Lubricants

17 pages, 9686 KiB

Open AccessArticle

Small Laser-Textured Dimples for Improved Tribological Performance of CoCrMo in Artificial Hip Joints

by William B. Bennett and Min Zou

Lubricants 2025, 13(4), 158; https://doi.org/10.3390/lubricants13040158 - 2 Apr 2025

This study investigates the impact of small dimples on the tribological properties of CoCrMo (CCM) surfaces. Laser-ablated textures with 5 µm diameter dimples were fabricated at varying aspect ratios (0.1, 0.2, 0.3) and surface densities (5%, 15%, 25%) to evaluate their effects on [...] Read more.

This study investigates the impact of small dimples on the tribological properties of CoCrMo (CCM) surfaces. Laser-ablated textures with 5 µm diameter dimples were fabricated at varying aspect ratios (0.1, 0.2, 0.3) and surface densities (5%, 15%, 25%) to evaluate their effects on friction and wear when paired with ultra-high molecular weight polyethylene (UHMWPE) counterfaces. The results showed that small dimples significantly reduced and stabilized the coefficient of friction (CoF) and wear compared to untextured CCM and larger dimples as reported in the literature. The texture configuration with a 5% surface density and 0.1 aspect ratio achieved the best combination of friction and wear performance by facilitating the formation of a stable and uniform lubricant film during sliding. These findings underscore the potential of small, precisely engineered surface textures to improve the tribological performance of CCM, offering a promising approach for reducing friction and wear in artificial hip joints. Full article

(This article belongs to the Special Issue Tribology of Textured Surfaces)

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18 pages, 14349 KiB

Open AccessArticle

Numerical Simulation of the Lubrication Performance of the Stator and Rotor Friction Pair Surface Rhombus-like Texture in Screw Pumps

by Xiangzhi Shi, Xinfu Liu, Chunhua Liu, Zhongxian Hao, Shouzhi Huang, Yi Sun and Xinglong Niu

Lubricants 2025, 13(4), 157; https://doi.org/10.3390/lubricants13040157 - 2 Apr 2025

Abstract

To address wear failure in screw pump stator and rotor friction pairs, this study constructed a numerical model of a rhombus-like micro-dimple texture on friction pair surfaces based on the scale structure of rhombus rattlesnakes. The model was based on the fluid dynamic [...] Read more.

To address wear failure in screw pump stator and rotor friction pairs, this study constructed a numerical model of a rhombus-like micro-dimple texture on friction pair surfaces based on the scale structure of rhombus rattlesnakes. The model was based on the fluid dynamic pressure lubrication mechanism. The CFD method was used to calculate the bearing capacity, friction coefficient, flow field pressure distribution, and flow trace distribution of an oil film carrying surface. The effects of the area rate, depth, shape, and angle of the rhombus-like dimple texture and the actual well fluid viscosity of shale oil on the surface lubrication performance of screw pump stator and rotor friction pairs were analyzed. The results demonstrated that increasing the texture area rate and the angle of the long sides and decreasing the texture angle resulted in a decrease in the oil film surface friction coefficient and an increase in the average pressure and net bearing capacity as well as the hydrodynamic lubrication performance. The average pressure increased and then decreased as the texture depth increased, while the friction coefficient of the oil film surface initially decreased and then increased. At a texture depth of 20 μm, the friction coefficient reached its lowest value while the average pressure and net bearing capacity of the oil film reached their highest value, which resulted in optimal hydrodynamic lubrication performance. When the texture depth became greater than 20 μm, vortices were gradually formed within the texture, which decreased the hydrodynamic lubrication performance. When the area rate of the rhombus-like dimple texture, depth, angle between long sides, and angle were, respectively, equal to 27%, 20 μm, 74°, and 0°, the net bearing capacity of the oil film was maximized, the friction coefficient was minimized, and the hydrodynamic lubrication performance and anti-wear effect reached their highest values. The increase in the viscosity of the actual well fluid could enhance the dynamic pressure lubrication performance and improve the bearing capacity. Full article

(This article belongs to the Special Issue Tribology of Textured Surfaces)

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19 pages, 31637 KiB

Open AccessArticle

Effect of Bio-Based, Mixed Ester Lubricant in Minimum Quantity Lubrication on Tool Wear and Surface Integrity in Ultra-Precision Fly-Cutting of KDP Crystals

by Xuelian Yao, Feihu Zhang, Shuai Zhang, Jianfeng Zhang, Defeng Liao, Xiangyang Lei, Jian Wang and Jianbiao Du

Lubricants 2025, 13(4), 156; https://doi.org/10.3390/lubricants13040156 - 1 Apr 2025

Abstract

Potassium dihydrogen phosphate (KDP) crystals, vital for high-power laser systems, pose significant machining challenges due to their brittleness, low hardness, and hygroscopic properties. Achieving crack-free, high-precision surfaces is essential but complex. Single-point diamond fly-cutting (SPDF) is the primary method, yet it exposes tools [...] Read more.

