Lubricants

15 pages, 5648 KiB

Open AccessArticle

The Influence of Friction Parameters and Material Type on Results in the Block-on-Ring Friction System

by Marcin Madej and Beata Leszczyńska-Madej

Lubricants 2025, 13(2), 94; https://doi.org/10.3390/lubricants13020094 - 19 Feb 2025

Viewed by 510

The block-on-ring friction system is one of the more universal methods of measuring the tribological properties of materials, where we are able to compare the properties of different materials using a prescribed counter sample. When preparing for a test, we usually determine the [...] Read more.

The block-on-ring friction system is one of the more universal methods of measuring the tribological properties of materials, where we are able to compare the properties of different materials using a prescribed counter sample. When preparing for a test, we usually determine the parameters that appear to be optimal for testing a given material for its applications. The question remains whether and how such a choice affects the results obtained. In this paper, tests have been carried out on two commonly used plain bearing alloys, B83 and B89. The T-05 tester used for the tests allows the rotation of the counter sample to be adjusted, and, in this study, this was varied in the range of 50, 100, 150, 200 and 250 rpm. Another parameter variable in the tests was the friction distance, and two distances of 100 and 250 m were used. As the tests were carried out under technically dry friction conditions, it was possible to capture both the effect of the running-in period and the stable friction path. The tests showed that the alloys tested over the longer friction distance of 250 m responded differently to a change in parameters, with alloy B83 showing a sinusoidal variation in wear resistance with a maximum at medium speed, whereas alloy B89 is characterized by a continuous increase in wear with increasing speed. The coefficient of friction is more dependent on speed, and the basic conclusion can be drawn that increasing speed results in a lower coefficient of friction. This research has confirmed the need for the careful selection of test parameters and the difficulty of comparing results when there is even a slight difference in the test parameters used at different test centers. Full article

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

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56 pages, 16932 KiB

Open AccessReview

Study of the Influence of Nanoparticle Reinforcement on the Mechanical and Tribological Performance of Aluminum Matrix Composites—A Review

by Varun Singhal, Daksh Shelly, Abhishek Saxena, Rahul Gupta, Vipin Kumar Verma and Appurva Jain

Lubricants 2025, 13(2), 93; https://doi.org/10.3390/lubricants13020093 - 19 Feb 2025

Cited by 1 | Viewed by 1269

Abstract

This study investigates the influence of nano-sized reinforcements on aluminum matrix composites’ mechanical and tribological properties. Microstructural analysis revealed that introducing nanoparticles led to grain refinement, reducing the grain size from 129.7 μm to 41.3 μm with 2 wt.% TiO₂ addition. Furthermore, [...] Read more.

This study investigates the influence of nano-sized reinforcements on aluminum matrix composites’ mechanical and tribological properties. Microstructural analysis revealed that introducing nanoparticles led to grain refinement, reducing the grain size from 129.7 μm to 41.3 μm with 2 wt.% TiO₂ addition. Furthermore, ultrasonic-assisted squeeze casting of AA6061 composites reinforced with TiO₂ and Al₂O₃ resulted in a 52% decrease in grain size, demonstrating nano-reinforcements’ effectiveness in refining the matrix structure. Despite these advantages, the high surface energy of nanoparticles causes agglomeration, which can undermine composite performance. However, ultrasonic-assisted stir casting reduced agglomeration by approximately 80% compared to conventional stir casting, and cold isostatic pressing improved dispersion uniformity by 27%. The incorporation of nano-reinforcements such as SiC, Al₂O₃, and TiC significantly enhanced the material properties, with hardness increasing by ~30% and ultimate tensile strength improving by ~80% compared to pure Al. The hardness of nano-reinforced composites substantially rose from 83 HV (pure Al) to 117 HV with 1.0 vol.% CNT reinforcement. Additionally, TiC-reinforced AA7075 composites improved hardness from 94.41 HB to 277.55 HB after 10 h of milling, indicating a nearly threefold increase. The wear resistance of Al-Si alloys was notably improved, with wear rates reduced by up to 52%, while the coefficient of friction decreased by 20–40% with the incorporation of graphene and CNT reinforcements. These findings highlight the potential of nano-reinforcements in significantly improving the mechanical and tribological performance of n-AMCs, making them suitable for high-performance applications in aerospace, automotive, and structural industries. Full article

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16 pages, 4247 KiB

Open AccessArticle

Tribological Assessment of Synthetic Grease (PDPLG-2) Derived from Partially Degraded Low-Density Polyethylene Waste

by Divyeshkumar Dave, Yati Vaidya, Kamlesh Chauhan, Sushant Rawal, Ankurkumar Khimani and Sunil Chaki

Lubricants 2025, 13(2), 92; https://doi.org/10.3390/lubricants13020092 - 18 Feb 2025

Viewed by 591

Abstract

This study focuses on addressing the pressing challenge of reusing plastic in an eco-friendly manner. This research aimed to produce synthetic grease through an environmentally friendly pyrolysis technique, utilizing 69% predegraded low-density polyethylene (LDPE) combined with visible-light-working TiO₂ thin film, protein-coated TiO [...] Read more.

This study focuses on addressing the pressing challenge of reusing plastic in an eco-friendly manner. This research aimed to produce synthetic grease through an environmentally friendly pyrolysis technique, utilizing 69% predegraded low-density polyethylene (LDPE) combined with visible-light-working TiO₂ thin film, protein-coated TiO₂ NPs, and Lactobacillus plantarum bacteria in a batch reactor. The optimized conditions of temperature (500 °C) and heating time (2 h) resulted in the creation of 166 gm of partially degraded polyethylene grease 2 (PDPLG2) with National Lubricating Grease Institute (NLGI 2) grade consistency. PDPLG2 grease exhibits a wide-range dropping point of 280 °C and effectively maintains lubrication under high friction and stress loads, thereby preventing wear. Thermal analysis using TG and DSC validated the grease’s stability up to 280 °C, with minimal degradation beyond this point. Taguchi analysis using substance, sliding speed, and load as factors identified the ideal process parameters as aluminum, 1500 rpm, and 150 N, respectively. The present study revealed that sliding speed has the greatest impact, contributing 31.74% to the coefficient of friction (COF) and 11.28% to wear, followed by material and load. Comparative tribological analysis with commercially available grease (NLGI2) demonstrated that PDPLG2 grease outperforms NLGI2 grease. Overall, this innovative eco-friendly approach presents PDPLG2 as a promising alternative lubricant with improved anti-wear and friction properties, while also contributing significantly to plastic waste reduction. Full article

(This article belongs to the Special Issue Wear-Resistant Coatings and Film Materials)

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19 pages, 6172 KiB

Open AccessArticle

Parametric Structure Optimization Design of High-Pressure Abrasive Water Jet Nozzle Based on Computational Fluid Dynamics-Discrete Element Method (CFD-DEM)

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

Lubricants 2025, 13(2), 91; https://doi.org/10.3390/lubricants13020091 - 18 Feb 2025

Viewed by 535

Abstract

High-pressure abrasive water jet (HP-AWJ) cutting is a prominent technology for processing a wide variety of materials. The structural parameters of the nozzle are important for the cutting performance of the HP-AWJ. This paper combines an abrasive particle kinetic energy model and a [...] Read more.

