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22 pages, 9674 KiB

Open AccessArticle

Friction Characteristics and Lubrication Properties of Spherical Hinge Structure of Swivel Bridge

by Yingsong Li, Wei Guo, Xiaoming Huang, Zeqi Chen and Ying Gao

Lubricants 2024, 12(4), 130; https://doi.org/10.3390/lubricants12040130 - 15 Apr 2024

Viewed by 392

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with [...] Read more.

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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13 pages, 5950 KiB

Open AccessArticle

The Performance of Carbon-Based Nanomaterials in Different Base Oils and an Oil Blend

by Jack Nasr and Diana-Luciana Cursaru

Lubricants 2024, 12(3), 90; https://doi.org/10.3390/lubricants12030090 - 13 Mar 2024

Viewed by 846

Abstract

Different carbon-based nanomaterials (fullerenes, graphene, SWCNTs, and SWCNT-COOH) were tested as additives in a base mineral oil, SN150; rapeseed oil (RSO); and a 50/50 by volume blend of the two using an HFRR (high-frequency reciprocating rig) tester for coefficient of friction (COF) and [...] Read more.

Different carbon-based nanomaterials (fullerenes, graphene, SWCNTs, and SWCNT-COOH) were tested as additives in a base mineral oil, SN150; rapeseed oil (RSO); and a 50/50 by volume blend of the two using an HFRR (high-frequency reciprocating rig) tester for coefficient of friction (COF) and wear scar diameter (WSD) determinations and a four-ball tester for welding point determinations. The concentrations considered for the HFRR tests were 0.1, 0.5, 1, and 2 wt.%, while the concentration considered for the welding point tests was 0.5 wt.%. The results of the welding point tests showed that the addition of different nanoparticles made it so that welding occurred at much lower pressures compared to the pure oils. This is due to the hardness of the nanoparticles, which increases the local temperature and pressure at the contact points between them and the surfaces, causing welding to occur much sooner. The results of the HFRR tests showed a possible synergistic effect between the fullerenes and SWCNT-COOH and the oil blend, which may be attributed to possible interactions that occurred at a molecular level between the nanoparticles and the different molecules of the oil blend. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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16 pages, 6291 KiB

Open AccessArticle

Evaluation of Antioxidant Properties and Molecular Design of Lubricant Antioxidants Based on QSPR Model

by Jianfang Liu, Yaoyun Zhang, Chenglingzi Yi, Rongrong Zhang, Sicheng Yang, Ting Liu, Dan Jia, Qing Yang and Shuai Peng

Lubricants 2024, 12(1), 3; https://doi.org/10.3390/lubricants12010003 - 22 Dec 2023

Viewed by 1230

Abstract

Two quantitative structure–property relationship (QSPR) models of hindered phenolic antioxidants in lubricating oils were established to help guide the molecular structure design of antioxidants. Firstly, stepwise regression (SWR) was used to filter out essential molecular descriptors without autocorrelation, including electronic, topological, spatial, and [...] Read more.

Two quantitative structure–property relationship (QSPR) models of hindered phenolic antioxidants in lubricating oils were established to help guide the molecular structure design of antioxidants. Firstly, stepwise regression (SWR) was used to filter out essential molecular descriptors without autocorrelation, including electronic, topological, spatial, and structural descriptors, and multiple linear regression (MLR) was used to construct QSPR models based on the screened variables. The two models are statistically sound, with R² values of 0.942 and 0.941, respectively. The models’ reliability was verified by the frontier molecular orbital energy gaps of the antioxidants. A hindered phenolic additive was designed based on the models. Its antioxidant property is calculated to be 20.9% and 11.0% higher than that of typical commercial antioxidants methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 2,2′-methylenebis(6-tert-butyl-4-methylphenol), respectively. The structure–property relationship of hindered phenolic antioxidants in lubricating oil obtained by computer-assisted analysis can not only predict the antioxidant properties of existing hindered phenolic additives but also provide theoretical basis and data support for the design or modification of lubricating oil additives with higher antioxidant properties. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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18 pages, 6266 KiB

