Journal Description
Lubricants
Lubricants
is an international, peer-reviewed, open access journal on tribology published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q2 (Mechanical Engineering)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 14.8 days after submission; acceptance to publication is undertaken in 3.5 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
3.5 (2022);
5-Year Impact Factor:
3.2 (2022)
Latest Articles
Research on the Preparation of Zirconia Coating on Titanium Alloy Surface and Its Tribological Properties
Lubricants 2024, 12(5), 154; https://doi.org/10.3390/lubricants12050154 (registering DOI) - 28 Apr 2024
Abstract
Titanium alloys have been widely used in aerospace and other fields due to their excellent properties such as light weight and high strength. However, the extremely poor tribological properties of titanium alloys limit their applications in certain special working conditions. In order to
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Titanium alloys have been widely used in aerospace and other fields due to their excellent properties such as light weight and high strength. However, the extremely poor tribological properties of titanium alloys limit their applications in certain special working conditions. In order to improve the tribological properties of titanium alloys, the zirconia coatings were prepared on the surface of a TC4 titanium alloy using the discharge plasma sintering method in this article. The influence of sintering parameters on properties such as density, adhesion, hardness, and phase composition, as well as tribological properties (friction coefficient, wear rate) were investigated, and the influence mechanism of the coating structure on its mechanical and frictional properties was analyzed. The results showed that, with the increase in sintering temperature, the density, bonding strength, and hardness of the zirconia coating were significantly improved. The zirconia coating prepared at a sintering temperature of 1500 °C and a sintering time of 20 min had the lowest friction coefficient and wear rate, which are 0.33 and 6.2 × 10−8 cm3·N−1·m−1, respectively. Numerical analysis showed that the increase in temperature and the extension of time contributed to the extension of the diffusion distance between zirconia and titanium, thereby improving the interfacial adhesion. The influence mechanism of different sintering temperatures and sintering times on the wear performance of zirconia coatings was explained through Hertz contact theory.
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(This article belongs to the Special Issue Friction and Wear of Ceramics)
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Open AccessArticle
Effect of Post-Plasma Nitrocarburized Treatment on Mechanical Properties of Carburized and Quenched 18Cr2Ni4WA Steel
by
Dazhen Fang, Jinpeng Lu, Haichun Dou, Zelong Zhou, Jiwen Yan, Yang Li and Yongyong He
Lubricants 2024, 12(5), 153; https://doi.org/10.3390/lubricants12050153 (registering DOI) - 28 Apr 2024
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Under extreme conditions such as high speed and heavy load, 18Cr2Ni4WA steel cannot meet the service requirements even after carburizing and quenching processes. In order to obtain better surface mechanical properties and tribological property, a hollow cathode ion source diffusion strengthening device was
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Under extreme conditions such as high speed and heavy load, 18Cr2Ni4WA steel cannot meet the service requirements even after carburizing and quenching processes. In order to obtain better surface mechanical properties and tribological property, a hollow cathode ion source diffusion strengthening device was used to nitride the traditional carburizing and quenching samples. Unlike traditional ion carbonitriding technology, the low-temperature ion carbonitriding technology used in this article can increase the surface hardness of the material by 50% after 3 h of treatment, from the original 600 HV0.1 to 900 HV0.1, while the core hardness only decreases by less than 20%. The effect of post-ion carbonitriding treatment on mechanical properties and tribological properties of the carburized and quenched 18Cr2Ni4WA steel was investigated. Samples in different treatment are characterized using optical microscopy (OM), scanning electron microscopy (SEM), optimal SRV-4 high temperature tribotester, as well as Vickers hardness tester. Under two conditions of 6N light load and 60 N heavy load, compared with untreated samples, the wear rate of ion carbonitriding samples decreased by more than 99%, while the friction coefficient remained basically unchanged. Furthermore, the careful selection of ion nitrocarburizing and carburizing tempering temperatures in this study has been shown to significantly enhance surface hardness and wear resistance, while preserving the overall hardness of the carburized sample. The present study demonstrates the potential of ion carbonitriding technology as a viable post-treatment method for carburized gears.
