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Lubricants
Volume 12
Issue 10
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Lubricants, Volume 12, Issue 10 (October 2024) – 33 articles

Cover Story (view full-size image): Cavitation erosion is a significant issue affecting the performance of engineering components, such as ship propellers, desalination systems, and hydraulic machinery. This study investigates the surface degradation of maritime structures made from Duplex stainless steel due to cavitation in marine and river environments. To improve erosion resistance, layers of austenitic manganese alloy were applied through welding. Cavitation tests, following ASTM standards, measured mass loss and examined the eroded zones using SEM and hardness testing. The deposited coatings improved erosion resistance by 8.5–10.5 times, with surface hardness increasing to 465–490 HV5, compared to 260–280 HV5 for base metals, demonstrating the effectiveness of hardfacing. View this paper
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16 pages, 10702 KiB  
Article
Difference in High-Temperature Tribological Performance of Oxide/Ag-MoS2-Based Composites
by Yufei Wang, Xibo Shao, Jianyu Liu, Xinyue Hu, Xuhui He and Guanyu Deng
Lubricants 2024, 12(10), 360; https://doi.org/10.3390/lubricants12100360 - 21 Oct 2024
Viewed by 786
Abstract
MoS2 has excellent vacuum lubricating performance. However, it is prone to be oxidized in a high-temperature atmospheric environment, leading to the deterioration of its lubricating performance and even serious space accidents. The high-temperature lubricating performance of MoS2-based solid lubricating materials [...] Read more.
MoS2 has excellent vacuum lubricating performance. However, it is prone to be oxidized in a high-temperature atmospheric environment, leading to the deterioration of its lubricating performance and even serious space accidents. The high-temperature lubricating performance of MoS2-based solid lubricating materials can be improved to some extent by the co-compounding of appropriate oxides and Ag. The tribological properties of several common nano-oxides (ZnO, TiO2, Al2O3, and ZrO2) composited with metal Ag of MoS2-based composites were compared at 450 °C. The results showed that the comprehensive tribological performance of MoS2-TiO2-Ag was the best, an the average friction coefficient of about 0.26, and a wear rate of about 1.2 × 10−5 mm3/Nm, which was 18% and 43% lower than that of MoS2-Ag, respectively. The excellent tribological properties of MoS2-TiO2-Ag composites were attributed to three aspects: Firstly, with the help of the oxidation resistance of TiO2 to MoS2 to some extent and its high ionic potential, its oxidation resistance was improved and its shear strength was reduced to provide low friction. Secondly, relying on the low shear strength and good film-forming tendency of soft metal Ag on the sliding surface, a low shear tribo-film was easily formed on the friction interface, which was helpful for the synergistic lubrication of Ag, MoS2, and TiO2.Thirdly, through the matching of hard TiO2 and soft Ag, the wear resistance and bearing capacity of the composites were improved to some extent. The research results can provide some reference for the selection and design of MoS2-based high-temperature lubricating materials and the enhancement of their tribological properties. Full article
(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)
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32 pages, 3090 KiB  
Review
Nanofluid Minimum Quantity Lubrication (NMQL): Overview of Nanoparticle Toxicity and Safer-Design Guidelines
by José V. Abellán-Nebot, Oscar Andreu-Sánchez, Carlos Fito-López and Rosa Mondragón
Lubricants 2024, 12(10), 359; https://doi.org/10.3390/lubricants12100359 - 21 Oct 2024
Viewed by 652
Abstract
Minimum Quantity Lubrication (MQL) has received much attention from the research community as a potential lubricating system to reduce environmental hazards and health issues that can be commonly found in flood cooling/lubricating systems based on metalworking fluids. The addition of nanoparticles in MQL [...] Read more.
Minimum Quantity Lubrication (MQL) has received much attention from the research community as a potential lubricating system to reduce environmental hazards and health issues that can be commonly found in flood cooling/lubricating systems based on metalworking fluids. The addition of nanoparticles in MQL systems (NMQL) has led to improved machining performance, increasing the cooling capability and reducing friction and tool wear, and some researchers have proved the applicability of this type of system for difficult-to-cut materials. However, the mist generated by MQL systems due to both the MQL system itself and the machining operation may pose an additional hazard to operators which is being overlooked by the research community. These hazards become more severe when using nanoparticles, but unfortunately very few works have paid attention to nanoparticle toxicity as applied in MQL systems, and this issue should be clearly understood before encouraging its implementation in industry. Furthermore, current legislation does not help since regulation of permissible exposure limits when dealing with nanoparticles is still ongoing in most cases. In this work, the toxicity of nanoparticles applied in MQL systems is analyzed, and recent research on studies of nanoparticle toxicity both in vitro and in vivo is presented. A relative comparison of toxicity is provided for those nanoparticles that have been reported in the literature as potential additives for MQL. The review is focused on analyzing the main factors of toxicity of nanoparticles which are identified as size, shape, surface properties, agglomeration and solubility. This review presents guidelines for safer nanolubricant formulations, guiding practitioners towards proper NMQL implementations in industry. Furthermore, current occupational exposure limits and recommendations are provided for all the nanoparticles potentially used in MQL systems, which is of interest in terms of work safety. Full article
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13 pages, 4564 KiB  
Article
Moringa Oil and Carbon Phases of Different Shapes as Additives for Lubrication
by Nadiège Nomède-Martyr, Philippe Bilas, Grégory Mathieu, Yves Bercion, Henry Joseph and Philippe Thomas
Lubricants 2024, 12(10), 358; https://doi.org/10.3390/lubricants12100358 - 19 Oct 2024
Viewed by 712
Abstract
Vegetable oils in the lubricant field are largely studied. Their efficiency depends on their viscosity parameters and their fatty acid composition. The actions of moringa oil used as a lubricant base and as a lubricant additive have been shown in this work. Graphite, [...] Read more.
Vegetable oils in the lubricant field are largely studied. Their efficiency depends on their viscosity parameters and their fatty acid composition. The actions of moringa oil used as a lubricant base and as a lubricant additive have been shown in this work. Graphite, carbon nanofibers, and carbon nanodots are carbon phases of different shapes used as solid additives. The tribological performances of lubricant blends composed of between 0.5 and 1 wt.% of particles have been evaluated using a ball-on-plane tribometer under an ambient atmosphere. No additional surfactant was used. The positive and important actions of a small amount of moringa oil added in the lubricant formulas are demonstrated. The results obtained allow us to point out the influence of the type and shape of particles. Physicochemical investigations allow us to propose a synergistic effect between the particles and moringa oil as additives in dodecane. Full article
(This article belongs to the Special Issue Preparation, Tribological Behavior, and Applications of Lubricant Additives)
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18 pages, 4698 KiB  
Article
Study on Atomization Mechanism of Oil Injection Lubrication for Rolling Bearing Based on Stratified Method
by Feng Wei, Hongbin Liu and Yongyan Liu
Lubricants 2024, 12(10), 357; https://doi.org/10.3390/lubricants12100357 - 18 Oct 2024
Viewed by 564
Abstract
The atomization mechanism of lubrication fluid in rolling bearings under high-speed airflow between the rings was investigated. A simulation model of gas–liquid two-phase flow in angular contact ball bearings was developed, and the jet lubrication process between the bearing rings was simulated using [...] Read more.