Open AccessArticle

Fullerene Oil Tribology in Compression Piston Rings under Thermal Considerations

by Elias Tsakiridis and Pantelis Nikolakopoulos

Lubricants 2023, 11(12), 505; https://doi.org/10.3390/lubricants11120505 - 30 Nov 2023

Viewed by 1234

Abstract

To enhance the efficiency of automotive engines, a comprehensive understanding of friction generation within their components is paramount. Moreover, extensive global research efforts have been dedicated to nanoparticles, leading to the emergence of nanolubricants. In this study, an investigation was conducted focused on [...] Read more.

To enhance the efficiency of automotive engines, a comprehensive understanding of friction generation within their components is paramount. Moreover, extensive global research efforts have been dedicated to nanoparticles, leading to the emergence of nanolubricants. In this study, an investigation was conducted focused on the piston ring–cylinder tribological interaction using fullerenes as additives. This is a very important issue since the friction forces can be significantly reduced. In order to solve this problem, a 2D CFD approach was implemented, taking into account a roughness model and temperature variations. The obtained results clearly show a friction reduction using fullerenes as additives compared to both synthetic and monograde oils. Furthermore, using fullerene oils, the performance of the compression piston ring system is improved due to friction reduction and the change of the temperature distribution. This study is beyond SOTA, since there is a limited contribution in the field of such nanolubricants in compression piston ring system. It is evident that the friction force is reduced by 42% compared to synthetic oils, showing a perspective on more tribologically efficient internal combustion engines. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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28 pages, 10851 KiB

Open AccessArticle

Enhancing the Performance of Rapeseed Oil Lubricant for Machinery Component Applications through Hybrid Blends of Nanoadditives

by Belal G. Nassef, Florian Pape and Gerhard Poll

Lubricants 2023, 11(11), 479; https://doi.org/10.3390/lubricants11110479 - 06 Nov 2023

Cited by 4 | Viewed by 2091

Abstract

Bio-lubricants have demonstrated promising tribological and physical properties, suggesting their potential advantages in the lubrication of critical machinery components. This study investigates the impact of using blended individual and hybrid nanoadditives, such as graphene nanoplatelets, ZnO, and an ionic liquid (IL) of Trihexyltetradecylphosphonium [...] Read more.

Bio-lubricants have demonstrated promising tribological and physical properties, suggesting their potential advantages in the lubrication of critical machinery components. This study investigates the impact of using blended individual and hybrid nanoadditives, such as graphene nanoplatelets, ZnO, and an ionic liquid (IL) of Trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate, on the rheological, tribological, and physical characteristics of rapeseed oil. A commercial cutting fluid (BLASER Vasco 6000) (VB 6000) is used for comparison. The results revealed a substantial improvement in viscosity index (VI) values for mixtures containing graphene nanoplatelets, reaching up to 150%, as compared to VB 6000. Regarding the tribological behavior, the friction coefficient achieved a reduction of up to 20% at room temperature (RT) and 26% at 60 °C for the hybrid containing all three nanoadditives (H3), outperforming the commercial fluid. Moreover, H3 demonstrated the most substantial reductions in wear volume (84%) and surface roughness (60%). The wettability of H3 benefited from the combined mechanisms of the applied nanoadditives; its application the contact angle decreased by 63%, revealing its outstanding spreadability. The results reveal the high potential of the H3 hybrid as a competitive and green metal working fluid that can replace hostile and toxic ones in industrial applications. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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16 pages, 8734 KiB

Open AccessArticle

Effects of Contamination on Selected Rheological and Tribological Properties of Lubricating Greases Working in Underground Mines

by Maciej Paszkowski, Piotr Aleksander Stelmaszek and Justyna Krzak

Lubricants 2023, 11(10), 425; https://doi.org/10.3390/lubricants11100425 - 02 Oct 2023

Cited by 1 | Viewed by 1092

Abstract

This study examines the effect of mining pollutants and wear products on the rheological and tribological properties of a lubricating grease working in the microclimate of the Polkowice-Sieroszowice mine belonging to the KGHM Polska Miedź Group (Polkowice, Poland). The material under investigation is [...] Read more.

