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Lubricants
Volume 13
Issue 6
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Lubricants, Volume 13, Issue 6 (June 2025) – 35 articles

Cover Story (view full-size image): The mechanical properties of composite materials depend on their composition as well as the geometry, distribution and orientation of the fillers. Our investigations on samples with different fiber orientations show that differences in morphology significantly influence both the mechanical properties and the tribological behavior. Based on tribological measurements with orthotropic samples and a unique fiber orientation with respect to the sliding plane, we propose a model to predict the tribological properties of any fiber orientation with respect to this plane. The material composition, in particular the presence of SiO2, can attenuate the fiber orientation influence, i.e., make the material more directionally tolerant. View this paper
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32 pages, 3956 KiB  
Article
Analysis of Unbalance Response and Vibration Reduction of an Aeroengine Gas Generator Rotor System
by Haibiao Zhang, Xing Heng, Ailun Wang, Tao Liu, Qingshan Wang and Kun Liu
Lubricants 2025, 13(6), 266; https://doi.org/10.3390/lubricants13060266 (registering DOI) - 15 Jun 2025
Abstract
To ensure the vibration safety of rotor support systems in modern aeroengines, this study develops a dynamic model of the aeroengine gas generator rotor system and analyzes its complex unbalance response characteristics. Subsequently, it investigates vibration reduction strategies based on these response patterns. [...] Read more.
To ensure the vibration safety of rotor support systems in modern aeroengines, this study develops a dynamic model of the aeroengine gas generator rotor system and analyzes its complex unbalance response characteristics. Subsequently, it investigates vibration reduction strategies based on these response patterns. This study begins by developing individual dynamic models for the disk–blade system, the circular arc end-teeth connection structure and the squeeze film damper (SFD) support system. These models are then integrated using the differential quadrature finite element method (DQFEM) to create a comprehensive dynamic model of the gas generator rotor system. The unbalance response characteristics of the rotor system are calculated and analyzed, revealing the impact of the unbalance mass distribution and the combined support system characteristics on the unbalance response of the rotor system. Drawing on the obtained unbalance response patterns, the vibration reduction procedures for the rotor support system are explored and experimentally verified. The results demonstrate that the vibration response of the modern aeroengine rotor support system can be reduced by adjusting the unbalance mass distribution, decreasing the bearing stiffness and increasing the bearing damping, thereby enhancing the vibration safety of the rotor system. This study introduces a novel integration of DQFEM with detailed component-level modeling of circular arc end-teeth connections, disk–blade interactions and SFD dynamics. This approach uniquely captures the coupled effects of unbalance distribution and support system characteristics, offering a robust framework for enhancing vibration safety in aeroengine rotor systems. The methodology provides both theoretical insights and practical guidelines for optimizing rotor dynamic performance under unbalance-induced excitations. Full article
16 pages, 2281 KiB  
Article
Impact of Lubrication on Shear Deformation During Asymmetrical Rolling: A Viscoplastic Analysis of Slip System Activity Using an Affine Linearization Scheme
by I Putu Widiantara, Siti Fatimah, Warda Bahanan, Jee-Hyun Kang and Young Gun Ko
Lubricants 2025, 13(6), 265; https://doi.org/10.3390/lubricants13060265 (registering DOI) - 15 Jun 2025
Abstract
In industrial applications, rolling is commonly performed with lubrication to prevent undesirable modification of the sheet. Although it is well established that lubrication influences the microstructure and texture of deformed sheets through its effect on shear deformation, the underlying mechanisms remain insufficiently understood. [...] Read more.
In industrial applications, rolling is commonly performed with lubrication to prevent undesirable modification of the sheet. Although it is well established that lubrication influences the microstructure and texture of deformed sheets through its effect on shear deformation, the underlying mechanisms remain insufficiently understood. In this study, we investigated how lubrication affects slip system activity during asymmetrical rolling, using viscoplastic modeling of BCC ferritic steel. Two conditions—lubricated and non-lubricated samples—were examined under asymmetrical rolling. Slip system activity was inferred from the rotation axes between pairs of orientations separated by low-angle grain boundaries, based on the assumption that such boundaries represent the simplest form of orientation change. A Viscoplastic Self-Consistent (VPSC) model employing an affine linearization scheme was used. This proved sufficient for evaluating slip system activity in BCC polycrystalline metals undergoing early-stage plastic deformation involving either plane strain or combined plane strain and shear. The results demonstrated that lubrication had a limiting effect by reducing the penetration of shear deformation through the thickness of the sample. Understanding this effect could enable the optimization of lubrication strategies—not only to minimize defects such as bending, but also to achieve microstructural characteristics favorable for industrial applications. Full article
14 pages, 7468 KiB  
Article
Wear of Stellite 6 Coatings Produced with High-Velocity Oxygen Fuel at Elevated Temperatures
by Alejandra Islas Encalada, Pantcho Stoyanov, Mary Makowiec, Christian Moreau and Richard R. Chromik
Lubricants 2025, 13(6), 264; https://doi.org/10.3390/lubricants13060264 (registering DOI) - 15 Jun 2025
Abstract
This paper investigates the tribological behavior of Stellite 6 coatings produced with high-velocity oxygen fuel (HVOF), with an emphasis on the transition between severe and mild wear regimes and the glaze layer formation. The development of these coatings involved two spray parameters modifying [...] Read more.
This paper investigates the tribological behavior of Stellite 6 coatings produced with high-velocity oxygen fuel (HVOF), with an emphasis on the transition between severe and mild wear regimes and the glaze layer formation. The development of these coatings involved two spray parameters modifying the oxygen fuel ratio and three post-heat treatment conditions at temperatures ranging between 600 °C and 1150 °C. The coatings were tested under conditions varying the normal load, temperature, sliding distance, and testing temperatures (up to 300 °C). The results show that the coating obtained from the HVOF process exhibited a microstructure different from the conventional bulk Co-alloys, significantly impacting the wear performance. The coating post-processing was essentialto enhance wear resistance at elevated temperatures. Full article
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12 pages, 1944 KiB  
Article
Perfluorotetradecanoic Acid as an Additive for Friction Reduction in Full-Film EHD Contacts: The Role of Functional Group, Base Oil Polarity, Additive Concentration and Contact Pressure
by Marko Polajnar, Tomaž Požar and Mitjan Kalin
Lubricants 2025, 13(6), 263; https://doi.org/10.3390/lubricants13060263 (registering DOI) - 14 Jun 2025
Abstract
Perfluorinated tetradecanoic acid was added as an additive to a base oil and tested under full film elastohydrodynamic (EHD) contact conditions between a steel ball and a steel disc. By varying key performance parameters, we aimed to assess the feasibility and limitations of [...] Read more.