The atomization mechanism of lubrication fluid in rolling bearings under high-speed airflow between the rings was investigated. A simulation model of gas–liquid two-phase flow in angular contact ball bearings was developed, and the jet lubrication process between the bearing rings was simulated using FLUENT computational fluid dynamics software (Ansys 19.2). The complex motion boundary conditions of the rolling elements were addressed through a layered approach. We can obtain more accurate boundary layer flow field changes and statistics of the diameter of oil particles in lubricating oil atomization, which lays the foundation for analyzing the law of influence on lubricating oil atomization. The results show that as the number of boundary layer layers increases, the influence of the boundary layer flow field on the lubricating oil is more obvious. The oil particle size is excessively flat, and the concentration of large particles of oil appears to decrease. As the speed increases, the amount of oil in the cavity decreases, but the oil droplets are also fragmented, which intensifies the atomization and reduces the particle diameter. This reduces the Sauter Mean Diameter (SMD), which is not conducive to the lubrication of the bearing. Under different injection pressures, when the injection pressure is large, it is beneficial to the lubrication of the bearing. Full article
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22 pages, 6478 KiB  
Article
Effect of Thermal Load Caused by Tread Braking on Crack Propagation in Railway Wheels on Long Downhill Ramps
by Jinyu Zhang, Xun Chen, Gongquan Tao and Zefeng Wen
Lubricants 2024, 12(10), 356; https://doi.org/10.3390/lubricants12100356 - 17 Oct 2024
Viewed by 557
Abstract
To investigate the propagation behavior of thermal cracks on the wheel tread under the conditions of long downhill ramps, a three-dimensional finite element model of a 1/16 wheel, including an initial thermal crack, was developed using the finite element software ANSYS 17.0. The [...] Read more.
To investigate the propagation behavior of thermal cracks on the wheel tread under the conditions of long downhill ramps, a three-dimensional finite element model of a 1/16 wheel, including an initial thermal crack, was developed using the finite element software ANSYS 17.0. The loading scenarios considered include mechanical wheel–rail loads, both with and without the superposition of thermal wheel–brake shoe friction loads. The virtual crack closure method (VCCM) is employed to analyze the variations in stress intensity factors (SIFs) for Modes I, II, and III (KI, KII, and KIII) at the 0°, mid, and 90° positions along the crack tip. The simulation results show that temperature is a critical factor for the propagation of thermal cracks. Among the SIFs, KII (Mode II) is larger than KI (Mode I) and KIII (Mode III). Specifically, the thermal load on the wheel tread during braking contributes up to 23.83% to KII when the wheel tread reaches the martensitic phase transition temperature due to brake failure. These results are consistent with the observed radial propagation of thermal cracks in wheel treads under operational conditions. Full article
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20 pages, 6428 KiB  
Article
Dynamic Models of Mechanical Seals for Turbomachinery Application
by Renat Badykov, Sergei Falaleev, Maxim Benedyuk and Dmitriy Diligenskiy
Lubricants 2024, 12(10), 355; https://doi.org/10.3390/lubricants12100355 - 16 Oct 2024
Viewed by 710
Abstract
One of the primary causes of mechanical face seal failure is rotor vibration. Traditional dynamic seal models often cannot fully explain failure mechanisms. The dynamic models of seals proposed in this paper, including those developed by the authors, are valuable for predicting seal [...] Read more.
One of the primary causes of mechanical face seal failure is rotor vibration. Traditional dynamic seal models often cannot fully explain failure mechanisms. The dynamic models of seals proposed in this paper, including those developed by the authors, are valuable for predicting seal dynamics during operation in specific turbomachinery and for explaining the causes of seal failure. The single-mass dynamic model is suitable for analyzing the dynamics of contact mechanical face seals and simply designed dry gas seals. The two-mass dynamic model is used to investigate the operational dynamics processes of classical dry gas seals under complex loading conditions. The three-mass dynamic model is used to study various complex types of mechanical face seals. This model can determine the normal operating condition range and explain leakage mechanisms in the presence of excessive rotor vibrations. Full article
(This article belongs to the Special Issue Gas Lubrication and Dry Gas Seal)
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17 pages, 4963 KiB  
Article
Predictive Model for Scuffing Temperature Field Rise of Spiral Bevel Gears under Different Machining Conditions
by Zhi-Jie Cai, Xi-Qing Zheng, Hui-Qing Lan, Liu-Na Wang, Si-Wei Yang and Rui Shen
Lubricants 2024, 12(10), 354; https://doi.org/10.3390/lubricants12100354 - 14 Oct 2024
Viewed by 578
Abstract
Spiral bevel gears are extensively employed in mechanical transmissions; however, they are prone to adhesive wear when operating under high-speed and heavy-load conditions. Research indicates that the tooth surface roughness of gears significantly influences the friction and wear of the meshing gears. The [...] Read more.
Spiral bevel gears are extensively employed in mechanical transmissions; however, they are prone to adhesive wear when operating under high-speed and heavy-load conditions. Research indicates that the tooth surface roughness of gears significantly influences the friction and wear of the meshing gears. The present study delves into the origins of tooth surface roughness through the integration of the W-M function and fractal theory. Utilizing an involute helical gear with surface roughness for tooth cutting, a three-dimensional model is established with roughened tooth surfaces. This paper introduces an approach to developing three-dimensional gear models with roughness and applies the finite element method to perform thermodynamic analysis on gears exhibiting diverse levels of surface roughness. The thermal analysis of gears with varying degrees of roughness was conducted using the finite element method. Comparative analysis of the results under specific operating conditions elucidated the impact of roughness on tooth surface temperature rise. In order to validate the simulation model, an experimental test platform for spiral bevel gears of identical size was established. This model integrates tooth surface roughness with thermodynamic analysis, allowing for the rapid assessment of tooth surface temperature rise under different machining conditions, and reducing the cost of validating predicted tooth surface load-carrying capacity. Full article
(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)
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19 pages, 19105 KiB  
Article
Investigation of Tribological Properties of Inconel 601 under Environmentally Friendly MQL and Nano-Fluid MQL with Pack Boronizing
by Gonca Uslu, Mehmet Erdi Korkmaz, Rajab Hussein Rajab Elkilani, Munish Kumar Gupta and Govind Vashishtha
Lubricants 2024, 12(10), 353; https://doi.org/10.3390/lubricants12100353 - 14 Oct 2024
Viewed by 588
Abstract
Friction and high temperatures greatly affect the hardness and processing efficiency of superalloys. Therefore, it is important to provide a coating on their surfaces with a hard layer. In this study, pack boronizing was applied on Inconel 601 to improve its microstructure and [...] Read more.