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Open AccessArticle
The Environmental and Economic Importance of Mixed and Boundary Friction
by
Robert Ian Taylor and Ian Sherrington
Lubricants 2024, 12(5), 152; https://doi.org/10.3390/lubricants12050152 (registering DOI) - 28 Apr 2024
Abstract
One route to reducing global CO2 emissions is to improve the energy efficiency of machines. Even small improvements in efficiency can be valuable, especially in cases where an efficiency improvement can be realized over many millions of newly produced machines. For example,
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One route to reducing global CO2 emissions is to improve the energy efficiency of machines. Even small improvements in efficiency can be valuable, especially in cases where an efficiency improvement can be realized over many millions of newly produced machines. For example, conventional passenger car combustion engines are being downsized (and also downspeeded). Increasingly, they are running on lower-viscosity engine lubricants (such as SAE 0W-20 or lower viscosity grades) and often also have stop–start systems fitted (to prevent engine idling when the vehicle is stopped). Some of these changes result in higher levels of mixed and boundary friction, and so accurate estimation of mixed/boundary friction losses is becoming of increased importance, for both estimating friction losses and wear volumes. Traditional approaches to estimating mixed/boundary friction, which employ real area of contact modelling, and assumptions such as the elastic deformation of asperities, are widely used, but recent experimental data suggest that some of these approaches underestimate mixed/boundary friction losses. In this paper, a discussion of the issues involved in reliably estimating mixed/boundary friction losses in machine elements is undertaken, highlighting where the key uncertainties lie. Mixed/boundary lubrication losses in passenger car and heavy-duty internal combustion engines are then estimated and compared with published data, and a detailed description of how friction is related to fuel consumption in these vehicles, on standard fuel economy driving cycles, is given. Knowing the amount of fuel needed to overcome mixed/boundary friction in these vehicles enables reliable estimates to be made of both the financial costs of mixed/boundary lubrication for today’s vehicles and their associated CO2 emissions, and annual estimates are reported to be approximately USD 290 billion with CO2 emissions of 480 million tonnes.
Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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Open AccessArticle
Experimental Research on Dynamic Characteristics of a Multi-Disc Rotor System Supported by Aerostatic Bearings
by
Zhimin Su, Jianbo Zhang, Yimou Cai and Dongjiang Han
Lubricants 2024, 12(5), 151; https://doi.org/10.3390/lubricants12050151 (registering DOI) - 27 Apr 2024
Abstract
Gas bearings have the advantages of small friction loss, wide applicable speed range, no pollution, etc., and have important application prospects in micro and small high-speed rotating machinery. However, due to its compressibility and low viscosity, its dynamic stability in high-speed rotating machinery
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Gas bearings have the advantages of small friction loss, wide applicable speed range, no pollution, etc., and have important application prospects in micro and small high-speed rotating machinery. However, due to its compressibility and low viscosity, its dynamic stability in high-speed rotating machinery is the key to constraining its development. The experimental study of shaft system dynamics is the main means to explore the mechanism of rotor behavior. On the test platform of dynamic characteristics of multi-disc rotor system supported by aerostatic bearings, experimental research on the nonlinear dynamic characteristics of a rotor system was carried out, and nonlinear vibration test and analysis methods, such as axial orbits, bifurcation diagrams, and spectral characteristics, were adopted, and vibration phenomena, including the critical rotational speed accumulating energy and low-frequency accumulating energy, were presented and the vibration characteristics of bearing fracture faults were presented. The bearing supply pressure and rubber damping pad were introduced as a method to suppress the low-frequency vibration of the aerostatic bearing rotor system, and its vibration-reduction effect was verified by experiments. The above results can provide technical support for vibration control and fault diagnosis of rotor systems supported by aerostatic bearings.
Full article
(This article belongs to the Special Issue Gas Lubrication and Dry Gas Seal)
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Open AccessArticle
The Effect of Ethanol Fuel-Diluted Lubricants on the Friction of Oil Control Ring Conjunction: A Combined Analytical and Experimental Investigation
by
Nich Morris, Sean Byrne, Michael Forder, Nader Dolatabadi, Paul King, Ramin Rahmani, Homer Rahnejat and Sebastian Howell-Smith
Lubricants 2024, 12(5), 150; https://doi.org/10.3390/lubricants12050150 (registering DOI) - 27 Apr 2024
Abstract
This paper presents an investigation of the frictional behaviour of three-piece piston oil control rings. A bespoke tribometer replicates the kinematics of the contact between a full oil control ring and the cylinder liner. The three-piece oil control ring is composed of two
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This paper presents an investigation of the frictional behaviour of three-piece piston oil control rings. A bespoke tribometer replicates the kinematics of the contact between a full oil control ring and the cylinder liner. The three-piece oil control ring is composed of two segments, separated by a waveform-type expander. The experimental results indicate the dominance of a mixed regime of lubrication throughout the stroke. This is particularly the case when the experiments are conducted at 80 °C, a typical engine sump temperature, when compared with those at 20 °C (a typical engine start-up temperature in the UK in the summer). A mixed hydrodynamic analytical model of the oil control ring–cylinder liner tribological interface is employed to apportion frictional contributions with their physical underlying mechanisms. Therefore, combined numerical and experimental investigations are extended to lubricant contamination/dilution by ethanol-based fuels. This study shows that the transition from E10 to E85 would have an insignificant effect on the friction generated in the oil control ring conjunction. This holistic approach, using a detailed predictive l mixed regime of lubrication model and a representative bespoke tribometry, has not hitherto been reported in the open literature.
