ball-disk device was developed to study the friction characteristics of aged grease in rolling bearings.Additionally,a grease lubrication and friction model were proposed to further evaluate the lubrication performance of aged grease,using measured rheological parameters and the kinematic velocities of the disk-ball-disk device as inputs.The calculated friction coefficients matched well with disk-ball-disk experimental results.FTIR analysis revealed that the non-soap thickener’s structure remained stable,but additives depleted at high speeds.The structure of lithium soap thickener decomposed severely,leading to oil bleeding and a shortened replenishment duration.Over aging time,both greases had lower friction and viscosity due to gradual thickener breakdown,releasing bled oil and extending replenishment.Radial load minimally affected the properties of aged grease.This study may provide valuable insights into the aging mechanisms of grease and the enhancement of rolling bearing lubrication.展开更多
As global populations grow, the generation of various waste materials like fats, oils, and grease (FOG), fruit waste, and other perishable wastes increases concurrently. Disposal of these highly putrescible waste prod...As global populations grow, the generation of various waste materials like fats, oils, and grease (FOG), fruit waste, and other perishable wastes increases concurrently. Disposal of these highly putrescible waste products in landfills consumes valuable landfill space. Anaerobic digestion can transform these waste materials into valuable components, including fertilizer and biogas, reducing the demand for landfill space. The current study is based on the hypothesis that incorporating high-strength organic waste into conventional wastewater sludge can enhance the production of onsite biogas at wastewater treatment plants, therefore contributing to the reduction of the plant’s energy demands from the grid. The batch anaerobic biodegradability test assays were performed for 63 days to observe the impact on the biomethane yield from adding high-strength organic waste to the wastewater sludge and to investigate the combined effects of co-digesting two different preselected high-strength organic waste streams. Additionally, physicochemical characterization was performed on different fruit waste juicing residuals to indicate which fruit wastes might increase anaerobic digestion efficiency. The highest methane yield of 243 mL/gVS and 280 mL/gVS, respectively, were obtained with two mixtures having 10% FOG as the sole substrate and 10% FOG along with 10% fruit waste. The study also assessed the siloxane concentrations present as trace contaminants in the biogas samples. An initial economic feasibility assessment of food waste co-digestion at two wastewater treatment plants in Florida was conducted using the Co-Digestion Economic Analysis Tool (CoEAT) model. Based on the laboratory results, the analysis indicated a net positive benefit of $39,472 for a medium-sized plant (10 - 30 MGD capacity) and $52,488 for a larger plant (>30 MGD capacity) after 15 years, while diverting 10 - 18 tons/day of food waste from landfills with an anticipated minimal increase in sludge volume production at food waste additions less than 10% of the digester feed as stated in the literature.展开更多
Three kinds of new conductive lubricating greases were prepared using lithium ionic liquids as the base oil and the polytetrafluoroethylene(PTFE)as the thickener.These lithium ionic liquids([Li(PEG)X])were obtained by...Three kinds of new conductive lubricating greases were prepared using lithium ionic liquids as the base oil and the polytetrafluoroethylene(PTFE)as the thickener.These lithium ionic liquids([Li(PEG)X])were obtained by blending lithium salts(LiBF4,LiPF6 and LiNTf2)with poly(ethylene glycol)(PEG)because lithium salts have an extremely high solubility in PEG.The conductivities and contact resistances of the prepared lubricating greases were investigated using the DDSJ‐308A conductivity meter and the reciprocating ball‐on‐disk UMT‐2MT sliding tester.In addition,their tribological properties were investigated in detail.Scanning electron microscopy and X‐ray photoelectron spectroscopy were employed to explore the friction mechanisms.The results suggest that the prepared lubricating greases have high conductivities and excellent tribological properties.The high conductivities are attributed to ion diffusion or migration of the lithium ionic liquids with an external electric field,and the excellent tribological properties depend on the formation of boundary protective films.展开更多