This study examines the effect of mining pollutants and wear products on the rheological and tribological properties of a lubricating grease working in the microclimate of the Polkowice-Sieroszowice mine belonging to the KGHM Polska Miedź Group (Polkowice, Poland). The material under investigation is a commercial lubricating grease thickened with complex lithium soap, based on mineral oil with a molybdenum disulfide (MoS₂) addition. A sample of the grease was taken from one of the friction junctions of a self-propelled drilling jumbo operated in the mine. Comparative tests of the fresh grease and the spent grease were carried out. For the two greases, rheological tests, i.e., dynamic oscillation tests and tests in steady flow conditions, were carried out at a constant shear rate. The rheological tests were conducted using a rotational rheometer. Moreover, the tribological characteristics of the tested greases under different friction junction loads were carried out using a ball-on-disc tribometer. Besides friction resistance, the lubrication ability of the two greases was also evaluated through an analysis of the wear of the steel disks after the friction process. Contour and topographic maps of the wear traces of the discs together with their wear profiles were compared. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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10 pages, 4334 KiB

Open AccessArticle

DFT Calculation of the Mechanism of the Acid-Catalyzed Aldol Condensation of a Lubricant Base Stock

by Yan Li, Lei Xia and Rendong Liu

Lubricants 2023, 11(8), 346; https://doi.org/10.3390/lubricants11080346 - 13 Aug 2023

Viewed by 901

Abstract

Aldehyde condensation is a reaction step in the oxidization of a lubricant base stock into high-molecular-weight products, forming sludge and a paint film, which lead to the failure of lubricating oil. Calculations on the basis of the density functional theory (DFT) were employed [...] Read more.

Aldehyde condensation is a reaction step in the oxidization of a lubricant base stock into high-molecular-weight products, forming sludge and a paint film, which lead to the failure of lubricating oil. Calculations on the basis of the density functional theory (DFT) were employed to investigate the reaction mechanism of the acid-catalyzed aldol condensation of a lubricant base stock. Carbonyl compounds could be converted into their resonant enol structures. However, the activation energy of the process was relatively high, and it was difficult to initiate. The existence of the acid could obviously decrease the activation energy of the reaction from 269.17–287.82 kJ/mol to 177.10–177.63 kJ/mol, and it significantly reduced the difficulty of initiating this reaction. The carbocation formed by the carbonyl compounds and acid could further react with the enol and produce an intermediate reaction product in which the chain of molecules grew longer. This process was not difficult to initiate, with a reaction activation energy of 65.10 kJ/mol. The intermediate product with a larger molecular weight could be converted into carbonyl compounds containing a β-hydroxy by removing a hydrogen proton from it. The energy barrier for this process was 193.15 kJ/mol, and it was not easy to initiate the reaction. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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18 pages, 5642 KiB

Open AccessArticle

The Enhancement of Overall Performance of Lubricating Grease by Adding Layered Double Hydroxides

by Yong Li, Weidong Zhou, Wanan Xue, Yongwang Huang, Qiang Zhang and Jingbin Han

Lubricants 2023, 11(6), 260; https://doi.org/10.3390/lubricants11060260 - 13 Jun 2023

Cited by 1 | Viewed by 1319

Abstract

In this work, MgAl-layered double hydroxides (LDH) were synthesized by co-precipitation method using a colloid mill and characterized by XRD and SEM. It was found that the environmentally friendly LDHs had greater performance than the traditional antioxidant. By adding LDHs into large electric [...] Read more.