Full article
(This article belongs to the Special Issue Selected Papers from the 8th Conference on Lubrication, Maintenance and Tribotechnology (LUBMAT))
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Open AccessReview
Two-Dimensional Nanomaterials in Hydrogels and Their Potential Bio-Applications
by
Zhongnan Wang, Hui Guo, Ji Zhang, Yi Qian and Yanfei Liu
Lubricants 2024, 12(5), 149; https://doi.org/10.3390/lubricants12050149 (registering DOI) - 27 Apr 2024
Abstract
Hydrogels with high hydrophilicity and excellent biocompatibility have been considered as potential candidates for various applications, including biomimetics, sensors and wearable devices. However, their high water content will lead to poor load-bearing and high friction. Currently, two-dimensional (2D) materials have been widely investigated
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Hydrogels with high hydrophilicity and excellent biocompatibility have been considered as potential candidates for various applications, including biomimetics, sensors and wearable devices. However, their high water content will lead to poor load-bearing and high friction. Currently, two-dimensional (2D) materials have been widely investigated as promising nanofillers to improve the mechanical and lubrication performances of hydrogels because of their unique physical–chemical properties. On one hand, 2D materials can participate in the cross-linking of hydrogels, leading to enhanced load-bearing capacity and fatigue resistance, etc.; on the other hand, using 2D materials as nanofillers also brings unique biomedical properties. The combination of hydrogels and 2D materials shows bright prospects for bioapplications. This review focusses on the recent development of high-strength and low-friction hydrogels with the addition of 2D nanomaterials. Functional properties and the underlying mechanisms of 2D nanomaterials are firstly overviewed. Subsequently, the mechanical and friction properties of hydrogels with 2D nanomaterials including graphene oxide, black phosphorus, MXenes, boron nitride, and others are summarized in detail. Finally, the current challenges and potential applications of using 2D nanomaterials in hydrogel, as well as future research, are also discussed.
Full article
(This article belongs to the Special Issue Tribology of 2D Nanomaterials)
Open AccessArticle
WLI, XPS and SEM/FIB/EDS Surface Characterization of an Electrically Fluted Bearing Raceway
by
Omid Safdarzadeh, Alireza Farahi, Andreas Binder, Hikmet Sezen and Jan Philipp Hofmann
Lubricants 2024, 12(5), 148; https://doi.org/10.3390/lubricants12050148 (registering DOI) - 27 Apr 2024
Abstract
Electrical bearing currents may disturb the performance of the bearings via electro-corrosion if they surpass a limit of ca. 0.1 to 0.3 A/mm2. A continuous current flow, or, after a longer time span, an alternating current or a repeating impulse-like current,
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Electrical bearing currents may disturb the performance of the bearings via electro-corrosion if they surpass a limit of ca. 0.1 to 0.3 A/mm2. A continuous current flow, or, after a longer time span, an alternating current or a repeating impulse-like current, damages the raceway surface, leading in many cases to a fluting pattern on the raceway. Increased bearing vibration, audible noise, and decreased bearing lubrication as a result may demand a replacement of the bearings. Here, an electrically corroded axial ball bearing (type 51208) with fluting patterns is investigated. The bearing was lubricated with grease lubrication and was exposed to 4 A DC current flow. It is shown that the electric current flow causes higher concentrations of iron oxides and iron carbides on the bearing raceway surface together with increased surface roughness, leading to a mixed lubrication also at elevated bearing speeds up to 1500 rpm. The “electrically insulating” iron oxide layer and the “mechanically hard” iron carbide layer on the bearing steel are analysed by WLI, XPS, SEM, and EDS. White Light Interferometry (WLI) is used to provide an accurate measurement of the surface topography and roughness. X-ray Photoelectron Spectroscopy (XPS) measurements are conducted to analyze the chemical surface composition and oxidation states. Scanning Electron Microscopy (SEM) is applied for high-resolution imaging of the surface morphology, while the Focused Ion Beam (FIB) is used to cut a trench into the bearing surface to inspect the surface layers. With the Energy Dispersive X-ray spectrometry (EDS), the presence of composing elements is identified, determining their relative concentrations. The electrically-caused iron oxide and iron carbide may develop periodically along the raceway due to the perpendicular vibrations of the rolling ball on the raceway, leading gradually to the fluting pattern. Still, a simulation of this vibration-induced fluting-generation process from the start with the first surface craters—of the molten local contact spots—to the final fluting pattern is missing.