The mechanism of grease replenishment in and around a starved point contact was studied in this work.Greases made of different thickeners and same base oil were tested and compared.Disappearing and re-formation of a d...The mechanism of grease replenishment in and around a starved point contact was studied in this work.Greases made of different thickeners and same base oil were tested and compared.Disappearing and re-formation of a dynamic grease reservoir during operation revealed that grease bled oil to replenish contact.However,the replenishment process was slow because of the presence of grease fingers along the track and thickener-deposited film inside the track.The contact angles of base oil on the chromium-coated surface and thickener-deposited surfaces were measured.Results proved that the contact angle on the deposited film remarkably increased compared with that on the chromium-coated surface from 25° to more than 40°.However,the deposited film could be consumed with continuous rolling,and replenishment was then enhanced.展开更多
Fluorographene(FG)with narrow lateral size and thickness distributions was prepared by a liquid-phase exfoliation method,based on liquid cascade centrifugation.The Rtec MFT-5000 tribo-meter was used to investigate the...Fluorographene(FG)with narrow lateral size and thickness distributions was prepared by a liquid-phase exfoliation method,based on liquid cascade centrifugation.The Rtec MFT-5000 tribo-meter was used to investigate the lubricating performance of bentonite grease enhanced by the as-prepared FG.The results showed that the coefficient of friction and the wear volume of bentonite grease with 0.3 wt%FG were decreased by 20.4%and 44.9%,respectively,as compared to those of the base grease.The main reason is that FG can promote the formation of the tribo-chemical reaction film consisting of complex carbon oxide,Fe_(2)O_(3)and FeF_(3)on the friction surface,which can remarkably improve the performance of friction reduction and prevent the appearance of severe wear.展开更多
This study prepared four types of ionic liquid-modified polypyrrole(IL-modified PPy)as conductive additives and investigated their tribological performance and conductivity in polytetrafluoroethylene lubricating greas...This study prepared four types of ionic liquid-modified polypyrrole(IL-modified PPy)as conductive additives and investigated their tribological performance and conductivity in polytetrafluoroethylene lubricating grease.The results indicated that IL-modified PPy effectively enhanced the anti-wear performance and conductivity of the base grease.Among the additives,1-octyl-3-methylimidazolium tetrafluoroborate([OMIm][BF4])modified PPy showed superior performance compared to the other three additives,with the best effect observed at a mass fraction of 0.5%.X-ray photoelectron spectroscopy analysis revealed that IL-modified PPy forms a stable friction chemical film during the friction process,effectively enhancing the lubrication performance and conductivity of the base grease.This indicates broad potential applications in the field of conductive lubrication.展开更多
3-(5-(2.4-dichlorophyenyl)-4.5-dihydro-1H-pyrazol-3-yl)-4hydroxy-1-methylquinolin(1H)-one, 5-((4-hydroxy-8-methyl-2-oxo-1.2-dihydroquinolin-3-yl)methylene)-1-phenyl-2-hioxodihydropyrimidine-4.6(1H.5H)-dione, and 1-but...3-(5-(2.4-dichlorophyenyl)-4.5-dihydro-1H-pyrazol-3-yl)-4hydroxy-1-methylquinolin(1H)-one, 5-((4-hydroxy-8-methyl-2-oxo-1.2-dihydroquinolin-3-yl)methylene)-1-phenyl-2-hioxodihydropyrimidine-4.6(1H.5H)-dione, and 1-butyl-4-hydroxy-3-(5-styryl-4.5-dihydro-1H-pyrazol-3yl)quinolin-2(1H)-one were synthesized and characterized by spectroscopy analysis. These compounds are designated I, II and III, respectively. The antioxidants efficiency of the synthesized compounds in lubricating greases had been investigated using ASTM d-942 and ASTM d-664. The obtained data showed that the total acid number and oxygen pressure drop of these compounds in lubricating greases decrease in the order: Comp.III. < Comp.I. < Comp.II. The antioxidant efficiency of the prepared quinolinones derivatives was discussed. Acceptable correlations were obtained between the obtained oxidation inhibition and the calculated quantum chemical parameters.展开更多
