Lubricants

18 pages, 15399 KiB

Open AccessArticle

Molecular Dynamics Study on the Tribological Characteristics of Grain Boundary-Containing Graphene/h-BN Heterostructure Films

by Bo Zhao, Shifan Huang, Yutao Zhang, Xiangcheng Ju, Chengbang Li, Zhenglin Li and Lingji Xu

Lubricants 2024, 12(8), 296; https://doi.org/10.3390/lubricants12080296 - 22 Aug 2024

Viewed by 481

Abstract

A heterostructure film composed of graphene and h-BN has superlubricity and long-term anti-corrosion performance, enabling its potential applications as low-friction and corrosion-resistant coatings, especially in marine environments. However, the grain boundaries (GBs) and point defects formed during the preparation process may significantly [...] Read more.

A heterostructure film composed of graphene and h-BN has superlubricity and long-term anti-corrosion performance, enabling its potential applications as low-friction and corrosion-resistant coatings, especially in marine environments. However, the grain boundaries (GBs) and point defects formed during the preparation process may significantly affect the performance of the film. In this study, the tribological properties and wear mechanism of heterostructure films with different GB misorientation angles were studied with the molecular dynamics method. The results show that the high-energy atoms generated by strain-induced hillocks along the GBs can lead to stress concentration, thus deteriorating the wear resistance of the heterostructure film. Furthermore, point defects occurring on high-energy atoms can significantly alleviate the stress concentration, which is conducive to improving the wear resistance of the film. This study sheds light on improving the tribological characteristics of a graphene/h-BN heterostructure coating by properly controlling its microstructure. Full article

(This article belongs to the Special Issue Advances in Molecular Rheology and Tribology)

► Show Figures

Figure 1

19 pages, 18791 KiB

Open AccessArticle

The Improvement of CrN Coatings Wear Resistance by Adjusting the Cycle Number of Electrochemical

by Xin Wang, Qianzhi Wang, Fei Zhou, Jizhou Kong and Zhifeng Zhou

Lubricants 2024, 12(8), 295; https://doi.org/10.3390/lubricants12080295 - 20 Aug 2024

Viewed by 436

Abstract

To further improve the sealing effect of electrochemical polarization (EP) on the CrN coatings, the EP treatment at different cycle numbers was conducted. The microstructure, mechanical, and tribological properties of CrN coatings were investigated. Findings indicated an elevation in oxygen content from 6.32% [...] Read more.

To further improve the sealing effect of electrochemical polarization (EP) on the CrN coatings, the EP treatment at different cycle numbers was conducted. The microstructure, mechanical, and tribological properties of CrN coatings were investigated. Findings indicated an elevation in oxygen content from 6.32% to 12.35% with increasing cycle number from 10 to 60 times, yet the crystal structure of CrN (111) and CrN (200) persisted. The X-ray photoelectron spectrum (XPS) and transmission electron microscope (TEM) revealed that a minimal quantity of oxides was produced. This led to a decrease in the coatings porosity from 16.79% to 5.83%. For this reason, the hardness of CrN coatings increased with a maximum degree of 18.3%, whilst the wear rate decreased with a maximum degree of 37.5% at the cycle number of 20 times. Full article

(This article belongs to the Special Issue Friction and Wear Properties of Composite Coatings in Air and Water)

► Show Figures

Figure 1

24 pages, 5059 KiB

Open AccessArticle

A Fast Numerical Approach for Investigating Adhesion Strength in Fibrillar Structures: Impact of Buckling and Roughness

by Turgay Eray

Lubricants 2024, 12(8), 294; https://doi.org/10.3390/lubricants12080294 - 19 Aug 2024

Viewed by 459

Abstract

This study presents a numerical investigation into the adhesion strength of micro fibrillar structures, incorporating statistical analysis and the effects of excessive pre–load leading to fibril buckling. Fibrils are modeled as soft cylinders using the Euler–Bernoulli beam theory, with buckling conditions described across [...] Read more.

This study presents a numerical investigation into the adhesion strength of micro fibrillar structures, incorporating statistical analysis and the effects of excessive pre–load leading to fibril buckling. Fibrils are modeled as soft cylinders using the Euler–Bernoulli beam theory, with buckling conditions described across three distinct states, each affecting the adhesive properties of the fibrils. Iterative simulations analyze how adhesion strength varies with pre–load, roughness, number of fibrils, and the work of adhesion. Roughness is modeled both in fibril heights and in the texture of a rigid counter surface, following a normal distribution with a single variance parameter. Results indicate that roughness and pre–load significantly influence adhesion strength, with excessive pre–load causing substantial buckling and a dramatic reduction in adhesion. This study also finds that adhesion strength decreases exponentially with increasing roughness, in line with theoretical expectations. The findings highlight the importance of buckling and roughness parameters in determining adhesion strength. This study offers valuable insights into the complex adhesive interactions of fibrillar structures, offering a scalable solution for rapid assessment of adhesion in various rough surface and loading scenarios. Full article

► Show Figures

Figure 1

17 pages, 7021 KiB

Open AccessArticle

Reliability-Based Robust Design Optimization with Fourth-Moment Method for Ball Bearing Wear

by Yanzhong Wang, Shiyuan E, Kai Yang, Bin Xie and Fengxia Lu

Lubricants 2024, 12(8), 293; https://doi.org/10.3390/lubricants12080293 - 19 Aug 2024

Viewed by 472

Abstract

Ball bearings operating at low speeds and under heavy loads are susceptible to wear failure, leading to significant economic losses. The existing reliability-based robust design optimization method of the fourth-moment method has high accuracy and does not need to determine the random distribution [...] Read more.

Ball bearings operating at low speeds and under heavy loads are susceptible to wear failure, leading to significant economic losses. The existing reliability-based robust design optimization method of the fourth-moment method has high accuracy and does not need to determine the random distribution of the input variables, but it is not possible to apply it to ball bearing wear due to the complexity of the bearing wear state function that cannot be characterized as an explicit form. To address this issue, this paper proposes a novel design method for ball bearing wear. Firstly, a surrogate model is constructed using the Kriging model method to establish a relationship between the bearing design parameters and the mechanical response. Subsequently, a wear reliability model is developed on the basis of the fourth-moment method, and reliability sensitivity analysis is conducted. Finally, the ball bearing wear reliability-based robust design optimization is accomplished through the use of a genetic algorithm. The results of the case calculations demonstrate that the proposed method effectively calculates the ball bearing wear reliability and analyzes the impact of design parameter randomness on reliability. Furthermore, optimizing the design parameters reduces the sensitivity of wear reliability to parameter randomness. Full article

► Show Figures

Figure 1

20 pages, 9369 KiB

Open AccessArticle

Predicting Low Sliding Friction in Al-Steel Reciprocating Sliding Experiment after a Controlled Grinding of the Steel Counterface

by Gopakumar Parameswaran, Vikram Jayaram and Satish V. Kailas

Lubricants 2024, 12(8), 292; https://doi.org/10.3390/lubricants12080292 - 18 Aug 2024

Viewed by 567

Abstract

The aim of this study was to identify the areal surface parameters that correlated with lowering of sliding friction. Different ground surfaces were created on stainless steel and the lubricated sliding friction generated at the contact interface with a flat-faced aluminum pin was [...] Read more.