Full article
(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 2nd Edition)
Open AccessArticle
Friction Coefficient of Wet Clutches as a Function of Service Mileage
by
Bangzhi Wu
Lubricants 2024, 12(5), 147; https://doi.org/10.3390/lubricants12050147 - 26 Apr 2024
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As a core component for efficient variable speed transmission and energy saving, wet clutches are widely used in the transmission systems of energy-saving and new energy vehicles. However, with an increase in the service mileage of the wet clutch, the friction coefficient undergoes
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As a core component for efficient variable speed transmission and energy saving, wet clutches are widely used in the transmission systems of energy-saving and new energy vehicles. However, with an increase in the service mileage of the wet clutch, the friction coefficient undergoes alterations. This leads to a deterioration of the control accuracy of the clutch transmission torque, which ultimately has a negative impact on the dynamic characteristics and driving safety of the entire vehicle. In order to understand the service behavior of the friction coefficient in a wet clutch, wet clutches with different service mileages were investigated experimentally and theoretically. The results show that as the service mileage increased, the hydrodynamic lubrication phase was extended. Analyses of the three-dimensional profile of the friction plate and the theoretical simulation of the friction revealed that the edge ridges of the friction pads were flattened. This increased the clutch engagement force when the asperities on the separator and friction plates came into contact.
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Open AccessArticle
Tribological Behavior of GTL Base Oil Improved by Ni-Fe Layered Double Hydroxide Nanosheets
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Shuo Xiang, Xinghao Zhi, Hebin Bao, Yan He, Qinhui Zhang, Shigang Lin, Bo Hu, Senao Wang, Peng Lu, Xin Yang, Qiang Tian and Xin Du
Lubricants 2024, 12(5), 146; https://doi.org/10.3390/lubricants12050146 - 26 Apr 2024
Abstract
The layered double hydroxide (LDH) has been practically applied in the field of tribology and materials science due to its unique physicochemical properties, weak bonding, flexible structural composition, and adjustable interlayer space. In this work, a series of ultrathin and flexible composition of
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The layered double hydroxide (LDH) has been practically applied in the field of tribology and materials science due to its unique physicochemical properties, weak bonding, flexible structural composition, and adjustable interlayer space. In this work, a series of ultrathin and flexible composition of Ni-Fe LDH samples were prepared via a cost-effective room-temperature co-precipitation process. Then, they were mechanically dispersed into GTL base oil and their lubricating performance were tested by a four-ball tribometer. It is found that the variation of Ni-Fe ratio of Ni-Fe LDH has a great influence on the improvement of lubricating performance of GTL base oil. At the same concentration (0.3 mg/mL), the Ni-Fe LDH with Ni/Fe ratio of 6 was demonstrated to exhibit the best lubricating performance and the AFC, WSD, the wear volume, surface roughness and average wear scar depth decreased 51.3%, 30.8%, 78.4%, 6.7% and 50.0%, respectively. SEM-EDS and X-ray photoelectron spectra illustrated that the tribo-chemical film consisting of iron oxides and NiO with better mechanical properties formed and slowly replaced the physical film, which resists scuffing and protect solid surface from severe collisions.
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(This article belongs to the Special Issue Tribology of 2D Nanomaterials)
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Open AccessArticle
An Experimental Study on the Distribution of Grease in Cylindrical Roller Bearings
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He Liang, Yan Lu, Wenzhong Wang, Yi Sun, Jingjing Zhao and Yulong Guo
Lubricants 2024, 12(5), 145; https://doi.org/10.3390/lubricants12050145 - 25 Apr 2024
Abstract
The lubrication performance of bearings is greatly influenced by the distribution of the lubricant. In this study, a cylindrical rolling bearing test rig was constructed and presented. The distribution of grease and lubricating oil along the contact region was examined using the laser-induced
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The lubrication performance of bearings is greatly influenced by the distribution of the lubricant. In this study, a cylindrical rolling bearing test rig was constructed and presented. The distribution of grease and lubricating oil along the contact region was examined using the laser-induced fluorescence technique, and the thickness of the layer was determined. The lubricating oil and grease layer thickness distribution map was acquired. The effects of supply amount, thickener content, and speed on grease distribution were examined. Mechanisms for replenishing the line contact area were investigated.