The graphene-based semi-solid grease with low friction coefficient was prepared by highly dispersed mixing method. The friction testing result showed that the friction coefficient of the graphene oxidebased semi-solid...The graphene-based semi-solid grease with low friction coefficient was prepared by highly dispersed mixing method. The friction testing result showed that the friction coefficient of the graphene oxidebased semi-solid grease reduced from ca. 0.105 of graphite-based one to ca. 0.075, approximately 30% decreasing. Further, the graphene-based semi-solid grease shows the more outstandingly lubricating property, and the friction coefficient approximately drops to the range of between 0.04 and 0.06. By comparing with the graphite-based grease, the friction coefficient decreases about 40%-60% and the wear reduced over 50%.展开更多
A new category of lithium greases was synthesized by using poly-a-olefin(PAO8) and alkyl-tetralin as base oil, where the alkyl-tetralins were synthesized by the alkylation of tetralin and olefins. The influence of thi...A new category of lithium greases was synthesized by using poly-a-olefin(PAO8) and alkyl-tetralin as base oil, where the alkyl-tetralins were synthesized by the alkylation of tetralin and olefins. The influence of thickener concentration, alkyl-tetralin content and type of blend oils on the rheological and tribological performance of lithium grease was investigated. The microstructures of soap fibers were measured to reveal the structure-property correlations. The concentration of thickener and alkyl-tetralin content obviously affect the lubricating performance of lithium grease, while the molecular structure of alkyltetralin has no obvious impact on their properties. It was found that alkyl-tetralin could significantly enhance the thickening ability of PAO8 base oils, and decrease the amount of thickeners by 1.5%(mass).Lithium greases prepared using 20%(mass) alkyl-tetralin as co-base oil exhibited high colloidal stability,excellent rheological behaviors and tribological properties.展开更多
The tribological properties of graphene(GN) and graphite(G) as lubricant additives in lithium greases were investigated with a four-ball tribotester. The micro-morphology as well as the content and chemical state of e...The tribological properties of graphene(GN) and graphite(G) as lubricant additives in lithium greases were investigated with a four-ball tribotester. The micro-morphology as well as the content and chemical state of elements on the worn surfaces was characterized by scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). The results showed that the tribological performance of lithium grease could be significantly improved by the addition of graphene. During the friction process, an adhesion film and a deposition film consisted of graphene as well as a tribochemical reaction film composed of FeO, Fe_2O_3, FeOOH and LiOH could be formed on the tribosurface, and these complex films were responsible for the improved tribological performance of lithium grease.展开更多
基金financially supported by the Chongqing Construction Project of Innovation Teams in Colleges and Universities-Petroleum Products Application Engineering and Technology(Project No.KJTD201342)the Chongqing Project of Innovation Research by Postgraduates(Project No.CYB16130)
文摘In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners with different surfactant dosages and constituents were synthesized through intercalation reaction between sodium montmorillonite(NaM MT) and quaternary ammonium surfactants in aqueous solvents. The lubricating greases were prepared with the resulting organoclays, while the penetration and oil separation of lubricating greases were evaluated, respectively. The surface modification process of montmorillonite(MMT) was analyzed and the thickening mechanism of OMMT was discussed in this study. The experimental results showed that, with an increasing amount of surfactant, the basal spacing between the clay platelets was increasing and the structure of modifier molecules layer in the interlayer was changing from lateral bilayer to paraffin-type bilayer. The optimal properties of lubricating greases were achieved, when the structure of surfactant molecules loaded in the interlayer was the paraffin-type monolayer, which meant that the dosage of modifier was equal to 120—140 mmol/(100g). Meanwhile, it was found that the thickening performance, colloid stability, anti-wear and friction-reducing performance of lubricating greases were improved, when the surfactants were mixed with octadecyl trimethyl ammonium chloride(OTAC) and hexadecyl trimethyl ammonium chloride(HTAC). And the optimum mole ratio of two surfactants is was 1:1.