High-pressure abrasive water jet (HP-AWJ) cutting is a prominent technology for processing a wide variety of materials. The structural parameters of the nozzle are important for the cutting performance of the HP-AWJ. This paper combines an abrasive particle kinetic energy model and a wall wear model of the nozzle to determine the multi-phase flow of a HP-AWJ nozzle. The flow field structure of the nozzle was optimized using a parametric multi-objective structure optimization design method. A Multi-Objective Heat Transfer Search (MOHTS) was utilized to generate the corresponding mathematical regression model for multiple response results, and the optimal solution sets of Pareto values were further obtained. The optimal HP-AWJ structural parameters could be selected according to the weight influence of multiple response indicators. Full article

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29 pages, 29665 KiB

Open AccessArticle

Experimental Research on the Effect of Thermophysical Characteristics of Cutting Fluid on Cutting Performance During Turning Ti-6Al-4V Alloy

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

Lubricants 2025, 13(2), 90; https://doi.org/10.3390/lubricants13020090 - 17 Feb 2025

Cited by 1 | Viewed by 670

Abstract

Cutting fluid has been widely used to enhance the heat dissipation of cutting systems. However, whether cutting fluid can fully play its role is closely correlated with its thermophysical characteristics, such as viscosity, surface tension, etc. In this work, to study the effect [...] Read more.

Cutting fluid has been widely used to enhance the heat dissipation of cutting systems. However, whether cutting fluid can fully play its role is closely correlated with its thermophysical characteristics, such as viscosity, surface tension, etc. In this work, to study the effect of the thermophysical characteristics of cutting fluid on cutting performance, three green vegetable oils (semi-synthetic fluid (L1), rapeseed oil (L2), canola oil (L3)) were selected as cutting fluids of the MQL system, and differences in cutting performance were compared and analyzed under varied lubrication environments. Firstly, the thermophysical characteristics of the vegetable oils were determined by experimental methods. Afterwards, parameters, including tool wear, cutting force, and temperature, as well as the quality of machined workpieces, were selected to evaluate cutting performance, and essential reasons for the difference in cutting performance under varied lubrication environments were clarified. The results demonstrated that the cutting force, cutting temperature, and tool wear produced in the three MQL environments were lower than those in the dry cutting environment, while only the L1 and L2 MQL environments exhibited higher machined surface quality than the dry cutting environment. Moreover, obvious differences in cutting performance under the three MQL environments were also observed due to the different thermophysical characteristics of the three vegetable oils. The best cutting performance was achieved when L2 was used as the MQL cutting fluid. The efforts of this study will give an important reference for the choosing of green cutting fluid in the cutting process of difficult-to-cut materials and be of great significance for accelerating the development of green processing. Full article

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

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26 pages, 10090 KiB

Open AccessArticle

Wear Resistance of Additively Manufactured Footwear Soles

by Shuo Xu, Shuvodeep De, Meysam Khaleghian and Anahita Emami

Lubricants 2025, 13(2), 89; https://doi.org/10.3390/lubricants13020089 - 17 Feb 2025

Viewed by 907

Abstract

This study systematically evaluated the wear resistance and mechanical performance of 3D-printed thermoplastic rubber (TPR) and flexible stereolithography (SLA) resin materials for footwear outsoles. Abrasion tests were conducted on 26 samples (2 materials × 13 geometries) to analyze the weight loss, variations in [...] Read more.

This study systematically evaluated the wear resistance and mechanical performance of 3D-printed thermoplastic rubber (TPR) and flexible stereolithography (SLA) resin materials for footwear outsoles. Abrasion tests were conducted on 26 samples (2 materials × 13 geometries) to analyze the weight loss, variations in the friction coefficient, temperature change, and deformation behavior. Finite element method (FEM) simulations incorporating the Ogden hyperelastic model were employed to investigate the stress distribution and wear patterns. The results revealed that TPR exhibits superior abrasion resistance and stable wear curves, making it suitable for high-load applications. On average, the TPR samples showed 27.3% lower weight loss compared to the SLA resin samples. The SLA resin samples exhibited a 65% higher mean coefficient of friction (COF) compared to the TPR samples. Furthermore, the SLA resin samples demonstrated a 94% higher temperature change during the sliding tests, reflecting greater friction-induced heating. The FEM simulations further validated TPR’s performance in high-stress regions and SLA resin’s deformation characteristics. This study’s findings not only highlight the performance differences between these two 3D-printed materials but also provide theoretical guidance for material selection based on wear behavior, contributing to the optimization of outsole design and its practical applications. Full article

(This article belongs to the Special Issue Wear and Friction in Hybrid and Additive Manufacturing Processes)

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12 pages, 3542 KiB

Open AccessArticle

Study on the Magnetic Contact Mechanical Properties of Polyurethane-Based Magnetorheological Elastomer Sealing Materials

by Xiuxu Zhao, Emmanuel Appiah and Haile Tang

Lubricants 2025, 13(2), 88; https://doi.org/10.3390/lubricants13020088 - 16 Feb 2025

Viewed by 746

Abstract

In order to meet the dual requirements of hydraulic dynamic sealing to ensure a reduction in friction, this study prepared polyurethane-based magnetorheological elastomers (MREs). The compression performance of isotropic and anisotropic samples under a magnetic field was tested in samples containing carbonyl iron [...] Read more.

In order to meet the dual requirements of hydraulic dynamic sealing to ensure a reduction in friction, this study prepared polyurethane-based magnetorheological elastomers (MREs). The compression performance of isotropic and anisotropic samples under a magnetic field was tested in samples containing carbonyl iron powder (CIP) particles with different volume contents and particle sizes. The compression performance of isotropic and anisotropic samples under the magnetic field was tested under static loading, and the friction coefficient changes in isotropic and anisotropic samples under a magnetic field were analyzed by a friction testing machine. The test results show that under static compression load, the contact stress of isotropic and anisotropic specimens increases with the increase in magnetic field strength, and the magnitude of the contact stress changes when the increase in magnetic field strength is proportional to the CIP content and CIP particle size of the specimen. The friction test results of the samples showed that an increase in magnetic field strength, CIP particle diameter, and CIP content reduces the friction coefficient of the CIP particle polyurethane-based magnetorheological elastomer samples, and the variation in the magnetic friction coefficient of anisotropic samples is greater than that of isotropic samples. This research result indicates that utilizing the magneto-mechanical properties of polyurethane-based magnetorheological elastomers can provide an innovative solution to the inherent contradiction between increasing contact stress and avoiding wear in the dynamic sealing of hydraulic systems, which can provide controllable sealing performance for hydraulic dynamic sealing components in specific application scenarios, enabling them to have a better sealing ability while reducing the friction coefficient of the sealing pair. Full article

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16 pages, 5271 KiB

Open AccessArticle

An Experimental Investigation of the Electrical Tribological Characteristics of a Copper–Silver Alloy Contact Wire/Novel Pure Carbon Slider

by Like Pan, Caizhi Yang, Tong Xing and Qun Yu

Lubricants 2025, 13(2), 87; https://doi.org/10.3390/lubricants13020087 - 16 Feb 2025

Viewed by 546

Abstract

The sliding electric contact that is established between the catenary wire and pantograph slider serves as the primary mechanism through which contemporary high-speed railway trains obtain their driving energy. The wear resistance of both the sliders and contact wires significantly influences their service [...] Read more.