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(This article belongs to the Special Issue Tribological Study in Rolling Bearing)
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Simulation Analysis and Experimental Study on the Fluid–Solid–Thermal Coupling of Traction Motor Bearings
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Hengdi Wang, Han Li, Zheming Jin, Jiang Lin, Yongcun Cui, Chang Li, Heng Tian and Zhiwei Wang
Lubricants 2024, 12(5), 144; https://doi.org/10.3390/lubricants12050144 - 25 Apr 2024
Abstract
The traction motor is a crucial component of high-speed electric multiple units, and its operational reliability is directly impacted by the temperature increase in the bearings. To accurately predict and simulate the temperature change process of traction motor bearings during operation, a fluid–solid–thermal
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The traction motor is a crucial component of high-speed electric multiple units, and its operational reliability is directly impacted by the temperature increase in the bearings. To accurately predict and simulate the temperature change process of traction motor bearings during operation, a fluid–solid–thermal simulation analysis model of grease-lubricated deep groove ball bearings was constructed. This model aimed to simulate the temperature rise of the bearing and the grease flow process, which was validated through experiments. The results from the simulation analysis and tests indicate that the temperature in the contact zone between the bearing rolling element and the raceway, as well as the ring temperature, initially increases to a peak and then gradually decreases, eventually stabilizing once the bearing’s heat generation power and heat transfer power reach equilibrium. Furthermore, the established fluid–solid–thermal coupling simulation analysis model can accurately predict the amount of grease required for effective lubrication in the bearing cavity, which stabilizes along with the bearing temperature. The findings of this research can serve as a theoretical foundation and technical support for monitoring the health status of high-speed EMU traction motor bearings.
Full article
(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 2nd Edition)
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Optimal Design of Boundary Angle for Gas Foil Thrust Bearing Thermal Performance
by
Bin Hu, Anping Hou, Rui Deng, Xiaodong Yang, Zhiyong Wu, Qifeng Ni and Zhong Li
Lubricants 2024, 12(5), 143; https://doi.org/10.3390/lubricants12050143 - 24 Apr 2024
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As the energy density and efficiency requirements of air compressors continue to increase, gas foil thrust bearings face a high risk of thermal failure due to their elevated speed and limited cooling space. This paper proposes a novel structure for gas foil thrust
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As the energy density and efficiency requirements of air compressors continue to increase, gas foil thrust bearings face a high risk of thermal failure due to their elevated speed and limited cooling space. This paper proposes a novel structure for gas foil thrust bearings with enhanced thermal characteristics. A thermo-elastic–hydrodynamic model is developed using a thermal-fluid–solid interaction approach to investigate aerodynamic and thermal performance. The load capacity and thermal characteristics of nine different boundary angles are analyzed. The model is validated, and the actual characteristics of gas foil bearings with various boundary angles are examined using a test rig. The results indicate that, compared to conventional gas foil thrust bearings with a boundary angle of 0°, the new structure with a boundary angle ranging from −10° to −5° not only maintains the load carrying capacity but also improves thermal characteristics. Furthermore, this improvement becomes more pronounced with higher rotational speeds. Therefore, the proposed optimization is advantageous in reducing the risk of thermal failure.
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Open AccessArticle
Vibration-Based Detection of Axlebox Bearing Considering Inner and Outer Ring Raceway Defects
by
Chuang Liu, Xinwen Zhang, Ruichen Wang, Qiang Guo and Junguo Li
Lubricants 2024, 12(5), 142; https://doi.org/10.3390/lubricants12050142 - 23 Apr 2024
Abstract
The occurrence of an axlebox bearing ring raceway defect is an inevitable and commonly observed phenomenon in railway wheels. It not only leads to surface damage but also poses the potential threat of further damage and degradation, thereby increasing the risks associated with
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The occurrence of an axlebox bearing ring raceway defect is an inevitable and commonly observed phenomenon in railway wheels. It not only leads to surface damage but also poses the potential threat of further damage and degradation, thereby increasing the risks associated with running safety and maintenance costs. Hence, it becomes imperative to detect raceway defects at an early stage to mitigate safety hazards and reduce maintenance efforts. In this study, the focus lies in investigating the effectiveness of vibration-based detection techniques for identifying raceway defects in high-speed train axlebox bearing systems. To achieve this, a dynamic model that accurately represents the coupling dynamics between the vehicle and the track is developed. This model incorporates various dynamic factors, such as traction transmission, gear transmission, and track geometry irregularities. By using the comprehensive dynamic model, the dynamic responses of the axlebox can be accurately calculated. The proposed methodology primarily revolves around analysing the vertical vibrations of the axlebox caused by raceway defects in both the time and frequency domains. Additionally, an envelope analysis using a developed band-pass filter is also employed. The results obtained from this study clearly demonstrate the successful detection of raceway defects in a more realistic vehicle model, thereby providing an efficient approach for the detection of axlebox bearing raceway defects. Consequently, this research contributes significantly to the field of high-speed train systems and paves the way for enhanced safety and maintenance practices.