The aim of this study was to identify the areal surface parameters that correlated with lowering of sliding friction. Different ground surfaces were created on stainless steel and the lubricated sliding friction generated at the contact interface with a flat-faced aluminum pin was studied. The frictional force encountered is an order of magnitude lower for a P1200-finished surface than the other ground surfaces. Using 3D surface profilometry, a unique surface parameter ratio “Spk/Sk” was found to predict the frictional performance of these surfaces. When this surface parameter ratio was less than 1, average sliding friction was close to 0.1. When this ratio was greater than 1, the coefficient was an order of magnitude lower. Using energy dispersive spectrometry, such surfaces after wear showed the presence of a uniform dispersed layer of iron oxide on the surface of the pin. This was absent on the surfaces having high friction, indicating the role of the steel counter surface in building this beneficial transfer layer. Scanning electron microscopy provided topography images to visualize the surface wear. The motivation for the authors was to use a commercially scaled process like precision grinding for the surface modifications on stainless steel. Full article

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

► Show Figures

Figure 1

22 pages, 10423 KiB

Open AccessArticle

Process-Integrated Component Microtexturing for Tribologically Optimized Contacts Using the Example of the Cam Tappet—Numerical Design, Manufacturing, DLC-Coating and Experimental Analysis

by Christian Orgeldinger, Manuel Reck, Armin Seynstahl, Tobias Rosnitschek, Marion Merklein and Stephan Tremmel

Lubricants 2024, 12(8), 291; https://doi.org/10.3390/lubricants12080291 - 16 Aug 2024

Viewed by 497

Abstract

To meet the demand for energy-efficient and, at the same time, durable, functional components, the improvement of tribological behavior is playing an increasingly important role. One approach to reducing friction in lubricated tribological systems is the microtexturing of the surfaces tailored to the [...] Read more.

To meet the demand for energy-efficient and, at the same time, durable, functional components, the improvement of tribological behavior is playing an increasingly important role. One approach to reducing friction in lubricated tribological systems is the microtexturing of the surfaces tailored to the application, but in most cases, this leads to increased manufacturing costs and thus often makes their use in industry more difficult. In this work, we, therefore, present an approach for an efficient design and fully integrated production process using a cam tappet as an example. For the used cam tappet contact, we first determined the optimal texture geometries using two differently complex EHL (elastohydrodynamic lubrication) simulation models. Based on these, textured tappets were manufactured in a combined manner using sheet-bulk metal-forming and deposition with a diamond-like-carbon (DLC) coating for additional wear protection without further post-processing of the coating. We show that the simulation approach used has a rather subordinate influence on the optimization result. The combined forming of components with textured surfaces is limited by the local material flow, the resulting texture distortion, and tool wear. However, a targeted process design can help to exploit the potential of single-stage forming. The applied DLC coating has good adhesion and can completely prevent wear in subsequent reciprocal pin-on-disc tests, while the friction in the run-in behavior is initially higher due to the soothing effects of the coating. The experiments also show a tendency for shallow textures to exhibit lower friction compared to deeper ones, which corresponds to the expectations from the simulation. Full article

(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)

► Show Figures

Figure 1

21 pages, 5827 KiB

Open AccessArticle

Machine-Learning-Based Wear Prediction in Journal Bearings under Start–Stop Conditions

by Florian König, Florian Wirsing, Ankit Singh and Georg Jacobs

Lubricants 2024, 12(8), 290; https://doi.org/10.3390/lubricants12080290 - 15 Aug 2024

Viewed by 509

Abstract

The present study aims to efficiently predict the wear volume of a journal bearing under start–stop operating conditions. For this purpose, the wear data generated with coupled mixed-elasto-hydrodynamic lubrication (mixed-EHL) and a wear simulation model of a journal bearing are used to develop [...] Read more.

The present study aims to efficiently predict the wear volume of a journal bearing under start–stop operating conditions. For this purpose, the wear data generated with coupled mixed-elasto-hydrodynamic lubrication (mixed-EHL) and a wear simulation model of a journal bearing are used to develop a neural network (NN)-based surrogate model that is able to predict the wear volume based on the operational parameters. The suitability of different time series forecasting NN architectures, such as Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU), and Nonlinear Autoregressive with Exogenous Inputs (NARX), is studied. The highest accuracy is achieved using the NARX network architectures. Full article

(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)

► Show Figures

Figure 1

14 pages, 3268 KiB

Open AccessArticle

DSU-LSTM-Based Trend Prediction Method for Lubricating Oil

by Ying Du, Yue Zhang, Tao Shao, Yanchao Zhang, Yahui Cui and Shuo Wang

Lubricants 2024, 12(8), 289; https://doi.org/10.3390/lubricants12080289 - 15 Aug 2024

Viewed by 542

Abstract

Oil monitoring plays an important role in early maintenance of mechanical equipment on account of the fact that lubricating oil contains a large amount of wear information. However, due to extreme industrial environment and long-term service, the data history and the sample size [...] Read more.

Oil monitoring plays an important role in early maintenance of mechanical equipment on account of the fact that lubricating oil contains a large amount of wear information. However, due to extreme industrial environment and long-term service, the data history and the sample size of lubricating oil are very limited. Therefore, to address problems due to a lack of oil samples, this paper proposes a new prediction strategy that fuses the domain shifts with uncertainty (DSU) method and long short-term memory (LSTM) method. The proposed DSU-LSTM model combines the advantages of the DSU model, such as increasing data diversity and uncertainty, reducing the impact of independent or identical domains on neural network training, and mitigating domain changes between different oil data histories, with the advantages of LSTM in predicting time series, thereby improving prediction capability. To validate the proposed method, a case study with real lubricating oil data is conducted, and comparisons are given by calculating the root-mean-square error (RMSE), mean absolute error (MAE), and mean relative error (MRE) with LSTM, support vector machine (SVM), and DSU-SVM models. The results illustrate the effectiveness of the proposed DSU-LSTM method for lubricating oil, and the robustness of the prediction model can be improved as well. Full article

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

► Show Figures

Figure 1

12 pages, 5875 KiB

Open AccessArticle

Material Optimization Method for a Spring-Energized Seal Based on Wear Analysis

by Xinni Zhao, Shuangxi Li, Dengyu Liu and Lele Huang

Lubricants 2024, 12(8), 288; https://doi.org/10.3390/lubricants12080288 - 15 Aug 2024

Viewed by 546

Abstract

Spring-energized seals demonstrate good sealing performance over a wide range of pressures and temperatures and can compensate for installation eccentricity, high-temperature aging, etc. However, as a contact seal, its polytetrafluoroethylene (PTFE) jacket material is easily worn during the rotation of the end face, [...] Read more.