Potassium dihydrogen phosphate (KDP) crystals, vital for high-power laser systems, pose significant machining challenges due to their brittleness, low hardness, and hygroscopic properties. Achieving crack-free, high-precision surfaces is essential but complex. Single-point diamond fly-cutting (SPDF) is the primary method, yet it exposes tools to high mechanical stress and heat, accelerating wear. In dry cutting, worn tools develop adhesive layers that detach, causing scratches and degrading surface quality. Traditional wet cutting improves surface finish but leaves residual fluids that contaminate the surface with metal ions, leading to optical degradation and fogging. To address these issues, this study explores mixed-fat-based minimum quantity lubrication (MQL) as a sustainable alternative, comparing two lubricants: biodegradable-base mixed ester lubrication (BBMEL) and hydrocarbon-based synthetic lubricant (HCBSL). A comprehensive evaluation method was developed to analyze surface roughness, tool wear, and subsurface damage under dry cutting, MQL-BBMEL, and MQL-HCBSL conditions. Experimental results show that MQL-BBMEL significantly enhances machining performance, reducing average surface roughness by 27.77% (Sa) and 44.77% (Sq) and decreasing tool wear by 25.16% compared to dry cutting, outperforming MQL-HCBSL. This improvement is attributed to BBMEL’s lower viscosity and higher proportion of polar functional groups, which form stable lubricating films, minimizing friction and thermal effects. Structural analyses confirm that MQL-BBMEL prevents KDP crystal deliquescence and surface fogging. These findings establish MQL-BBMEL as an eco-friendly, high-performance solution for machining brittle optical materials, offering significant advancements in precision machining for high-power laser systems. Full article

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

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37 pages, 12247 KiB

Open AccessArticle

Enhancing Fault Diagnosis: A Hybrid Framework Integrating Improved SABO with VMD and Transformer–TELM

by Jingzong Yang, Xuefeng Li and Min Mao

Lubricants 2025, 13(4), 155; https://doi.org/10.3390/lubricants13040155 - 31 Mar 2025

Abstract

Rolling bearings, as core components in mechanical systems, directly influence the overall reliability of equipment. However, continuous operation under complex working conditions can easily lead to gradual performance degradation and sudden faults, which not only result in equipment failure but may also trigger [...] Read more.

Rolling bearings, as core components in mechanical systems, directly influence the overall reliability of equipment. However, continuous operation under complex working conditions can easily lead to gradual performance degradation and sudden faults, which not only result in equipment failure but may also trigger a cascading failure effect, significantly amplifying downtime losses. To address this challenge, this study proposes an intelligent diagnostic method that integrates variational mode decomposition (VMD) optimized by the improved subtraction-average-based optimizer (ISABO) with transformer–twin extreme learning machine (Transformer–TELM) ensemble technology. Firstly, ISABO is employed to finely optimize the initialization parameters of VMD. With the improved initialization strategy and particle position update method, the optimal parameter combination can be precisely identified. Subsequently, the optimized parameters are used to model and decompose the signal through VMD, and the optimal signal components are selected through a constructed two-dimensional evaluation system. Furthermore, diversified time-domain features are extracted from these components to form an initial feature set. To deeply mine feature information, a multi-layer Transformer model is introduced to refine more discriminative feature representations. Finally, these features are input into the constructed TELM fault diagnosis model to achieve precise diagnosis of rolling bearing faults. The experimental results demonstrate that this method exhibits excellent performance in terms of noise resistance, accurate fault feature capture, and fault classification. Compared with traditional machine learning techniques such as kernel extreme learning machine (KELM), extreme learning machine (ELM), support vector machine (SVM), and Softmax, this method significantly outperforms other models in terms of accuracy, recall, and F1 score. Full article

(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 3rd Edition)

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22 pages, 5002 KiB

Open AccessArticle

Thermal–Mechanical Coupling Model of a Double-Piece Inner Ring Ball Bearing Based on ADAMS Secondary Development

by Yujun Xue, Fanjing Meng, Yongjian Yu and Haichao Cai

Lubricants 2025, 13(4), 154; https://doi.org/10.3390/lubricants13040154 - 31 Mar 2025

Abstract

The double-piece inner ring ball bearing is an important part of an aero-engine. An excessive bearing temperature leads to bearing thermal expansion, lubricating oil performance degradation, and other problems that seriously affect the service life and reliability of the bearing. Thus, it is [...] Read more.