In this work, MgAl-layered double hydroxides (LDH) were synthesized by co-precipitation method using a colloid mill and characterized by XRD and SEM. It was found that the environmentally friendly LDHs had greater performance than the traditional antioxidant. By adding LDHs into large electric shovel grease (GRK-A) in open-pit coal mine, the service lifetime of grease was extended by 20%. With the increase in LDH addition, the grease sample attains greater activation energy, and the thermal oxidation and decomposition resistance become stronger. Comparing the energy storage modulus and flow transition index at different temperatures, adding the right amount of LDHs needs close attention for the system oxidation resistance and viscoelasticity. For the electric shovel grease, the best oxidation resistance and rheological properties can be achieved by adding 2% of LDHs. The rheological viscosity–temperature curves show that the grease samples with different ratios of solid LDHs have better low-temperature properties than the mine grease. This work outlines a simple method for creating an environmentally sustainable lubricant additive with the use of LDH. LDH serves as a novel inorganic antioxidant additive that is optimal for open gear lubrication and sliding friction. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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14 pages, 9668 KiB

Open AccessArticle

Tribological Behavior of WS₂ Nanoparticles as Additives in Calcium Sulfonate Complex–Polyurea Grease

by Hong Zhang, Yimin Mo, Juncheng Lv and Jun Wang

Lubricants 2023, 11(6), 259; https://doi.org/10.3390/lubricants11060259 - 12 Jun 2023

Cited by 2 | Viewed by 1125

Abstract

In order to improve the tribological properties of calcium sulfonate complex–polyurea grease, WS₂ nanoparticles were used as additives to prepare WS₂ calcium sulfonate complex–polyurea grease. The tribological behavior of WS₂ grease on the GCr15 surface was systematically studied. The results [...] Read more.

In order to improve the tribological properties of calcium sulfonate complex–polyurea grease, WS₂ nanoparticles were used as additives to prepare WS₂ calcium sulfonate complex–polyurea grease. The tribological behavior of WS₂ grease on the GCr15 surface was systematically studied. The results indicate that WS₂ nanoparticles can significantly improve the extreme pressure performance of calcium sulfonate complex–polyurea grease. When the concentration of WS₂ nanoparticles is 2 wt.%, the friction coefficient decreases by 14.94%, and the maximum nonseizure load PB increases by 31.41%. As the temperature increases, the friction coefficient and wear rate of WS₂ grease first decrease and then increase. This is mainly attributed to the adsorption and frictional chemical reaction between WS₂ nanoparticles and the matrix. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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Review

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21 pages, 762 KiB

Open AccessReview

Tribological Application of Nanocomposite Additives in Industrial Oils

by Milan Bukvić, Sandra Gajević, Aleksandar Skulić, Slobodan Savić, Aleksandar Ašonja and Blaža Stojanović

Lubricants 2024, 12(1), 6; https://doi.org/10.3390/lubricants12010006 - 24 Dec 2023

Cited by 4 | Viewed by 1676

Abstract

The demand for an improvement in the tribological properties of lubricants used in various industrial plants, the automotive industry, and other power transmissions has resulted in the development of a whole family of improved lubricants based on nanotechnology. Especially important are nanotube additives, [...] Read more.

The demand for an improvement in the tribological properties of lubricants used in various industrial plants, the automotive industry, and other power transmissions has resulted in the development of a whole family of improved lubricants based on nanotechnology. Especially important are nanotube additives, which significantly improve the tribological properties of lubricants, primarily by reducing the friction coefficient and wear of the coupled elements but also by reducing the temperature load and increasing the stability of the oil film between the lubricated surfaces. The properties of nanotube-based additives were further improved using elements such as metal oxides and compounds based on titanium, molybdenum, aluminum, etc. This paper presents the results obtained in the field of research and application of nanocomposite lubricant additives. It also gives a partial comparative analysis of the research conducted in this field. The primary goal of this paper is to analyze the research results in the field of the application of nanotubes in lubricants and to indicate the importance of their application, such as improving the tribological properties of machines and reducing power losses. Furthermore, this paper shows the negative impact of nanoparticles on the environment and human health and the costs of applying some types of nanoparticles. Full article

(This article belongs to the Special Issue Additives for Lubricating Oil and Grease: Mechanism, Properties and Applications)

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