Friction and high temperatures greatly affect the hardness and processing efficiency of superalloys. Therefore, it is important to provide a coating on their surfaces with a hard layer. In this study, pack boronizing was applied on Inconel 601 to improve its microstructure and tribological properties. In this regard, tribological tests were performed under MQL, nano-MQL1 (MQL + CuO), and nano-MQL2 (MQL + TiO2) environments. The research results showed that the lowest wear depth, friction force, coefficient of friction (CoF), and volume loss values were obtained in pack-boronized Inconel 601 in a nano-MQL2 environment. In the nano-MQL2 environment, the wear depth decreased by 17.81% (from 57.922 µm to 47.605 µm) with package-boronized Inconel 601 compared to as-received Inconel 601 at a 45 N load. Pack-boronized Inconel 601 experienced an average reduction of 30.23%, 41.60%, and 52.32% in friction force when switching from dry to MQL, nano-MQL1, and nano-MQL2 environments, respectively. It was also observed that the coefficient of friction (CoF) and volume loss values decreased with pack boronizing in an MQL/nano-MQL environment. In a nano-MQL2 environment at 15 N load, volume losses for as-received and boron-coated Inconel 601 were determined as 0.288 mm3 and 0.249 mm3, respectively (13.54% decrease). The findings of this study demonstrate that pack boronizing and MQL and nano-MQL techniques enhance the tribological characteristics of Inconel 601 alloys. Full article
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16 pages, 7493 KiB  
Article
On Lubrication Regime Changes during Forward Extrusion, Forging, and Drawing
by Man-Soo Joun, Yun Heo, Nam-Hyeon Kim and Nam-Yun Kim
Lubricants 2024, 12(10), 352; https://doi.org/10.3390/lubricants12100352 - 14 Oct 2024
Viewed by 704
Abstract
The tribological phenomena concerning the lubrication regime change (LRC) during bulk metal forming are comprehensively studied. A multi-step cold forward extrusion process shows the evolution of LRC and reveals the shortcomings of the traditional Coulomb friction law. The previous works of the specific [...] Read more.
The tribological phenomena concerning the lubrication regime change (LRC) during bulk metal forming are comprehensively studied. A multi-step cold forward extrusion process shows the evolution of LRC and reveals the shortcomings of the traditional Coulomb friction law. The previous works of the specific author’s research group on friction are reviewed, focusing on the LRC during bulk metal forming. Various LRC phenomena from various examples are revealed. It has been found that the drawing and forward extrusion processes are vulnerable to LRC because of significant sliding motion at the material–die interface, and that when the strain hardening of the material is slight, the influence of friction increases, and as a result, the influence of LRC increases excessively. The new findings also include the impact of LRC on the macroscopic phenomena of the process and the reason for the sharp increase in friction coefficient via LRC, which is validated by the work of Wilson. This paper aims to make engineers and researchers think much of the tribology with lubricant in bulk metal forming with a focus on the dependence of tribological phenomena on the state of the lubricants and the irrationality of traditional friction law, especially in the forging of materials with a low strain hardening capability. Full article
(This article belongs to the Special Issue Mechanical Tribology and Surface Technology)
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12 pages, 1852 KiB  
Article
Mixed Friction in Fully Lubricated Elastohydrodynamic Contacts—Theory or Reality
by Dirk Bartel
Lubricants 2024, 12(10), 351; https://doi.org/10.3390/lubricants12100351 - 14 Oct 2024
Viewed by 797
Abstract
Mixed friction in liquid-lubricated tribosystems is characterized by the simultaneous presence of liquid and solid friction. Liquid friction results from the shearing of the lubricant, and solid friction from deformation and adhesion. Elastic hysteresis and plastic deformation of the solids cause energy losses [...] Read more.
Mixed friction in liquid-lubricated tribosystems is characterized by the simultaneous presence of liquid and solid friction. Liquid friction results from the shearing of the lubricant, and solid friction from deformation and adhesion. Elastic hysteresis and plastic deformation of the solids cause energy losses during deformation and the separation of molecular bonds between the solids causes energy losses during adhesion. The classic conception of mixed friction presupposes direct contact between rough solids for solid friction to exist. However, if hysteresis losses are fully accepted as a cause for solid friction, every fully lubricated elastohydrodynamic contact would ultimately be a mixed friction contact since the elastic deformations of the solids also cause a loss of energy induced by hysteresis. Thus, the classic conception of mixed friction should be expanded since mixed friction can occur even when solids do not have any direct contact. Full article
(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)
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50 pages, 12506 KiB  
Review
Review of Wear and Mechanical Characteristics of Al-Si Alloy Matrix Composites Reinforced with Natural Minerals
by Varun Singhal, Daksh Shelly, Atul Babbar, Seul-Yi Lee and Soo-Jin Park
Lubricants 2024, 12(10), 350; https://doi.org/10.3390/lubricants12100350 - 14 Oct 2024
Viewed by 1656
Abstract
Al-Si alloys are vital in the aerospace and automotive industries due to their high strength-to-weight ratio, excellent ductility, and superior corrosion resistance. These properties, along with good thermal conductivity, low thermal expansion, and enhanced wear resistance due to silicon, make them ideal for [...] Read more.
Al-Si alloys are vital in the aerospace and automotive industries due to their high strength-to-weight ratio, excellent ductility, and superior corrosion resistance. These properties, along with good thermal conductivity, low thermal expansion, and enhanced wear resistance due to silicon, make them ideal for lightweight, high-performance components like engine parts exposed to harsh conditions and thermal cycling. In recent years, the development of aluminium metal matrix composites using Al-Si alloys as the base material has gathered significant attention. These composites are engineered by integrating various reinforcing particles into the aluminium matrix, which results in remarkable improvements in the wear resistance, hardness, and overall mechanical performance of the material. The stir casting process, a well-established and cost-effective method, is frequently employed to ensure a uniform distribution of these reinforcing particles within the matrix. This review delves into the influence of different types of reinforcing particles on the properties of Al-Si alloy-based AMCs. The incorporation of these reinforcements has been shown to significantly enhance wear resistance, reduce friction, and improve the overall strength and toughness of the composites, making them ideal candidates for high-performance applications in the automotive and aerospace sectors. Moreover, this review highlights the challenges associated with the fabrication of these composites, such as achieving a homogeneous particle distribution and minimizing porosity. It also discusses the latest advancements in processing techniques aimed at overcoming these challenges. Additionally, this review addresses the potential environmental and economic benefits of using natural reinforcements, which not only reduce material costs but also contribute to sustainable manufacturing practices. Full article
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25 pages, 10949 KiB  
Review
Research Progress on Current-Carrying Friction with High Stability and Excellent Tribological Behavior
by Peng Wei, Xueqiang Wang, Guiru Jing, Fei Li, Pengpeng Bai and Yu Tian
Lubricants 2024, 12(10), 349; https://doi.org/10.3390/lubricants12100349 - 13 Oct 2024
Viewed by 1044
Abstract
Current-carrying friction affects electrical contact systems like switches, motors, and slip rings, which determines their performance and lifespan. Researchers have found that current-carrying friction is influenced by various factors, including material type, contact form, and operating environment. This article first reviews commonly used [...] Read more.