The double-piece inner ring ball bearing is an important part of an aero-engine. An excessive bearing temperature leads to bearing thermal expansion, lubricating oil performance degradation, and other problems that seriously affect the service life and reliability of the bearing. Thus, it is important to study the temperature field of a double-piece inner ring ball bearing. In this study, considering the heat exchange of lubricant circulating in the oil tank–tubing–bearing and the influence of the flow field in the bearing chamber on the bearing’s temperature rise, a modified transient thermal network equation for an oil tank–tubing–bearing system was established. Based on ADAMS software and considering the thermal–mechanical coupling effect on the bearing’s contact force, a thermal–mechanical coupling dynamic model for double-piece inner ring ball bearings was established. Combined with the bearing dynamics and modified transient thermal network equation, a thermal–mechanical coupling transient temperature field model for double-piece inner ring ball bearings was constructed. A temperature rise test was carried out on a double-piece inner ring ball bearing, and the accuracy of the bearing temperature rise simulation model was verified by the test results. The model can simulate the oil temperature change process, calculate the heat absorbed by the lubricating oil more accurately, and provide a theoretical basis for the design of bearing and lubrication systems. Full article

(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 3rd Edition)

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18 pages, 1997 KiB

Open AccessArticle

Experimental Research and Parameter Optimization of High-Pressure Abrasive Water Jet Machining

by Lin Wu, Xiang Zou, Yuan Guo and Liandong Fu

Lubricants 2025, 13(4), 153; https://doi.org/10.3390/lubricants13040153 - 31 Mar 2025

Abstract

Machining of No. 45 steel (AISI 1045) becomes more vital due to its widespread use. In this study, machining performances of abrasive water jet machining (AWJM) of No. 45 steel, including material removal rate, notch depth, and nozzle wear rate, were obtained by [...] Read more.

Machining of No. 45 steel (AISI 1045) becomes more vital due to its widespread use. In this study, machining performances of abrasive water jet machining (AWJM) of No. 45 steel, including material removal rate, notch depth, and nozzle wear rate, were obtained by experimental and computational results. The Taguchi L16 orthogonal array design was used to study the influence of process parameters on machining performance. The optimal material removal rate and notch depth were achieved when abrasive particle size, operating pressure, and abrasive feed rate were 80 #, 400 MPa, and 840 g/min, respectively. The optimal nozzle wear rate was achieved when abrasive particle size, operating pressure, and abrasive feed rate were 80 #, 400 MPa, and 260 g/min, respectively. When the abrasive particle size is 80 # (namely the mesh number is 80), the particle diameter is usually between 0.18 and 0.25 mm according to the corresponding relationship between the international standard mesh number and particle diameter. Analysis of Variance was conducted to evaluate the statistical significance of the experimental results. Using regression analysis, an empirical model was developed to predict the response values of the AWJM process. Multi-response optimization was then carried out using the Decision Engineering Analysis and Resolution method. The optimal parameter solution for a higher material removal rate, a bigger notch depth, and a smaller nozzle wear rate was achieved when abrasive particle size, operating pressure, and abrasive feed rate were 120 #, 400 MPa, and 870 g/min, respectively. Full article

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15 pages, 7956 KiB

Open AccessArticle

A Study on the Surfactant and Tribological Properties of Water-Based Nano-Rolling Lubricants on Non-Ferrous Metal Surfaces

by Yuchuan Zhu, Zixuan Li and Changyu Han

Lubricants 2025, 13(4), 152; https://doi.org/10.3390/lubricants13040152 - 31 Mar 2025

Abstract

This study proposes a composite-surfactant-assisted method for preparing Fe₃O₄ water-based nanolubricants to enhance environmental and tribological performance in rolling applications. The dispersion stability of nanoparticles in the suspension was analyzed. The optimal concentration of the nanolubricant was identified. In addition, [...] Read more.

This study proposes a composite-surfactant-assisted method for preparing Fe₃O₄ water-based nanolubricants to enhance environmental and tribological performance in rolling applications. The dispersion stability of nanoparticles in the suspension was analyzed. The optimal concentration of the nanolubricant was identified. In addition, the reaction mechanism between nanoparticles and water-based nanolubricants was discussed. The experimental results demonstrated that the lubricant containing 6 wt% Fe₃O₄ nanoparticles exhibited the best anti-friction and anti-wear performance. The aqueous lubricant with composite surfactants showed improved dispersion stability, with its Zeta potential increasing to −43.45 mV, and the intensity curve exhibited a single peak. Through contact angle measurements, wettability was also significantly improved. The molecular interactions of composite surfactants in the prepared water-based nanolubricants were investigated using numerical simulations. The water-based nanolubricant containing composite surfactants displayed enhanced adsorption capacity on Fe₃O₄ crystals. Compared to other surfactants, the Fe₃O₄ water-based nanolubricant prepared with composite surfactants exhibited stable dispersion properties. Therefore, composite surfactants can enhance the stability and wettability of water-based nanolubricants. This method enables the preparation of high-performance water-based rolling nanolubricants. Full article