Spring-energized seals demonstrate good sealing performance over a wide range of pressures and temperatures and can compensate for installation eccentricity, high-temperature aging, etc. However, as a contact seal, its polytetrafluoroethylene (PTFE) jacket material is easily worn during the rotation of the end face, which leads to a decline in sealing performance and, ultimately, seal failure. Based on the Archard wear model, a performance prediction model of the spring-energized seal was established by combining tests and numerical analyses. In order to improve the tribological performance of spring-energized seals made of PTFE, varied fillers were added to modify the PTFE, and the tribological and mechanical properties of PTFE composites with varied fillers were measured in experiments. Using a performance prediction model for spring-energized seals, the variation in the friction performance of seals made of these filled PTFEs during the operating cycle was analyzed. The results showed that the performance prediction model can accurately simulate this variation. After a certain amount of wear, the deviation between the simulated data and the experimental data was within ±5%. Compared with spring-energized seals made of pure PTFE, the friction torque of spring-energized seals made of GF/PTFE was reduced by 28.97% at most, and the friction torque reduction rate was lowered by 22.25%. Full article

► Show Figures

Figure 1

16 pages, 9540 KiB

Open AccessArticle

Influence of Lubrication Cycle Parameters on Hydrodynamic Linear Guides through Simultaneous Monitoring of Oil Film Pressure and Floating Heights

by Burhan Ibrar, Volker Wittstock, Joachim Regel and Martin Dix

Lubricants 2024, 12(8), 287; https://doi.org/10.3390/lubricants12080287 - 14 Aug 2024

Viewed by 408

Abstract

Hydrodynamic linear guides in machine tools offer a high load capacity and excellent damping characteristics, improving stability, precision, and vibration reduction. This study builds on previous research where floating heights were verified with a simulation model limited to measured floating heights. Advancements include [...] Read more.

Hydrodynamic linear guides in machine tools offer a high load capacity and excellent damping characteristics, improving stability, precision, and vibration reduction. This study builds on previous research where floating heights were verified with a simulation model limited to measured floating heights. Advancements include incorporating pressure sensors into a fixed steel rail, enabling simultaneous measurement of oil film pressure and floating heights for a comprehensive understanding of lubrication conditions within the lubrication gap. The experimental results explore the effects of different lubrication methods, providing valuable insights into cavitation and lubrication adequacy. The results demonstrate the feasibility of utilizing pressure sensors to measure oil film pressure within the lubrication gap, providing a nuanced understanding of lubrication dynamics. By measuring both floating heights and pressure measurement, distinctions between hydrodynamic lubrication, mixed friction regions, and instances of lubricant deficiency become readily discernible. The variations in real-time oil film pressure and floating heights help to optimize the lubrication cycle for hydrodynamic linear guides, enhancing system performance and longevity. Full article

(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)

► Show Figures

Graphical abstract

18 pages, 5914 KiB

Open AccessArticle

Study on the Effect of Thermal Characteristics of Grease-Lubricated High-Speed Silicon Nitride Full Ceramic Ball Bearings in Motorized Spindles

by Yonghua Wang, Songhua Li, Chao Wei, Bo Liu, Yu Zhang, Gefei Lin, Kun Wang and Jining Zhao

Lubricants 2024, 12(8), 286; https://doi.org/10.3390/lubricants12080286 - 14 Aug 2024

Viewed by 419

Abstract

Grease lubrication is cost-effective and low-maintenance for motorized spindles, but standard steel bearings can fail at high speeds. This study focuses on high-speed full ceramic ball bearings lubricated with grease. The coefficient of friction torque in the empirical formula is corrected by establishing [...] Read more.

Grease lubrication is cost-effective and low-maintenance for motorized spindles, but standard steel bearings can fail at high speeds. This study focuses on high-speed full ceramic ball bearings lubricated with grease. The coefficient of friction torque in the empirical formula is corrected by establishing the heat generation model of full ceramic ball bearing and combining it with experiments. A simulation model of grease flow is established to study the influence of grease filling amount on grease distribution. The simulation model of the temperature field of a full ceramic ball bearing is established to analyze the influence of rotating speed on bearing heat generation, and experiments verify the calculation results of the theoretical model. The results show that an optimal grease filling amount of 15~25% ensures even distribution without accumulation. Additionally, when the amount of grease is constant, the outer ring temperature increases with higher rotating speeds. The test results show that when the grease filling is 0.9~1.2 g, it accounts for about 9~12% of the volume of the bearing cavity, and the temperature of the outer ring is the lowest. At a rotation speed of 24,000 rpm, the outer ring temperature of the grease-lubricated bearing is 50.1 °C, indicating a reasonable range for use in motorized spindles. It provides a theoretical basis for the optimization design of macro-structural parameters of full ceramic ball bearings in the future, which can minimize heat generation and maximize bearing capacity. Full article

(This article belongs to the Special Issue Tribological Research on Transmission Systems)

► Show Figures

Figure 1

14 pages, 6351 KiB

Open AccessArticle

Comparative Study on the Lubrication of Ti₃C₂T_X MXene and Graphene Oxide Nanofluids for Titanium Alloys

by Yaru Tian, Ye Yang, Heyi Zhao, Lina Si, Hongjuan Yan, Zhaoliang Dou, Fengbin Liu and Yanan Meng

Lubricants 2024, 12(8), 285; https://doi.org/10.3390/lubricants12080285 - 9 Aug 2024

Viewed by 576

Abstract

Titanium alloys are difficult to machine and have poor tribological properties. Nanoparticles have good cooling and lubricating properties, which can be used in metal cutting fluid. The lubrication characteristics of the two-dimensional materials Ti₃C₂T_X MXene and graphene oxide [...] Read more.

