Lubricants

27 pages, 4277 KiB

Open AccessArticle

Probability Density Evolution and Reliability Analysis of Gear Transmission Systems Based on the Path Integration Method

by Hongchuan Cheng, Zhaoyang Shi, Guilong Fu, Yu Cui, Zhiwu Shang and Xingbao Huang

Lubricants 2025, 13(6), 275; https://doi.org/10.3390/lubricants13060275 - 19 Jun 2025

Viewed by 433

Abstract

Aimed at dealing with the problems of high reliability solution cost and low solution accuracy under random excitation, especially Gaussian white noise excitation, this paper proposes a probability density evolution and reliability analysis method for nonlinear gear transmission systems under Gaussian white noise [...] Read more.

Aimed at dealing with the problems of high reliability solution cost and low solution accuracy under random excitation, especially Gaussian white noise excitation, this paper proposes a probability density evolution and reliability analysis method for nonlinear gear transmission systems under Gaussian white noise excitation based on the path integration method. This method constructs an efficient probability density evolution framework by combining the path integration method, the Chapman–Kolmogorov equation, and the Laplace asymptotic expansion method. Based on Rice’s theory and combined with the adaptive Gauss–Legendre integration method, the transient and cumulative reliability of the system are path integration method calculated. The research results show that in the periodic response state, Gaussian white noise leads to the diffusion of probability density and peak attenuation, and the system reliability presents a two-stage attenuation characteristic. In the chaotic response state, the intrinsic dynamic instability of the system dominates the evolution of the probability density, and the reliability decreases more sharply. Verified by Monte Carlo simulation, the method proposed in this paper significantly outperforms the traditional methods in both computational efficiency and accuracy. The research reveals the coupling effect of Gaussian white noise random excitation and nonlinear dynamics, clarifies the differences in failure mechanisms of gear systems in periodic and chaotic states, and provides a theoretical basis for the dynamic reliability design and life prediction of nonlinear gear transmission systems. Full article

(This article belongs to the Special Issue Nonlinear Dynamics of Frictional Systems)

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23 pages, 6546 KiB

Open AccessArticle

Bidirectionally Coupled FE-CFD Simulation Study on MQL Machining Process of Ti-6Al-4V Alloy

by Xiaorong Zhou, Lin He, Sen Yuan, Hongwan Jiang, Jing Deng, Feilong Du, Jingdou Yang and Zebin Su

Lubricants 2025, 13(6), 274; https://doi.org/10.3390/lubricants13060274 - 19 Jun 2025

Viewed by 694

Abstract

In the context of sustainable manufacturing practices, minimum quantity lubrication (MQL) has been extensively employed in machining operations involving hard-to-cut materials. While substantial experimental and numerical investigations on MQL-assisted machining have been conducted, existing simulation approaches remain inadequate for modeling the dynamic flow [...] Read more.

In the context of sustainable manufacturing practices, minimum quantity lubrication (MQL) has been extensively employed in machining operations involving hard-to-cut materials. While substantial experimental and numerical investigations on MQL-assisted machining have been conducted, existing simulation approaches remain inadequate for modeling the dynamic flow field variations inherent to MQL processes, significantly compromising the predictive reliability of current models. This study introduced an innovative bidirectional iterative coupling framework integrating finite element (FE) analysis and computational fluid dynamics (CFD) to enhance simulation accuracy. Since fluid flow characteristics critically influence tribological and thermal management at the tool–workpiece interface during machining, CFD simulations were initially performed to evaluate how MQL parameters govern fluid flow behavior. Subsequently, an integrated FE-CFD modeling approach was developed to simulate Ti-6Al-4V alloy turning under MQL conditions with varying feed rates. The novel methodology involved transferring thermal flux data from FE simulations to CFD’s heat source domain, followed by incorporating CFD-derived convective heat transfer coefficients back into FE computations. This repetitive feedback process continued until the thermal exchange parameters reached convergence. Validation experiments demonstrated that the proposed method achieved improved alignment between the simulated and experimental results for both cutting temperature profiles and principal force components across different feed conditions, confirming the enhanced predictive capability of this coupled simulation strategy. Full article

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21 pages, 6191 KiB

Open AccessArticle

Single-Step Drilling Using Novel Modified Drill Bits Under Dry, Water, and Kerosene Conditions and Optimization of Process Parameters via MOGA-ANN and RSM

by Sumitava Paul, Barun Haldar, Hillol Joardar, Nripen Mondal, Naser A. Alsaleh and Maaz Akhtar

Lubricants 2025, 13(6), 273; https://doi.org/10.3390/lubricants13060273 - 18 Jun 2025

Viewed by 951

Abstract

The burr removal and finishing of drilled hole walls typically require multiple post-processing steps. This experimental study introduces a novel single-step drilling approach using modified drill bits for simultaneous burr removal and surface finishing in aluminum 6061-T6. The odified-1 drill, equipped with a [...] Read more.

