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Lubricants, Volume 9, Issue 4 (April 2021) – 12 articles

Cover Story (view full-size image): Relatively little is known about the evolution of the coefficient of friction (CoF) during a gait cycle in total knee replacement. Here, we describe the CoF during a gait cycle and investigate its association with joint kinematics, contact load, and relative velocity. The artificial knee was simulated by a cobalt–chromium wheel that slides and rolls on a polyethylene flat lubricated by water or proteinaceous solution. We found that the CoF is not a constant but fluctuates between 0.15 and close to zero. Cross-correlation suggests that this is primarily an effect of the slide-to-roll ratio and the contact load. View this paper.
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13 pages, 4455 KiB  
Article
Novel Uses of Al2O3/Mos2 Hybrid Nanofluid in MQCL Hard Milling of Hardox 500 Steel
by Tran Minh Duc, Tran The Long and Ngo Minh Tuan
Lubricants 2021, 9(4), 45; https://doi.org/10.3390/lubricants9040045 - 16 Apr 2021
Cited by 18 | Viewed by 2797
Abstract
In recent years, the application of environmentally friendly cutting fluids in the metal cutting industry has been a growing concern in all over the world. In this study, the minimum quantity cooling lubrication (MQCL) technique, which uses very small amount of cutting oil, [...] Read more.
In recent years, the application of environmentally friendly cutting fluids in the metal cutting industry has been a growing concern in all over the world. In this study, the minimum quantity cooling lubrication (MQCL) technique, which uses very small amount of cutting oil, is motivated to apply to the hard milling process of Hardox 500 steel. Further, rice bran oil, a natural biodegradable oil, is used as the base fluid of Al2O3/MoS2 hybrid nanofluid. ANOVA analysis is used to study the influences of nanoparticle concentration, cutting speed, and feed rate on surface roughness. The obtained results indicate that good surface quality is achieved and the cutting speed is significantly increased to 140 m/min (about 2.55–2.80 times higher than the recommended values) due to the better cooling and lubricating effects from MQCL system and Al2O3/MoS2 hybrid nanofluid. Moreover, the microstructure of the machined surface proves the formation of MoS2 tribo film by using Al2O3/MoS2 hybrid nanofluid, indicating that the effectiveness of each type of nanoparticle in hybrid nanofluid has been promoted. Furthermore, the important technical guides for machining Hardox 500 steel are provided. Full article
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23 pages, 11160 KiB  
Article
Run-Up Simulation of a Semi-Floating Ring Supported Turbocharger Rotor Considering Thrust Bearing and Mass-Conserving Cavitation
by Christian Ziese, Cornelius Irmscher, Steffen Nitzschke, Christian Daniel and Elmar Woschke
Lubricants 2021, 9(4), 44; https://doi.org/10.3390/lubricants9040044 - 16 Apr 2021
Cited by 6 | Viewed by 2799
Abstract
The vibration behaviour of turbocharger rotors is influenced by the acting loads as well as by the type and arrangement of the hydrodynamic bearings and their operating condition. Due to the highly non-linear bearing behaviour, lubricant film-induced excitations can occur, which lead to [...] Read more.