Full article
(This article belongs to the Special Issue Condition Monitoring and Simulation Analysis of Bearings)
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Open AccessArticle
Cold-Flow Properties of Estolides: The Older (D97 and D2500) versus the Mini-(D5773 and D5949) Methods
by
Grigor B. Bantchev, Helen Ngo, Yunzhi Chen, DeMichael D. Winfield and Steven C. Cermak
Lubricants 2024, 12(5), 141; https://doi.org/10.3390/lubricants12050141 - 23 Apr 2024
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There is growing research on developing new and sustainable lubricants. Sustainable lubricants with adequate cold-flow properties are of particular interest for many applications. One limitation of the established methods for measuring cold flow properties is the large volume needed to test samples. This
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There is growing research on developing new and sustainable lubricants. Sustainable lubricants with adequate cold-flow properties are of particular interest for many applications. One limitation of the established methods for measuring cold flow properties is the large volume needed to test samples. This makes initial screening of many hard-to-synthesize samples difficult. In the current study, we compared the results of the older, widely accepted ASTM methods D97 (pour point, PP) and D2500 (cloud point, CP) to the newer, smaller-volume, and easier-to-perform methods D5949 and D5773 for bio-based base oils (estolides and iso-estolides). The CP results were in good agreement for less colored samples, but D5773 gave lower values for some darker (Gardner color >8) samples, especially esters. The D5949 showed a tendency to report slightly higher PP, especially for the lower values. Viscosities and densities in a wide temperature range (15 to 120 °C) were also measured. The surface tensions were estimated by a literature group method. Viscosity and density effects can only partially explain the differences in the PP values from the two methods. In conclusion, the newer mini-methods are an acceptable substitution when larger volumes are not accessible, unless the sample is too dark.
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Open AccessArticle
Analysis of Thermo-Hydrodynamic Lubrication of Three-Lobe Semi-Floating Ring Bearing Considering Temperature–Viscosity Effect and Static Pressure Flow
by
Jiwei Dong, Huabing Wen, Junchao Zhu, Junhua Guo and Chen Zong
Lubricants 2024, 12(4), 140; https://doi.org/10.3390/lubricants12040140 - 18 Apr 2024
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High-power diesel engine turbochargers predominantly utilize floating ring bearings as their primary supporting components. To further enhance their load capacity, multi-lobe noncircular bearings have been progressively employed. This study focuses on the investigation of noncircular three-lobe SFRBs (semi-floating ring-bearing structures) in marine turbochargers.
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High-power diesel engine turbochargers predominantly utilize floating ring bearings as their primary supporting components. To further enhance their load capacity, multi-lobe noncircular bearings have been progressively employed. This study focuses on the investigation of noncircular three-lobe SFRBs (semi-floating ring-bearing structures) in marine turbochargers. Employing the half-step center Finite Difference Method (FDM) and the Newton–Raphson iterative procedure, the impact of operational parameters such as the journal speed, external load, oil supply pressure, and oil supply temperature on the static and dynamic characteristics of the inner oil film is analyzed. Subsequently, the accuracy of the theoretical model is validated through a comparative analysis of simulation results obtained from Dyrobes and Fluent. The findings indicate that as the oil supply pressure and temperature increase, the temperature rise and maximum oil film pressure of the three-lobe SFRBs gradually decrease, while the oil film thickness progressively increases, thereby significantly improving the lubrication state. The load capacity of the three-lobe SFRBs is primarily sustained by the bottom tile, where wall friction is most likely to occur. Additionally, within the actual speed range, the stiffness and damping of the three-lobe SFRBs exhibit noticeable nonlinear characteristics.