文摘Oxidation induction time(OIT) testing by differential scanning calorimetry(DSC) was used to evaluate the oxidation resistance of lubricating greases. Under the high temperature condition, bearing noise was detected when grease passed the initial stable stage of oxidation. The chemical and physical structure of grease samples before and after high temperature oxidation were also analyzed by FT-IR spectrometry and scanning electron microscopy(SEM), then the effects of oxidation at high temperature on bearing noise were investigated. It is found out that for lithium greases, oxidation of base oil and thickener is the main reason responsible for the increasing bearing noise. As regards the polyurea greases, the change of fiber microstructure at high temperature is the main reason for the increasing bearing noise.
文摘The wax gel grease (S0) was prepared from a mixture of 2.3:1 base oil blend (base oil grade 260/290, transformer oil), and microcrystalline wax in the presence of 0.1% - 2% of polyoxyethylene sorption nano-palmitate as antioxidant and 2,2 methylene bis (4-methyle-6-tertiary butyl phenol) as anticorrosion. It was found that the prepared Wax gel grease has inconvenient physico-chemical and dielectric properties, so in order to improve its physico-chemical properties (viscosity, penetration, dropping point and water resistance) and dielectric Properties (dielectric constant, dielectric loss and volume resistivity), Butyl rubber, isoprene rubber and bitumen were added separately as thickening agents to the prepared wax gel in certain proportion at certain frequency range 1 - 1000 KHz at 35°C. The best dielectric properties were achieved by adding butyl rubber to the prepared wax gel.
文摘Grease life refers to the time it takes for the grease to lose its ability to keep the lubrication due to grease degradation. As grease life is generally shorter than fatigue life of bearing, the service life of grease-lubricated rolling bearings is often dominated by grease life. When designing a bearing systemolecular weightith grease lubrication, it is necessary to define the operating conditions limits of the bearing, for which grease life becomes a determining factor. Prolongation of grease life becomes an especially important challenge when the bearing is to be operated trader high-speed, high-temperature, and other severe conditions. Selecting a number of commercially sold greases composed of varying base oils, the author evaluated their properties and analyzed how each property affected the grease life by performing a multiple regression analysis. The optimum grease composition to best exploit each property was also examined. The results revealed among others that one would need to first determine the base oil type and then maximize ultimate bleeding while minimizing the evaporation rate.
文摘Greases are composed by lubricating oil dispersed in a thickener that can be a metal soap, polymers or clays. Grease production using vegetable oils is increasing due to biodegradability requirements. Since vegetable oils present a worse oxidation and hydrolysis stability than mineral oils, it is usually difficult to produce a neutral grease using them. Four greases were produced using soybean oil as lubricating oil and lithium 12-hydroxy- stearate as thickener. The maximum temperature of reaction ranged from 230°C to 120°C in a bench process and a reduction in the final product acidity was observed (from 8.2% acid to 0.05% alkaline). Traditional tests to evaluate thickener structure resistance like 10,000-time worked penetration, roll stability and dropping point were performed and results compared. In addition, rheological tests were performed and the results were also compared. Results indicate that it is possible to produce a quite neutral grease using vegetable oils with good thickener structure properties.
基金support extended for this academic work by the Beijing Natural Science Foundation(No.2232066)the Open Project Foundation of State Key Laboratory of Solid Lubrication(No.LSL-2212).