The vibration behaviour of turbocharger rotors is influenced by the acting loads as well as by the type and arrangement of the hydrodynamic bearings and their operating condition. Due to the highly non-linear bearing behaviour, lubricant film-induced excitations can occur, which lead to sub-synchronous rotor vibrations. A significant impact on the oscillation behaviour is attributed to the pressure distribution in the hydrodynamic bearings, which is influenced by the thermo-hydrodynamic conditions and the occurrence of outgassing processes. This contribution investigates the vibration behaviour of a floating ring supported turbocharger rotor. For detailed modelling of the bearings, the Reynolds equation with mass-conserving cavitation, the three-dimensional energy equation and the heat conduction equation are solved. To examine the impact of outgassing processes and thrust bearing on the occurrence of sub-synchronous rotor vibrations separately, a variation of the bearing model is made. This includes run-up simulations considering or neglecting thrust bearings and two-phase flow in the lubrication gap. It is shown that, for a reliable prediction of sub-synchronous vibrations, both the modelling of outgassing processes in hydrodynamic bearings and the consideration of thrust bearing are necessary. Full article
(This article belongs to the Special Issue Advances in Lubricated Bearings)
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16 pages, 8492 KiB  
Article
Tribological Evaluation of Turbostratic 2D Graphite as Oil Additive
by Halley Welther Jacques Dias, Alessandra Batista Medeiros, Cristiano Binder, João Batista Rodrigue Neto, Aloísio Nelmo Klein and José Daniel Biasoli de Mello
Lubricants 2021, 9(4), 43; https://doi.org/10.3390/lubricants9040043 - 15 Apr 2021
Cited by 8 | Viewed by 2344
Abstract
In this study, powder technology was used to obtain Fe-SiC composites in which SiC particles act as precursors to generate a large amount of turbostratic graphite dispersed in the composite matrix. The selection of the alloy composition was studied employing Thermo-Calc® software [...] Read more.
In this study, powder technology was used to obtain Fe-SiC composites in which SiC particles act as precursors to generate a large amount of turbostratic graphite dispersed in the composite matrix. The selection of the alloy composition was studied employing Thermo-Calc® software to obtain the temperature and composition range for the stabilization of the graphite phase in iron with a high yield. The extracted turbostratic 2D graphite particles were dispersed in mineral oil in order to evaluate the potential of these particles as a lubricating oil additive. The structure and morphology of the extracted graphite were examined by Raman spectroscopy and transmission electron microscopy (TEM), indicating the highly disordered nature of turbostratic graphite. Reductions in the friction coefficient and wear rate of a tribological pair were observed when compared to the pure mineral oil and mineral oil with commercial graphite particles added. The misorientation and increase in interplanar distances of turbostratic 2D graphite induce a low degree of interaction between these atomic planes, which contributes to the low-friction coefficient and the lower wear rate obtained for this system. Full article
(This article belongs to the Special Issue Carbon Nano-materials for Controlling Friction and Wear)
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22 pages, 8074 KiB  
Article
A Numerical Model for the Analysis of the Bearings of a Diesel Engine Subjected to Conditions of Wear and Misalignment
by Carlos Pardo García, Jhan Piero Rojas and Sofia Orjuela Abril
Lubricants 2021, 9(4), 42; https://doi.org/10.3390/lubricants9040042 - 9 Apr 2021
Cited by 4 | Viewed by 2100
Abstract
In the present work, a numerical model is developed to investigate the influence of wear and misalignment on the bearings of a stationary diesel engine. The model implemented considers the effects of surface wear on the bearing, cavitation effects, and surface roughness. For [...] Read more.
In the present work, a numerical model is developed to investigate the influence of wear and misalignment on the bearings of a stationary diesel engine. The model implemented considers the effects of surface wear on the bearing, cavitation effects, and surface roughness. For the numerical analysis, changes in the surface roughness of σμσ=0.75 μm, σμσ=1 μm, and σμσ=1.25 μm are defined, and changes in the bearing load of 50%, 75%, and 100%. The results demonstrated that increasing the surface roughness intensifies the bearing wear, which represents 18% and 140% of the bearing clearance for the roughness of σμσ=1 μm and σμσ=1.25 μm, respectively. Additionally, the surface roughness causes a considerable increase in the bearing wear rate. The results described a maximum wear rate of μ20 μm/s. In general, increasing the bearing load by 25% doubles the hydrodynamic pressure conditions increases friction force by 33%, and reduces lubrication film thickness by 12%. The analysis of the angle of deflection, ϕx and ϕy, shows that the moment and the degree of misalignment tend to increase significantly with the increase in the magnitude of the angle ϕy. Negative angles of deflection, ϕx, produce a greater increase in the degree of misalignment and the moment. This implies a greater chance of contact with the bearing surface. In conclusion, the proposed methodology serves as a reliable tool to simultaneously evaluate key parameters on the tribological behavior of bearings that further extend their endurance and minimize wear damage. Full article
(This article belongs to the Special Issue Advances in Tribology and LCA Applied to Thermal Machines)
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19 pages, 11509 KiB  
Article
Mathematical Development of a Novel Discrete Hip Deformation Algorithm for the In Silico Elasto-Hydrodynamic Lubrication Modelling of Total Hip Replacements
by Alessandro Ruggiero and Alessandro Sicilia
Lubricants 2021, 9(4), 41; https://doi.org/10.3390/lubricants9040041 - 9 Apr 2021
Cited by 7 | Viewed by 2475
Abstract
In this paper, the procedure to achieve an accurate deformation model of a total hip replacement (THR) was proposed with the aim to obtain a numerical tool to be simply merged into THR elasto-hydrodynamic computational synovial lubrication algorithms. The approach was based on [...] Read more.