Titanium alloys are difficult to machine and have poor tribological properties. Nanoparticles have good cooling and lubricating properties, which can be used in metal cutting fluid. The lubrication characteristics of the two-dimensional materials Ti₃C₂T_X MXene and graphene oxide in water-based fluid for titanium alloys were comparatively investigated in this paper. Graphene oxide had smaller friction coefficients and wear volume than Ti₃C₂T_X MXene nanofluid. As to the mechanism, MXene easily formed TiO₂ for the tribo-chemical reaction, which accelerated wear. Moreover, GO nanofluid can form a more uniform and stable friction layer between the frictional interface, which reduces the friction coefficient and decreases the adhesive wear. The effects of different surfactants on the lubricating properties of MXene were further investigated. It was found that the cationic surfactant Hexadecyl trimethyl ammonium chloride (1631) had the lowest friction coefficient and anti-wear properties for the strong electrostatic attraction with MXene nanoparticles. The results of this study indicate that 2D nanoparticles, especially graphene oxide, could improve the lubricating properties of titanium alloys. It provides insight into the application of water-based nanofluids for difficult-to-machine materials to enhance surface quality and cutting efficiency. The developed nanofluid, which can lubricate titanium alloys, effectively has very broad applications in prospect. Full article

(This article belongs to the Special Issue Advanced Polymeric and Colloidal Lubricants)

► Show Figures

Figure 1

20 pages, 8839 KiB

Open AccessArticle

Theoretical and Experimental Study of Flexible Structure Tilting Pad Bearings Considering Deformation

by Yunyu Wu, Weiwei Zhang, Shuxiang Yi, Xiaojing Wang, Yanyan Qin and Shuxia Peng

Lubricants 2024, 12(8), 284; https://doi.org/10.3390/lubricants12080284 - 9 Aug 2024

Viewed by 501

Abstract

In high-speed and heavy-load conditions, ordinary rigid tilting pad journal bearings experience significant contact stress at the pad pivot points, leading to severe pad deformation and increased wear. A flexible structure tilting pad bearing (FSTPB) is presented in this paper, using spring supports [...] Read more.

In high-speed and heavy-load conditions, ordinary rigid tilting pad journal bearings experience significant contact stress at the pad pivot points, leading to severe pad deformation and increased wear. A flexible structure tilting pad bearing (FSTPB) is presented in this paper, using spring supports to replace the traditional pivot supports and flexible hinge supports. A theoretical calculation model for tilting pad radial journal bearings considering flexible structure deformation is established, and the impact of elastic deformation on the performance of the flexible structure tilting pad bearings is discussed. Based on theoretical research, vibration experiments on flexible tilting pad bearings under different loading conditions were conducted. The influence of various structural parameters on the vibration characteristics of the flexible tilting pad radial bearings was studied. The results indicate that, compared to ordinary tilting pad bearings, flexible structure tilting pad bearings exhibit excellent vibration reduction characteristics at high speeds. Reducing the bearing clearance, lowering the stiffness of the flexible structure, and increasing the offset angle of the flexible structure contribute to enhancing the operational stability of the bearing–rotor system. Full article

► Show Figures

Figure 1

20 pages, 20915 KiB

Open AccessArticle

Study of Lubrication Performance and Churning Loss under Mixed Lubrication Mode in Gearbox

by Lina Wang, Yi Liu, Kailin Zhang, Yuan Yao, Shuai Shao and Kuangzhou He

Lubricants 2024, 12(8), 283; https://doi.org/10.3390/lubricants12080283 - 8 Aug 2024

Viewed by 481

Abstract

In order to clarify the effect of mixed lubrication methods on the oil flow and power loss of the gearbox, this study adopts a high-precision moving particle semi-implicit (MPS) method to investigate the lubrication of the gearbox under the joint influence of splash [...] Read more.

In order to clarify the effect of mixed lubrication methods on the oil flow and power loss of the gearbox, this study adopts a high-precision moving particle semi-implicit (MPS) method to investigate the lubrication of the gearbox under the joint influence of splash lubrication and oil injection lubrication. The accuracy of the numerical method to calculate the churning torque was verified by the constructed test rig. The effects of rotational speed, immersion depth, injection volume rate, and oil injection angle were analyzed and evaluated for lubrication. The results show that better lubrication can be achieved with relatively small churning torques by using a hybrid lubrication method. This provides some references for engineering applications of gearboxes. Full article

► Show Figures

Figure 1

11 pages, 1928 KiB

Open AccessArticle

Assessing Antioxidant and Pour Point Depressant Capacity of Turmeric Rhizome Extract in Biolubricants

by Joseph Samuel, Muhammad U. Kaisan, Yinka S. Sanusi, Sunny Narayan, Brahim Menacer, Marian Valenzuela, Alexis Salas, Angelo Oñate, Faisal O. Mahroogi and Víctor Tuninetti

Lubricants 2024, 12(8), 282; https://doi.org/10.3390/lubricants12080282 - 7 Aug 2024

Viewed by 622

Abstract

Natural polyphenols found in plants are secondary metabolites and act as natural antioxidants. Phenols prevent lipid oxidation by donating their hydrogen to free radicals generated between reactions of oxygen with unsaturated fatty acids. This work aims to examine turmeric extract for its capacity [...] Read more.

Natural polyphenols found in plants are secondary metabolites and act as natural antioxidants. Phenols prevent lipid oxidation by donating their hydrogen to free radicals generated between reactions of oxygen with unsaturated fatty acids. This work aims to examine turmeric extract for its capacity to act as an antioxidant and pour point depressant additive in biolubricants. The study involved extracting turmeric rhizome and analyzing the extract using the gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR) techniques to identify phenolic compounds and the nature of bonds in terms of abundance peak areas. The yield of concentrated turmeric rhizome extract by weight was 3.7%. The FTIR analysis revealed O-H band at 3336 cm⁻¹, C-H asymmetric and symmetric stretching at 2940 and 2834 cm⁻¹, C=C cyclic ring at 1680–1515 cm⁻¹. The phenols detected by the GC-MS technique are phenol, 2 -methoxy-3-(2-propenyl) occupying 36.3% area at 16.5 min retention time and Phenol, 2-methoxy-4-(2-propenyl)-, acetate having 3.8% area at 3.8 min retention time. The results show promising capacity of turmeric rhizome extract to act as antioxidant and pour point depressant additive in biolubricants. Full article

► Show Figures

Figure 1

17 pages, 4518 KiB

Open AccessArticle

Optimization of Fused Filament Fabrication for High-Performance Polylactic Acid Parts under Wear Conditions

by Moises Batista, Magdalena Ramirez-Peña, Jorge Salguero and Juan Manuel Vazquez-Martinez

Lubricants 2024, 12(8), 281; https://doi.org/10.3390/lubricants12080281 - 6 Aug 2024

Viewed by 644

Abstract

This paper investigates the impact of various manufacturing parameters on the mechanical and tribological properties of high-performance PLA (polylactic acid) parts produced using Fused Filament Fabrication (FFF). It addresses the challenges associated with optimizing additive manufacturing processes, particularly for polymer-based materials, and emphasizes [...] Read more.