Perfluorinated tetradecanoic acid was added as an additive to a base oil and tested under full film elastohydrodynamic (EHD) contact conditions between a steel ball and a steel disc. By varying key performance parameters, we aimed to assess the feasibility and limitations of perfluorinated carboxylic acids in reducing friction in lubricated contacts. The results demonstrate that the tested perfluorinated additive is effective in reducing friction when blended with a non-polar synthetic poly-alpha-olefin oil. However, no significant friction reduction was observed when the same additive was used in a slightly polar synthetic ester. The carboxylic acid functional group plays a crucial role in the observed friction-reducing effect. Adjusting the additive concentration further plays an important role in reducing friction. A concentration of at least 0.35 wt.% is required to achieve a notable friction reduction of approximately 10%. Increasing the concentration beyond this threshold continues to improve the friction-reducing effect. Conversely, increasing the contact pressure has a detrimental impact on friction reduction. The greatest reduction in friction—over 20% compared to the base oil—was achieved at the lowest contact pressure tested (0.69 GPa). Full article
(This article belongs to the Special Issue Novel Lubricant Additives in 2025)
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17 pages, 7359 KiB  
Article
Modeling of the Dynamics of Conical Separate Plates in a Wet Multi-Disc Clutch
by Qin Zhao, Biao Ma, Cenbo Xiong, Liang Yu, Bing Fu and Shufa Yan
Lubricants 2025, 13(6), 262; https://doi.org/10.3390/lubricants13060262 - 12 Jun 2025
Viewed by 69
Abstract
Wet multi-disc clutches in transmission systems suffer from the incomplete separation of the friction components, which raises the drag torque and results in power loss and heightened fuel consumption. This incomplete separation arises from the force imbalance between resistance forces, such as the [...] Read more.
Wet multi-disc clutches in transmission systems suffer from the incomplete separation of the friction components, which raises the drag torque and results in power loss and heightened fuel consumption. This incomplete separation arises from the force imbalance between resistance forces, such as the oil viscosity force, and the lack of an axial separating force. Therefore, providing an axial separating force is a potential solution to this problem. In this investigation, small-angle conical separate plates were designed which can provide the elastic restoring force during the separation process. Based on its structural properties, a model describing the clutch engagement and separation process was established. Through bench tests, the feasibility of the model was verified. The influence of the conical plate on the dynamics of the clutch was studied, including the influence of the separation gap, uniformity, and drag torque. Though the transmitted torque was reduced by 10.31% in the low-piston-pressure condition and by less than 2% in the high-piston-pressure condition, the problem of incomplete separation was successfully resolved. The results show that when applying the conical plates, the separation time was reduced by 18.78%, with a 25.31% increase in the uniformity of the gaps. Accordingly, the drag torque was reduced by 37.73%. Full article
(This article belongs to the Special Issue Tribology in Vehicles)
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20 pages, 9230 KiB  
Article
Research on Ground Contact Characteristics and Influencing Factors of Tires with Complex Tread Patterns Based on Inverse Modeling
by Xianbin Du, Haoyu Li, Mengdi Xu and Yunfei Ge
Lubricants 2025, 13(6), 261; https://doi.org/10.3390/lubricants13060261 - 12 Jun 2025
Viewed by 130
Abstract
The contact characteristics of radial tires are crucial for optimizing stress distribution, deformation, and wear. The non-uniform contact stress behavior induced by complex tread patterns remains under-explored in existing tire mechanics research. Taking the 205/50R17 radial tire as a representative case, a reverse [...] Read more.
The contact characteristics of radial tires are crucial for optimizing stress distribution, deformation, and wear. The non-uniform contact stress behavior induced by complex tread patterns remains under-explored in existing tire mechanics research. Taking the 205/50R17 radial tire as a representative case, a reverse modeling approach was employed to develop an accurate finite element model for tires incorporating intricate tread pattern features. The fidelity of the proposed tire simulation model was confirmed utilizing high-precision contour profiling techniques. The impact of diverse usage conditions and design parameters on the tire outer profile and ground contact characteristics under static and free-rolling states was analyzed. Experimental observations demonstrate that the increased inflation pressure leads to a proportional decrease in contact area. Under incremental vertical loading, the contact patch develops progressively into a saddle-shaped geometry featuring elevated shoulder regions and a recessed central zone. Increasing the belt angle compromises its hoop-stiffening function, thereby inducing elliptical contact patch geometry. Larger design diameters compromise contact length symmetry in shoulder regions. Variation in shoulder thickness at 85% of the tread width results in a significant difference in contact length between the left and right tread blocks in the rolling state. This work enables refinement strategies for both tread configurations and tire dimensional designs in industrial applications. Full article
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17 pages, 3125 KiB  
Article
Tribocorrosion Behavior of a Medium-Entropy Austenitic Stainless Steel in 3.5 wt.% NaCl: A Comparative Study with 304 and S31254 Stainless Steels
by Chun-Hao Wang, Shih-Yen Huang, Yu-Ren Chu, Peng-Shu Hsu, Hung-Wei Yen, I-Chung Cheng, Peng-Wei Chu and Yueh-Lien Lee
Lubricants 2025, 13(6), 260; https://doi.org/10.3390/lubricants13060260 - 11 Jun 2025
Viewed by 134
Abstract
This study investigates the tribocorrosion behavior of 304 stainless steel (304SS), S31254 super austenitic stainless steel (S31254 SASS), and a medium-entropy austenitic stainless steel (MEASS) in 3.5 wt.% NaCl solution under sliding conditions. The objective is to clarify the performance differences among these [...] Read more.
This study investigates the tribocorrosion behavior of 304 stainless steel (304SS), S31254 super austenitic stainless steel (S31254 SASS), and a medium-entropy austenitic stainless steel (MEASS) in 3.5 wt.% NaCl solution under sliding conditions. The objective is to clarify the performance differences among these alloys when exposed to simultaneous mechanical wear and corrosion. Electrochemical techniques, including potentiodynamic polarization and potentiostatic sliding tests, were used to evaluate corrosion resistance and repassivation behavior. Quantitative analysis based on ASTM G119 revealed that MEASS showed a 68% lower total material loss compared to 304SS and a 55% lower loss compared to S31254. MEASS also exhibited the lowest corrosion current density (1.46 μA/cm2) under tribocorrosion conditions, representing an 83% reduction compared to 304SS. These improvements are attributed to the higher chromium and nickel contents of MEASS, which enhance passive film stability and reduce susceptibility to localized corrosion. The results demonstrate that MEASS offers superior resistance to combined mechanical and corrosive degradation in chloride-containing environments. Full article
(This article belongs to the Special Issue Tribology of Metals and Alloys)
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26 pages, 1183 KiB  
Review
The Combined Use of Simulation and Friction and Wear Experiments in the Research of Green Lubricants
by Xuan Yin, Dingyao Zhang, Haosheng Pang, Bing Zhang and Dameng Liu
Lubricants 2025, 13(6), 259; https://doi.org/10.3390/lubricants13060259 - 11 Jun 2025
Viewed by 270
Abstract
During the operation of mechanical equipment, due to the intense friction among raw material or filler particles, there is conspicuous wear on the contact surfaces of components. Using green lubricants assumes a crucial role in mitigating the friction and wear, enhancing the equipment’s [...] Read more.