The sliding electric contact that is established between the catenary wire and pantograph slider serves as the primary mechanism through which contemporary high-speed railway trains obtain their driving energy. The wear resistance of both the sliders and contact wires significantly influences their service life. This paper reports an experimental investigation into the electrical tribological characteristics of a copper–silver alloy contact wire in conjunction with a novel pure carbon slider, conducted under AC 300–500 A at sliding velocities ranging from 150 to 250 km/h. The experimental tests reveal that the coefficient of friction changes from 0.20 to 0.28, and the wear rate of the sliders varies from 0.0028 to 0.0147 g/km. The observed wear mechanisms for the slider encompass arc ablation, abrasive wear, delamination wear, and adhesive wear. Full article

(This article belongs to the Special Issue Advances in Dry and Lubricated Electrical Contacts)

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8 pages, 3611 KiB

Open AccessArticle

Some Considerations to the Energy Dissipation of Frictionally Stressed Lubricating Greases

by Erik Kuhn

Lubricants 2025, 13(2), 86; https://doi.org/10.3390/lubricants13020086 - 16 Feb 2025

Viewed by 476

Abstract

The introduction of mechanical energy during a friction process stimulates the system to eliminate this disturbance and find ways for energy dissipation. There are two principal situations: the system is either near equilibrium or far from equilibrium. Near equilibrium, it can be expected [...] Read more.

The introduction of mechanical energy during a friction process stimulates the system to eliminate this disturbance and find ways for energy dissipation. There are two principal situations: the system is either near equilibrium or far from equilibrium. Near equilibrium, it can be expected that the disturbance will be damped after a certain time, and the system will settle in a stationary state at a level where it began. However, the situation could be entirely different when the system is far from equilibrium. After a phase of instability and crossing a critical parameter, there is a probability of a change in the order level. This means that a new structure will be formed. This paper describes some aspects of the criteria that lead a friction process inside the grease film to instability and examines the influence of different dependencies. In this publication, the dependencies are extended to verify the stability criterion. Finally, the rest phase of a thixotropic experiment is examined from the perspective of potential instability and, thus, the possibility of self-organizing processes occurring. Full article

(This article belongs to the Special Issue Synthetic Greases and Oils)

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22 pages, 8734 KiB

Open AccessArticle

Analysis of Temperature Characteristics of Double-Row Spherical Roller Bearings Based on CFD

by Chengguo Fu, Ting Chen, Hui Yang, Haibo Li, Yuhao Li, Yaqi Zhang, Weiwei He and Hongbin Cong

Lubricants 2025, 13(2), 85; https://doi.org/10.3390/lubricants13020085 - 15 Feb 2025

Viewed by 639

Abstract

Double-row spherical roller bearings are frequently employed as supporting components in mining machinery. In practice, these bearings are lubricated manually, and the bearing chamber is filled with grease, which can lead to issues such as grease wastage and increased bearing temperatures. Additionally, factors [...] Read more.

Double-row spherical roller bearings are frequently employed as supporting components in mining machinery. In practice, these bearings are lubricated manually, and the bearing chamber is filled with grease, which can lead to issues such as grease wastage and increased bearing temperatures. Additionally, factors such as load and speed also influence the bearing temperature, collectively contributing to inadequate lubrication and potential bearing failure. Consequently, it is essential to investigate the temperature of the bearing under operating conditions. Utilizing tribology theory and the principles of bearing heat generation, a numerical model of fluid–structure interaction heat transmission within the bearing was developed, and finite element analysis was conducted through the ANSYS-Fluent module. The model was verified, and the temperature field of the bearing under varying operating conditions was studied. The findings of this research are as follows: (1) The numerical model demonstrates high accuracy, with a relative error of less than 5% when comparing the experimental temperature values of the jaw crusher bearing to the simulated values. (2) Under diverse operating conditions, the inner ring of the bearing has the highest temperature of all parts of the bearing, while the bearing cavity’s flow field has the lowest temperature. (3) The average temperature amplitude across different areas of the bearing system will rise as a result of increases in radial load or the bearing rotational speed. (4) When the grease filling volume increases from minimal to maximal, the average temperature in each bearing area initially decreases before subsequently rising, with the optimal grease filling amount identified as 60%. In operational scenarios, if the bearing temperature exceeds 70 °C, it is imperative to shut down the machine immediately to avert bearing failure. This study on bearing lubrication has practical guiding significance. Full article

(This article belongs to the Special Issue New Conceptions in Bearing Lubrication and Temperature Monitoring)

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25 pages, 13823 KiB

Open AccessArticle

Thermal Analysis of Grease-Lubricated Double Row Tapered Roller Bearings

by Xianwen Zhou, Zhenyu Ge, Xuejun Li, Miaohong Rao and Qingkai Han

Lubricants 2025, 13(2), 84; https://doi.org/10.3390/lubricants13020084 - 14 Feb 2025

Viewed by 610

Abstract

A steady-state thermal model of double-row tapered roller bearings (DTRB) with grease lubrication under a combined load is established in this paper. The influence of the internal load distribution on the temperature allotment of bearings in the circumferential, axial, and radial directions is [...] Read more.

A steady-state thermal model of double-row tapered roller bearings (DTRB) with grease lubrication under a combined load is established in this paper. The influence of the internal load distribution on the temperature allotment of bearings in the circumferential, axial, and radial directions is considered. Firstly, the local heat generation of the bearing is calculated based on the kinematic relationship inside the bearing, the internal load distribution, and the rheological properties of the grease. Then, combined with the heat dissipation analysis of the bearing, the three-dimensional steady-state temperature field of the DTRB is obtained. Ultimately, an analysis is conducted to examine how working conditions, including radial load, axial load, and rotational speed, impact the allotment of temperature fields in a DTRB along its circumferential, axial, and radial directions. The theoretical analysis outcome agrees with the experimental test outcome, providing theoretical guidance for the analysis of the bearing’s three-dimensional temperature field. Full article

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

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26 pages, 4491 KiB

Open AccessArticle

Advanced Machine Learning Approaches for Predicting Machining Performance in Orthogonal Cutting Process

by Sabrina Al Bukhari and Salman Pervaiz

Lubricants 2025, 13(2), 83; https://doi.org/10.3390/lubricants13020083 - 13 Feb 2025

Viewed by 756

Abstract

We investigated the orthogonal cutting process by using machine learning models to predict its performance. This study used the AZ91 magnesium alloy as the workpiece material, and machining was performed under the Minimum Quantity Lubrication (MQL) technique. The input parameters were the feed, [...] Read more.