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16 pages, 10350 KiB

Open AccessArticle

Modeling and Analysis of Oil Film Thickness with Viscosity–Pressure–Temperature Effects Under Hybrid Lubrication in the Cold Rolling Process of High-Strength Thin Sheets

by Yujin Liu, Xuechang You, Lei Liu, Yanli Xin, Xiaomin Zhou and Zhiying Gao

Lubricants 2025, 13(4), 151; https://doi.org/10.3390/lubricants13040151 - 30 Mar 2025

Abstract

With the development of steel sheets towards higher strength and lower thickness, the process of rolling is facing more challenges, and one of the most important issues is lubrication, which directly determines the rolling stability, product quality, and production efficiency. This study focuses [...] Read more.

With the development of steel sheets towards higher strength and lower thickness, the process of rolling is facing more challenges, and one of the most important issues is lubrication, which directly determines the rolling stability, product quality, and production efficiency. This study focuses on the modeling and analysis of oil film thickness with viscosity–pressure–temperature (VPT) coupling effects under a hybrid lubrication system. Firstly, the mechanisms and limitations of direct spray and recirculation lubrication systems are systematically compared, highlighting the advantages of hybrid lubrication for high-speed tandem cold rolling. Subsequently, the mathematical models corresponding to different positions within the rolling interface between the roll and strip, are presented; the initial oil film thickness is described based on both plate-out and dynamic concentration formation mechanisms under the hybrid lubrication; and the model of inlet oil film thickness integrates the Reynolds equation, VPT effects, energy conservation, and continuity equations to quantify temperature-driven viscosity degradation. Furthermore, the influences of rolling process and lubrication parameters on the oil film thickness are analyzed, and a dynamic regulation strategy is proposed to optimize direct emulsion flow with regard to the actual rolling speed and the expected oil film thickness. This work bridges the gap between theoretical models and industrial requirements, providing actionable insights for high-speed rolling of advanced high-strength steel sheets. Full article

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18 pages, 17302 KiB

Open AccessArticle

Mechanistic Study of Groove Parameters on the Thermoelastic Instability of Wet Clutch

by Zhigang Zhang, Zhihua Mu and Xiaoxia Yu

Lubricants 2025, 13(4), 150; https://doi.org/10.3390/lubricants13040150 - 30 Mar 2025

Abstract

The groove parameters on the friction base of wet clutches significantly affect the temperature distribution of the steel plates. However, existing methods have not thoroughly investigated the mechanisms by which these parameters influence the thermoelastic instability of wet clutches. To address this gap, [...] Read more.

The groove parameters on the friction base of wet clutches significantly affect the temperature distribution of the steel plates. However, existing methods have not thoroughly investigated the mechanisms by which these parameters influence the thermoelastic instability of wet clutches. To address this gap, a comprehensive co-simulation model of the friction sub-multi-physical field was developed to systematically examine the effects of groove inclination, groove density, and groove depth on the surface temperature and mechanical response of the steel plates. The results indicate that both the tilt angle of the grooves and the number of grooves substantially influence the surface temperature distribution of the steel plates. Specifically, increasing the number of grooves leads to a more concentrated distribution of high-temperature hot spots in the circumferential direction, gradually transitioning the surface temperature–hot spot pattern from isolated hot spots to a more uniform high-temperature tropical distribution, which subsequently reduces the maximum surface temperature. On the other hand, increasing the groove inclination angle causes the high-temperature distribution to shift from localized hot spots to a more tropical pattern, with a relatively minor impact on the peak surface temperature. Furthermore, increasing the groove depth results in the dispersion of the high-temperature tropical zone in the circumferential direction, causing the maximum temperature to initially decrease and then increase. Full article

(This article belongs to the Special Issue Thermal Hydrodynamic Lubrication)

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19 pages, 8838 KiB

Open AccessArticle

Proteinaceous Spirulina Biomass as a Sustainable Drilling Fluid Additive for Lubricity

by Garrett M. Thibodeaux, Nicholas A. Baudoin and William M. Chirdon

Lubricants 2025, 13(4), 149; https://doi.org/10.3390/lubricants13040149 - 29 Mar 2025

Abstract

This study investigates the potential of Spirulina biomass as a lubricating additive for drilling fluid formulations. In this work, this waste protein is evaluated as a lubricant alternative that may decrease the coefficient of friction while improving the rheological profiles and/or reducing fluid [...] Read more.