Current-carrying friction affects electrical contact systems like switches, motors, and slip rings, which determines their performance and lifespan. Researchers have found that current-carrying friction is influenced by various factors, including material type, contact form, and operating environment. This article first reviews commonly used materials, such as graphite, copper, silver, gold, and their composites. Then different contact forms like reciprocating, rotational, sliding, rolling, vibration, and their composite contact form are also summarized. Finally, their environmental conditions are also analyzed, such as air, vacuum, and humidity, on frictional force and contact resistance. Additionally, through experimental testing and theoretical analysis, it is found that factors such as arcing, thermal effects, material properties, contact pressure, and lubrication significantly influence current-carrying friction. The key mechanisms of current-carrying friction are revealed under different current conditions, including no current, low current, and high current, thereby highlighting the roles of frictional force, material migration, and electroerosion. The findings suggest that material selection, surface treatment, and lubrication techniques are effective in enhancing current-carrying friction performance. Future research should focus on developing new materials, intelligent lubrication systems, stronger adaptability in extreme environments, and low friction at the microscale. Moreover, exploring stability and durability in extreme environments and further refining theoretical models are essential to providing a scientific basis for designing efficient and long-lasting current-carrying friction systems. Full article
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27 pages, 15223 KiB  
Article
Effects of Structure Parameters on Static Performance of Gas Foil Bearings Based on a New Fully Coupled Elastic–Aerodynamic Model
by Pengjing Ding, Yang Hu, Xiaojing Wang and Yonggang Meng
Lubricants 2024, 12(10), 348; https://doi.org/10.3390/lubricants12100348 - 13 Oct 2024
Viewed by 512
Abstract
Accurately predicting the performance of gas foil bearings (GFBs) is important. This paper presents a new fully coupled elastic–aerodynamic model for analyzing the static performance of gas foil journal bearings (GFJBs). The gas compressible lubrication model was solved in MATLAB to obtain the [...] Read more.
Accurately predicting the performance of gas foil bearings (GFBs) is important. This paper presents a new fully coupled elastic–aerodynamic model for analyzing the static performance of gas foil journal bearings (GFJBs). The gas compressible lubrication model was solved in MATLAB to obtain the gas pressure. The foil structure deformation was solved in COMSOL by considering the Coulomb friction and allowing the contact surfaces to be separated from each other. Under given load and rotational speed conditions, the calculated minimum gas film thickness and attitude angle match well with the literature data, validating the accuracy of the developed model. Based on the model developed, a comprehensive and systematic analysis of the effects of the structural parameters on the static performance was performed. The results showed that as the bump height, top foil thickness, and bump foil thickness increased, the load capacity could be improved to different degrees. The bump foil thickness had the greatest effect on the load capacity. These results provide theoretical guidance for the structural design and practical applications of GFJBs. Full article
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18 pages, 1552 KiB  
Article
The Anisotropic Mechanical and Tribological Behaviors of Additively Manufactured (Material Extrusion) Implant-Grade Polyether Ether Ketone (PEEK)
by Mohammad Reza Maydanshahi, Mohammad Reza Najari, Tom Slatter and Mahdi Mohammadpour
Lubricants 2024, 12(10), 347; https://doi.org/10.3390/lubricants12100347 - 12 Oct 2024
Viewed by 716
Abstract
In this study, we investigated the mechanical and tribological properties of the layer-by-layer structure of additively manufactured implant-grade Polyether Ether Ketone (PEEK) through the Material Extrusion (ME) process as a potential substitute for artificial joints. The effective elasticity modulus of the anisotropic 3D-printed [...] Read more.
In this study, we investigated the mechanical and tribological properties of the layer-by-layer structure of additively manufactured implant-grade Polyether Ether Ketone (PEEK) through the Material Extrusion (ME) process as a potential substitute for artificial joints. The effective elasticity modulus of the anisotropic 3D-printed PEEK was determined to be 2.505 GPa along the vertical and horizontal build orientations. The lubricated friction and wear performance were assessed using a pin-on-disk test under various loads, including 14, 30, 50, and 70 N, with a sliding speed of 50 mm/s over a total distance of 1 km at 37 °C. The contact parameters between the hemispherical steel pin and 3D-printed PEEK disks, involving contact pressures over the circle of contact, were observed to increase as the load increased. The results indicated that the wear coefficient exhibited a rise from 1.418 × 10−5 to 2.089 × 10−1  as the applied loads increased, signaling a shift from mild to severe wear regimes. Fetal Bovine Serum (FBS) as a lubricant exhibited a mixed mechanism, ascertained through the Stribeck curve, as well as a minimum fluid film thickness of 1.346 nm under an isoviscous–elastic regime, as calculated by the maximum load. Moreover, the mechanism governing wear during sliding, influenced by both normal axial and shear loads, primarily involved adhesion. Full article
(This article belongs to the Special Issue Wear in Additive Manufacturing)
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11 pages, 3173 KiB  
Article
Carrying Capacity of Spherical Hydrostatic Bearings Including Dynamic Pressure
by Shengdong Zhang, Dongjiang Yang, Guangming Li, Yongchao Cheng, Jichao Li, Fangqiao Zhao and Wenlong Song
Lubricants 2024, 12(10), 346; https://doi.org/10.3390/lubricants12100346 - 10 Oct 2024
Viewed by 577
Abstract
To calculate the carrying capacity of spherical hydrostatic bearings, a numerical calculation model was presented. The influence law of dynamic pressure effect on the carrying characteristics of liquid hydrostatic spherical bearings is revealed. Under general working conditions, the dynamic pressure effect caused by [...] Read more.