In this paper, the procedure to achieve an accurate deformation model of a total hip replacement (THR) was proposed with the aim to obtain a numerical tool to be simply merged into THR elasto-hydrodynamic computational synovial lubrication algorithms. The approach was based on the Finite Element Method (FEM) and was developed in a Matlab code, allowing the definition of the influence matrix and of a boundary conditions vector. It works with linear tetrahedra and performs the displacement calculation for both the acetabular cup and the femoral head, taking into account the anatomical hip relative motion, by coupling them with a cubic interpolation matrix. Two simulations were conducted in order to validate the algorithm and the results were compared with the ones obtained by the commercial software Ansys. The comparison provides a satisfactory agreement in terms of surface deformation, Von Mises stress and strain energy, proving the reliability of the model and the possibility to use the model in the in silico prostheses tribological simulations, avoiding the complexity and the high computational resource requirement coming from the coupling between complex lubrication algorithms and FEM commercial software, and with the possibility to directly act on many key parameter characteristics of the investigated problem. Full article
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16 pages, 2482 KiB  
Perspective
Grease Performance Requirements and Future Perspectives for Electric and Hybrid Vehicle Applications
by Raj Shah, Simon Tung, Rui Chen and Roger Miller
Lubricants 2021, 9(4), 40; https://doi.org/10.3390/lubricants9040040 - 6 Apr 2021
Cited by 16 | Viewed by 5825
Abstract
Electric vehicle sales are growing globally in response to the move towards a greener environment and a reduction in greenhouse gas emissions. As in any machine, grease lubricants will play a significant role in the component life of these new power plants and [...] Read more.
Electric vehicle sales are growing globally in response to the move towards a greener environment and a reduction in greenhouse gas emissions. As in any machine, grease lubricants will play a significant role in the component life of these new power plants and drivetrains. In this paper, the role of grease lubrication in electric vehicles (EVs) and hybrid vehicles (HVs) will be discussed in terms of performance requirements. Comparisons of grease lubrication in EVs and HVs for performance requirements to current internal combustion engines (ICEs) will be reviewed to contrast the major differences under different operating conditions. The operating conditions for grease lubrication in these EVs and HVs are demanding. Greases formulated and manufactured to meet specific performance specifications in EVs and HVs, which will operate within these specific electrification components, will be reviewed. Specifically, the thermal and electrified effects from the higher operating temperatures and electromagnetic fields on lubricant degradation, rheology, elastomer compatibility, and corrosion protection of the grease need to be evaluated to accurately meet the performance requirements for EVs and HV. The major differences between EVs and conventional ICEVs can be grouped into the following technical areas: energy efficiency, noise, vibration, and harshness (NVH), the presence of electrical current and electromagnetic fields from electric modules, sensors and circuits, and bearing lubrication. Additional considerations include thermal heat transfer, seals, corrosion protection, and materials’ compatibility. The authors will review the future development trends of EVs/HVs on driveline lubrication and thermal management requirements. The future development of electric vehicles will globally influence the selection and development of gear oils, coolants, and greases as they will be in contact with electric modules, sensors, and circuits and will be affected by electrical current and electromagnetic fields. The increasing presence