We investigated the orthogonal cutting process by using machine learning models to predict its performance. This study used the AZ91 magnesium alloy as the workpiece material, and machining was performed under the Minimum Quantity Lubrication (MQL) technique. The input parameters were the feed, cutting speed and MQL flow rate. Additionally, the outputs were flank tool wear, the chip contact length, peak distance, valley distance, pitch distance, chip segmentation ratio, compression ratio and shear angle. Studies on machine learning (ML) models being employed to evaluate the performance of the MQL-assisted orthogonal machining of AZ91 are very rarely found in the literature. This study explored machine learning (ML) as a data-driven alternative, evaluating decision tree regression, Bayesian Optimization, Random Forest Regression and XGBoost for predicting machinability. A comprehensive dataset of the cutting parameters and outcomes was utilized to train and validate these models, aiming to enhance the accuracy of the predictive analysis. The performance of each model was evaluated based on error metrics such as the mean squared error (MSE) and R-squared values. Among these models, XGBoost demonstrated a superior predictive accuracy, outperforming the other methods in terms of its precision and generalizability. These findings suggest that XGBoost provides a more robust solution for modeling the complexities of the orthogonal cutting process, offering valuable insights into process optimization. The analysis supports that the XGBoost model is the most accurate, with a 34.1% reduction in the mean squared error and a 17.1% reduction in the mean absolute error over these values for the Decision Tree. It also outperforms the Random Forest Regression model, achieving a 19.8% decrease in the mean squared error and a 7.1% decrease in the mean absolute error. Full article

(This article belongs to the Special Issue Advances in Tool Wear Monitoring 2024)

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20 pages, 30551 KiB

Open AccessArticle

Effect of Gear Body Temperature on the Dynamic Characteristics of Spiral Bevel Gears

by Xi-Qing Zheng, Jun-Hong Hui and Hui-Qing Lan

Lubricants 2025, 13(2), 82; https://doi.org/10.3390/lubricants13020082 - 13 Feb 2025

Viewed by 624

Abstract

Thermal effect is an important cause of gear system engineering failure. Spiral bevel gears are widely used in helicopter transmissions, but scuffing often occurs during operation. Tooth surface body temperature is an important factor influencing scuffing in scuffing standards. A thermal dynamic model [...] Read more.

Thermal effect is an important cause of gear system engineering failure. Spiral bevel gears are widely used in helicopter transmissions, but scuffing often occurs during operation. Tooth surface body temperature is an important factor influencing scuffing in scuffing standards. A thermal dynamic model of spiral bevel gear transmission was developed based on varying tooth body temperatures under different oil spray conditions. Vibration acceleration experiments were conducted using a dedicated scuffing test rig. The results indicate that higher oil spray temperatures intensify vibrations, with a 24.3% increase in the maximum variance of vibration acceleration. Mesh frequency and stiffness decrease, increasing the likelihood of tooth surface failures such as scuffing. Accurate monitoring of tooth body temperature is critical to ensuring the reliable operation of spiral bevel gears in helicopter transmissions. Full article

(This article belongs to the Special Issue Novel Tribology in Drivetrain Components)

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21 pages, 19793 KiB

Open AccessArticle

RUL Prediction of Rolling Bearings Based on Fruit Fly Optimization Algorithm Optimized CNN-LSTM Neural Network

by Jiaping Shen, Haiting Zhou, Muda Jin, Zhongping Jin, Qiang Wang, Yanchun Mu and Zhiming Hong

Lubricants 2025, 13(2), 81; https://doi.org/10.3390/lubricants13020081 - 12 Feb 2025

Cited by 1 | Viewed by 826

Abstract

Due to the complex changes in the physical and chemical properties of rolling bearings from degradation to failure, most model-driven and data-driven methods generally suffer from insufficient accuracy and robustness in predicting the remaining useful life of rolling bearings. To address this challenge, [...] Read more.

Due to the complex changes in the physical and chemical properties of rolling bearings from degradation to failure, most model-driven and data-driven methods generally suffer from insufficient accuracy and robustness in predicting the remaining useful life of rolling bearings. To address this challenge, this paper proposes a data-driven artificial neural network method, namely the CNN-LSTM bearing remaining life prediction model based on the fruit fly optimization algorithm (FOA). This method utilizes the deep feature mining capabilities of convolutional neural networks (CNN) and long short-term memory networks (LSTM) to effectively extract spatial features and temporal information sequences from the dataset. In addition, introducing FOA enables the model to dynamically adjust the hidden layers and thresholds while optimizing the optimal path, thereby finding the best solution. This article conducts ablation experiments on the model using the acceleration life dataset of IEEE PHM 2012 rolling bearings. The experimental results show that the FOA-CNN-LSTM model proposed in this paper significantly outperforms other comparative methods in RUL prediction accuracy and stability, verifying its effectiveness and innovation in dealing with complex degradation processes. This method helps to take preventive measures before faults occur, thereby reducing economic losses and having important practical significance for predicting the remaining life of rolling bearings. Full article

(This article belongs to the Special Issue New Horizons in Machine Learning Applications for Tribology)

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19 pages, 6696 KiB

Open AccessArticle

Tribo-Dynamic Behavior of Double-Row Cylindrical Roller Bearings Under Raceway Defects and Cage Fracture

by Longqing Fan, Xingwang Zhao, Wei Hao, Chaoyang Miao, Xiuyuan Hu and Congcong Fang

Lubricants 2025, 13(2), 80; https://doi.org/10.3390/lubricants13020080 - 11 Feb 2025

Cited by 1 | Viewed by 556

Abstract

High-quality data samples are essential for the early detection of bearing failures and the analysis of bearing behavior. The accurate simulation of bearing fault conditions can provide valuable insights into understanding failure mechanisms. This paper establishes a new numerical simulation method for double-row [...] Read more.