This paper investigates the impact of various manufacturing parameters on the mechanical and tribological properties of high-performance PLA (polylactic acid) parts produced using Fused Filament Fabrication (FFF). It addresses the challenges associated with optimizing additive manufacturing processes, particularly for polymer-based materials, and emphasizes the importance of understanding how factors such as build orientation, layer thickness, and infill density influence the final properties of the printed parts. This study highlights the improvements that can be achieved by incorporating reinforcements such as carbon fibers and graphene nanoplatelets into PLA, enhancing its mechanical strength and wear resistance. Experimental results show that optimizing printing parameters can significantly reduce the coefficient of friction and wear, leading to better performance in applications involving movement and mechanical stress. Key findings include the observation that higher infill densities and specific build orientations improve the fatigue life and tensile strength of PLA parts. Additionally, post-printing thermal treatments can alleviate internal stresses and enhance interlayer adhesion, further improving mechanical properties. The article concludes that with proper optimization, high-performance PLA can be a viable material for industrial applications, offering both environmental benefits and enhanced performance. Full article

(This article belongs to the Special Issue Wear in Additive Manufacturing)

► Show Figures

Graphical abstract

15 pages, 3071 KiB

Open AccessArticle

The Target Detection of Wear Particles in Ferrographic Images Based on the Improved YOLOv8

by Jinyi Wong, Haijun Wei, Daping Zhou and Zheng Cao

Lubricants 2024, 12(8), 280; https://doi.org/10.3390/lubricants12080280 - 5 Aug 2024

Viewed by 578

Abstract

An enhanced YOLOv8 algorithm is proposed in the following paper to address challenging issues encountered in ferrographic image target detection, such as the identification of complex-shaped wear particles, overlapping and intersecting wear particles, and small and edge-wear particles. This aim is achieved by [...] Read more.

An enhanced YOLOv8 algorithm is proposed in the following paper to address challenging issues encountered in ferrographic image target detection, such as the identification of complex-shaped wear particles, overlapping and intersecting wear particles, and small and edge-wear particles. This aim is achieved by integrating the main body network with the improved Deformable Convolutional Network v3 to enhance feature extraction capabilities. Additionally, the Dysample method is employed to optimize the upsampling technique in the neck network, resulting in a clearer fused feature image and improved precision for detecting small and edge-wear particles. In the head network, parameter sharing simplifies the detection head while enhancing convergence speed and precision through improvements made to the loss function. The experimental results of the present study demonstrate that compared to the original algorithm, this enhanced approach achieves an average precision improvement of 5.6% without compromising the detection speed (111.6FPS), therefore providing valuable support for online monitoring device software foundations. Full article

(This article belongs to the Special Issue Intelligent Algorithms for Triboinformatics)

► Show Figures

Figure 1

19 pages, 31566 KiB

Open AccessArticle

Effect of Grease Composition on Impact-Sliding Wear

by Xinqing Wang, Zhendong Lv, Yiming Han and Jing Wang

Lubricants 2024, 12(8), 279; https://doi.org/10.3390/lubricants12080279 - 4 Aug 2024

Viewed by 569

Abstract

Impact-sliding experiments were performed by using four self-made lithium-based greases, namely Yangtze Grease 1, Yangtze Grease 2, Yangtze Grease 3, and Yangtze Grease 4. The influence of base oil viscosity, thickener content, and morphology of thickener fiber clusters on the lubricating state were [...] Read more.

Impact-sliding experiments were performed by using four self-made lithium-based greases, namely Yangtze Grease 1, Yangtze Grease 2, Yangtze Grease 3, and Yangtze Grease 4. The influence of base oil viscosity, thickener content, and morphology of thickener fiber clusters on the lubricating state were visually explored, combined with field-emission microscopy and two-light interference technology. The grease film distribution at the middle section was measured using Dichromatic Interference Intensity Modulation (DIIM) software. All experiments were executed in a completely flooded environment. The results show that among the components of grease, the base oil’s viscosity has the greatest impact on the anti-wear performance of the grease. As the viscosity of the base oil increases, the grease exhibits better anti-wear performance. The grease film thickness under the condition of high-viscosity base oil is about 10 times higher than that under the condition of low-viscosity base oil. Secondly, the content of thickener in the grease needs to be controlled within a reasonable range. The experiments indicate that the effect of thickener content on the grease’s film-forming properties becomes more pronounced at higher speeds. From the experiment using YG 4, it can be seen that a higher thickener content under high-speed conditions increases the thickness of the lubricating grease film by about 10 times. The dimensions of the thickener fibers and the density of their entanglement structure significantly influence the rheological properties and load-bearing capacity of the grease. Larger fiber sizes and higher entanglement densities result in reduced grease fluidity and recovery but enhance its load-bearing capabilities. In order to obtain the best anti-wear performance during impact-sliding motion, the size of the thickener fiber and the density of the entanglement structure need to be controlled within an appropriate range. Full article

(This article belongs to the Special Issue Friction and Wear of Rolling-Element Bearings)

► Show Figures

Figure 1

17 pages, 6345 KiB

Open AccessArticle

Enhancing the Tribological Properties of Bearing Surfaces in Hip Arthroplasty by Shot-Peening the Metal Surface

by Chavarat Jarungvittayakon, Anak Khantachawana and Paphon Sa-ngasoongsong

Lubricants 2024, 12(8), 278; https://doi.org/10.3390/lubricants12080278 - 3 Aug 2024

Viewed by 534

Abstract

Total hip arthroplasty (THA) is a surgical procedure for patients with pain and difficulty walking due to hip osteoarthritis. In primary THA, the acetabulum and femoral head are replaced by a prosthesis where the modular femoral head and inner liner of the acetabulum [...] Read more.

Total hip arthroplasty (THA) is a surgical procedure for patients with pain and difficulty walking due to hip osteoarthritis. In primary THA, the acetabulum and femoral head are replaced by a prosthesis where the modular femoral head and inner liner of the acetabulum form the bearing surface. The most popular bearing surface used in the United States, metal-on-polyethylene, consists of a cobalt–chromium molybdenum (CoCrMo) alloy femoral head that articulates with a polyethylene acetabular liner, typically made of highly cross-linked polyethylene. While successful in most cases, THA sometimes fails, commonly from aseptic loosening due to the wear debris of polyethylene. Fine-particle shot peening (FPSP) is a simple method for enhancing the mechanical properties and surface properties of metal, including reducing friction and enhancing the lubrication properties of the metal surface. In this study, we applied FPSP to the CoCr in the femoral head of a hip prosthesis to improve its surface properties and conducted experiments with pin-on-disc tribometers using CoCr as a pin and highly cross-linked polyethylene as a disc to mimic the THA implant. The results show that FPSP significantly enhances the tribological properties of the CoCr surface, including lubrication; decreases the friction coefficient; and decreases the polyethylene wear volume. Full article

(This article belongs to the Special Issue Biomechanics and Tribology)

► Show Figures

Figure 1

17 pages, 6261 KiB

Open AccessArticle

Impact of Oil Viscosity on Emissions and Fuel Efficiency at High Altitudes: A Response Surface Methodology Analysis

by Milton Garcia Tobar, Oscar Cabrera Ojeda and Fredy Crespo Montaño

Lubricants 2024, 12(8), 277; https://doi.org/10.3390/lubricants12080277 - 3 Aug 2024

Viewed by 933

Abstract

This study investigates the effect of oil viscosity on pollutant emissions and fuel consumption of an internal combustion engine (ICE) at high altitudes using a response surface methodology (RSM). A Chevrolet Corsa Evolution 1.5 SOHC gasoline engine was used in Cuenca, Ecuador (2560 [...] Read more.