This study investigates the potential of Spirulina biomass as a lubricating additive for drilling fluid formulations. In this work, this waste protein is evaluated as a lubricant alternative that may decrease the coefficient of friction while improving the rheological profiles and/or reducing fluid loss via permeation in drilling fluids. A processed and dried Arthrospira platensis (Spirulina) biomass is incorporated into drilling fluid formulations and compared to standard lubricant additives for the drilling fluid properties of lubricity, rheology, and fluid loss. Rheological characterization includes the determination of yield stress, gel strength, and viscosity measurements. The major findings of this study include a friction value reduction of up to 30% and a fluid loss reduction of up to 51% by using 3 vol.% Spirulina. Parameters were fit to two rheological models (Bingham plastic and Herschel–Bulkley). After experimentation and analyzing the data gathered, it was determined that Spirulina and the Spirulina–Coastalube mixture in drilling fluids are good potential candidates as more environmentally benign and cost-effective alternative technologies for drilling fluids for decreasing the coefficient of friction, which results in increasing the lubrication performance of the drilling fluids. Full article

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48 pages, 10094 KiB

Open AccessArticle

Comparing the Effectiveness of R and S Roughness Parameters on Surfaces Lubricated with Standardized Nominal Particle Size Lubricants

by Leire Mendieta-Echevarría, María Ana Sáenz-Nuño and Eva María Rubio

Lubricants 2025, 13(4), 148; https://doi.org/10.3390/lubricants13040148 - 27 Mar 2025

Abstract

The aim of this article is to simulate the distribution of oil or lubricants on the surface by the characterization of the R and S roughness parameters. It is considered that undesirable particles may appear in the oil due to friction, the wear [...] Read more.

The aim of this article is to simulate the distribution of oil or lubricants on the surface by the characterization of the R and S roughness parameters. It is considered that undesirable particles may appear in the oil due to friction, the wear of parts, or dirt in the lubrication circuit. One of the problems that can generate the appearance of particles in the oil is the poor distribution of this along the surface, using standards, standardised particle sizes, and following the standard. This research aims to implement effective algorithms for the calculation of profile and surface roughness parameters following existing standards, as well as the development of a morphological filter that will simulate particles on the surface. The analysis of the surface roughness of the surface in contact with the lubricant can help to decide the maximum particle size that is permissible in the system; therefore, analysing the oil will help to decide when it is necessary to filter or replace that lubricant. This research is carried out form the geometrical point of view of the morphological filter effect. This paper represents a first approach to researching the calculation of all standardized profile and surface roughness parameters. As a result, only a selection of parameters has been chosen from the full range of available ones, in order to improve effectiveness. Full article

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14 pages, 10258 KiB

Open AccessArticle

Atomic Simulation of Wear and Slip Behavior Between Monocrystalline Silicon and 6H-SiC Friction Pair

by Jiansheng Pan, Jianwei Wu, Daiyi Lei, Huan Liu, Pengyue Zhao, Bo Zhao, Jiang Liu and Qingshan Yang

Lubricants 2025, 13(4), 147; https://doi.org/10.3390/lubricants13040147 - 27 Mar 2025

Abstract

The slip mechanism between the chunk and wafer during high-speed dynamic scanning of the extreme ultraviolet lithography (EUV) motion stage remains unclear. Considering real-machined roughness, molecular dynamics (MD) simulations were performed to investigate the nanotribological behavior of 6H-SiC sliders on single-crystal silicon substrates. [...] Read more.

The slip mechanism between the chunk and wafer during high-speed dynamic scanning of the extreme ultraviolet lithography (EUV) motion stage remains unclear. Considering real-machined roughness, molecular dynamics (MD) simulations were performed to investigate the nanotribological behavior of 6H-SiC sliders on single-crystal silicon substrates. The effects of sinusoidal asperity parameters and normal loads on wear and slip were systematically analyzed. Results indicate that, for friction between sinusoidal asperities and ideal flat surfaces, the amplitude of surface parameters exhibits negligible influence on friction. In contrast, reduced normal loads and lower periods significantly increase both friction force and coefficient of friction (COF). Full article

(This article belongs to the Special Issue Recent Advances in Lubricated Tribological Contacts)

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20 pages, 8978 KiB

Open AccessArticle

Method for Maintaining Technical Condition of Marine Diesel Engine Bearings

by Sergii Sagin, Arsenii Sagin, Yurii Zablotskyi, Oleksij Fomin, Václav Píštěk and Pavel Kučera

Lubricants 2025, 13(4), 146; https://doi.org/10.3390/lubricants13040146 - 25 Mar 2025

Abstract

The aim of the research was to determine the impact of antifriction coatings on the technical condition of marine diesel engine bearings. Various epilams were used as antifriction coatings, with a thin layer applied to the surfaces of the bearings of the marine [...] Read more.