High-quality data samples are essential for the early detection of bearing failures and the analysis of bearing behavior. The accurate simulation of bearing fault conditions can provide valuable insights into understanding failure mechanisms. This paper establishes a new numerical simulation method for double-row cylindrical roller bearing (DCRB) faults based on the augmented Lagrange dynamics method, overcoming the limitations of previous models by incorporating fault conditions related to cage fracture. This method accounts for the dynamic behavior of the rollers during the motion cycle and their interactions with other DCRB components. By comparing the characteristic frequencies of the fault components, the model not only replicates the dynamic behavior of faulty DCRBs more accurately but also offers a deeper understanding of fault-induced dynamics. This advancement provides a more comprehensive and realistic tool for bearing fault analysis. Full article

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25 pages, 13746 KiB

Open AccessArticle

Analysis of the Wear Mechanism and the Influence of the Chemical Composition and Repair Welds of the Pig Iron Wagon Wheels

by Janusz Krawczyk, Łukasz Frocisz and Piotr Matusiewicz

Lubricants 2025, 13(2), 79; https://doi.org/10.3390/lubricants13020079 - 11 Feb 2025

Viewed by 753

Abstract

The aim of the present study was to develop a concept for the inverse analysis of wear mechanisms in cast steel wheels of a pig iron wagon after long-term operation. Samples were taken from the flange and the tread edge area of fourteen [...] Read more.

The aim of the present study was to develop a concept for the inverse analysis of wear mechanisms in cast steel wheels of a pig iron wagon after long-term operation. Samples were taken from the flange and the tread edge area of fourteen wheels. The impact of wheel parameters and repair methods on their wear was assessed. An analysis was carried out to determine whether welds were made as part of casting correction or as repair welds. Changes in the microstructure of the weld area, the heat-affected zone, and the parent material resulting from operation were determined. The main wear mechanism in the area of the welds and the parent material is the plastic flow of the material resulting from high unit pressures. The hardness of the material is found to be contingent upon its chemical composition, the microstructural components, and the degree of plastic deformation resulting from wear (it has been established that increasing alloying results in increased hardness; a comparable effect is observed in the formation of non-equilibrium structures (bainite)). The increase in hardness is attributed to strain hardening, a consequence of exploitation. Research and analytical methods have been developed to differentiate the results of repair processes for wear effects in a highly loaded friction node with non-stationary lubrication conditions from repair processes applied to castings of large structural components. Full article

(This article belongs to the Special Issue Tribology in Vehicles)

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19 pages, 13056 KiB

Open AccessArticle

Vibration-Based Wear Evolution Characterisation of Lubricated Rolling-Sliding Contact

by Chan Xu, Qiuxia Fan, Qianqian Zhang, Yunqi Tong, Shuo Wang and Tonghai Wu

Lubricants 2025, 13(2), 78; https://doi.org/10.3390/lubricants13020078 - 11 Feb 2025

Viewed by 763

Abstract

This paper presents a comprehensive study on the vibration-based wear evolution characterisation by coupling the dynamic behaviour, surface roughness, and lubrication effects under rolling-sliding contact. Initially, a dynamic model is developed to examine the contact vibration characteristics induced by a randomly rough surface. [...] Read more.

This paper presents a comprehensive study on the vibration-based wear evolution characterisation by coupling the dynamic behaviour, surface roughness, and lubrication effects under rolling-sliding contact. Initially, a dynamic model is developed to examine the contact vibration characteristics induced by a randomly rough surface. A contact resonance frequency (CRF) can be obtained, and it is only positively correlated with the load, while the amplitude of CRF (CRFA) negatively correlates with the load and positively correlates with the velocity and surface profile height. Thereafter, a mixed-EHL model is employed to simulate the wear and lubrication progression of rolling-sliding contact. The surface roughness, contact load ratio (CLR), and contact area ratio (CAR) within this process are assigned specific physical interpretations and incorporated into the dynamic model. Given the nonlinear and coupled interactions of these three factors, the CRF and CRFA can distinguish the normal wear and severe wear stages. When the tribo-pair is in a normal wear stage, the CRF and CRFA show an increasing trend with the increase in surface roughness. Upon reaching a severe wear stage, the CRF gradually stabilises while the CRFA exhibits noticeable irregular fluctuations as the roughness increases. Finally, experiments are conducted to demonstrate the effectiveness of this method. Full article

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24 pages, 39562 KiB

Open AccessArticle

Synergistic Lubrication and Anti-Corrosion Effects of Benzotriazole and Ionic Liquid Under Current-Carrying Friction

by Taiyu Su, Kun Peng, Duo Zhang, Luyi Sun, Yuxin Chen, Yiheng Yu and Ming Zhou

Lubricants 2025, 13(2), 77; https://doi.org/10.3390/lubricants13020077 - 11 Feb 2025

Viewed by 768

Abstract

The corrosive nature of ionic liquids (ILs) limits their potential as high-performance conductive lubricants in practical engineering applications. This study systematically investigates the effects of benzotriazole (BTA) as a corrosion inhibitor on the lubricating performance of ILs at different concentrations and applied currents, [...] Read more.

The corrosive nature of ionic liquids (ILs) limits their potential as high-performance conductive lubricants in practical engineering applications. This study systematically investigates the effects of benzotriazole (BTA) as a corrosion inhibitor on the lubricating performance of ILs at different concentrations and applied currents, along with the underlying mechanisms. In the 0.5–5 A current range, BTA effectively reduces friction, wear, and arc erosion damage to the friction surface. As the applied current increases, the BTA-Fe reaction film suppresses oxide formation, thereby reducing electrical contact resistance (ECR). Moreover, the effectiveness of BTA is concentration-dependent: at 0.5 A and a BTA concentration of 0.5 wt%, the coefficient of friction (COF) decreases by 16.5%, and wear volume is reduced by 53.4%. Friction testing and surface analysis show that the BTA-IL combination exhibits synergistic lubrication and anti-corrosion effects under current-carrying conditions, with varying wear and lubrication mechanisms depending on the applied current. Full article

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14 pages, 6405 KiB

Open AccessArticle

Effects of Driving Conditions on Tire Hydroplaning Performance

by Tuo Deng, Shukun Wang, Dichuan Cheng, Long Zheng and Luquan Ren

Lubricants 2025, 13(2), 76; https://doi.org/10.3390/lubricants13020076 - 10 Feb 2025

Viewed by 916

Abstract

Hydroplaning occurs as standing water on the road surface not only acts as a lubricant but also generates hydrodynamic pressure, causing the tire to lose contact with the ground. This significantly reduces the friction between the tire and the road, thereby increasing the [...] Read more.