of electrical parts in EVs/HVs will demand the corrosion protection of bearings and other remaining mechanical components. Thus, it is imperative that specialized greases should be explored for specific applications in EVs/HVs to ensure maximum protection from friction, wear, and corrosion to guarantee the longevity of the operating automobile. Low-viscosity lubricants and greases will be used in EVs to achieve improvements in energy efficiency. However, low-viscosity fluids reduce the film thickness in the driveline application. This reduced film thickness increases the operating temperature and reduces the calculated fatigue life of the bearings. Bearing components for EVs/HVs will be even more crucial as original equipment manufacturers (OEMs) specify these low-viscosity fluids. The application of premium bearing components using low-viscosity grease will leverage materials, bearing geometries, and surface topography to combat the impact of low-viscosity lubricants. In addition, EVs and HVs will create their own NVH challenges. Wind and road noise are more prominent, with no masking noise from the ICE. Increasing comfort, quality, and reliability issues will be more complicated with the introduction of new electrified powertrain and E-driveline subsystems. This paper elaborates on the current development trends and industrial test standard for the specified grease used for electrical/hybrid driveline lubrication. Full article
(This article belongs to the Special Issue Grease)
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11 pages, 4975 KiB  
Article
Study of Jatropha curcas Linn and Olea europaea as Bio-Oil Lubricant to Physical Properties and Wear Rate
by Iis Siti Aisyah, Wahyu Caesarendra, Dini Kurniawati, Maftuchah Maftuchah, Deva Agung, Adam Glowacz, Krzysztof Oprzędkiewicz and Hui Liu
Lubricants 2021, 9(4), 39; https://doi.org/10.3390/lubricants9040039 - 5 Apr 2021
Cited by 9 | Viewed by 3120
Abstract
This paper presents a study on the effect of the mixed volume fraction of Jatropha curcas Oil (JCO) and Olea europea or extra virgin olive oil (EVOO) on the physical properties of the oil, especially viscosity, density and water content. This study also [...] Read more.
This paper presents a study on the effect of the mixed volume fraction of Jatropha curcas Oil (JCO) and Olea europea or extra virgin olive oil (EVOO) on the physical properties of the oil, especially viscosity, density and water content. This study also presents the mechanical properties examination result, especially its effect on the wear rate of the pin on disc tribometer results on ST 41 steel specimens, using optical microscopy. The independent variables used were variations of the oil mixture: 0, 20, 40, 60, 80 and 100% EVOO. With the increase in the percentage of the EVOO mixture in JCO, the density decreases. The result of water content in a higher percentage of JCO, the higher the water content value of 0.1217%. Pure JCO has the higher viscosity value of 1.9084 m2/s. The higher the percentage of JCO, the lower the wear rate value obtained. In the tribometer test, the pin on disk mixture of pure JCO has the lower wear value of 5.09 m2/s. Full article
(This article belongs to the Special Issue Advances in Green Eco-friendly Lubricants)
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31 pages, 44644 KiB  
Article
Experimental Analysis of Friction and Wear of Self-Lubricating Composites Used for Dry Lubrication of Ball Bearing for Space Applications
by Guillaume Colas, Aurélien Saulot, Yann Michel, Tobin Filleter and Andreas Merstallinger
Lubricants 2021, 9(4), 38; https://doi.org/10.3390/lubricants9040038 - 3 Apr 2021
Cited by 12 | Viewed by 4225
Abstract
Lubricating space mechanisms are a challenge. Lubrication must be sustained in different environments, for a very long period of time, and without any maintenance possible. This study focuses on the self-lubricating composite used in the double transfer lubrication of ball bearing. Ball/races contacts [...] Read more.