文摘This study employs a stacking ensemble learning framework to establish a regression model for predicting the tribological properties of amide-based lubricating grease and determining the optimal additive ratios.Melamine cyanuric acid(MCA)was selected as the thickener,and three extreme-pressure anti-wear additives were used to prepare the lubricating grease.The tribological performance was tested using an MFT-R4000 reciprocating friction and wear machine.Based on the tribological experimental data,the synthetic minority oversampling technique(SMOTE)was utilized for data augmentation,and a stacking ensemble algorithm with Bayesian optimization of hyperparameters was used to construct a predictive model for tribological performance.Subsequently,within this model framework,single and multi-objective optimization models were developed,and the fruit fly algorithm was employed to find the optimal additive combination ratios,which were experimentally validated.The results demonstrated that the learning framework based on the stacking ensemble model could effectively predict the tribological properties of amide-based lubricating grease in small sample datasets,with the R2 for the average friction coefficient prediction reaching 0.9939 and for the wear scar width prediction reaching 0.9535.In the experimental validation of the optimal additive ratios,the relative error of the friction coefficient ratio scheme was 0.51%,and the relative error of the wear scar width was 1.10%.This finding suggests that the learning framework provides a novel approach for predicting the performance of amide-based lubricating grease and studying additive combinations.
基金supported by the Natural Science Basic Research Plan in Shaanxi Province of China(2022JM-251)the National Natural Science Foundation of China(51675409)the Liaoning Key Laboratory of Aeroengine Materials Tribology(LKLAMTF202401).
文摘In modern high-tech industries,such as aerospace,nuclear energy,and electric power,there is increasing demand for materials with high-temperature adaptability and superior lubrication properties.Grease is an essential mechanical component that is widely used to reduce mechanical friction,wear,and vibration.This paper comprehensively reviews recent progress in high-temperature grease,including design,performance indices,lubrication characteristics,development,and applications.This paper starts by outlining novel insights into the relationship between the composition and physicochemical properties of high-temperature greases,as well as other factors,emphasizing typical strategies for matrix reinforcement and high-temperature performance enhancement.The gravity analysis focuses on the intrinsic properties of high-temperature grease and the influence of working conditions on its tribological properties,leading to a detailed discussion of the lubrication mechanism.The innovative fusion of high-temperature grease with new materials such as nanomaterials and ionic liquids(ILs)and interdisciplinary research involving modern emerging fields such as artificial intelligence have led to further progress in the development of high-temperature grease,which has a wide range of applications in aerospace components,automotive parts,and turbines.Finally,this review concludes briefly with prospects for the challenges and future directions in high-temperature grease.
文摘This work investigated the temperature changes inside the bulk of lubricating greases under controlled high-shear stress conditions(250-500 s-1).For this purpose,a newly developed temperature-measuring cell called Calidus was successfully tested.The temperature changes(ΔT)have been related to the greases'components(thickener,base oil-type,and composition)and the structural degradation of the lubricating greases.Furthermore,a theoretical approach was proposed for calculating the internal temperature change of lubricating greases during shear stress.All greases showed an internal temperature profile characterised by a sudden rise inΔT within the first 4 h from starting the test and subsequentΔT decay until it reaches the steady state value.Furthermore,it was found that greases C1 and C5,formulated with lithium and calcium soap,respectively,with different soap content(16.1 wt%and 9.7 wt%,respectively),but the same base castor oil,showed the highest value of the maximumΔT,c.a.3.2 K,and the most drastic drop ofΔT.These greases showed both the highest specific densities and heat capacities.In addition,they showed the lowest ratio of expended energies(Rtee),which means more structural degradation in the stressed grease.On the contrary,the grease C3,with 13 wt%of Li-soap but the lowest base oil's viscosity,showed the lowest maximumΔT and the temperature profile was characterised by a moderate variation ofΔT along the test.The biogenic grease B3 developed a low-temperature change in the group of pure bio-genic greases close to grease C3.