During the operation of mechanical equipment, due to the intense friction among raw material or filler particles, there is conspicuous wear on the contact surfaces of components. Using green lubricants assumes a crucial role in mitigating the friction and wear, enhancing the equipment’s service life and the production’s reliability. This review centers on investigating the wear mechanism of green lubricants and undertakes a comprehensive summary and in-depth analysis of the research approach, integrating numerical simulation and friction and wear experiments. Moreover, the construction of the friction and wear testing machine and the intelligence of the testing system were probed, offering valuable design theories and research schemes for the development of effective anti-wear green lubricants. Full article
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27 pages, 13005 KiB  
Review
The Application and Development of Static Pressure Air Floating in the Field of Micro-Low-Gravity Simulation Experiments for Spacecraft
by Libin Zang, Weijie Hou, Lei Liu, Haixia Hu, Xingze Wang, Yong Jia, Yongbo Hao, Yuehua Li and Baoshan Zhao
Lubricants 2025, 13(6), 258; https://doi.org/10.3390/lubricants13060258 - 11 Jun 2025
Viewed by 191
Abstract
The force conditions experienced by spacecraft and astronauts in space are vastly different from those in Earth’s gravitational environment, hence it is necessary to conduct adequate micro-low-gravity environment simulation tests on the ground before launch. In this paper, an overview is provided of [...] Read more.
The force conditions experienced by spacecraft and astronauts in space are vastly different from those in Earth’s gravitational environment, hence it is necessary to conduct adequate micro-low-gravity environment simulation tests on the ground before launch. In this paper, an overview is provided of the current status of micro-low-gravity simulation test technology for spacecraft based on hydrostatic air-bearing. The paper systematically organizes the application of hydrostatic air-bearing technology in micro-low-gravity simulation tests, such as the deployment of space mechanisms, spacecraft GNC (Guidance, Navigation, and Control), on-orbit operations of space manipulators, and astronaut training. It summarizes the principles of air-flotation micro-low-gravity simulation technology in different scenarios and distills suitable solutions for various requirements. Finally, the paper looks forward to the development trends of air-flotation micro-low-gravity simulation test technology and proposes key technical challenges that need to be overcome in aerostatic bearing. Full article
(This article belongs to the Special Issue Space Tribology)
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32 pages, 23138 KiB  
Review
Improving Wear Resistance of DLC-Coated Metal Components During Service: A Review
by Luji Wu, Zhongchao Bai, Qingle Hao and Jiayin Qin
Lubricants 2025, 13(6), 257; https://doi.org/10.3390/lubricants13060257 - 11 Jun 2025
Viewed by 256
Abstract
Diamond-like carbon (DLC) coatings have emerged as a focal point in advanced carbon materials research due to exceptional tribological properties, including ultralow friction coefficient, exceptional wear resistance, ultrahigh hardness, and chemical inertness. Deposition of DLC coatings on metal components represents an innovative solution [...] Read more.
Diamond-like carbon (DLC) coatings have emerged as a focal point in advanced carbon materials research due to exceptional tribological properties, including ultralow friction coefficient, exceptional wear resistance, ultrahigh hardness, and chemical inertness. Deposition of DLC coatings on metal components represents an innovative solution to enhance wear resistance in engineering applications. However, suboptimal adhesion strength between coatings and substrates, coupled with inherent material limitations, critically compromises the tribological performance. This review systematically examines recent advances in improving the wear resistance of DLC-coated metal components. First, the fundamental wear mechanisms governing both metallic substrates and DLC coatings under service conditions are elucidated. Next, three pivotal technologies, substrate material treatment/strengthening, coating structure design, and elemental doping, all demonstrating significant efficacy in wear resistance enhancement, are critically analyzed. Furthermore, a comparative assessment of these techniques reveals the synergistic potential in hybrid approaches. Finally, a concise summary of the outlook is presented. Full article
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16 pages, 2284 KiB  
Article
Experimental Evaluation of the Tribological Properties of Rigid Gas-Permeable Contact Lens Under Different Lubricants
by Chen-Ying Su, Hsu-Wei Fang, Mousa Nimatallah, Zain Qatmera and Haytam Kasem
Lubricants 2025, 13(6), 256; https://doi.org/10.3390/lubricants13060256 - 11 Jun 2025
Viewed by 395
Abstract
Myopia patients wear rigid gas-permeable contact lenses during the day to achieve normal vision, but they might feel uncomfortable, since they are made of hard materials that can cause inappropriate friction and adhesion. These forces affect the biological tissues of the cornea and [...] Read more.
Myopia patients wear rigid gas-permeable contact lenses during the day to achieve normal vision, but they might feel uncomfortable, since they are made of hard materials that can cause inappropriate friction and adhesion. These forces affect the biological tissues of the cornea and eyelid. In this study, an in vitro rigid gas-permeable contact lens friction testing method was established to mimic the friction between the eyelid and the rigid contact lens. The lens was rubbed against a gelatin membrane to investigate the tribological properties of artificial tear, saline, and two kinds of care solutions using a dedicated experimental setup. The viscosity, pH value, and surface tension of each lubricant was also analyzed. The friction coefficient of the artificial tear solution was the highest: 0.18 for its static friction and 0.09 for its dynamic friction. In contrast, polysaccharide-containing care solution demonstrated the lowest friction coefficient. The viscosity of artificial tear solutions ranged from 0.97 ± 00 to 1.15 ± 0.16 mPa·s, when the shear rate was increased from 19.2 to 192 1/s, while it ranged from 2.26 ± 1.12 to 2.91 ± 0.00 for polysaccharide-containing care solution. Although the physical–chemical properties of various lubricants could not explain the distinct tribological outcomes, the in vitro tribological testing method for rigid gas-permeable lenses was successfully established in this study. Full article
(This article belongs to the Special Issue Biomaterials and Tribology)
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26 pages, 9313 KiB  
Article
Investigating Resulting Surface Topography and Residual Stresses in Bending DC01 Sheet Under Tension Friction Test
by Krzysztof Szwajka, Tomasz Trzepieciński, Marek Szewczyk, Joanna Zielińska-Szwajka and Marek Barlak
Lubricants 2025, 13(6), 255; https://doi.org/10.3390/lubricants13060255 - 9 Jun 2025
Viewed by 90
Abstract
This article presents the results of experimental studies aimed at determining the values of residual stresses and coefficient of friction (CoF) in bending under tension friction test, which simulates friction conditions in sheet metal forming. The influence of surface modification of the countersample [...] Read more.