The burr removal and finishing of drilled hole walls typically require multiple post-processing steps. This experimental study introduces a novel single-step drilling approach using modified drill bits for simultaneous burr removal and surface finishing in aluminum 6061-T6. The odified-1 drill, equipped with a deburring micro-insert, achieved superior results, with a chamfer height of −2.829 mm, drilling temperature of 40.28 ◦C, and surface roughness of 0.082 µm under optimal conditions. Multi-objective optimization using the RSM and MOGA-ANN identified the optimal drilling parameters for the Modified-1 drill at 3000 rpm under water lubrication as compared to dry conditions and kerosene. Experimental validation confirmed the high prediction accuracy, with deviations under 6%. These results establish the Modified-1 twist drill bit with a deburring
micro-insert as a highly effective tool for burr-free high-quality drilling in a single operation. This innovative drill design presents an efficient, single-step solution for burr elimination, chamfer formation, and surface finishing in drilling operations. Full article

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12 pages, 2315 KiB

Open AccessArticle

Programmable Control of Droplets on Phase-Change Lubricant-Infused Surfaces Under Low Voltage

by Lingjie Sun, Chunlei Gao and Wei Li

Lubricants 2025, 13(6), 272; https://doi.org/10.3390/lubricants13060272 - 18 Jun 2025

Viewed by 668

Abstract

This study presents a bioinspired phase-change transparent flexible heater (PTFH) for programmable droplet manipulation under ultralow voltage. By embedding a self-junctioned copper nanowire network into paraffin-infused, porous PVDF-HFP gel matrices, the PTFH achieves rapid, non-contact, and reversible control of microdroplet mobility. The PTFH [...] Read more.

This study presents a bioinspired phase-change transparent flexible heater (PTFH) for programmable droplet manipulation under ultralow voltage. By embedding a self-junctioned copper nanowire network into paraffin-infused, porous PVDF-HFP gel matrices, the PTFH achieves rapid, non-contact, and reversible control of microdroplet mobility. The PTFH can be bent or tailored into diverse shapes (e.g., V/X configurations), enabling multidirectional droplet transport. Under ultralow voltage actuation (<1 V), the surface of PTFH melts the phase-change lubricant within 2 s, switching surface wettability from high adhesion (Wenzel state) to low adhesion (SLIPS state). By combining Laplace pressure and temperature gradients (up to 22 °C/mm), drive droplets at ~2.0 mm/s over distances of ~13.9 mm. Programmable droplet coalescence, curved-surface transport, and a microreactor design for batch reactions were also demonstrated. The PTFH exhibits excellent transparency (89% when activated), mechanical flexibility, and cyclic stability, offering a versatile platform for microreactors, microengines, and smart windows. Full article

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24 pages, 6378 KiB

Open AccessArticle

Fluid Characteristics of Radial Hydrodynamic Bearings Using Supercritical Carbon Dioxide as Lubricant

by Chengtao Niu, Sung-Ki Lyu, Yu-Ting Wu, Zhen Qin and Jie Zhang

Lubricants 2025, 13(6), 271; https://doi.org/10.3390/lubricants13060271 - 18 Jun 2025

Viewed by 582

Abstract

Hydrodynamic journal bearings play a vital role in high-speed, heavy-load machinery. Their performance directly affects system efficiency and reliability. Supercritical carbon dioxide (S-CO₂), with its favorable thermophysical properties, is a promising lubricant. This study focused on a four-oil-cavity hydrodynamic journal bearing [...] Read more.