文摘This study investigates the development of novel montmorillonite/castor oil blends to formulate sustainable lubricating greases to promote the replacement of petrochemicals industry-derived materials by substances obtained from renewable sources.Specifically,the effect of the thickener concentration on the rheological,chemical,thermal,tribological properties,and atomic force microscopy(AFM)microstructure of these systems were studied.The results showed that the C20A nanoclay content could be used to modulate the viscosity values,the linear viscoelastic functions,and tribological properties of these montmorillonite dispersions.In general,these gel-like dispersions exhibited remarkable lubricant properties;the samples showed values of the friction coefficient and wear scars similar or lower than those obtained with model bentonite grease.
基金supported by the open project of State Key Laboratory of Solid Lubrication,Lanzhou Institute of Chemical Physics,Chinese Academy of Sciences(1211)Natural Science foundation of Ningxia University(ZR1216).
文摘In this study,we synthesized two types of calcium sulfonate complex greases(barium soap and calcium soap)and investigated their physical,rheological,and tribological properties in detail.The test results showed that the evolution of their linear viscoelasticity functions with frequency were quite similar to those of traditional lubricating greases.Moreover,these two calcium sulfonate complex greases had good friction-reducing and antiwear properties at room temperature and at 150°C.In addition,by adding an organic molybdenum compound(MoDTC)to the base greases,we obtained a very low friction coefficient(0.065)for one of the greases(calcium soap)at 400 N and 500 N(maximum Hertzian pressures of 3.47 GPa and 3.74 GPa,respectively)at 150°C.X-ray photoelectron spectroscopy(XPS)analysis showed that the tribofilm was composed of some complex oxide species and CaCO3 that had formed on the worn surface.
基金Supported by National Natural Science Foundation of China(Grant No.52275206).
文摘Grease is extensively used in rolling bearings due to its inherent sealing properties.However,mechanical degradation typically occurs,resulting in a significantly shorter lifespan for the grease compared to the bearing.Investigating aging mechanisms is essential.This study utilized rolling bearings to obtain mechanically aged greases.The aged samples were then subjected to do rheological test,FTIR test and friction test to examine the effects of aging time,radial load,and rotational speed.An innovative disk-ball-disk device was developed to study the friction characteristics of aged grease in rolling bearings.Additionally,a grease lubrication and friction model were proposed to further evaluate the lubrication performance of aged grease,using measured rheological parameters and the kinematic velocities of the disk-ball-disk device as inputs.The calculated friction coefficients matched well with disk-ball-disk experimental results.FTIR analysis revealed that the non-soap thickener’s structure remained stable,but additives depleted at high speeds.The structure of lithium soap thickener decomposed severely,leading to oil bleeding and a shortened replenishment duration.Over aging time,both greases had lower friction and viscosity due to gradual thickener breakdown,releasing bled oil and extending replenishment.Radial load minimally affected the properties of aged grease.This study may provide valuable insights into the aging mechanisms of grease and the enhancement of rolling bearing lubrication.
文摘As global populations grow, the generation of various waste materials like fats, oils, and grease (FOG), fruit waste, and other perishable wastes increases concurrently. Disposal of these highly putrescible waste products in landfills consumes valuable landfill space. Anaerobic digestion can transform these waste materials into valuable components, including fertilizer and biogas, reducing the demand for landfill space. The current study is based on the hypothesis that incorporating high-strength organic waste into conventional wastewater sludge can enhance the production of onsite biogas at wastewater treatment plants, therefore contributing to the reduction of the plant’s energy demands from the grid. The batch anaerobic biodegradability test assays were performed for 63 days to observe the impact on the biomethane yield from adding high-strength organic waste to the wastewater sludge and to investigate the combined effects of co-digesting two different preselected high-strength organic waste streams. Additionally, physicochemical characterization was performed on different fruit waste juicing residuals to indicate which fruit wastes might increase anaerobic digestion efficiency. The highest methane yield of 243 mL/gVS and 280 mL/gVS, respectively, were obtained with two mixtures having 10% FOG as the sole substrate and 10% FOG along with 10% fruit waste. The study also assessed the siloxane concentrations present as trace contaminants in the biogas samples. An initial economic feasibility assessment of food waste co-digestion at two wastewater treatment plants in Florida was conducted using the Co-Digestion Economic Analysis Tool (CoEAT) model. Based on the laboratory results, the analysis indicated a net positive benefit of $39,472 for a medium-sized plant (10 - 30 MGD capacity) and $52,488 for a larger plant (>30 MGD capacity) after 15 years, while diverting 10 - 18 tons/day of food waste from landfills with an anticipated minimal increase in sludge volume production at food waste additions less than 10% of the digester feed as stated in the literature.