Hydroplaning occurs as standing water on the road surface not only acts as a lubricant but also generates hydrodynamic pressure, causing the tire to lose contact with the ground. This significantly reduces the friction between the tire and the road, thereby increasing the risk of traffic accidents. In this study, a 185/65R14 passenger radial tire was selected as the research subject. A complex fluid–structure interaction model was employed to thoroughly analyze the mechanisms influencing tire hydroplaning under various conditions. The results indicate that hydroplaning was more likely to occur with an increase in water depth or vehicle speed. Furthermore, increasing the tire inflation pressure and load was found to significantly enhance the friction between the tire and the ground, with the improvement exhibiting a nonlinear accelerating trend. Full article

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12 pages, 2383 KiB

Open AccessArticle

Experimental Verification and Multi-Physics-Based Computer-Aided Engineering Simulation Methods for Dynamic Characteristics Analysis of Gas Foil Bearings at Lift-Off State

by Tai-Yuan Yu and Pei-Jen Wang

Lubricants 2025, 13(2), 75; https://doi.org/10.3390/lubricants13020075 - 10 Feb 2025

Viewed by 745

Abstract

This paper presents an analysis of the dynamic characteristics observed and studied during the startup process of a gas foil radial bearing. It utilizes a comparison of both experimental data and three-dimensional fluid–solid interaction computational fluid dynamics simulations to investigate a gas foil [...] Read more.

This paper presents an analysis of the dynamic characteristics observed and studied during the startup process of a gas foil radial bearing. It utilizes a comparison of both experimental data and three-dimensional fluid–solid interaction computational fluid dynamics simulations to investigate a gas foil bearing with three bump-type pads. The analytical model employs the fluid–structure interaction finite element method to examine the relationship between the components and the thin working fluid film within the bearing. This analysis was conducted under various operational conditions, including ambient pressure and temperature, shaft rotational speed, and the load applied to the shaft within the bearing. The foil structure of the bearing was modeled by representing the top and bump foils as a series of linear springs that are interconnected with the rigid housing. Meanwhile, the hydrodynamic pressure distribution acting on the top foil was modeled as a gas film operating under steady-state lubrication conditions. The comprehensive three-dimensional multi-physics model was developed using a commercial computer-aided engineering package, enabling independent finite element calculations for both fluid and solid domains. Following these calculations, the model exchanged analysis results across the interface between domains, allowing simulations to continue until the system achieved a quasi-steady state. An in-house experimental system was designed to evaluate the performance of the gas foil bearing under different working conditions, including the load applied to the shaft and the rotational speed. The experiment investigated the operational state of a gas foil radial bearing under ambient pressure (1 bar), ambient temperature (303 K), rotational speeds ranging from 1.5 to 9.5 krpm, and a load of 0.5602 kgw. Some operational conditions of the bearing were defined as boundary condition inputs for the simulation model. The model’s results, notably the predicted lift-off rotational speed of the bearing, show strong alignment with results from in-house experiments. Full article

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

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20 pages, 5823 KiB

Open AccessArticle

Oil Film Thickness and Meshing Efficiency for a Novel Closed Movable Tooth Gear Reducer

by Shuo Yang and Lizhong Xu

Lubricants 2025, 13(2), 74; https://doi.org/10.3390/lubricants13020074 - 7 Feb 2025

Viewed by 637

Abstract

Equations are developed for the relative sliding velocities, entrainment velocities, forces, friction coefficients, effective radius of curvature, oil film thickness, friction loss, and meshing efficiency for a novel closed movable tooth gear reducer. Using these equations, the relative sliding velocities and entrainment velocities [...] Read more.

Equations are developed for the relative sliding velocities, entrainment velocities, forces, friction coefficients, effective radius of curvature, oil film thickness, friction loss, and meshing efficiency for a novel closed movable tooth gear reducer. Using these equations, the relative sliding velocities and entrainment velocities of the reducer are studied. The meshing efficiencies and their changes along with meshing positions and main parameters are analyzed. Changes of the meshing efficiencies along with load torque are also studied. An efficiency experiment of the reducer prototype is carried out. Results indicate that the meshing efficiency of the novel closed reducer increases with increasing eccentric distance. When an error in the eccentric distance occurs, the meshing efficiency is significantly reduced. The measured efficiency is close to the calculated one, supporting the theoretical studies. Full article

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20 pages, 15883 KiB

Open AccessArticle

Tribology and Hot Corrosion Behavior of MCrAlY-Based Multicomponent Coatings Containing Copper

by Bruno C. N. M. de Castilho, Navid Sharifi, Mary Makowiec, Pantcho Stoyanov, Christian Moreau and Richard R. Chromik

Lubricants 2025, 13(2), 73; https://doi.org/10.3390/lubricants13020073 - 7 Feb 2025

Viewed by 882

Abstract

The use of composite coatings containing solid lubricants is widely reported in the literature, in particular thermally sprayed coatings containing silver. However, these coatings are often limited in their maximum operating temperature due to the melting point of silver and due to reactions [...] Read more.

The use of composite coatings containing solid lubricants is widely reported in the literature, in particular thermally sprayed coatings containing silver. However, these coatings are often limited in their maximum operating temperature due to the melting point of silver and due to reactions between the components at temperatures above 500 °C. In this study, a novel coating is proposed, which consists of an MCrAlY-based matrix and the addition of components (Cu, Mo, and BaF₂) to improve the wear resistance at elevated temperatures. The coatings were sprayed by high-velocity oxy-fuel, heat-treated at 1040 °C, and tribologically tested at room and elevated temperatures. Raman spectroscopy and scanning electron microscopy were used on worn and unworn regions of the coating to characterize the changes in microstructure caused by wear. The coatings were also exposed to oxidation and hot corrosion conditions to evaluate the resistance to high-temperature environments. The results have shown an improvement in wear rates of the coatings upon heat treatment and the formation of a smooth tribolayer at 300 °C. The as-sprayed coating was able to withstand the attack by molten salts without exposing the substrate, and minor weight gain was observed, indicating that the MCrAlY matrix was effective to protect the coating and the substrate against damages induced by salt penetration. Full article

(This article belongs to the Special Issue Coatings and Lubrication in Extreme Environments)

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13 pages, 4111 KiB

Open AccessArticle

A Novel Tool Wear Identification Method Based on a Semi-Supervised LSTM

by Xin He, Meipeng Zhong, Chengcheng He, Jinhao Wu, Haiyang Yang, Zhigao Zhao, Wei Yang, Cong Jing, Yanlin Li and Chen Gao

Lubricants 2025, 13(2), 72; https://doi.org/10.3390/lubricants13020072 - 7 Feb 2025

Viewed by 786

Abstract

Machine learning models have been widely used in the field of cutting tool wear identification, achieving favorable results. However, in actual industrial scenarios, obtaining sufficient labeled samples is time consuming and costly, while unlabeled samples are abundant and easy to collect. This situation [...] Read more.