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Open AccessArticle
Mechanical and Tribological Behaviour of Surface-Graphitised Al-1100 Alloy
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Baidehish Sahoo, Jinu Paul and Abhishek Sharma
Lubricants 2024, 12(4), 139; https://doi.org/10.3390/lubricants12040139 - 18 Apr 2024
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This study details the mechanical incorporation of graphite particles into the surface of aluminium (Al-1100) to fabricate surface composites using an electrical resistance heating-assisted pressing method. Initially, the aluminium surface is coated with graphite via solution casting. Incorporation is accomplished by locally heating
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This study details the mechanical incorporation of graphite particles into the surface of aluminium (Al-1100) to fabricate surface composites using an electrical resistance heating-assisted pressing method. Initially, the aluminium surface is coated with graphite via solution casting. Incorporation is accomplished by locally heating the graphite–aluminium interface with electrical resistance heating and subsequent mechanical pressure application. The magnitude of softening of the aluminium surface can be regulated by process considerations such as the applied current and heating duration. Microstructural assessment of the aluminium–graphite composite was conducted using SEM, TEM, Raman spectroscopy, and XRD. The surface mechanical properties and reduced Young’s modulus were improved by more than 200% and 150%, respectively. A detailed tribological study was conducted, and the study suggested that the wear resistance and COF improved by more than 50%. The progress in wear resistance and COF is corroborated by the microstructural changes in the matrix suggested by the Raman spectroscopy and XRD results.
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Open AccessReview
Structural Superlubricity of Two-Dimensional Materials: Mechanisms, Properties, Influencing Factors, and Applications
by
Fan-Bin Wu, Sheng-Jian Zhou, Jia-Hu Ouyang, Shu-Qi Wang and Lei Chen
Lubricants 2024, 12(4), 138; https://doi.org/10.3390/lubricants12040138 - 18 Apr 2024
Abstract
Structural superlubricity refers to the lubrication state in which the friction between two crystalline surfaces in incommensurate contact is nearly zero; this has become an important branch in recent tribological research. Two-dimensional (2D) materials with structural superlubricity such as graphene, MoS2,
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Structural superlubricity refers to the lubrication state in which the friction between two crystalline surfaces in incommensurate contact is nearly zero; this has become an important branch in recent tribological research. Two-dimensional (2D) materials with structural superlubricity such as graphene, MoS2, h-BN, and alike, which possess unique layered structures and excellent friction behavior, will bring significant advances in the development of high-performance microelectromechanical systems (MEMS), as well as in space exploration, space transportation, precision manufacturing, and high-end equipment. Herein, the review mainly introduces the tribological properties of structural superlubricity among typical 2D layered materials and summarizes in detail the underlying mechanisms responsible for superlubricity on sliding surfaces and the influencing factors including the size and layer effect, elasticity effect, moiré superlattice, edge effect, and other external factors like normal load, velocity, and temperature, etc. Finally, the difficulties in achieving robust superlubricity from micro to macroscale were focused on, and the prospects and suggestions were discussed.
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(This article belongs to the Special Issue 2D Materials in Tribology)
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Open AccessArticle
Effect of Copper Nanoparticles Surface-Capped by Dialkyl Dithiophosphate on Different Base Oil Viscosity
by
Xufei Wang, Shuguang Fan, Ningning Song, Laigui Yu, Yujuan Zhang and Shengmao Zhang
Lubricants 2024, 12(4), 137; https://doi.org/10.3390/lubricants12040137 - 18 Apr 2024
Abstract
In order to more accurately characterize the effects of nanoparticles on lubricant viscosity, the effects of copper dialkyl dithiophosphate (HDDP)-modified (CuDDP) nanoparticles on the dynamic viscosity of mineral oils 150N, alkylated naphthalene (AN5), diisooctyl sebacate (DIOS), and polyalphaolefins (PAO4, PAO6, PAO10, PAO40, and
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In order to more accurately characterize the effects of nanoparticles on lubricant viscosity, the effects of copper dialkyl dithiophosphate (HDDP)-modified (CuDDP) nanoparticles on the dynamic viscosity of mineral oils 150N, alkylated naphthalene (AN5), diisooctyl sebacate (DIOS), and polyalphaolefins (PAO4, PAO6, PAO10, PAO40, and PAO100) were investigated at an experimental temperature of 40 °C and additive mass fraction ranging from 0.5% to 2.5%. CuDDP exhibits a viscosity-reducing effect on higher-viscosity base oils, such as PAO40 and PAO100, and a viscosity-increasing effect on lower-viscosity base oils, namely, 150N, AN5, DIOS, PAO4, PAO6, and PAO10. These effects can be attributed to the interfacial slip effect and the shear resistance of the nanoparticles. The experimental dynamic viscosity of the eight base oils containing CuDDP was compared with that calculated by the three classical formulae of nanofluid viscosity, The predicted viscosity values of the formulae deviated greatly from the experimental viscosity values, with the maximum deviation being 7.9%. On this basis, the interface slip effect was introduced into Einstein’s formula, the interface effect was quantified with the aniline point of the base oil, and a new equation was established to reflect the influence of CuDDP nanoparticles on lubricating oil viscosity. It can better reflect the influence of CuDDP on the viscosity of various base oils, and the deviation from the experimental data is less than 1.7%.