This article presents the results of experimental studies aimed at determining the values of residual stresses and coefficient of friction (CoF) in bending under tension friction test, which simulates friction conditions in sheet metal forming. The influence of surface modification of the countersample and CoFs between the countersample and DC01 steel sheet on the residual stress were analysed. This study also focused on the influence of surface modification of countersamples on the change of the main parameters of DC01 steel sheets. The hole-drilling method was used to determine residual stresses. Electron beam melting, lead-ion implantation and a combination of these two techniques were used to modify the surface layer of 145Cr6 steel countersamples. The maximum value of the CoF, about 0.31, was found for the electron beam melted countersample. As a result of the surface modification process, this countersample was characterised by the lowest value of average roughness, which directly influenced the increase in the real contact area. The occurrence of residual tensile stresses was observed near the surface layer of the sheet strip in contact with the countersample. With the increase of the considered depth of residual stress measurement, the residual tensile stresses were transformed into compressive residual stresses with a value between −75 and −50 MPa, depending on the type of friction pair. SEM analyses allowed us to identify two main friction mechanisms for all friction pairs: adhesion and abrasive wear. Full article
(This article belongs to the Special Issue Advanced Surface Treatments and Coatings for Friction and Wear Reduction)
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22 pages, 5743 KiB  
Article
Influence of N2 Flow Rate on Mechanical and Tribological Properties of TAlN Coatings Deposited on 300M Substrate and Nitrocarburized Layer
by Shiwei Zuo, Qinghua Li, Zhehang Fan, Xiaoyong Tao, Xiangjie Wang, Hui Xie, Qianqian Shen, Tianshi Jia and Hongyan Wu
Lubricants 2025, 13(6), 254; https://doi.org/10.3390/lubricants13060254 - 6 Jun 2025
Viewed by 221
Abstract
This study systematically investigates the influence of nitrogen (N2) flow rates and nitrocarburized (PNC) interlayers on the mechanical and tribological properties of TiAlN coatings deposited on 300M steel substrates via magnetron sputtering. The coatings were fabricated under three N2 flow [...] Read more.
This study systematically investigates the influence of nitrogen (N2) flow rates and nitrocarburized (PNC) interlayers on the mechanical and tribological properties of TiAlN coatings deposited on 300M steel substrates via magnetron sputtering. The coatings were fabricated under three N2 flow rates (30, 90, and 150 sccm), with microstructure evolution, elemental composition, and phase transitions analyzed using SEM, EDS, AFM, and XRD. The results indicate that the PNC/TiAlN composite coatings exhibited superior interfacial adhesion and load-bearing capacity compared to standalone TiAlN coatings, attributed to the graded hardness transition and stress distribution optimization at the coating–substrate interface. Nanoindentation tests revealed enhanced hardness and elastic modulus in PNC/TiAlN systems under high N2 flow conditions. Tribological evaluations demonstrated that the composite coatings achieved lower specific wear rates (25.23 × 10−8 mm3·N−1·m−1) under 7.3 N, outperforming monolithic TiAlN coatings by mitigating abrasive wear and delamination. The synergy between N2 flow modulation and nitrocarburizing pretreatment effectively optimized coating–substrate compatibility, establishing a robust framework for designing wear-resistant TiAlN coatings in extreme service environments. This work provides critical insights into tailoring PVD coating architectures for aerospace and heavy-load applications. Full article
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26 pages, 3344 KiB  
Review
A Holistic Review of Surface Texturing in Sheet Metal Forming: From Sheet Rolling to Final Forming
by Paulo L. Monteiro, Jr. and Henara L. Costa
Lubricants 2025, 13(6), 253; https://doi.org/10.3390/lubricants13060253 - 5 Jun 2025
Viewed by 363
Abstract
Skin-pass cold rolling is a crucial step in sheet metal production, modifying the sheet surface topography, ensuring thickness uniformity, and enhancing tribological performance. A key factor in this process is the surface texturing of work rolls, which, when transferred to the rolled sheet, [...] Read more.
Skin-pass cold rolling is a crucial step in sheet metal production, modifying the sheet surface topography, ensuring thickness uniformity, and enhancing tribological performance. A key factor in this process is the surface texturing of work rolls, which, when transferred to the rolled sheet, directly affects lubrication distribution and formability in subsequent stamping operations. Properly textured sheets promote lubricant retention, reducing friction and wear, while roll wear can compromise texture transfer, leading to defects in the final product. This review presents a holistic view of surface texturing from the roll topography to the final product. First, it explores different texturing methods for work rolls, analyzing their efficiency, durability, and impact on texture transfer. Then, alternative texturing techniques and coatings are discussed as strategies to mitigate roll wear. By assessing the relationship between roll texturing and sheet drawability, this study provides insights to improve industrial processes, enhance product quality, and promote more sustainable manufacturing solutions. Full article
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16 pages, 5250 KiB  
Article
Hybrid Additives of 1,3-Diketone Fluid and Nanocopper Particles Applied in Marine Engine Oil
by Yuwen Xu, Yan Yang, Li Zhong, Xingyuan Jing, Xiaoyu Yin, Tao Xia, Jingsi Wang, Tobias Amann and Ke Li
Lubricants 2025, 13(6), 252; https://doi.org/10.3390/lubricants13060252 - 4 Jun 2025
Viewed by 305
Abstract
The lubrication performance of the cylinder liner–piston ring (CLPR) is crucial for the energy efficiency and operating reliability of marine diesel engines. To enhance the boundary lubrication of marine engine oil, a 1,3-diketone fluid HPTD (1-(4-hexylphenyl) tridecane-1,3-dione, HPTD) was introduced as an ash-free [...] Read more.