To calculate the carrying capacity of spherical hydrostatic bearings, a numerical calculation model was presented. The influence law of dynamic pressure effect on the carrying characteristics of liquid hydrostatic spherical bearings is revealed. Under general working conditions, the dynamic pressure effect caused by the radial eccentricity of the bearing has little influence on the bearing load characteristics parameters; when the minimum width of the gap between the sealing edge is very small and the bearing rotational speed is high, the dynamic pressure effect is more obvious. Full article
(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 2nd Edition)
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16 pages, 7942 KiB  
Article
Enhancing the Wear Performance of 316L Stainless Steel with Nb2O5 Coatings Deposited via DC Sputtering at Room Temperature under Varied Environmental Conditions
by Murilo Oliveira Alves Ferreira, Victor Auricchio Fernandes Morgado, Kauê Ribeiro dos Santos, Rogério Valentim Gelamo, Fábio Edson Mariani, Natália Bueno Leite Slade, Mateus Mota Morais, Carlos Alberto Fortulan, Rodrigo Galo, Renato Goulart Jasinevicius, Haroldo Cavalcanti Pinto and Jéferson Aparecido Moreto
Lubricants 2024, 12(10), 345; https://doi.org/10.3390/lubricants12100345 - 6 Oct 2024
Viewed by 805
Abstract
Niobium-based oxides have garnered increased attention in recent years for their remarkable enhancement of corrosion resistance, as well as biofunctional properties of various metallic materials, including 316L SS. However, the mechanical properties of these promising coatings have not been fully elucidated. This study [...] Read more.
Niobium-based oxides have garnered increased attention in recent years for their remarkable enhancement of corrosion resistance, as well as biofunctional properties of various metallic materials, including 316L SS. However, the mechanical properties of these promising coatings have not been fully elucidated. This study investigated how much the environmental conditions (air, artificial saliva, and NaCl solution) impact the wear performance of 316L SS without and with Nb2O5 coatings deposited via the reactive sputtering technique. The results exhibited a notable decrease in friction coefficient (55% in air, 18% in artificial saliva, 10% in 0.9 wt% NaCl solution), wear area (46% in air, 36% in AS, 17.5% in 0.9 wt% NaCl solution), and wear rate (44.0% in air, 19.5% in AS, 12.0% in 0.9 wt% NaCl solution). Ultimately, the results obtained in the present study elucidate the synergistic mechanisms of corrosion and wear in 316L SS containing Nb2O5 coatings, highlighting its significant potential for applications in the biomedical sector. Full article
(This article belongs to the Special Issue Coatings and Lubrication in Extreme Environments)
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23 pages, 10212 KiB  
Article
Combining Artificial Neural Networks and Mathematical Models for Unbalance Estimation in a Rotating System under the Nonlinear Journal Bearing Approach
by Ioannis Tselios and Pantelis Nikolakopoulos
Lubricants 2024, 12(10), 344; https://doi.org/10.3390/lubricants12100344 - 6 Oct 2024
Viewed by 679
Abstract
Rotating systems are essential components and play a critical role in many industrial sectors. Unbalance is a very common and serious fault that can cause machine downtime, unplanned maintenance, and potential damage to vital rotating machines. Accurately estimating unbalance in rotor–bearing systems is [...] Read more.
Rotating systems are essential components and play a critical role in many industrial sectors. Unbalance is a very common and serious fault that can cause machine downtime, unplanned maintenance, and potential damage to vital rotating machines. Accurately estimating unbalance in rotor–bearing systems is crucial for ensuring the reliable and efficient operation of machinery. This research paper presents a novel approach utilizing artificial neural networks (ANNs) to estimate the unbalance masses in a multidisk system based on simulation data from a nonlinear rotor–bearing system. Additionally, this study explores the effect of various operating parameters on oil film stability and vibration response through a combination of bifurcation diagrams, spectrum cascades, Poincare maps, and orbit and FFT plots. This study demonstrates the effectiveness of ANNs for unbalance estimation in a fast and accurate way and discusses the potential of ANNs in smart online condition monitoring systems. Full article
(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 2nd Edition)
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15 pages, 5583 KiB  
Article
Molecular Dynamics Simulations of Lubricant Supply in Porous Polyimide Bearing Retainers
by Wenbin Chen, Chong Wang, Gang Zhou, Fengbin Liu, Wenzhong Wang and Pengzhe Zhu
Lubricants 2024, 12(10), 343; https://doi.org/10.3390/lubricants12100343 - 5 Oct 2024
Viewed by 694
Abstract
Space bearing retainers are widely made of a porous, oil-impregnated material due to the unmaintainability of spacecraft. Porous polyimide (PI) material with a certain micropore structure can be used as a lubricant storage and migration channel to realize the lubricant circulation supply in [...] Read more.
Space bearing retainers are widely made of a porous, oil-impregnated material due to the unmaintainability of spacecraft. Porous polyimide (PI) material with a certain micropore structure can be used as a lubricant storage and migration channel to realize the lubricant circulation supply in the bearing system. In this work, molecular dynamics simulations are adopted to model the lubricant outflow process from the pore of the PI material. Coarse-grained models are constructed to investigate the lubricant migration behaviors with different rotation speeds, rotation radii, and pore sizes. The results show that a lubricant within the pore fails to outflow due to the capillary effect in a static state. However, for the rotating pores, if the centrifugal forces resulting from rotation exceed the capillary forces, the lubricants will begin to flow out. Furthermore, the lubricant in the large pore is easier to outflow due to the smaller capillary force, which is the main mechanism of lubricant outflow from the pores. Full article
(This article belongs to the Special Issue Tribological Properties of Porous Polyimide Retainer Materials)
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21 pages, 11802 KiB  
Article
Thermal–Elastohydrodynamic Lubrication Characteristics of the Flow Distribution Pair of Balanced Double-Row Axial Piston Pumps
by Haishun Deng, Binbin Guo, Zhixiang Huang, Pan Xu and Pengkun Zhu
Lubricants 2024, 12(10), 342; https://doi.org/10.3390/lubricants12100342 - 2 Oct 2024
Viewed by 697
Abstract
A theoretical model for the calculation of thermal elastohydrodynamic lubrication performance of the flow distribution pair of piston pumps is established, which is composed of the oil film pressure governing equation and energy equation, and solved by means of numerical solution and simulation. [...] Read more.
A theoretical model for the calculation of thermal elastohydrodynamic lubrication performance of the flow distribution pair of piston pumps is established, which is composed of the oil film pressure governing equation and energy equation, and solved by means of numerical solution and simulation. We carry out quantitative analysis of the influence of various parameters on the thermal elastohydrodynamic lubrication characteristics of the flow distribution pair. The results indicate that both the oil film thickness and the cylinder tilt angle of the flow distribution pair vary in a periodic manner. The increase in the rotational speed of the cylinder block will increase the film thickness of the oil film and reduce the fluctuation, and the inclination angle of the cylinder block and its fluctuation amplitude will decrease. An increase in working pressure will lead to a decrease in the average oil film thickness, an increase in fluctuations, and an elevation in both the tilt angle of the cylinder block and its fluctuation amplitude. The increase in the rotational speed of the cylinder block and the increase in the working pressure will lead to the increase in the viscous friction dissipation of the flow distribution pair, the increase in the oil film temperature and the increase in the leakage. The reduction in the sealing belt will lead to the reduction in oil film friction torque and leakage. Full article
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16 pages, 8291 KiB  
Article
Mechanical Properties and Tribological Study of Bottom Pouring Stir-Cast A356 Alloy Reinforced with Graphite Solid Lubricant Extracted from Corn Stover
by Vavilada Satya Swamy Venkatesh and Pandu Ranga Vundavilli
Lubricants 2024, 12(10), 341; https://doi.org/10.3390/lubricants12100341 - 2 Oct 2024
Viewed by 664
Abstract
The present work epitomises extracting the graphite (Gr) solid lubricant from the corn stover. The extracted Gr was incorporated as reinforcement in the A356 alloy (Al-7Si), and the effect of the Gr particles on the mechanical and tribological properties was investigated. In spite [...] Read more.