Machine learning models have been widely used in the field of cutting tool wear identification, achieving favorable results. However, in actual industrial scenarios, obtaining sufficient labeled samples is time consuming and costly, while unlabeled samples are abundant and easy to collect. This situation significantly affects the model’s performance. To address this challenge, a novel semi-supervised method, based on long short-term memory (LSTM) networks, is provided. The proposed method leverages both small labeled and abundant unlabeled data to improve tool wear identification performance. The proposed method trains an initial tool wear regression model using LSTM, using a small amount of labeled samples. It then uses manifold regularization to generate pseudo-labels for the unlabeled samples. These pseudo-labeled samples are combined with the original labeled samples to retrain the MR–LSTM model iteratively to improve its performance. This process continues until a termination condition is met. The method considers the correlation between sample labels and feature structures, as well as the correlation between global and local sample labels. Experiments involving milling tool wear identification demonstrate that the proposed method significantly outperforms support vector regression (SVR) and recurrent neural network (RNN)-based methods, when a small amount of labeled samples and abundant unlabeled samples are available. The average R² values in terms of the proposed method’s predicted results can reach above 0.95. The proposed method is a potential technique for low-cost tool wear identification, without the need to collect a large number of labeled samples. Full article

(This article belongs to the Special Issue Advanced Computational Studies in Frictional Contact)

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20 pages, 4934 KiB

Open AccessArticle

Curbing Petrochemical Lubricants by Plant-Based Chemicals: A Reliable Opportunity to Align with Sustainable Development Goals

by Jaime Nácher-Mestre, David Leal Cano, Kudama A. Habib, Clemente M. Branchadell and Jaume Pérez-Sánchez

Lubricants 2025, 13(2), 71; https://doi.org/10.3390/lubricants13020071 - 6 Feb 2025

Viewed by 976

Abstract

The use of plant-based lubricants is a sustainable alternative to petrochemical lubricants. Their main advantages include proven tribological performance, higher biodegradability in the environment, and the absence of health hazards when inhaled, ingested, or in contact with the skin. In this study, nine [...] Read more.

The use of plant-based lubricants is a sustainable alternative to petrochemical lubricants. Their main advantages include proven tribological performance, higher biodegradability in the environment, and the absence of health hazards when inhaled, ingested, or in contact with the skin. In this study, nine best-selling commercial lubricants were purchased and compared with two proposed sustainable alternatives derived from plant-based resources. The alternative wet lubricant that was developed demonstrated superior tribological performance compared to the selected commercial lubricants. Meanwhile, the alternative dry lubricant exhibited a greater load capacity and high wear resistance in the presence of micrometric Al₂O₃ particles at 20 N. The results indicated that a proper formulation of plant-based resources in lubricants can achieve the same or even better functional performance than conventional lubricants, which are currently classified as hazardous under European regulations. Full article

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21 pages, 8879 KiB

Open AccessArticle

Theoretical and Experimental Investigation of the Thermal Stability of a Cycloid Speed Reducer

by Milan Vasić, Mirko Blagojević, Milan Banić, Lorenzo Maccioni and Franco Concli

Lubricants 2025, 13(2), 70; https://doi.org/10.3390/lubricants13020070 - 6 Feb 2025

Viewed by 925

Abstract

High-precision drives are essential for ensuring accuracy and repeatability in positioning systems within robotics and industrial automation. Among these, cycloidal reducers are widely utilized due to their ability to deliver a high transmission ratio alongside high power density. However, compact designs often face [...] Read more.

High-precision drives are essential for ensuring accuracy and repeatability in positioning systems within robotics and industrial automation. Among these, cycloidal reducers are widely utilized due to their ability to deliver a high transmission ratio alongside high power density. However, compact designs often face challenges such as elevated operating temperatures caused by limited heat dissipation areas, making it crucial to assess thermal stability within the design process. While engineering practice typically determines the thermal stability of gear drives using ISO/TR 14179-2:2001, no specific methodologies have yet been developed for cycloidal reducers. To address this gap, this paper presents a novel mathematical model fine-tuned to quantify power dissipation and predict lubricant stabilization temperatures under varying operating conditions. The model employs a global energy balance approach, correlating total power losses with the heat dissipated from the reducer to the environment. Moreover, in this study, an experimental campaign was carried out to monitor the thermal behaviour of a cycloidal reducer under various operating conditions in terms of speed and transmitted torque. This was achieved through the analysis of images collected with an infrared thermal camera, both during the transient phase and under steady-state thermal conditions. The results demonstrate good alignment with experimental findings, although further refinements are required to develop specialized tools for cycloidal drives. Additional contributions of the present paper include the understanding of the time required to achieve thermal stability, as well as insights into heat generation and propagation. Beyond advancing scientific knowledge, this work also provides valuable practical guidance for engineering applications. 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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15 pages, 2406 KiB

Open AccessArticle

Effect of Split Doublet Mode Pair on Brake Squeal of the Slightly Asymmetric Disc

by Dongwoo Seo and Jaeyoung Kang

Lubricants 2025, 13(2), 69; https://doi.org/10.3390/lubricants13020069 - 5 Feb 2025

Viewed by 636

Abstract

In this paper, the stability of the split doublet mode pair in a disc brake squeal is analytically investigated. A reduced-order doublet mode model is derived based on the formulation of annular plate vibration, sliding contact kinematics, and the assumed mode method. The [...] Read more.

In this paper, the stability of the split doublet mode pair in a disc brake squeal is analytically investigated. A reduced-order doublet mode model is derived based on the formulation of annular plate vibration, sliding contact kinematics, and the assumed mode method. The solution is approximated using a two-mode expansion for the doublet mode pair. The time-varying motion of the slightly asymmetric rotating disc is described through the moving mode shape function method. A stability analysis of the frequency split between the doublet mode pair is performed by calculating the characteristic multipliers using the Floquet theory. The stability boundary is determined within the domain of frequency split variations and other parameters. Finally, the influence of mode splitting on the squeal behaviour of the asymmetric disc is analysed and discussed. Full article

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17 pages, 15072 KiB

Open AccessArticle

Effect of Pipe Wall Wear Defects on the Flow Characteristics of Slurry Shield Discharge Pipe

by Yingran Fang, Xinggao Li, Xingchun Li, Yidong Guo and Hongzhi Liu

Lubricants 2025, 13(2), 68; https://doi.org/10.3390/lubricants13020068 - 4 Feb 2025

Viewed by 837

Abstract

During slurry shield tunneling in hard rock or cobble strata, the discharge pipes suffer serve wear and damage. However, the effect mechanism of pipe wall wear defects on the flow characteristics of two-phase flow is unclear. In this study, a three-dimensional slurry particle [...] Read more.