The lubrication performance of the cylinder liner–piston ring (CLPR) is crucial for the energy efficiency and operating reliability of marine diesel engines. To enhance the boundary lubrication of marine engine oil, a 1,3-diketone fluid HPTD (1-(4-hexylphenyl) tridecane-1,3-dione, HPTD) was introduced as an ash-free friction modifier. Besides that, octadecylamine-functionalized nanocopper particles (ODA-Cu) were also added to the marine oil to improve its anti-wear behavior. Through cylinder-on-disk friction tests, the appropriate contents of HPTD and ODA-Cu were determined, which then formed hybrid additives and modified the engine oil. The tribological performance of the modified oil was analyzed under various normal loads, reciprocating frequencies, and testing temperatures. Based on the synergy of the tribochemical reaction of HPTD and the mending effect of ODA-Cu on the sliding surface, the modified oil not only had lower sulfated ash content but also exhibited superior lubrication performance (i.e., reduced coefficient of friction by 15%, smaller wear track by 43%, and higher maximum non-seizure load by 11%) than the pristine engine oil. The results of this study would be helpful for the design of novel hybrid eco-friendly additives for marine engine oil. Full article
(This article belongs to the Special Issue Marine Tribology)
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16 pages, 9251 KiB  
Article
Topology Optimization of Textured Journal Bearings
by Hanqian Kong, Chunxing Gu, Di Zhang and Lanfei Wu
Lubricants 2025, 13(6), 251; https://doi.org/10.3390/lubricants13060251 - 4 Jun 2025
Viewed by 256
Abstract
The journal bearing, a critical component of the rotating shaft, is influenced by various factors including friction, wear, and heat effects under actual working conditions. This study developed an advanced approach for optimizing the performance of journal bearings with surface texture. This approach [...] Read more.
The journal bearing, a critical component of the rotating shaft, is influenced by various factors including friction, wear, and heat effects under actual working conditions. This study developed an advanced approach for optimizing the performance of journal bearings with surface texture. This approach allows for finding the influences of bearing parameters such as journal clearance, rotational speed, and shaft eccentricity ratio on the optimization results. The results show that whether under smaller journal clearances, higher rotational speeds, or larger shaft eccentricity ratios, the formation of intricate bifurcation patterns and enhanced branching in surface textures is consistently promoted. The optimized texture’s shape leads to a reduction in texture depth while significantly improving both the load-carrying capacity (LCC) and oil film thickness. This approach precisely determines the spatial and depth characteristics of texture elements, ensuring their optimal placement and geometry, and offers valuable insights and directions for future research. Full article
(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 3rd Edition)
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24 pages, 4367 KiB  
Article
Thermoplastic Labyrinth Seals Under Rub Impact: Deformation Leakage Mechanisms and High Efficiency Optimization
by Fei Ma, Zhengze Yang, Yue Liu, Shuangfu Suo and Peng Su
Lubricants 2025, 13(6), 250; https://doi.org/10.3390/lubricants13060250 - 4 Jun 2025
Viewed by 293
Abstract
Labyrinth seals, extensively used in aerospace and turbomachinery as non-contact sealing devices, undergo accelerated wear and enhanced leakage due to repeated rub-impact between rotating shafts and sealing rings. To address the problem of increased leakage under rub-impact conditions, this research integrates experimental and [...] Read more.
Labyrinth seals, extensively used in aerospace and turbomachinery as non-contact sealing devices, undergo accelerated wear and enhanced leakage due to repeated rub-impact between rotating shafts and sealing rings. To address the problem of increased leakage under rub-impact conditions, this research integrates experimental and numerical methods to investigate the deformation mechanisms and leakage characteristics of thermoplastic labyrinth seals. A custom designed rub-impact test rig was constructed to measure dynamic forces and validate finite element analysis (FEA) models with an error of 5.1% in predicting tooth height under mild interference (0.25 mm). Computational fluid dynamics (CFD) simulations further demonstrated that thermoplastic materials, such as PAI and PEEK, displayed superior resilience (with rebound ratios of 57% and 70.3%, respectively). Their post-impact clearances were 4.8–18.3% smaller than those of PTFE and F500. Leakage rates were predominantly correlated with interference, causing a substantial increase compared to the original state; at 0.25 mm interference (reverse flow), increases ranged from 151% (PAI) to 217% (PTFE), highlighting material-dependent performance degradation. Meanwhile, tooth orientation modulated leakage by 0.5–3% through the vena contracta effect. Based on these insights, two optimized inclined-tooth geometries were designed, reducing leakage by 28.2% (Opt1) and 28.1% (Opt2) under rub-impact. These findings contribute to the development of high-performance labyrinth seals suitable for extreme operational environments. Full article
(This article belongs to the Special Issue Recent Advances in Sealing Technologies)
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42 pages, 13512 KiB  
Article
Dynamic Characteristic Analysis of Angular Contact Ball Bearings with Two-Piece Inner Rings in Aero-Engine Main Shafts Under Unsteady-State Conditions
by Haisheng Yang, Qiang Liu and Si’er Deng
Lubricants 2025, 13(6), 249; https://doi.org/10.3390/lubricants13060249 - 30 May 2025
Viewed by 308
Abstract
The dynamic interactions among the internal components of aero-engine main shaft bearings under unsteady-state conditions are intricate, involving clearance collisions, contact, friction, and lubrication. The dynamic characteristics of bearings significantly influence the performance and stability of mechanical systems. This study establishes a rigid–flexible [...] Read more.
The dynamic interactions among the internal components of aero-engine main shaft bearings under unsteady-state conditions are intricate, involving clearance collisions, contact, friction, and lubrication. The dynamic characteristics of bearings significantly influence the performance and stability of mechanical systems. This study establishes a rigid–flexible coupling dynamic model for angular contact ball bearings with two-piece inner rings based on Hertz contact theory and lubrication theory. It systematically analyzes the dynamic characteristics of bearings under the coupling effects of acceleration, deceleration, and impact load. This study explores the influence of various loads, bearing speeds, and groove curvature radius coefficients on the dynamic characteristics of bearings. The findings indicate that the uniform speed phase of a bearing is highly responsive to impact load, followed by the deceleration phase, while the acceleration phase shows lower sensitivity to impact load. The groove curvature radius coefficient significantly affects the contact stress between the ball and its corresponding raceway, with contact stress increasing as the groove curvature radius coefficient rises. As the axial load decreases and the radial load, bearing speed, and groove curvature radius coefficient increase, there is a rise in pocket force, guiding force, and maximum equivalent stress of the flexible cage. Impact load leads to short-term intense fluctuations in the thickness of the bearing oil film, which can be alleviated by an increase in axial load. The oil film thickness firstly increases and then decreases with respect to the groove curvature radius coefficient. Furthermore, variations in bearing speed notably influence the thickness of the bearing oil film. This study analyzes the dynamic characteristics of bearings under the coupling effects of acceleration, deceleration, and impact load, offering insights for the design and optimization of angular contact ball bearings with two-piece inner rings. Full article
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21 pages, 669 KiB  
Article
On the Non-Dimensional Modelling of Friction Hysteresis of Conformal Rough Contacts
by Kristof Driesen, Sylvie Castagne, Bert Lauwers and Dieter Fauconnier
Lubricants 2025, 13(6), 248; https://doi.org/10.3390/lubricants13060248 - 30 May 2025
Viewed by 309
Abstract
Friction hysteresis, ingaphenomenon observed when a sliding contact is subjected to an oscillatory motion has significant implications in fields such as tribology and robotics. Understanding and quantifying friction hysteresis is essential for improving the performance and efficiency of many sliding contacts. In this [...] Read more.