The present work epitomises extracting the graphite (Gr) solid lubricant from the corn stover. The extracted Gr was incorporated as reinforcement in the A356 alloy (Al-7Si), and the effect of the Gr particles on the mechanical and tribological properties was investigated. In spite of this, the input process parameters for the dry sliding wear test at room temperature against the EN31 steel disc were optimised through ANOVA analysis. The fabricated A359—X wt% (X = 0, 2.5, 5, 7.5) composite through bottom pouring stir casting techniques was analysed microstructurally by using XRD and FESEM analysis. The micro Brinell hardness and tensile strength were investigated per ASTME10 and ASTME8M standards. A wear test was performed for the composite pins against the EN31 steel disc according to ASTM G99 specifications. The XRD analysis results depict the presence of carbon (C), aluminium (Al), and silicon (Si) in all the wt% of the Gr reinforcement. However, along with the elements, the Al2Mg peak was confirmed for the A356—7.5 wt% Gr composite and the corresponding cluster element was confirmed in FESEM analysis. The maximum micro Brinell hardness of 92 BHN and U.T.S of 123 MPa and % elongation of 7.11 was attained at 5 wt% Gr reinforcement due to uniform Gr dispersion in the A356 alloy. Based on the ANOVA analysis, the optimal process parameters were obtained at 20 N applied load, 1 m/s sliding velocity, and 1000 m sliding distance for the optimal wear rate of 0.0052386 g/km and 0.364 COF. Full article
(This article belongs to the Special Issue Tribology for Lightweighting)
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11 pages, 3940 KiB  
Article
Effect of Grinding Media Grading on Liner Wear and Load Behavior in a Ball Mill by Using Rocky DEM
by Zixin Yin, Daoming Ma and Tongqing Li
Lubricants 2024, 12(10), 340; https://doi.org/10.3390/lubricants12100340 - 30 Sep 2024
Viewed by 885
Abstract
The liner is a wear-prone component in ball mills, subject to continuous impacts, squeezing, and abrasion from the grinding media during operation. Its service performance directly affects the working efficiency of the ball mill. The service life of mining ball mill liners is [...] Read more.
The liner is a wear-prone component in ball mills, subject to continuous impacts, squeezing, and abrasion from the grinding media during operation. Its service performance directly affects the working efficiency of the ball mill. The service life of mining ball mill liners is about 8 months, and frequent downtimes occur due to liner wear and loss of effectiveness, with liner replacement accounting for about 6% of the total cost, resulting in huge economic losses. This paper focuses on a Φ305 mm × 150 mm experimental ball mill, using the discrete element software Rocky Discrete Element Method (DEM) (software version number Rocky 2022 R2) for simulation modeling analysis. With Φ10 mm and Φ20 mm mono-size particle simulations serving as reference groups, this study investigates the motion states and liner abrasion patterns under different liner heights for both sizes of grinding media in Equilibrium Quality Manufacturer (EQM) and Original Equipment Manufacturer (OEM) gradations. The results indicate that the impact of liner height on the wear of the ball mill liners is related to the size and gradation of the grinding media. The degree of liner wear from highest to lowest is as follows: EQM > Φ20 mm > OEM > Φ10 mm. Due to the effect of the cylinder end cap, the wear at the axial center of the ball mill liner is more severe than at both ends, and the wear on the facing side of the liner is more severe than on the backside. A thorough study of the influence of ball mill grinding media gradation on the wear pattern of liners is of great theoretical significance for optimizing liner structures, improving grinding efficiency, and promoting energy saving and cost reduction in ball mills. This study provides theoretical guidance for understanding the mechanisms behind liner wear in ball mills and predicting the liner lifespan. Full article
(This article belongs to the Special Issue Modeling and Characterization of Wear)
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16 pages, 8237 KiB  
Article
Development of a Machine Vision System for the Average Roughness Measurement of Shot- and Sand-Blasted Surfaces
by Kyungmok Kim
Lubricants 2024, 12(10), 339; https://doi.org/10.3390/lubricants12100339 - 30 Sep 2024
Viewed by 635
Abstract
This article presents a machine vision system for measuring the arithmetic average roughness of shot- and sand-blasted surfaces. In the developed system, a digital microscope was used for capturing surface images after shot- and sand-blasting processes. The captured grayscale images were analyzed with [...] Read more.
This article presents a machine vision system for measuring the arithmetic average roughness of shot- and sand-blasted surfaces. In the developed system, a digital microscope was used for capturing surface images after shot- and sand-blasting processes. The captured grayscale images were analyzed with the proposed algorithm using Otsu’s global thresholding and a size bandpass filter. The algorithm detected white regions associated with the specular reflection of light on a binary image, and then calculated the size of selected regions. One-way ANOVA was used to identify the relation between the size of the regions and the arithmetic average roughness of blasted surfaces. It was noted that the average size of white regions showed a linear relation to the arithmetic average roughness of both shot- and sand-blasted surfaces. Different abrasives (shot or sand) were found to bring about differences in the rate of change of the average size within a chosen roughness range. When a surface image with unknown roughness is given, it is possible to predict the arithmetic average roughness on the basis of the relation. This machine vision system enables the fast and low-cost roughness measurement of shot- and sand-blasted surfaces. Thus, it could be useful in a quality inspection for shot- and sand-blasting. Full article
(This article belongs to the Special Issue Mechanical Tribology and Surface Technology)
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17 pages, 8375 KiB  
Article
Tyre Wear under Urban, Rural, and Motorway Driving Conditions at Two Locations in Spain and China
by Barouch Giechaskiel, Theodoros Grigoratos, Liang Li, Sheng Zang, Bo Lu, David Lopez and Juan J. García
Lubricants 2024, 12(10), 338; https://doi.org/10.3390/lubricants12100338 - 30 Sep 2024
Viewed by 1032
Abstract
The recently introduced Euro 7 emissions standard regulation foresees the addition of abrasion limits for tyres sold in the European Union. The measurement procedures for tyre abrasion are described in the newly introduced Annex 10 of the United Nations (UN) Regulation 117. However, [...] Read more.