The aim of the research was to determine the impact of antifriction coatings on the technical condition of marine diesel engine bearings. Various epilams were used as antifriction coatings, with a thin layer applied to the surfaces of the bearings of the marine diesel engines 12V32/40 MAN-Diesel&Turbo. The thickness of the epilam coating adsorbed on the metal surface was controlled by ellipsometry. It was found that the thickness of the epilam layer on the surfaces of marine diesel engine bearings could reach 11.2 nm to 17.0 nm. The adsorption time required does not exceed 10 min. It was shown that the epilam nanolayer applied to the metal surface led to an increase in the structural characteristics of the oil boundary layer (thickness: from 12.3 µm to 15.2–18.3 µm; contact angles: from 10.2 deg to 15.8–17.4 deg). It was experimentally confirmed that the epilam coating of bearing surfaces significantly reduced their wear. For the 12V32/40 MAN-Diesel&Turbo marine diesel engine, in the case of epilaminating, the wear of the bearing shell surface was reduced by 6.1–27.6%, with the greatest reduction in wear occurring for the stern (most loaded) bearings. This helped to maintain the technical condition of the bearings of marine diesel engines. Full article

(This article belongs to the Special Issue Anti-Wear Lubricating Materials)

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16 pages, 2486 KiB

Open AccessArticle

Remaining Useful Life Prediction Based on Wear Monitoring with Multi-Attribute GAN Augmentation

by Xiaojun Zhu, Yan Pan, Bin Lan, He Wang and Huixin Huang

Lubricants 2025, 13(4), 145; https://doi.org/10.3390/lubricants13040145 - 25 Mar 2025

Abstract

With the growing imperative for advanced prognostics and health management (PHM) systems, remaining useful life (RUL) prediction through lubricating oil monitoring has become pivotal for intelligent preventive maintenance. However, existing methodologies face dual challenges: the inherent sparsity of wear monitoring data and the [...] Read more.

With the growing imperative for advanced prognostics and health management (PHM) systems, remaining useful life (RUL) prediction through lubricating oil monitoring has become pivotal for intelligent preventive maintenance. However, existing methodologies face dual challenges: the inherent sparsity of wear monitoring data and the complex interdependencies among multiple indicators, leading to compromised prediction accuracy that fails to satisfy reliability requirements. To address these limitations, this study proposes a novel multi-indicator RUL prediction framework with three technical innovations. First, a fuzzy probabilistic characterization method is proposed to quantify multivariate wear state in the lubricating system, using the weighted fusion of multi-source indicators. Second, a novel CMC-GAN (Centralized Multi-channel Constrained Generative Adversarial Network) architecture is designed. It can increase data using physical knowledge. This solves the problem of sparse data and keeps the important relationships between indicators. Furthermore, we establish a Wiener-process-based degradation model with time-varying coefficients to capture stochastic wear deterioration patterns. The expectation-maximization algorithm with Bayesian updating is employed for real-time parameter calibration, enabling a dynamic derivation of the probability density functions for RUL estimation. Finally, the validity and practicality of the proposed model are verified through actual engineering case studies. Full article

(This article belongs to the Special Issue Wear Mechanism Identification and State Prediction of Tribo-Parts)

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21 pages, 24767 KiB

Open AccessArticle

Dynamic Characteristic Analysis of Bogie Gearbox Bearings Under Typical Wheel-Rail Excitation

by Meiling Wang, Qi Yang, Xinyu Liu, Zhihao Zan, Baogang Wen and Jingyu Zhai

Lubricants 2025, 13(4), 144; https://doi.org/10.3390/lubricants13040144 - 25 Mar 2025

Abstract

The bogie gearbox bearing is one of the critical components in the running gear of trains, and its dynamic characteristics significantly influence the safety and stability of the entire system. In addition to internal excitations within the gearbox, during actual operation, the system [...] Read more.

The bogie gearbox bearing is one of the critical components in the running gear of trains, and its dynamic characteristics significantly influence the safety and stability of the entire system. In addition to internal excitations within the gearbox, during actual operation, the system is notably affected by wheel-rail disturbances, such as wheel tread wear and track irregularities. As train operating speeds increase, these impacts become more complex and pronounced. This study focuses on the cylindrical roller bearings at the input end of the bogie gearbox. A dynamic model accounting for the effects of centrifugal force and lubrication was proposed by analyzing the force characteristics of the rolling elements, inner and outer rings, and the cage, respectively. The model was verified through the velocity characteristics of the internal components. Furthermore, a method for obtaining wheel-rail excitation based on a coupled dynamic model of the bogie and wheel-rail system was proposed. Based on this, a comparative analysis was conducted on the internal contact load characteristics and the vibration characteristics of each component of the bogie gearbox bearings under different wheel polygonal excitation amplitudes and orders, as well as under the combined influence of track irregularities and wheel polygons. The results indicate that wheel polygonal excitation and track irregularity excitation have significant effects on bearing vibration and contact load. An increase in the polygonal order and amplitude intensifies the contact load between the rolling elements and the outer ring, thereby increasing bearing vibration. Additionally, a higher polygonal order leads to more frequent impacts between the rolling elements and the outer ring. The coupling effect of wheel-rail excitations further amplifies bearing vibration and contact load. Full article