Friction hysteresis, ingaphenomenon observed when a sliding contact is subjected to an oscillatory motion has significant implications in fields such as tribology and robotics. Understanding and quantifying friction hysteresis is essential for improving the performance and efficiency of many sliding contacts. In this paper, we introduce six non-dimensional groups to characterize and study friction hysteresis behaviour for rough conformal sliding contacts. The proposed non-dimensional groups are specifically designed to capture the essential features of friction hysteresis loops encountered based upon previous work of present authors. The non-dimensional groups are derived from a mixed friction model composed of the transient Reynolds equation, a statistical mixed friction contact model, and the load balance. The non-dimensional groups capture physical parameters that influence friction behaviour, including normal load, sliding speed, viscosity, density, and surface roughness. By expressing these parameters in non-dimensional form, the proposed groups provide a concise and generalizable framework for analysing friction hysteresis across different systems and scales. To demonstrate the effectiveness of the non-dimensional groups, we establish a comprehensive relationship between the proposed groups and typical friction hysteresis loops encountered. Through numerical simulations, we find relationships that govern the transition between different hysteresis loop shapes and sizes. This knowledge can inform the design and optimization of systems where friction hysteresis plays a crucial role. Full article
(This article belongs to the Special Issue Advanced Computational Studies in Frictional Contact)
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25 pages, 6613 KiB  
Article
Microstructure, Mechanical Strength, and Tribological Behavior of B4C/WS2-Hybrid-Reinforced B319 Aluminum Matrix Composites
by Ufuk Tasci
Lubricants 2025, 13(6), 247; https://doi.org/10.3390/lubricants13060247 - 29 May 2025
Viewed by 295
Abstract
Hybrid B319 aluminum matrix composites reinforced with 10 wt% B4C and varying WS2 contents were fabricated to improve mechanical and tribological performance. The composite containing 2 wt% WS2 showed the best overall results, with a 29% increase in microhardness [...] Read more.
Hybrid B319 aluminum matrix composites reinforced with 10 wt% B4C and varying WS2 contents were fabricated to improve mechanical and tribological performance. The composite containing 2 wt% WS2 showed the best overall results, with a 29% increase in microhardness (104.3 HV) and a 20% improvement in transverse rupture strength (196.3 MPa) compared to unreinforced B319. Additionally, the friction coefficient dropped by 64% (from 0.497 to 0.178), and the specific wear rate was reduced to 4.34 × 10−6 mm3/N·m. Microstructural analyses confirmed homogeneous reinforcement distribution and adequate interfacial bonding. These enhancements are attributed to the dual action of B4C-induced strengthening and WS2-mediated tribo-film formation, offering a promising solution for lightweight, wear-resistant components in engineering applications. Full article
(This article belongs to the Special Issue Tribological and Mechanical Characteristics of Aluminum Metal Matrix Composites and Their Applications)
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26 pages, 7153 KiB  
Article
Dynamic Precision and Reliability of Multi-Link Linkages with Translational Pair Clearance
by Quanzhi Zuo, Mingyang Cai, Yuyang Lian, Jianuo Zhu and Shuai Jiang
Lubricants 2025, 13(6), 246; https://doi.org/10.3390/lubricants13060246 - 29 May 2025
Viewed by 309
Abstract
This study investigates the dynamic behavior and reliability of planar multi-link linkages with clearance in translational pairs. Using the Lagrange multiplier method, a dynamic model that accounts for clearance effects is developed. Furthermore, a reliability model is established by combining the first-order second-moment [...] Read more.
This study investigates the dynamic behavior and reliability of planar multi-link linkages with clearance in translational pairs. Using the Lagrange multiplier method, a dynamic model that accounts for clearance effects is developed. Furthermore, a reliability model is established by combining the first-order second-moment method with the stress-strength interference theory. Numerical simulations were performed to evaluate the impact of varying clearance sizes and driving speeds on motion errors and system reliability. This study also explores the nonlinear dynamics of the end-effector. The results indicate that increased clearance and higher driving speeds lead to certain changes in motion errors and operational reliability. Phase diagrams and Poincaré maps reveal directional differences in dynamic stability: chaotic motion along the X-direction and periodic oscillations along the Y-direction. These findings provide valuable insights for optimizing mechanism design and enhancing operational reliability. Full article
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14 pages, 4846 KiB  
Article
Study of Corrosion, Power Consumption, and Wear Characteristics of Herringbone-Grooved Fan Bearings in High-Temperature and High-Humidity Environments
by Jim-Chwen Yeh, Yu-Chang Lee, Chun-Hsiang Huang, Ming-Yuan Li and Chin-Chung Wei
Lubricants 2025, 13(6), 245; https://doi.org/10.3390/lubricants13060245 - 28 May 2025
Viewed by 356
Abstract
Fans are essential electronic components for heat dissipation in electronic systems, with fan bearings being critical parts that determine fan performance and lifespan. This paper investigates the corrosion, wear, power consumption, temperature, and vibration characteristics of a newly designed and manufactured powder metallurgy [...] Read more.
Fans are essential electronic components for heat dissipation in electronic systems, with fan bearings being critical parts that determine fan performance and lifespan. This paper investigates the corrosion, wear, power consumption, temperature, and vibration characteristics of a newly designed and manufactured powder metallurgy bearing with herringbone oil grooves for fans under high-humidity and high-temperature conditions. Corrosion experiments on iron–copper powder metallurgy bearings show that a higher environmental temperature and humidity result in greater corrosion current and reduced corrosion resistance. Bearings operated under high humidity (85% RH) and a high temperature (80 °C) for 0, 3, and 8 days, respectively, revealed that wear and corrosion occur simultaneously. The longer the operating time, the more significant the wear and corrosion. After 3 and 8 days, the lubricating oil flow in the oil grooves decreased by 9.8% and 51.5%, respectively. When bearings subjected to varying degrees of corrosion were tested under the same standard operating conditions, it was found that the bearings corroded for 3 and 8 days, resulting in a significant increase in the number of wear debris particles, higher RMS vibration values, and a power consumption increase of 6.9% and 7.8%, respectively. The percentage of iron elements on the surface gradually decreased, with the copper elements being the primary wear particles during the wear process. However, due to the increased clearance between the rotating shaft and the bearing caused by wear, the fan temperature slightly decreased with increased surface wear. Full article
(This article belongs to the Special Issue Recent Advances in Tribological Properties of Machine Tools)
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18 pages, 7950 KiB  
Article
Combined Effects of DLC Coating and Surface Texturing on Seizure and Friction in Reciprocating Sliding
by Slawomir Wos, Waldemar Koszela, Andrzej Dzierwa and Pawel Pawlus
Lubricants 2025, 13(6), 244; https://doi.org/10.3390/lubricants13060244 - 28 May 2025
Viewed by 350
Abstract
Surface texturing is designed to improve the functional properties of machine elements by generating dimples on the surface contacted. Friction and wear resistance can also be improved by creating diamond-like carbon (DLC) coatings. These two techniques were combined to extend the lifetime of [...] Read more.