Lubricating space mechanisms are a challenge. Lubrication must be sustained in different environments, for a very long period of time, and without any maintenance possible. This study focuses on the self-lubricating composite used in the double transfer lubrication of ball bearing. Ball/races contacts are lubricated via the transfer of materials from the cage that is made of the composite. A dedicated tribometer has been designed for the study. A specificity of the tribometer is to not fully constrain the composite sample but to let it move, as the cage would do in the bearing. Four composites (PTFE, MoS2, glass or mineral fibers) where tested in ultrahigh vacuum and humid air environments. Transfer was achieved with morphologies and composition similar to what is observed on real bearings. Adhesion measurements performed on composite materials before and after friction allowed one to explain the differences in tribological behaviors observed (transfer quality and contact instabilities). Beyond strengthening the composites, fibers are shown to be critical in trapping mechanically and chemically the transferred material to lubricate and prevent instabilities. Equilibrium between internal cohesion of transferred material, and adhesion to counterparts must be satisfied. Mass spectrometry showed that water appears also critical in the establishment of stable transfer film, even in vacuum. Full article
(This article belongs to the Special Issue Tribology of Space Mechanisms)
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13 pages, 5056 KiB  
Article
UV-Visible Spectrophotometer for Distinguishing Oxidation Time of Engine Oil
by Torrey Holland, Ali Mazin Abdul-Munaim, Christopher Mandrell, Robinson Karunanithy, Dennis G. Watson and Poopalasingam Sivakumar
Lubricants 2021, 9(4), 37; https://doi.org/10.3390/lubricants9040037 - 3 Apr 2021
Cited by 11 | Viewed by 4660
Abstract
Samples of gasoline engine oil (SAE 5W20) that had been exposed to various oxidation times were inspected with a UV-Visible (UV-Vis) spectrophotometer to select the best wavelengths and wavelength ranges for distinguishing oxidation times. Engine oil samples were subjected to different thermal oxidation [...] Read more.
Samples of gasoline engine oil (SAE 5W20) that had been exposed to various oxidation times were inspected with a UV-Visible (UV-Vis) spectrophotometer to select the best wavelengths and wavelength ranges for distinguishing oxidation times. Engine oil samples were subjected to different thermal oxidation periods of 0, 24, 48, 72, 96, 120, and 144 hours, resulting in a range of total base number (TBN) levels. Each wavelength (190.5 – 849.5 nm) and selected wavelength ranges were evaluated to determine the wavelength or wavelength ranges that could best distinguish among all oxidation times. The best wavelengths and wavelength ranges were analyzed with linear regression to determine the best wavelength or range to predict oxidation time. Full article
(This article belongs to the Special Issue Automotive Tribology II)
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14 pages, 3687 KiB  
Article
Analysis of Friction in Total Knee Prosthesis during a Standard Gait Cycle
by Matúš Ranuša, Markus A. Wimmer, Spencer Fullam, Martin Vrbka and Ivan Křupka
Lubricants 2021, 9(4), 36; https://doi.org/10.3390/lubricants9040036 - 3 Apr 2021
Cited by 7 | Viewed by 3809
Abstract
Total knee arthroplasty is on the rise worldwide. Despite its success, revision surgeries are also increasing. According to the American Joint Replacement Registry 2020, 3.3% of revision surgeries are due to wear, and 24.2% are due to mechanical loosening. The combination of shear [...] Read more.