基金This work is supported by Hundreds Talent Program of Chinese Academy of Science.
文摘Three kinds of new conductive lubricating greases were prepared using lithium ionic liquids as the base oil and the polytetrafluoroethylene(PTFE)as the thickener.These lithium ionic liquids([Li(PEG)X])were obtained by blending lithium salts(LiBF4,LiPF6 and LiNTf2)with poly(ethylene glycol)(PEG)because lithium salts have an extremely high solubility in PEG.The conductivities and contact resistances of the prepared lubricating greases were investigated using the DDSJ‐308A conductivity meter and the reciprocating ball‐on‐disk UMT‐2MT sliding tester.In addition,their tribological properties were investigated in detail.Scanning electron microscopy and X‐ray photoelectron spectroscopy were employed to explore the friction mechanisms.The results suggest that the prepared lubricating greases have high conductivities and excellent tribological properties.The high conductivities are attributed to ion diffusion or migration of the lithium ionic liquids with an external electric field,and the excellent tribological properties depend on the formation of boundary protective films.
基金This research is supported by the National Natural Science Foundation of China
文摘The mechanism of grease replenishment in and around a starved point contact was studied in this work.Greases made of different thickeners and same base oil were tested and compared.Disappearing and re-formation of a dynamic grease reservoir during operation revealed that grease bled oil to replenish contact.However,the replenishment process was slow because of the presence of grease fingers along the track and thickener-deposited film inside the track.The contact angles of base oil on the chromium-coated surface and thickener-deposited surfaces were measured.Results proved that the contact angle on the deposited film remarkably increased compared with that on the chromium-coated surface from 25° to more than 40°.However,the deposited film could be consumed with continuous rolling,and replenishment was then enhanced.
基金Funded by Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJZD-K202212905)Natural Science Foundation of Chongqing,China(No.cstc2019jcyj-msxmX0453)。
文摘Fluorographene(FG)with narrow lateral size and thickness distributions was prepared by a liquid-phase exfoliation method,based on liquid cascade centrifugation.The Rtec MFT-5000 tribo-meter was used to investigate the lubricating performance of bentonite grease enhanced by the as-prepared FG.The results showed that the coefficient of friction and the wear volume of bentonite grease with 0.3 wt%FG were decreased by 20.4%and 44.9%,respectively,as compared to those of the base grease.The main reason is that FG can promote the formation of the tribo-chemical reaction film consisting of complex carbon oxide,Fe_(2)O_(3)and FeF_(3)on the friction surface,which can remarkably improve the performance of friction reduction and prevent the appearance of severe wear.
基金The authors would like to appreciate the financial support extended for this academic work by the Beijing Natural Science Foundation(Grants 2172053,2232066)the Open Project Foundation of State Key Laboratory of Solid Lubrication(Grant LSL-2212).
文摘This study prepared four types of ionic liquid-modified polypyrrole(IL-modified PPy)as conductive additives and investigated their tribological performance and conductivity in polytetrafluoroethylene lubricating grease.The results indicated that IL-modified PPy effectively enhanced the anti-wear performance and conductivity of the base grease.Among the additives,1-octyl-3-methylimidazolium tetrafluoroborate([OMIm][BF4])modified PPy showed superior performance compared to the other three additives,with the best effect observed at a mass fraction of 0.5%.X-ray photoelectron spectroscopy analysis revealed that IL-modified PPy forms a stable friction chemical film during the friction process,effectively enhancing the lubrication performance and conductivity of the base grease.This indicates broad potential applications in the field of conductive lubrication.