Surface texturing is designed to improve the functional properties of machine elements by generating dimples on the surface contacted. Friction and wear resistance can also be improved by creating diamond-like carbon (DLC) coatings. These two techniques were combined to extend the lifetime of the elements and minimise friction in reciprocating conformal sliding contact. This work is functionally important for assemblies operating under high normal loads. Experiments were carried out in initially lubricated reciprocating sliding contact using an Optimol SRV 5 tribotester in the flat-on-flat configuration. The disc samples were untextured, laser textured, and DLC-coated untextured and textured. The combination of DLC coating and surface texturing caused an enhancement of the tribological performance of the sliding pair compared to that of untextured discs with and without DLC coating and textured discs without DLC coating. The DLC coating of the untextured disc caused a growth in the lifetime of a friction pair by a factor of 2.4. Seizure resistance also increased due to surface texturing of the steel disc for pit area ratios of 9 and 13%. Combining surface texturing with pit area ratios of 3 and 9% and DLC coating led to a decrease in the coefficients of friction of sliding pairs compared to only textured and coated discs. The DLC coating caused a decrease in the wear of the disc sample and reduction in wear levels of the counter samples in comparison to those of textured discs without DLC coatings. Full article
(This article belongs to the Special Issue Tribology of Textured Surfaces)
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28 pages, 11569 KiB  
Article
Optimization of Micro-Texture Parameters for Machine Tool Guide Rail Combination Based on Response Surface Methodology and Research on Its Anti-Friction and Lubrication Performance
by Youzheng Cui, Bingyang Yan, Minli Zheng, Haijing Mu, Chengxin Liu, Dongyang Wang, Xinmiao Li, Qingwei Li, Hui Jiang, Fengjuan Wang and Qingming Hu
Lubricants 2025, 13(6), 243; https://doi.org/10.3390/lubricants13060243 - 27 May 2025
Viewed by 386
Abstract
In the process of heavy-duty cutting, the reciprocating motion of the sliding guide pair surface is prone to local wear, which seriously affects the overall machining accuracy and service life of the machine tool. This study proposes a biomimetic micro-texture design scheme combining [...] Read more.
In the process of heavy-duty cutting, the reciprocating motion of the sliding guide pair surface is prone to local wear, which seriously affects the overall machining accuracy and service life of the machine tool. This study proposes a biomimetic micro-texture design scheme combining elliptical grooves and shell-shaped grooves on the surface of carp as biomimetic prototypes to enhance the oil film bearing capacity, drag reduction, and wear resistance of guide rail pairs. Based on Fluent fluid simulation research, it has been shown that this texture has a better dynamic pressure lubrication effect. We used response surface methodology to optimize the texture design parameters and further verify the accuracy of the optimal parameters with the NSGA-II genetic algorithm. The results show that under lubricated conditions, the load-bearing pressure of the combined micro-textured guide rail pair increased by 53.79%, the friction coefficient decreased by 39.04%, and the temperature decreased by 15.83%. This texture can still significantly improve drag reduction and wear resistance in a low-oil state. Full article
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20 pages, 10062 KiB  
Article
Experimental Study on Vibration Characteristics of Journal Bearing-Rotor System Under Base Roll and Pitch Motions
by Fangcheng Xu, Jiyu Wang, Kaidi Zhu, Guilong Wang, Jingwei Yi and Zhongliang Xie
Lubricants 2025, 13(6), 242; https://doi.org/10.3390/lubricants13060242 - 27 May 2025
Viewed by 371
Abstract
Currently, there is limited experimental research on the stability of journal bearing-rotor systems under base motion, and the influence of rocking motion on the stability of such systems remains unclear. This study develops an experimental test rig for a journal bearing-rotor system and [...] Read more.
Currently, there is limited experimental research on the stability of journal bearing-rotor systems under base motion, and the influence of rocking motion on the stability of such systems remains unclear. This study develops an experimental test rig for a journal bearing-rotor system and employs a six-degrees-of-freedom shaking table to apply complex alternating loads, with the aim of investigating the effects of rocking amplitude and frequency on the vibration characteristics of the shaft system. The experimental results show that, under the excitation of base roll and pitch motions, the critical speed of the sliding bearing-rotor system remains nearly unchanged, while the resonance amplitude increases significantly, and the instability speed occurs earlier. In addition, base rocking motion not only induces periodic and uniform changes in the vibration amplitude of the shaft system but also demonstrates a strong positive correlation between the amplitude of system vibration and the amplitude of base rocking. Full article
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16 pages, 4930 KiB  
Article
Trade-Off for CFRP Quality Using High-Frequency Ultrasonic-Assisted Drilling Under Lubricant Absence
by Khaled Hamdy and Saood Ali
Lubricants 2025, 13(6), 241; https://doi.org/10.3390/lubricants13060241 - 26 May 2025
Viewed by 277
Abstract
Carbon fiber reinforced polymers (CFRPs) are significantly vital for industries. However, the drilling process of a CFRP is considered a challenge due to its nature, which causes delamination, fiber pull-out, peel-up, high friction, and a decrease in cutting tool life. Wet drilling is [...] Read more.
Carbon fiber reinforced polymers (CFRPs) are significantly vital for industries. However, the drilling process of a CFRP is considered a challenge due to its nature, which causes delamination, fiber pull-out, peel-up, high friction, and a decrease in cutting tool life. Wet drilling is necessary for minimizing defects, and lubricants are very costly. In the current work, ultrasonic-assisted drilling (UAD) with a longitudinal vibration of 39.7 kHz was applied to the drill bit in the feed direction, used for CFRPs, and compared with conventional drilling (CD). Low spindle speeds under 5000 rpm were applied with different feed rates. The morphology, delamination factor, and cutting forces were investigated through the specific input machining parameters for CD and UAD. SEM was applied to study the morphology of the hole entrance and exit as well as the burr heights of evacuated chips. UAD with 39.7 kHz succeeded in minimizing the surface roughness by 50% compared with the surface roughness resulting from CD and could drill high-precision holes for CFRPs with a trade-off concept, besides achieving near-zero delamination (K ≃ 1) in the absence of a lubricant, which is being extended for industrial application. Full article
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17 pages, 2429 KiB  
Article
Experimental Investigation on Cutting Forces in Sustainable Hard Milling of Hardox 500 Steel Under Al2O3/MoS2 Hybrid Nanofluid MQCL Environment
by Tran The Long
Lubricants 2025, 13(6), 240; https://doi.org/10.3390/lubricants13060240 - 26 May 2025
Viewed by 340
Abstract
Hardox 500 is a special low-alloy, martensitic steel possessing extraordinary wear resistance, high hardness, and high ductility; thus, it has been widely used in many industrial applications. Nevertheless, this type of steel has a low machinability and is grouped among the difficult-to-machine materials. [...] Read more.