This study investigates the effect of oil viscosity on pollutant emissions and fuel consumption of an internal combustion engine (ICE) at high altitudes using a response surface methodology (RSM). A Chevrolet Corsa Evolution 1.5 SOHC gasoline engine was used in Cuenca, Ecuador (2560 m above sea level), testing three lubricating oils with kinematic viscosities of 9.66, 14.08, and 18.5 mm²/s, measured at a temperature of 100 °C under various engine speeds and loads. Key findings include the following: hydrocarbon (HC) emissions were minimized from 150.22 ppm at the maximum load to 7.25 ppm with low viscosity and load; carbon dioxide (CO₂) emissions peaked at 15.2% vol with high viscosity and load; carbon monoxide (CO) ranged from 0.04% to 3.74% depending on viscosity and load; nitrogen oxides (NOx) were significantly influenced by viscosity, RPM, and load, indicating a need for model refinement; and fuel consumption was significantly affected by load and viscosity. RSM-based optimization identified optimal operational conditions with a viscosity of 13 mm²/s, 1473 rpm, and a load of 78%, resulting in 52.35 ppm of HC, 13.97% vol of CO₂, 1.2% vol of CO, 0 ppm of NOx, and a fuel consumption of 6.66 L/h. These conditions demonstrate the ability to adjust operational variables to maximize fuel efficiency and minimize emissions. This study underscores the critical role of optimizing lubricant viscosity and operational conditions to mitigate environmental impact and enhance engine performance in high-altitude environments. Full article

(This article belongs to the Special Issue Recent Advances in Automotive Powertrain Lubrication)

► Show Figures

Figure 1

21 pages, 3989 KiB

Open AccessArticle

The Effect of Plastic Deformation on the Flattening of Friction Surfaces

by Alexey Moshkovich, Igor Lapsker and Lev S. Rapoport

Lubricants 2024, 12(8), 276; https://doi.org/10.3390/lubricants12080276 - 2 Aug 2024

Viewed by 527

Abstract

This work aims to demonstrate the discrepancy between the results achieved in the application of ball-on-flat devices. Meanwhile, the interaction between contact parameters and the morphology of friction surfaces will be considered. Flattening depends on the mechanical properties of contact materials and the [...] Read more.

This work aims to demonstrate the discrepancy between the results achieved in the application of ball-on-flat devices. Meanwhile, the interaction between contact parameters and the morphology of friction surfaces will be considered. Flattening depends on the mechanical properties of contact materials and the variation in the deformed structure in surface layers. To evaluate the interaction between roughness parameters and contact pressure, wear, and morphology of the surfaces, a ball-on-disk rig was applied. The average groove sizes were measured on micro- and macroscales. The relation between groove sizes on micro- and macro scales is close to the same. The flattening sinusoidal ball-on-flat model was considered. The real friction and wear tests were used to analyze plastic deformation by accounting for dislocation gliding and the interaction between neighboring asperities. The relation of shear stresses to the interference of rough asperities was established. The effective plastic strain gradient was evaluated. The formation of a highly effective plastic strain gradient is associated with a high dislocation density. The effect of dislocation density on the hardening–softening of surface layers is considered. Full article

(This article belongs to the Special Issue Tribology of Metals and Alloys)

► Show Figures

Figure 1

16 pages, 59589 KiB

Open AccessArticle

Revealing the Molecular Interaction between CTL Base Oil and Additives and Its Application in the Development of Gasoline Engine Oil

by Chunfeng Zhang, Xiaojun Zhang, Qiang Yan, Liyang Wang and Xiangqiong Zeng

Lubricants 2024, 12(8), 275; https://doi.org/10.3390/lubricants12080275 - 31 Jul 2024

Viewed by 508

Abstract

In order to improve fuel economy to meet the standard for passenger car oil, a new formulation with good viscosity–temperature performance for gasoline engine oil is required. In this study, coal-to-liquid (CTL) base oil, with a high viscosity index and good low-temperature performance, [...] Read more.

In order to improve fuel economy to meet the standard for passenger car oil, a new formulation with good viscosity–temperature performance for gasoline engine oil is required. In this study, coal-to-liquid (CTL) base oil, with a high viscosity index and good low-temperature performance, was selected as the base oil to develop the gasoline engine oil. A systematic study on the molecular interaction between the CTL base oil and the viscosity index improver (VII), including three kinds of hydrogenated styrene diene copolymers (HSD-type) and four kinds of ethylene propylene copolymers (OCP-type), was conducted. It was found that in general, in CTL base oil, the HSD-type VII exhibited a much higher viscosity index, a significantly lower shear stability index, a higher thickening ability, and a lower cold-cranking simulator (CCS) viscosity than that of OCP-type VII. Moreover, when comparing CTL base oil with mineral oil 150N, the combination of CTL base oil and the VII displayed a lower CCS viscosity than that of mineral oil, suggesting it had better low-temperature performance and was able to quickly form a protective oil film on the surface, which was beneficial for the cold start. The functional group distribution state of the VII in base oil was analyzed using synchrotron radiation micro-infrared microscope (SR Micro-IR) technology, which revealed that HSD-1 had a better molecular interaction with CTL6 than 150N because of the better uniformity of the C=C group distribution. Based on this, a SP 0W-20 gasoline engine oil was developed by the combination of CTL base oil and the HSD-1 viscosity index improver, together with an additive package, a polymethacrylate pour point depressant, and a non-silicone defoamer, which showed excellent low-temperature performance, thermal oxidation stability, and detergency performance compared to the reference oil. Full article

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

► Show Figures

Figure 1

25 pages, 9517 KiB

Open AccessArticle

Stability Analysis of the Secondary Motion of a Textured Piston

by Igal Cohen, Shachar Tresser and Roman Goltsberg

Lubricants 2024, 12(8), 274; https://doi.org/10.3390/lubricants12080274 - 31 Jul 2024

Viewed by 479

Abstract

Piston–cylinder pairs are very common in industrial mechanisms. While a piston is primarily designed for axial reciprocating motion, the occurrence of secondary motions—lateral and rotational—due to the small clearance between the piston and the cylinder may lead to frictional contact, energy loss, wear [...] Read more.