The recently introduced Euro 7 emissions standard regulation foresees the addition of abrasion limits for tyres sold in the European Union. The measurement procedures for tyre abrasion are described in the newly introduced Annex 10 of the United Nations (UN) Regulation 117. However, the limits are not yet defined as there is no data available regarding the new procedure. For this reason, a market assessment campaign is ongoing under the auspices of the UN Task Force on Tyre Abrasion (TFTA). Recent reviews on the topic also concluded that there is a lack of studies measuring the abrasion rates of tyres. In this study, we measured the abrasion rate of one tyre model at two different locations (Spain and China) with the aim of deep diving into possible influencing factors. Additionally, wear rates were studied separately for urban, rural, and motorway routes to get more insight into the impact of the route characteristics. The abrasion rates varied from 22 mg/km to 123 mg/km per vehicle, depending on the route (urban, rural, motorway) and ambient temperature. The overall average trip abrasion rates were 75 mg/km and 45 mg/km per vehicle at the two locations, respectively. However, when corrected for the different ambient temperatures, the rates were 63 mg/km and 60 mg/km per vehicle, respectively. The impacts of other parameters, such as driving dynamics and road surface, on the final results are also discussed. The average tread depth reduction was estimated to be 0.8–1.4 mm every 10,000 km. Full article
(This article belongs to the Special Issue Emission and Transport of Wear Particles)
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22 pages, 12430 KiB  
Article
Electrification of a Mini Traction Machine and Initial Test Results
by Peter Lee, Carlos Sanchez, Michael Moneer and Andrew Velasquez
Lubricants 2024, 12(10), 337; https://doi.org/10.3390/lubricants12100337 - 30 Sep 2024
Viewed by 1086
Abstract
Electric vehicles (EVs) continue to evolve, and sales continue to increase as the world pushes toward improved sustainability. This drives the need for research to understand the unique environments in which fluids operate within the Electric Drive Units (EDUs) of EVs in order [...] Read more.
Electric vehicles (EVs) continue to evolve, and sales continue to increase as the world pushes toward improved sustainability. This drives the need for research to understand the unique environments in which fluids operate within the Electric Drive Units (EDUs) of EVs in order to improve durability and reduce frictional losses. However, for this to happen, test rigs are required to operate with an electric current passing across the test parts and through the lubricant. Very few electrified test rigs currently exist, with most being adaptations of rigs undertaken by academia and independent and national research labs. In this work, the PCS Mini Traction Machine (MTM) was modified to supply a voltage across a tribological contact. New parts for the MTM were designed in collaboration with the instrument manufacturer. Work was undertaken in both the author’s labs and the manufacturer’s labs with the aim of bringing a commercially available unit to market as quickly as possible. A test matrix was completed on the MTM utilizing a range of temperatures, loads, and voltage inputs for three different lubricants commonly used in EDUs. The test matrix consisted of 36 test conditions, with some runs performed in triplicate, resulting in 81 tests for each oil and a total matrix of 243 tests. The test matrix was run to obtain the results and to test the robustness of the rig design. After testing was completed, the MTM disc wear scars were measured. The results from these measurements indicate that the application of alternating current (AC) and direct current (DC) causes a significant increase in the wear scar compared to non-electrified test conditions. This, in turn, results in increased traction values under non-electrified conditions. It was also noted that the repeatability of the traction curves and end-of-test wear was reduced under both AC and DC electrified conditions. Full article
(This article belongs to the Special Issue Tribology of Electric Vehicles)
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20 pages, 11340 KiB  
Article
Synergistic Effects of Surface Texture and Cryogenic Treatment on the Tribological Performance of Aluminum Alloy Surfaces
by Rui Liu, Xiwen Deng, Xuejian Sun, Jilin Lei, Dewen Jia, Wengang Chen and Qiang Ji
Lubricants 2024, 12(10), 336; https://doi.org/10.3390/lubricants12100336 - 30 Sep 2024
Viewed by 673
Abstract
In order to improve the tribological properties of the 7075-T6 aluminum alloy used on the rotor surface, a combined method of cryogenic treatment and laser surface texture treatment was applied. Various tests, including metallographic microscopy, scanning electron microscopy, elemental analysis, microhardness measurements, were [...] Read more.
In order to improve the tribological properties of the 7075-T6 aluminum alloy used on the rotor surface, a combined method of cryogenic treatment and laser surface texture treatment was applied. Various tests, including metallographic microscopy, scanning electron microscopy, elemental analysis, microhardness measurements, were conducted to examine the wear morphology and modification mechanism of the treated 7075-T6 aluminum alloy surface. A numerical simulation model of surface texture was established using computational fluid dynamics to analyze the lubrication characteristics of V-shaped texture. The research finding that the 7075-T6 aluminum alloy experienced grain refinement during the cryogenic treatment process, enhancing the wear resistance of the V-shaped textures. This improvement delayed the progression of fatigue wear, abrasive wear, and oxidative wear, thereby reducing friction losses. The designed V-shaped texture contributes to reducing contact area, facilitating the capture and retention of abrasives, and enhancing oil film load-bearing capacity, thereby improving tribological performance. The synergistic effect of cryogenic treatment reduced the friction coefficient by 24.8% and the wear loss by 66.4%. Thus, the combination of surface texture and cryogenic treatment significantly improved the tribological properties of the 7075-T6 aluminum alloy. Full article
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15 pages, 3831 KiB  
Article
Numerical Simulation of the Temperature in a Train Brake Disc Using the Barycentric Rational Interpolation Collocation Method
by Bing Wu, Yuanying Zhuo, Linquan Yao, Quan Shen, Guangwen Xiao and Zhaoyang Wang
Lubricants 2024, 12(10), 335; https://doi.org/10.3390/lubricants12100335 - 30 Sep 2024
Viewed by 589
Abstract
The thermal analysis of brake discs is crucial for studying issues such as wear and cracking. This paper establishes a symmetric two-dimensional brake disc model using the barycentric rational interpolation collocation method (BRICM). The model accounts for the effects of thermal radiation and [...] Read more.
The thermal analysis of brake discs is crucial for studying issues such as wear and cracking. This paper establishes a symmetric two-dimensional brake disc model using the barycentric rational interpolation collocation method (BRICM). The model accounts for the effects of thermal radiation and is linearized using Newton’s linear iteration method. In the spatial dimension, the two-dimensional heat conduction equation is discretized using BRICM, while in the temporal dimension, it is discretized using the finite difference method (FDM). The resulting temperature distribution of the brake disc during two consecutive braking events is consistent with experimental data. Additionally, factors affecting the accurate calculation of the temperature are examined. Compared to other models, the proposed model achieves accurate temperature distributions with fewer nodes. Furthermore, the numerical results highlight the significance of thermal radiation within the model. The results obtained using BRICM can be used to predict the two-dimensional temperature distribution of train brake discs. Full article
(This article belongs to the Special Issue Advanced Computational Studies in Frictional Contact)
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19 pages, 9138 KiB  
Article
Analysis of Surface Drag Reduction Characteristics of Non-Smooth Jet Coupled Structures
by Jinming Kou, Qiannan Lou, Yunqing Gu, Junjun Zhang, Chengqi Mou, Jiayun Yu, Youting Ding and Chengbo Xu
Lubricants 2024, 12(10), 334; https://doi.org/10.3390/lubricants12100334 - 29 Sep 2024
Viewed by 598
Abstract
To enhance the service life of shipping equipment and minimize surface wear, this study employs biomimetic principles, integrating fitted structures with jet dynamics to model three configurations: non-smooth structures, single jet structures, and non-smooth jet-coupled structures. We utilized the SST k-ω turbulence model [...] Read more.