文摘3-(5-(2.4-dichlorophyenyl)-4.5-dihydro-1H-pyrazol-3-yl)-4hydroxy-1-methylquinolin(1H)-one, 5-((4-hydroxy-8-methyl-2-oxo-1.2-dihydroquinolin-3-yl)methylene)-1-phenyl-2-hioxodihydropyrimidine-4.6(1H.5H)-dione, and 1-butyl-4-hydroxy-3-(5-styryl-4.5-dihydro-1H-pyrazol-3yl)quinolin-2(1H)-one were synthesized and characterized by spectroscopy analysis. These compounds are designated I, II and III, respectively. The antioxidants efficiency of the synthesized compounds in lubricating greases had been investigated using ASTM d-942 and ASTM d-664. The obtained data showed that the total acid number and oxygen pressure drop of these compounds in lubricating greases decrease in the order: Comp.III. < Comp.I. < Comp.II. The antioxidant efficiency of the prepared quinolinones derivatives was discussed. Acceptable correlations were obtained between the obtained oxidation inhibition and the calculated quantum chemical parameters.
基金supported by the talent introduction fund of Yangzhou University
文摘The graphene-based semi-solid grease with low friction coefficient was prepared by highly dispersed mixing method. The friction testing result showed that the friction coefficient of the graphene oxidebased semi-solid grease reduced from ca. 0.105 of graphite-based one to ca. 0.075, approximately 30% decreasing. Further, the graphene-based semi-solid grease shows the more outstandingly lubricating property, and the friction coefficient approximately drops to the range of between 0.04 and 0.06. By comparing with the graphite-based grease, the friction coefficient decreases about 40%-60% and the wear reduced over 50%.
基金financially supported by the National Natural Science Foundation of China (U1910202, 21978194)the Key Research and Development Program of Shanxi Province (202102090301005)+1 种基金the Fund for Shanxi “1331 Project”the Shanxi Natural Science Foundation for Young Scientists (202103021223064)。
文摘A new category of lithium greases was synthesized by using poly-a-olefin(PAO8) and alkyl-tetralin as base oil, where the alkyl-tetralins were synthesized by the alkylation of tetralin and olefins. The influence of thickener concentration, alkyl-tetralin content and type of blend oils on the rheological and tribological performance of lithium grease was investigated. The microstructures of soap fibers were measured to reveal the structure-property correlations. The concentration of thickener and alkyl-tetralin content obviously affect the lubricating performance of lithium grease, while the molecular structure of alkyltetralin has no obvious impact on their properties. It was found that alkyl-tetralin could significantly enhance the thickening ability of PAO8 base oils, and decrease the amount of thickeners by 1.5%(mass).Lithium greases prepared using 20%(mass) alkyl-tetralin as co-base oil exhibited high colloidal stability,excellent rheological behaviors and tribological properties.
基金financially supported by the program of the General Logistics Department (AX214C002)the Chongqing Postgraduate Research and Innovation Project (CYB16130)the Young Scientist Fund of Logistical Engineering University (YQ16-420801)
文摘The tribological properties of graphene(GN) and graphite(G) as lubricant additives in lithium greases were investigated with a four-ball tribotester. The micro-morphology as well as the content and chemical state of elements on the worn surfaces was characterized by scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). The results showed that the tribological performance of lithium grease could be significantly improved by the addition of graphene. During the friction process, an adhesion film and a deposition film consisted of graphene as well as a tribochemical reaction film composed of FeO, Fe_2O_3, FeOOH and LiOH could be formed on the tribosurface, and these complex films were responsible for the improved tribological performance of lithium grease.