Piston–cylinder pairs are very common in industrial mechanisms. While a piston is primarily designed for axial reciprocating motion, the occurrence of secondary motions—lateral and rotational—due to the small clearance between the piston and the cylinder may lead to frictional contact, energy loss, wear and an increase in unwanted leakage. This study focuses on mitigating the secondary motion of a ringless piston. The influence of a Rayleigh step bearing and partial surface texturing with numerous micro-dimples on the dynamic stability of the secondary motion is studied. A linear model was used to obtain the trajectory of the secondary motion and Floquet theory was applied to analyze the stability and draw stability maps. The influence of various texturing and step parameters, including the dimple area density and aspect ratio for partial texturing, as well as the length and depth of treatment for both partial texturing and step profiles, on the stability of the secondary motion was examined. The normalization method is presented, enabling the expansion of the results for various operating conditions and geometries. Conclusions and guidelines regarding the optimal parameters, in terms of a wider stability range and higher decay rate, are formulated. Full article

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

► Show Figures

Figure 1

23 pages, 7795 KiB

Open AccessReview

Theoretical Model Development and Mixed Lubrication Analyses of Rolling Piston Type Rotary Compressors: A Review

by Chengwei Wen, Pengpeng Bai, Hang Zhang, Shuaijun Zhang, Xianghui Meng, Yonggang Meng and Yu Tian

Lubricants 2024, 12(8), 273; https://doi.org/10.3390/lubricants12080273 - 30 Jul 2024

Viewed by 627

Abstract

Owing to the requirements for high performance and long life, the friction and wear problems of rolling piston type rotary compressors have drawn much attention. Various theoretical models have been developed and improved to reveal the inner state of the compressor and obtain [...] Read more.

Owing to the requirements for high performance and long life, the friction and wear problems of rolling piston type rotary compressors have drawn much attention. Various theoretical models have been developed and improved to reveal the inner state of the compressor and obtain the optimization schemes. However, there remain some disadvantages and research gaps in the corresponding modeling and mixed lubrication analyses, and a comprehensive summary is lacking. To have a better understanding of the research status, this paper reviews the theoretical model development and mixed lubrication analyses of the compressor in the past decades. The determination of compression pressure, the modeling process of moving components, and the key findings are presented in detail. On this basis, some important influencing factors and the problems remaining to be solved are also discussed. This paper provides multifaceted guidance for manufacturers and researchers to conduct further theoretical analysis and optimal design. Full article

(This article belongs to the Special Issue Comprehensive Progress in Mixed Lubrication)

► Show Figures

Figure 1

17 pages, 17800 KiB

Open AccessArticle

Triboelectric Performance of Ionic Liquid, Synthetic, and Vegetable Oil-Based Polytetrafluoroethylene (PTFE) Greases

by Nur Aisya Affrina Mohamed Ariffin, Chiew Tin Lee, Arunkumar Thirugnanasambandam, King Jye Wong and William Woei Fong Chong

Lubricants 2024, 12(8), 272; https://doi.org/10.3390/lubricants12080272 - 30 Jul 2024

Viewed by 606

Abstract

Within electrical contacts, poor electrical conductivity of lubricants can lead to triboelectric charging, causing electrostatic currents and thermal effects, which accelerate lubrication failure. This study aimed to address these challenges by producing and testing three greases with different base oils: ionic liquid ([Oley][Oleic]), [...] Read more.

Within electrical contacts, poor electrical conductivity of lubricants can lead to triboelectric charging, causing electrostatic currents and thermal effects, which accelerate lubrication failure. This study aimed to address these challenges by producing and testing three greases with different base oils: ionic liquid ([Oley][Oleic]), synthetic oil (PAO4), and vegetable oil-based synthetic ester (trimethylolpropane oleate). Each grease was prepared with polytetrafluoroethylene powder as the thickener. The greases were tested using a custom-made tribometer, integrated with a grounded electrical current system, with friction tests conducted with up to a 2 A electrical current flow at a constant voltage supply of 4.5 V. Under triboelectric friction testing, [Oley][Oleic] grease outperformed a commercial perfluoropolyether grease by 27.7% in friction and 16.3% in wear. This grease also showed better performance than formulated lithium grease with extreme pressure additives. The study demonstrates that greases with low interfacial resistance can retain their lubrication capacity under triboelectric conditions. These results indicate that [Oley][Oleic] grease, with its ionic liquid base oil, offers a promising solution for applications involving electrical contacts. This study highlights the potential of using advanced base oils and thickeners to enhance the performance and sustainability of lubricants in demanding environments. Full article

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

► Show Figures

Figure 1

12 pages, 7734 KiB

Open AccessArticle

Investigation of Failure Mechanisms in Oil-Lubricated Rolling Bearings under Small Oscillating Movements: Experimental Results, Analysis and Comparison with Theoretical Models

by Fabian Halmos, Sandro Wartzack and Marcel Bartz

Lubricants 2024, 12(8), 271; https://doi.org/10.3390/lubricants12080271 - 29 Jul 2024

Viewed by 594

Abstract

Bearing life calculation is a well-researched and standardized topic for rotating operation conditions. However, there is still no validated and standardized calculation for oscillating operation, only different calculation approaches. Due to the increasing number of oscillating rolling bearings, for example, in wind turbines, [...] Read more.

Bearing life calculation is a well-researched and standardized topic for rotating operation conditions. However, there is still no validated and standardized calculation for oscillating operation, only different calculation approaches. Due to the increasing number of oscillating rolling bearings, for example, in wind turbines, industrial robots, or 3D printers, it is becoming more and more important to validate one of these approaches or to formulate a new one. In order to achieve this goal, the damage mechanisms for oscillating operating conditions must first be analyzed in more detail by means of experimental investigations. The open question is whether fatigue is the relevant damage mechanism or whether wear damage, such as fretting corrosion or false brinelling, dominates. The present work therefore shows under which oscillation angle and frequency fatigue occur in oil-lubricated cylindrical roller bearings. Full article

(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)

► Show Figures

Figure 1

20 pages, 8410 KiB

Open AccessArticle

A Study on the Lubrication Characteristics and Parameter Influence of a High-Speed Train Herringbone Gearbox

by Shuai Shao, Kailin Zhang, Yuan Yao, Yi Liu, Jieren Yang, Zhuangzhuang Xin and Kuangzhou He

Lubricants 2024, 12(8), 270; https://doi.org/10.3390/lubricants12080270 - 29 Jul 2024

Viewed by 547

Abstract

To investigate the lubrication characteristics in high-speed train gearboxes, a two-stage herringbone gearbox with an idle gear was analyzed. The lubricant flow and distribution were shown using the moving particle semi-implicit (MPS) method. A liquid film flow model was brought in to enhance [...] Read more.