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21 pages, 7601 KiB

Open AccessArticle

Study on the Dynamic Characteristics of the Gear Lubrication Flow Field with Baffles and Optimization Design Strategies

by Yihong Gu, Lin Li and Gaoan Zheng

Lubricants 2025, 13(4), 143; https://doi.org/10.3390/lubricants13040143 - 25 Mar 2025

Cited by 1

Abstract

The gear transmission system occupies a core position in mechanical equipment due to its numerous advantages such as high efficiency, high reliability, and long durability, making it an indispensable key component. Investigating the distribution mechanism of the two-phase flow field in gear transmission [...] Read more.

The gear transmission system occupies a core position in mechanical equipment due to its numerous advantages such as high efficiency, high reliability, and long durability, making it an indispensable key component. Investigating the distribution mechanism of the two-phase flow field in gear transmission systems and its optimization design strategies is crucial for enhancing the efficiency and reliability of gearboxes. This paper couples the Lattice Boltzmann Method (LBM) with Large Eddy Simulation (LES) to construct a dynamic modeling and solution method suitable for the lubrication flow field of high-speed gears with baffles. The core objective is to explore the distribution mechanism and dynamic characteristics of the lubrication flow field in gears with baffles. Based on the LBM–LES coupled model, this paper sets up a two-phase flow dynamic model for the high-speed gear lubrication flow field. By conducting a detailed analysis of the dynamic evolution of the lubrication process in the gearbox with the presence of baffles, this study reveals the changing patterns of flow field dynamics under different flow velocities and configurations of mixing components. The research findings indicate that when the radial speed of the gears reaches 8 m/s, a stable oil film can be formed on the gear surface, which is crucial for ensuring smooth operation and reducing wear. Additionally, it has been confirmed that larger baffle diameters and hole diameters can effectively increase the enthalpy of the fluid, thereby optimizing energy transfer and thermal performance. However, it is noted that a larger baffle diameter is not always better; when it exceeds a certain limit, the performance improvement effect gradually diminishes, indicating the existence of an optimal baffle diameter value. By optimizing the design of the baffle, the flow characteristics and energy dissipation of the fluid within the gearbox can be controlled, improving thermal management and lubrication performance. These research findings provide valuable references for the lubrication design and optimization of gear transmission systems in high-tech fields such as aviation and aerospace. They can help relevant technicians gain a deeper understanding of the complex mechanisms involved in the lubrication process, allowing for the design of more efficient and reliable lubrication systems, effectively enhancing the performance of the entire transmission system, and promoting progress and development in related technological fields. Full article

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33 pages, 15014 KiB

Open AccessArticle

Dynamic Response and Nonlinear Characteristic Analysis of Rigid–Flexible Coupling Mechanism with Lubricated Revolute Clearance and Prismatic Clearance

by Jun Niu, Kai Meng, Mingxuan An and Shuai Jiang

Lubricants 2025, 13(4), 142; https://doi.org/10.3390/lubricants13040142 - 25 Mar 2025

Abstract

Revolute and prismatic pair clearances are common in various mechanisms, and their motion state seriously affects the accuracy of the mechanism. Adding lubricant to a kinematic pair can effectively counteract the adverse influence of a collision force. Thus, this work introduces an advanced [...] Read more.

Revolute and prismatic pair clearances are common in various mechanisms, and their motion state seriously affects the accuracy of the mechanism. Adding lubricant to a kinematic pair can effectively counteract the adverse influence of a collision force. Thus, this work introduces an advanced modeling method that considers the combined effects of a lubricated revolute and prismatic clearance, as well as component flexibility, and studies the influence of their coupling effect on the dynamic response and nonlinear characteristic of mechanisms. The specific content of this paper is as follows: Firstly, revolute lubrication clearance and prismatic pair clearance models are established. Secondly, rigid components and flexible components are described based on the reference point coordinate method and absolute nodal coordinate formulation. Then, based on the Lagrange multiplier method, a rigid–flexible coupling dynamics model with revolute lubrication clearance and prismatic clearance is established. Finally, the dynamic responses of the mechanism are analyzed, including the displacement, velocity, and acceleration of the slider, the driving torque of the crank, and the center trajectories of the revolute clearance and prismatic clearance. Qualitative research is conducted on the nonlinear characteristics of the system through a phase diagram and Poincaré map. This quantitative study is conducted on the nonlinear characteristics of a system using the maximum Lyapunov exponent. The influences of different parameters on the dynamic response and nonlinear characteristic of the mechanism are analyzed. The results indicate that lubrication effectively reduces the influence of the clearance on the dynamic response and nonlinear characteristic of the mechanism, resulting in a decrease in the peak dynamic response and a weakening of the chaotic phenomenon. Further, as the driving speed increases, the dynamic viscosity decreases the clearance value increases, and the stability of the mechanism decreases. Full article