Hardox 500 is a special low-alloy, martensitic steel possessing extraordinary wear resistance, high hardness, and high ductility; thus, it has been widely used in many industrial applications. Nevertheless, this type of steel has a low machinability and is grouped among the difficult-to-machine materials. Hence, this paper’s objective was to study its hard milling performance under minimum quantity cooling lubrication (MQCL) conditions using an Al2O3/MoS2 hybrid nano cutting oil. The Box–Behnken response surface methodology was used to investigate the effects of the nanoparticle concentration (NC), cutting speed (v), and feed rate (f) on the total cutting force F and cutting force coefficient Fy/Fz. The obtained results indicate that the cutting efficiency of Hardox 500 steel was improved thanks to the enhancement in cooling lubrication from the MQCL using the Al2O3/MoS2 hybrid nano cutting oil. The applicability of vegetable oil and coated carbide inserts is thus extended to the hard milling of difficult-to-cut materials. Moreover, the provision of the appropriate ranges and optimal set of investigated variables obtained in this paper will be useful guides for technologists and further studies. Concretely, NC = 0.5–0.7%, v = 110–115 m/min, and f = 0.08–0.10 mm/tooth are the optimal set for the total cutting force F, while NC = 0.5%, v = 138–140 m/min, and f = 0.08–0.09 mm/tooth are suggested for the cutting force coefficient Fy/Fz. Full article
(This article belongs to the Special Issue Recent Advances in Tribological Properties of Machine Tools)
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18 pages, 5787 KiB  
Article
Use of Advanced Piston Ring Coatings on Agricultural Engines
by Xiaochao He, Bang Liu, Eduardo Tomanik, Grzegorz Koszalka and Anna Orlova
Lubricants 2025, 13(6), 239; https://doi.org/10.3390/lubricants13060239 - 26 May 2025
Viewed by 605
Abstract
The use of combustion engines on agricultural vehicles will persist much longer than on-road vehicles. Introducing new technologies in agricultural engines is crucial to mitigating emissions while accounting for customer cost-sensitivity, harsh operation conditions, and typically sub-optimal maintenance. This work describes the use [...] Read more.
The use of combustion engines on agricultural vehicles will persist much longer than on-road vehicles. Introducing new technologies in agricultural engines is crucial to mitigating emissions while accounting for customer cost-sensitivity, harsh operation conditions, and typically sub-optimal maintenance. This work describes the use of CrN and tetrahedral amorphous carbon (ta-C) DLC-coated rings in small agricultural diesel engines. Compared with the gas nitride rings, the CrN and the ta-C DLC coatings exhibited, respectively, 74% and 86% lower wear in rig tests. The DLC also presented a very low coefficient of friction and high resistance to scuffing. A similar wear trend was observed on durability engine tests, where the CrN top ring showed an 80% lower wear rate than the GNS used in a similar engine. Wear on the DLC oil ring was below the measurement capability. Liner radial wear was measured on the piston ring reversal points in four angular positions, and except for one position, was lower than 3 µm. At the end of the test, engine performance and emissions are nearly identical to those at the test’s start, demonstrating that the use of advanced tribological solutions can significantly contribute to emissions mitigation in agricultural engines. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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15 pages, 5949 KiB  
Article
The Influence of Graphite Orientation on the Current-Carrying Friction Performance of Copper–Graphite Composite Materials
by Zhenghai Yang, Wenbo Li, Yingjian Song, Xiaomeng Zheng and Yongzhen Zhang
Lubricants 2025, 13(6), 238; https://doi.org/10.3390/lubricants13060238 - 26 May 2025
Viewed by 314
Abstract
In response to the need to optimize the performance of copper–graphite current-carrying friction materials, spark plasma sintering (SPS) technology was used to prepare copper–graphite composite materials with different graphite orientations. A self-made current-carrying friction testing machine was used to study the effect of [...] Read more.
In response to the need to optimize the performance of copper–graphite current-carrying friction materials, spark plasma sintering (SPS) technology was used to prepare copper–graphite composite materials with different graphite orientations. A self-made current-carrying friction testing machine was used to study the effect of graphite orientation on the current-carrying friction performance of copper–graphite composites. The results showed that as the graphite orientation increased, the current-carrying friction performance of the copper–graphite composites initially improved and then deteriorated. The performance was optimal when the graphite orientation of the 7.5 wt% graphite–copper composite was 90°, primarily constrained by the wear rate. The main wear mechanism was furrowing, and graphite enrichment occurred on the worn surface, where the graphite content on the wear surface was higher than that in the bulk material. The degree of enrichment varied under different wear mechanisms. The graphite content near the entry region of the friction surface was significantly lower than that near the exit region. Full article
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22 pages, 7683 KiB  
Article
Surface Characterization of Cylinder Liner–Piston Ring Friction Pairs Under Different Temperature and Load by Power Spectral Density Method
by Xiaori Liu, Xiaofei Cao, Xuan Ma and Menghan Li
Lubricants 2025, 13(6), 237; https://doi.org/10.3390/lubricants13060237 - 25 May 2025
Viewed by 383
Abstract
Piston ring–cylinder liner is one of the most important friction pairs in internal combustion engines. The surfaces of the piston ring and the cylinder liner are affected by high temperature and high pressure, and the influence mechanism of temperature and pressure on their [...] Read more.
Piston ring–cylinder liner is one of the most important friction pairs in internal combustion engines. The surfaces of the piston ring and the cylinder liner are affected by high temperature and high pressure, and the influence mechanism of temperature and pressure on their microscopic morphology parameters is yet to be revealed. In this paper, high temperature friction and wear experiments on the piston ring and cylinder liner are carried out to obtain the microscopic morphology of the cylinder liner and piston ring at different temperatures and pressures, and their changes under different temperatures and pressures are investigated by using two methods, namely, fractal dimension and three-dimensional surface roughness characterization. The results show that, as the temperature increases, the texture patterns on the cylinder liner’s friction surface become simpler, with the fractal dimension showing a decreasing trend while the roughness shows an increasing trend. Compared to the condition at 80 °C, the surface roughness (Sa) of the cylinder liner increased by approximately 58.43% at 190 °C, while that of the piston ring increased by about 96.5%. With increasing pressure, both the fractal dimension and the roughness of the friction surface first decrease and then increase. Full article
(This article belongs to the Special Issue Thermal Hydrodynamic Lubrication)
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