Hydrodynamic journal bearings play a vital role in high-speed, heavy-load machinery. Their performance directly affects system efficiency and reliability. Supercritical carbon dioxide (S-CO₂), with its favorable thermophysical properties, is a promising lubricant. This study focused on a four-oil-cavity hydrodynamic journal bearing using S-CO₂ as the working fluid. A numerical model was established in ANSYS Workbench 2024 R1 using a fluid–structure interaction (FSI) method. The model was validated through comparison with literature data. Parametric studies were conducted by varying radial clearance, eccentricity, inlet diameter, and oil cavity size. Results showed that reducing the oil cavity wrap angle enhanced load capacity. Larger inlet diameters improved lubrication but could increase deformation. An appropriate combination of inlet diameter and eccentricity effectively reduced shell deformation. These findings offer design guidance for S-CO₂-lubricated bearings in high-speed applications. Full article

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15 pages, 4529 KiB

Open AccessArticle

Experimental Investigation on Sanding Effect of Rail Vehicles Under Low-Adhesion Conditions

by Feng Qiao, Chao Chen, Ming Zhao, Chuan Yang, Jiajun Zhou and Chun Tian

Lubricants 2025, 13(6), 270; https://doi.org/10.3390/lubricants13060270 - 17 Jun 2025

Viewed by 373

Abstract

To investigate the adhesion characteristics and sanding effect of rail vehicles on a contaminated rail surface, an innovative wheel/ring configuration test rig, named the PLS-Circulator, was employed. Based on the equivalence principle, the sanding condition relationship between the test rig and the field [...] Read more.

To investigate the adhesion characteristics and sanding effect of rail vehicles on a contaminated rail surface, an innovative wheel/ring configuration test rig, named the PLS-Circulator, was employed. Based on the equivalence principle, the sanding condition relationship between the test rig and the field was first established. Then, extensive and quantitative experiments on the enhancement of rail vehicle adhesion in sanding conditions were conducted. The results show that the maximum adhesion coefficient of various media increases with an increase in the amount of sand, and the adhesion-enhancing effects gradually reach the threshold when the amount of sand is high. On the other hand, after a single application of sand, the increase in the adhesion coefficient gradually decreases over time, and the pattern of adhesion enhancement degradation varies in different media. It was found that oil is the most unfavorable condition, where the adhesion-enhancing effect deteriorates the fastest. The appropriate amount of sand on the PLS-Circulator is 0.3 g/m, corresponding to 4.8 g/m of sand in the field. Full article

(This article belongs to the Special Issue Tribology in Railway Engineering)

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23 pages, 6061 KiB

Open AccessArticle

Monitoring and Prediction of the Real-Time Transient Thermal Mechanical Behaviors of a Motorized Spindle Tool

by Tria Mariz Arief, Wei-Zhu Lin, Jui-Pin Hung, Muhamad Aditya Royandi and Yu-Jhang Chen

Lubricants 2025, 13(6), 269; https://doi.org/10.3390/lubricants13060269 - 16 Jun 2025

Viewed by 409

Abstract

The spindle is a critical component that significantly influences the performance of machine tools. In motorized spindles, heat generation from both the bearings and built-in motor leads to thermal deformation of structural components, which, in turn, affects machining accuracy. This study investigates the [...] Read more.

The spindle is a critical component that significantly influences the performance of machine tools. In motorized spindles, heat generation from both the bearings and built-in motor leads to thermal deformation of structural components, which, in turn, affects machining accuracy. This study investigates the thermo-mechanical behavior of motorized spindles under various operational conditions, with the aim of accurately predicting thermally induced axial deformation and determining optimal temperature sensor placement. To achieve this, temperature rise and deformation data were simultaneously collected using appropriate data acquisition systems across varying spindle speeds. A correlation analysis confirmed a strong positive relationship exceeding 97.5% between temperature rise at all sensor locations and axial thermal deformation. Multivariate regression analysis was then applied to identify optimal combinations of sensor data for accurate deformation prediction. Additionally, a finite element (FE) thermal–mechanical model was developed to simulate spindle behavior, with the results validated against experimental measurements and regression model predictions. The four-variable regression model and FE simulation achieved Root Mean Square Errors (RMSEs) of 0.84 µm and 0.82 µm, respectively, both demonstrating close agreement with experimental data and effectively capturing the trend of thermal deformation over time under different operating conditions. Finally, an optimal sensor configuration was identified that minimizes pre-diction error while reducing the number of required sensors. Overall, the proposed methodology offers valuable insights for optimizing spindle design to enhance thermal–mechanical performance. Full article

(This article belongs to the Special Issue High Performance Machining and Surface Tribology)

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15 pages, 4481 KiB

Open AccessArticle

Tribological Evaluation and Model of Wear Behavior in the Boundary Lubrication of the Contact Surfaces of Cycloidal Reducers

by Juozas Padgurskas, Oleksandr Dykha, Raimundas Rukuiža, Darius Volskis, Rima Mickevičienė, Giorgi Abramishvili and Jumber Iosebidze

Lubricants 2025, 13(6), 268; https://doi.org/10.3390/lubricants13060268 - 16 Jun 2025

Viewed by 377

Abstract

Cycloidal reducers are widely used in precision drive systems due to their reduced backlash in meshing and compact design. However, their operational durability is limited by surface wear and lubricant degradation under elevated contact loads and boundary lubrication conditions. This study introduces a [...] Read more.