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20 pages, 11906 KiB

Open AccessArticle

Effects of Substrate Pulse Bias on Corrosion Behavior of Tetrahedral Amorphous Carbon Thin Films in Acidic and Chloride Solutions

by Nay Win Khun and Adrian Wei-Yee Tan

Lubricants 2025, 13(4), 141; https://doi.org/10.3390/lubricants13040141 - 25 Mar 2025

Abstract

Filtered cathodic vacuum arc (FCVA) deposition technology was applied to prepare tetrahedral amorphous carbon (taC) thin films with different substrate pulse biases. Their structure, adhesion strength, and corrosion behavior in 5 × 10⁻² M hydrochloric (HCl), sodium chloride (NaCl), calcium chloride (CaCl [...] Read more.

Filtered cathodic vacuum arc (FCVA) deposition technology was applied to prepare tetrahedral amorphous carbon (taC) thin films with different substrate pulse biases. Their structure, adhesion strength, and corrosion behavior in 5 × 10⁻² M hydrochloric (HCl), sodium chloride (NaCl), calcium chloride (CaCl₂), lead (II) chloride (PbCl₂), and mercury (II) chloride (HgCl₂) solutions were studied with respect to the substrate pulse bias. Increasing the substrate pulse bias from 0 to 1000 V increased the graphitization of the taC thin films and thereby resulted in a 9.9% increase in their adhesion strength from 406 mN to 446 mN. The taC thin films exhibited the lowest (8.48 × 10⁴ Ω to 11.55 × 10⁴ Ω) and highest (146.89 × 10⁴ Ω to 387.44 × 10⁴ Ω) corrosion resistance in the PbCl₂ and HgCl₂ solutions, respectively, while they had higher corrosion in the HCl (62.07 × 10⁴ Ω to 131.73 × 10⁴ Ω) solution than in both the NaCl (143 × 10⁴ Ω to 231.31 × 10⁴ Ω) and CaCl₂ (102.13 × 10⁴ Ω to 351.92 × 10⁴ Ω) solutions. Nevertheless, the taC thin films with higher substrate pulse biases had lower corrosion resistance in all the solutions used in this study. The substrate pulse bias emerged as a significant parameter in the FCVA deposition process, playing a crucial role in influencing the structure, adhesion strength, and corrosion resistance of taC thin films. Full article

(This article belongs to the Special Issue Tribology of Diamond-Like Carbon Films: Recent Progress and Future Trends)

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16 pages, 16027 KiB

Open AccessFeature PaperArticle

An Experimentally Validated Cavitation Model for Hydrodynamic Bearings Using Non-Condensable Gas

by Sören Wettmarshausen, Alexander Engels, Thomas Hagemann, Michael Stottrop, Christoph Weißbacher, Hubert Schwarze and Beate Bender

Lubricants 2025, 13(4), 140; https://doi.org/10.3390/lubricants13040140 - 25 Mar 2025

Abstract

Despite great research effort in recent decades, cavitation in hydrodynamic journal bearings is still a not completely understood phenomenon. In particular, it is unclear which proportions of different cavitation types are present in a bearing. Novel experimental results show a clear deviation from [...] Read more.

Despite great research effort in recent decades, cavitation in hydrodynamic journal bearings is still a not completely understood phenomenon. In particular, it is unclear which proportions of different cavitation types are present in a bearing. Novel experimental results show a clear deviation from the predictions of hydrodynamic lubrication theory. This article presents a new approach for modeling cavitation in hydrodynamic bearings by using computational fluid dynamics with the volume of fluid method and a phase of non-condensable gas in the lubrication oil. The validation of the model is achieved through the simulation of a large Offset-Halves Bearing and a subsequent comparison of the results with various experimental data, including the fractional film content. In the results, cavitation also occurs in the convergent gap due to a pressure drop caused by inertia forces. The findings indicate that the cavitation effects in oil-lubricated hydrodynamic bearings are caused by a special form of gaseous cavitation, designated as pseudo-cavitation. The presented model with non-condensable gas is able to reproduce the observed phenomena excellently. Full article

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