During slurry shield tunneling in hard rock or cobble strata, the discharge pipes suffer serve wear and damage. However, the effect mechanism of pipe wall wear defects on the flow characteristics of two-phase flow is unclear. In this study, a three-dimensional slurry particle model of pipeline transport was established using the coupled computational fluid dynamics–discrete element method (CFD-DEM) considering the pipe wall wear defect, and the typical pipeline forms of straight pipe and 90° elbow pipe were selected as the research targets. The results indicated that the localized wear defect of pipes can lead to increased inhomogeneity in the velocity distribution, generating localized low-flow zones and resulting in a reduced flow rate or stagnancy in parts of the pipe. Meanwhile, the wear defect of the pipe results in local shape changes, so that the fluid flow path through the pipe is no longer smooth, causing more vortex/turbulence and secondary flow, where an increased vortex promotes localized kinetic energy reduction and creates larger pressure losses at the elbow. In addition, for the elbow pipe without wear defect, the pressure drop of the elbow increases quadratically from an increase of 6.5% to an increase of 16.9%, with the maximum wear depth increasing from 4 mm to 19 mm. For the straight pipe without wear defect, the pressure drop of the elbow increases linearly, from an increase of 2.2% to an increase of 10.2% with the maximum wear depth increasing from 4 mm to 19 mm. The paper investigates the potential mechanism of pipe flow characteristics influenced by wear defect and provides practical guidelines for the efficient operation of a slurry shield circulating system. Full article

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

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14 pages, 4464 KiB

Open AccessArticle

Effects of Graphene Nanoplatelets and Nanosized Al₄C₃ Formation on the Wear Properties of Hot Extruded Al-Based Nanocomposites

by Mihail Kolev, Rumyana Lazarova, Veselin Petkov and Rositza Dimitrova

Lubricants 2025, 13(2), 67; https://doi.org/10.3390/lubricants13020067 - 4 Feb 2025

Viewed by 822

Abstract

This study investigates the influence of graphene nanoplatelets (GNPs) and the formation of nanosized Al₄C₃ on the tribological performance of hot extruded aluminum-based nanocomposites. Al/GNP nanocomposites with varying GNP contents (0, 0.1, 0.5, and 1.1 wt.%) were fabricated through powder [...] Read more.

This study investigates the influence of graphene nanoplatelets (GNPs) and the formation of nanosized Al₄C₃ on the tribological performance of hot extruded aluminum-based nanocomposites. Al/GNP nanocomposites with varying GNP contents (0, 0.1, 0.5, and 1.1 wt.%) were fabricated through powder metallurgy, including ball milling, compaction, and hot extrusion at 500 °C, which was designed to facilitate the formation of nanosized carbides during the extrusion process. The effect of GNPs and nanosized carbides on the tribological properties of the composites was evaluated using dry friction pin-on-disk tests to assess wear resistance and the coefficient of friction (COF). Microstructural analyses using scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed the uniform distribution of GNPs and the formation of nanosized Al₄C₃ in the samples. Incorporating 0.1 wt.% GNPs resulted in the lowest wear mass loss (1.40 mg) while maintaining a stable COF (0.52), attributed to enhanced lubrication and load transfer. Although a higher GNP content (1.1 wt.%) resulted in increased wear due to agglomeration, the nanocomposite still demonstrated superior wear resistance compared to the unreinforced aluminum matrix. These findings underscore the potential of combining nanotechnology with precise processing techniques to enhance the wear and friction properties of aluminum-based composites. Full article

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

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17 pages, 5487 KiB

Open AccessArticle

Friction in Cylindrical Joints

by Andrei Marius Mihalache, Vasile Merticaru, Vasile Ermolai, Oana Dodun, Gheorghe Nagiț, Adelina Hrițuc, Marius Ionuț Rîpanu and Laurențiu Slătineanu

Lubricants 2025, 13(2), 66; https://doi.org/10.3390/lubricants13020066 - 4 Feb 2025

Viewed by 793

Abstract

Cylindrical clearance joints are commonly employed in mechanisms that involve the rotation of a shaft spindle within a cylindrical sliding bearing. The intensity of the friction process in such joints is governed by several factors, including the clearance size between components, the materials [...] Read more.

Cylindrical clearance joints are commonly employed in mechanisms that involve the rotation of a shaft spindle within a cylindrical sliding bearing. The intensity of the friction process in such joints is governed by several factors, including the clearance size between components, the materials of the interacting surfaces, the properties and characteristics of the lubricant, the surface roughness (asperities), and the magnitude of the relative velocity between the joint’s components. To experimentally determine the friction coefficient in cylindrical clearance joints, a custom device was designed and implemented. This device is adaptable to a universal lathe and enables the measurement of the friction coefficient under varying normal forces and relative movement speeds between the joint components. The experimental data were subjected to mathematical analysis, leading to the development of an empirical model. This model effectively characterizes the direction and intensity of the influence of various factors on the friction coefficient, accounting for the use of different lubricants. The findings provide valuable insights into optimizing cylindrical clearance joints for improved performance in practical applications. Full article

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

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27 pages, 9743 KiB

Open AccessArticle

Improved Calculation of Dynamic Load Capacity for Cylindrical Roller Thrust Bearings: Numerical Update of the Lifetime Reduction Factor η for Bearings with Small and Medium Spin-to-Roll Ratios

by Paul Sauvage, Torben Terwey, Benjamin Lehmann and Georg Jacobs

Lubricants 2025, 13(2), 65; https://doi.org/10.3390/lubricants13020065 - 3 Feb 2025

Viewed by 1093

Abstract

The standard procedures for calculating the lifetime of rolling bearings, defined by DIN ISO 281 and ISO/TS 16281, have been revisited in this work with a specific focus on redefining the η factor for cylindrical roller thrust bearings (CRTBs). The new η factor [...] Read more.

The standard procedures for calculating the lifetime of rolling bearings, defined by DIN ISO 281 and ISO/TS 16281, have been revisited in this work with a specific focus on redefining the η factor for cylindrical roller thrust bearings (CRTBs). The new η factor proposed in this study accounts for the additional spinning motion of the rolling elements on the raceway, which affects the lifetime of thrust roller bearings. By considering different spin-to-roll ratios (SRRs), the revised η factor results in a smaller lifetime reduction, improving from a 42% reduction with η = 0.85 to a 27% reduction with η = 0.91. This modification opens industrial opportunities for bearings that can handle higher loads or feature fewer or smaller rolling elements while maintaining the same lifespan target as bearings sized with the original η factor. An analytical and numerical methodology was developed to calculate the η factor for various bearing configurations. Two bearing geometries were selected to assess the influence of the SRR on bearing life. The methodology integrates calculations of the total friction coefficient, 2D and 3D stress distributions, and lifetime predictions based on subsurface-initiated fatigue failure modes. The numerical results demonstrate the impact of contact stresses and bearing kinematics on η. Although this study was based on numerical simulations, it sets the groundwork for experimental validation. Future work includes experimental testing to validate these findings, with a focus on subscale CRTBs subjected to varying γ values. Accelerated testing strategies, including higher rotational speeds and optimized lubrication, are proposed to enhance the accuracy of the results. These experiments would provide further insights into the life expectancy differences between various configurations, contributing to more precise lifetime calculations for CRTBs. Full article

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

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Lubricants, Volume 13, Issue 2 (February 2025) – 54 articles

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