Total knee arthroplasty is on the rise worldwide. Despite its success, revision surgeries are also increasing. According to the American Joint Replacement Registry 2020, 3.3% of revision surgeries are due to wear, and 24.2% are due to mechanical loosening. The combination of shear stresses and wear particles occurring at the bone/implant interface can lead to local osteolysis. Although the shear stresses are partially driven by joint friction, relatively little is known about the evolution of the coefficient of friction (CoF) during a gait cycle in total knee replacement. Here we describe the CoF during a gait cycle and investigate its association with kinematics (slide–roll-ratio), applied load, and relative velocity. The artificial knee was simulated by cobalt–chromium condyle on a flat ultra-high-molecular-weight polyethylene (UHMWPE) tibial plateau, lubricated by either water or proteinaceous solution. We found that the CoF is not a constant but fluctuates between the values close to 0 and 0.15. Cross-correlation suggested that this is primarily an effect of the slide–roll ratio and the contact pressure. There was no difference in the CoF between water and proteinaceous solution. Knowledge about the CoF behavior during a gait cycle will help to increase the accuracy of future computational models of total knee replacement. Full article
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14 pages, 4915 KiB  
Article
Synergistic and Competitive Effects between Zinc Dialkyldithiophosphates and Modern Generation of Additives in Engine Oil
by Khai K. Huynh, Kiet A. Tieu and Sang T. Pham
Lubricants 2021, 9(4), 35; https://doi.org/10.3390/lubricants9040035 - 31 Mar 2021
Cited by 22 | Viewed by 3609
Abstract
The increasing demand for low-viscosity engine oil has underscored the role of zinc dialkyldithiophosphates (ZDDP) as a conventional anti-wear and antioxidant additive. It is essential to investigate the influence of modern additives such as cyclopropanecarboxylic acid (CPCa) and Ni nanoparticles on the tribological [...] Read more.
The increasing demand for low-viscosity engine oil has underscored the role of zinc dialkyldithiophosphates (ZDDP) as a conventional anti-wear and antioxidant additive. It is essential to investigate the influence of modern additives such as cyclopropanecarboxylic acid (CPCa) and Ni nanoparticles on the tribological performance of ZDDP for practical commercial oil application. According to the experimental results, Ni nanoparticles formed a protective film that exhibited a synergistic effect with ZDDP. A significantly higher concentration of sulphur in the tribofilm was detected compared to ZDDP by itself, which was responsible for a 27.6% lower wear loss. Meanwhile, a competitive effect between CPCa and ZDDP resulted in a dramatic increase in friction and unstable anti-wear performance. This was demonstrated by a localized formation of the ZDDP tribofilm on the wear surfaces after the friction test. These results have highlighted the synergistic and competitive effects of emerging additives (CPCa and Ni nanoparticles) in the ZDDP tribofilm formation between the sliding steel contacts. This further suggests a new approach to increase the efficiency of ZDDP’s tribological performance at cold start-up processes. Full article
(This article belongs to the Special Issue Advanced Lubrication for Energy Efficiency II)
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14 pages, 14454 KiB  
Article
Investigation of the Tribological Properties of Different Textured Lead Bronze Coatings under Severe Load Conditions
by Adolfo Senatore, Giacomo Risitano, Lorenzo Scappaticci and Danilo D’Andrea
Lubricants 2021, 9(4), 34; https://doi.org/10.3390/lubricants9040034 - 26 Mar 2021
Cited by 23 | Viewed by 2799
Abstract
The purpose of this paper is to investigate the variation in the coefficient of friction (CoF) and also the wear in a lead bronze coating under different texture conditions. The tribological tests were performed using a tribometer with pin on disk configuration. Several [...] Read more.
The purpose of this paper is to investigate the variation in the coefficient of friction (CoF) and also the wear in a lead bronze coating under different texture conditions. The tribological tests were performed using a tribometer with pin on disk configuration. Several kinds of textures, realised by a surface laser texturing, were tested by varying the diameter, depth, and density of the dimples under severe working conditions. The innovative aspect concerns the behaviour of the textured lead bronze coating and the lubrication conditions when the sample is subjected to extreme load conditions. Confocal microscopies and SEM (Scanning Electron Microscopy)/EDS (Energy Dispersive X-Ray Spectroscopy) analyses were performed to evaluate the texture behaviour and also the surface deterioration of the coating. The results show that the application of texture processing leads to an improvement in the tribological properties of the coating. By analysing separately the variation of the different geometric parameters of the dimples, it has been shown that the best results are obtained with a diameter of 50 μm, a density of 5%, and a depth of 5 μm. Full article
(This article belongs to the Special Issue Automotive Tribology II)
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