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(This article belongs to the Special Issue Functional Lubricating Materials)
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The Effect of Lubricant’s Viscosity on Reducing the Frictional-Induced Fluctuation on the Onset of Friction
by
Shutian Liu, Juncheng Lv and Chuanbo Liu
Lubricants 2024, 12(4), 136; https://doi.org/10.3390/lubricants12040136 - 17 Apr 2024
Abstract
The initial friction stage between the contacting materials would generate a maximum shear force and an unstable fluctuating time, which had a negative effect on the entire frictional system, especially at low temperature conditions. In order to decrease the occurring shear force and
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The initial friction stage between the contacting materials would generate a maximum shear force and an unstable fluctuating time, which had a negative effect on the entire frictional system, especially at low temperature conditions. In order to decrease the occurring shear force and fluctuating time on the onset of friction, two different lubricating oils were applied in this study to investigate the influence of lubricant’s viscosity on these friction behaviors. The frictional experiments were conducted between the steel ball and the 40CrMnMo, and special attention was paid to the relationship between maximum friction force, fluctuating time, frictional vibration and the initial lubricant temperature. The results showed that the friction force first increased to the maximum value and then experienced an oscillation damping period (fluctuating time) before it reached a stable state. And this fluctuating behavior caused corresponding vibrations on the initial contacting. However, compared to the high viscosity lubricating oil (HO), the low viscosity lubricating oil (LO) contributed to more than 50% reductions on max friction force, fluctuating time and vibration at the cold start (0 °C). Moreover, the weakened initial frictional fluctuation was conducive to generating a low and stable friction coefficient (COF) and wear loss of the long-term test. The discrepancy on lubricating performance was that the low viscosity provided high fluidity, which allowed rapid distribution of the lubricant between the contacting surfaces and formed an intact lubricating film. Similarly, the high temperature decreased the viscosity of HO and thus led to satisfactory friction reductions. The knowledge gained herein provides a supporting theory on the design and preparation of a lubricating oil with high performance.
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(This article belongs to the Special Issue Friction–Vibration Interactions)
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Open AccessArticle
Effect of Sodium Alkane Sulfonate Addition on Tribological Properties of Emulsion for Cold Rolling Strips: Experimental and Simulation Investigations
by
Daoxin Su, Jianlin Sun, Erchao Meng, Yueting Xu and Mengxiao Zhang
Lubricants 2024, 12(4), 135; https://doi.org/10.3390/lubricants12040135 - 17 Apr 2024
Abstract
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Cold rolling emulsion contains a variety of functional additives, which often exhibit complex interactions with each other. Sodium alkane sulfonate (SAS) is a common corrosion inhibitor used in cold rolling emulsions for temporary rust prevention. In this study, it was found that SAS
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Cold rolling emulsion contains a variety of functional additives, which often exhibit complex interactions with each other. Sodium alkane sulfonate (SAS) is a common corrosion inhibitor used in cold rolling emulsions for temporary rust prevention. In this study, it was found that SAS would deteriorate the tribological properties of the emulsion. Emulsions containing SAS and different friction modifiers were prepared. Tribology tests were carried out on a four-ball friction and wear tester. White light interferometer was used to investigate the 3D morphology of the friction surface and wear volume. Microscopic morphology of friction surfaces was observed using a scanning electron microscope (SEM). The chemical activity and electrostatic potential of the molecules were calculated based on density functional theory (DFT). The adsorption energies of additives on metal surfaces were calculated via molecular dynamics (MD) simulation. The results indicate that the strong electrostatic force gives SAS an advantage in competitive adsorption with ester friction modifiers due to the positive charge on the metal surface. This results in the friction modifier not functioning properly and the tribological properties of the emulsion being significantly reduced.
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