Cycloidal reducers are widely used in precision drive systems due to their reduced backlash in meshing and compact design. However, their operational durability is limited by surface wear and lubricant degradation under elevated contact loads and boundary lubrication conditions. This study introduces a modified wear prediction model based on four-ball tribological testing, specifically adapted to simulate the complex tribological conditions in cycloidal gear contacts. The model incorporates the total acid number (TAN) and thermal conductivity coefficient of the lubricant as dimensionless factors, enabling a dynamic prediction of wear intensity as the lubrication degrades. This innovation allows an accurate estimation of service life and reliability in high-load, small-contact-area mechanical systems and offers a practical diagnostic tool for the predictive maintenance of gear transmissions. Full article

(This article belongs to the Special Issue Tribology of Cycloidal Reducers: Enhancing Efficiency, Durability and Reliability through Experimental and Numerical Methods)

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27 pages, 5180 KiB

Open AccessArticle

Nano-Enhanced Cactus Oil as an MQL Cutting Fluid: Physicochemical, Rheological, Tribological, and Machinability Insights into Machining H13 Steel

by Nada K. ElBadawy, Mohamed G. A. Nassef, Ibrahem Maher, Belal G. Nassef, Mohamed A. Daha, Florian Pape and Galal A. Nassef

Lubricants 2025, 13(6), 267; https://doi.org/10.3390/lubricants13060267 - 15 Jun 2025

Viewed by 680

Abstract

The widespread use of mineral cutting fluids in metalworking poses challenges due to their poor wettability, toxicity, and non-biodegradability. This study explores cactus oil-based nanofluids as sustainable alternatives for metal cutting applications. Samples of cactus oil are prepared in plain form and with [...] Read more.

The widespread use of mineral cutting fluids in metalworking poses challenges due to their poor wettability, toxicity, and non-biodegradability. This study explores cactus oil-based nanofluids as sustainable alternatives for metal cutting applications. Samples of cactus oil are prepared in plain form and with 0.025 wt.%, 0.05 wt.%, and 0.1 wt.% activated carbon nanoparticles (ACNPs) from recycled plastic waste. Plain cactus oil exhibited a 34% improvement in wettability over commercial soluble oil, further enhanced by 60% with 0.05 wt.% ACNPs. Cactus oil displayed consistent Newtonian behavior with a high viscosity index (283), outperforming mineral-based cutting fluid in thermal stability. The addition of ACNPs enhanced the dynamic viscosity by 108–130% across the temperature range of 40–100 °C. The presence of nano-additives reduced the friction coefficient in the boundary lubrication zone by a maximum reduction of 32% for CO2 compared to plain cactus oil. The physical and rheological results translated directly to the observed improvements in surface finish and tool wear during machining operations on H13 steel. Cactus oil with 0.05 wt.% ACNP outperformed conventional fluids, reducing surface roughness by 35% and flank wear by 57% compared to dry. This work establishes cactus oil-based nanofluids as a sustainable alternative, combining recycled waste-derived additives and non-edible feedstock for greener manufacturing. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials and Active Control of Friction Behavior)

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30 pages, 5714 KiB

Open AccessArticle

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 - 15 Jun 2025

Viewed by 397

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

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16 pages, 2524 KiB

Open AccessArticle

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 - 15 Jun 2025

Viewed by 353

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

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14 pages, 7468 KiB

Open AccessArticle

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 - 15 Jun 2025

Viewed by 449

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

Open AccessArticle

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 - 14 Jun 2025

Viewed by 512

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

Open AccessArticle

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 335

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

Open AccessArticle

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 545

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

Open AccessArticle

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 448

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

Open AccessReview

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 672

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

Open AccessReview

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 475

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

Open AccessReview

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 826

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

Open AccessArticle

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 1008

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

Open AccessArticle

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 438

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

Open AccessArticle

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 503

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

Open AccessReview

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

Cited by 1 | Viewed by 809

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

Open AccessArticle

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 519

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

Open AccessArticle

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 503

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

Open AccessArticle

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 531

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

Open AccessArticle

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 530

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

Open AccessArticle

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 507

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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24 pages, 6613 KiB

Open AccessArticle

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 473

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

Open AccessArticle

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 502

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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Lubricants, Volume 13, Issue 6 (June 2025) – 44 articles

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