To enhance the service life of shipping equipment and minimize surface wear, this study employs biomimetic principles, integrating fitted structures with jet dynamics to model three configurations: non-smooth structures, single jet structures, and non-smooth jet-coupled structures. We utilized the SST k-ω turbulence model for numerical simulations to investigate the drag reduction characteristics of these structural models. By varying the jet angle and speed, we analyzed the changes in viscous resistance, pressure differential resistance, and drag reduction rates at the wall surface. Furthermore, the mechanisms of compressive stress, velocity fields, vortex structures, and shear stress on drag-reducing surfaces were elucidated, revealing how these factors contribute to drag reduction in non-smooth jet-coupled structures. The results indicate that the non-smooth jet-coupled structure exhibits superior drag reduction performance at a main flow field velocity of 20 m/s. As the jet velocity increases, the viscous drag on the surface of the non-smooth jet-coupled structure decreases, while the pressure differential drag increases. Conversely, variations in the jet angle have a minimal effect on viscous drag but lead to a reduction in pressure differential drag. Specifically, when the jet velocity is set at 1 m/s, and the jet angle is 60°, the drag reduction achieved by the non-smooth jet-coupled structure peaks at 7.48%. Additionally, the non-smooth jet-coupled structure features a larger area characterized by low shear stress, along with an increased boundary layer thickness at the bottom; this configuration effectively reduces surface velocity and consequent viscous drag. Full article
(This article belongs to the Special Issue Marine Tribology)
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13 pages, 6681 KiB  
Article
Experimental Research on Pollution-Free Alcohol Cutting Fluid in Scratching of Single-Crystal Copper Material
by Xian Wu, Benchi Li, Ke Sun, Congfu Fang and Jianyun Shen
Lubricants 2024, 12(10), 333; https://doi.org/10.3390/lubricants12100333 - 28 Sep 2024
Viewed by 703
Abstract
Cutting fluid can improve the heat dissipation and lubrication in the cutting process and thus increase the machining quality. In this work, a pollution-free alcohol solution was proposed as the cutting fluid in an ultra-precision cutting process to explore green cutting fluids. The [...] Read more.
Cutting fluid can improve the heat dissipation and lubrication in the cutting process and thus increase the machining quality. In this work, a pollution-free alcohol solution was proposed as the cutting fluid in an ultra-precision cutting process to explore green cutting fluids. The scratching experiments were conducted with the alcohol cutting fluid to study its effect on the cutting process. It is found that the use of an alcohol cutting fluid, on average, reduces the tangential and normal force about 27–53%, but exhibits few effects on the friction coefficient in the cutting process. Compared to dry cutting, the alcohol cutting fluid reduces the exposed shear slip steps on the outside surface of the chip, which implies the decreased chip deformation degree of workpiece material in the cutting process. The alcohol cutting fluid can reduce microburrs and decrease the machined surface roughness Ra from 21 nm to 9.9 nm in the ultra-precision turning application on single-crystal copper material. Full article
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54 pages, 25769 KiB  
Review
Progress of Multidimensional Nano-Additives under Dry/Liquid Wear: A Review
by Na Xiao, Chao Wu, Kang Yang and Jun Tang
Lubricants 2024, 12(10), 332; https://doi.org/10.3390/lubricants12100332 - 27 Sep 2024
Viewed by 843
Abstract
An investigation of the interaction between multidimensional nano-additives and tribofilms is crucial for enhancing mechanical efficiency, extending equipment lifespan, and reducing environmental impacts. Improved tribofilm performance is obtained via several mechanisms: filling surface defects with 0D nano-additives, directional lubrication for 1D nano-additives, interlayer [...] Read more.
An investigation of the interaction between multidimensional nano-additives and tribofilms is crucial for enhancing mechanical efficiency, extending equipment lifespan, and reducing environmental impacts. Improved tribofilm performance is obtained via several mechanisms: filling surface defects with 0D nano-additives, directional lubrication for 1D nano-additives, interlayer slippage for 2D nano-additives, and improved film durability for 3D nano-additives. Under dry lubrication, the formation of tribofilms via mechanical mixing is influenced by material hardness, surface roughness, and frictional conditions, with their thicknesses increasing by 20–30% under high loading. Conversely, liquid-lubricated films result from the physical adsorption and chemical reactions of the lubricants, with extremely high pressure additives reducing the friction coefficient by 30–50% at high pressure. A greater understanding of these mechanisms is beneficial for optimizing industrial technologies and developing efficient, eco-friendly lubrication systems. Full article
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13 pages, 64133 KiB  
Article
A Tribological Study of ta-C, ta-C:N, and ta-C:B Coatings on Plastic Substrates under Dry Sliding Conditions
by Paul Neubauer, Frank Kaulfuss and Volker Weihnacht
Lubricants 2024, 12(10), 331; https://doi.org/10.3390/lubricants12100331 - 27 Sep 2024
Viewed by 547
Abstract
In this study, we analyze the extent to which thin hard coatings can serve as tribological protective layers for the selected plastic substrate materials PA12 (polyamide 12) und PEEK (polyetheretherketone), with and without fiber reinforcement. The approximately 1 µm thick coating variants ta-C, [...] Read more.
In this study, we analyze the extent to which thin hard coatings can serve as tribological protective layers for the selected plastic substrate materials PA12 (polyamide 12) und PEEK (polyetheretherketone), with and without fiber reinforcement. The approximately 1 µm thick coating variants ta-C, ta-C:N, and ta-C:B, which were applied using the laser arc process, are investigated. In oscillating sliding wear tests against a steel ball in an air atmosphere without lubricant, the wear of the coating and counter body is compared to analogous coating variants applied in parallel to AISI 52100 steel. The ta-C-based coatings show good adhesion strength and basic suitability as wear protection layers on the plastic substrates in the tribological tests. However, there are variations depending on the coating type and substrate material. The use of a Cr interlayer and its thickness also plays an important role. It is demonstrated that by coating under conditions where the uncoated plastic substrate would normally fail, a similarly good performance as with analogously coated steel substrates can be achieved by ta-C:N. Full article
(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)
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