To investigate the lubrication characteristics in high-speed train gearboxes, a two-stage herringbone gearbox with an idle gear was analyzed. The lubricant flow and distribution were shown using the moving particle semi-implicit (MPS) method. A liquid film flow model was brought in to enhance the non-slip wall boundary conditions, enabling MPS to predict the film flow characteristics. This study investigates the influence of gear rotating speed, lubricant volume, and temperature on lubricant flow, liquid film distribution, lubrication state in the meshing zone, and churning power loss. The results indicate that lubrication characteristics depend on the splashing effect of rotating gears and lubricant fluidity. Increasing gear rotating speed and lubricant temperature can improve liquid film distribution on the inner wall, increase lubricant volume, and thus enhance film thickness. The lubricant particles in the meshing zone correlate positively with the gear rotating speed and lubricant volume, correlate negatively with a temperature above 20 °C, and decrease notably at low temperatures. Churning power loss mainly comes from the output gear. As lubricant volume and gear rotating speed increase, churning torque and power loss increase. Above 20 °C, viscosity decreases, reducing power loss; low temperatures lessen lubricant fluidity, reducing churning power loss. Full article

(This article belongs to the Special Issue Friction–Vibration Interactions)

► Show Figures

Figure 1

16 pages, 10351 KiB

Open AccessArticle

An Investigation of the Output Performances of a Triboelectric Nanogenerator Lubricated with TiO₂-Doped Oleic Acid

by Jiaqi Shao, Guoyan Yu, Yixing He, Jun Li, Mingxing Hou, Xianmin Wang, Ping Zhang and Xianzhang Wang

Lubricants 2024, 12(8), 269; https://doi.org/10.3390/lubricants12080269 - 29 Jul 2024

Viewed by 541

Abstract

In the past decade, triboelectric nanogenerators (TENGs) have attracted significant attention across various fields due to their compact size, light weight, high output voltage, versatile shapes, and strong compatibility. However, substantial wear at solid–solid contact interfaces presents a major obstacle to the electrical [...] Read more.

In the past decade, triboelectric nanogenerators (TENGs) have attracted significant attention across various fields due to their compact size, light weight, high output voltage, versatile shapes, and strong compatibility. However, substantial wear at solid–solid contact interfaces presents a major obstacle to the electrical output stability of TENGs. The objective of this study is to investigate the output performances of TENGs lubricated with TiO₂-doped oleic acid. The results suggest that the triboelectrical performances of the polyimide (PI) film sliding against a steel ball under 0.1 wt% TiO₂-doped oleic acid are significantly improved compared to those under dry conditions; the growth rates are 35.2%, 103.6, and 85.6%, respectively. Moreover, the coefficient of friction dropped from 0.31 to 0.066. The wear and performance enhancement mechanism are also analyzed. This study provides an effective approach to improve both the electrical performances and tribological behaviors. Full article

► Show Figures

Figure 1

16 pages, 10786 KiB

Open AccessArticle

Exploring the Boundaries of Electrically Induced Bearing Damage in Grease-Lubricated Rolling Contacts

by Jack R. Janik, Sudip Saha, Robert L. Jackson and German Mills

Lubricants 2024, 12(8), 268; https://doi.org/10.3390/lubricants12080268 - 28 Jul 2024

Viewed by 1533

Abstract

As public attention is increasingly drawn toward more sustainable transportation methods, the popularity of electric vehicles (EVs) as part of the solution is rapidly expanding. Operating conditions within EVs can be severe compared to standard combustion powertrains, and the risk of electrical arcing [...] Read more.

As public attention is increasingly drawn toward more sustainable transportation methods, the popularity of electric vehicles (EVs) as part of the solution is rapidly expanding. Operating conditions within EVs can be severe compared to standard combustion powertrains, and the risk of electrical arcing across mechanical surfaces from electric leakage currents incites additional concern. This study employed a series of electro-tribological tests utilizing various moving patterns to improve understanding of the driving conditions for electrically induced bearing damage (EIBD). Rolling ball-on-disk tests were performed with different polyurea-thickened greases. Rotational tests were initially run at various speeds and test durations, but electrical damage was limited. However, electrical damage was unmistakable when a reciprocating motion was used at different track lengths and speeds. These results suggest that the conditions associated with the track length, such as the number of directional changes and speed-dependent film thickness, play a considerable role in forming electrical damage. This work provides critical insights into the mechanisms of EIBD in EVs and other electrical systems. It highlights the importance of understanding the operational conditions that contribute to EIBD, which can lead to improved designs and maintenance practices, ultimately enhancing the efficiency and lifespan of these systems. Full article

(This article belongs to the Special Issue Tribology of Electric Vehicles)

► Show Figures

Graphical abstract

12 pages, 8053 KiB

Open AccessArticle

Improved Tribological Properties of Epoxy Cement Reinforced with Impact-Resistant Core-Shell Structured Polymer Nanoparticles

by Ling Qiu, Yuan Wang, Xiaolan Kong, Yanan Li, Shiyu Cao, Wenbin Hu, Gangqiang Zhang and Chenchen Wang

Lubricants 2024, 12(8), 267; https://doi.org/10.3390/lubricants12080267 - 27 Jul 2024

Viewed by 847

Abstract

Traditional cement epoxy pavements suffer from inherent limitations such as terrible tribological properties, poor wear resistance, and weak impact resistance, presenting significant challenges to ensure the safety and continuous operation of urban roads. As a solution, high-performance cement epoxy composite grouting materials have [...] Read more.

Traditional cement epoxy pavements suffer from inherent limitations such as terrible tribological properties, poor wear resistance, and weak impact resistance, presenting significant challenges to ensure the safety and continuous operation of urban roads. As a solution, high-performance cement epoxy composite grouting materials have emerged as the preferred option for engineering construction and road maintenance. In this study, CSP/epoxy cement (CSEC) composite materials were prepared by emulsion polymerization. The thermal properties of the materials were characterized, revealing that CSP enhances the thermal properties of epoxy cement (EC) to a certain extent. Furthermore, the frictional properties of CSEC composite materials and pure epoxy cement under different normal loads were investigated. The results indicated that the CSEC composite material exhibited a slight increase in friction coefficient and a notable decrease in wear rate compared to pure epoxy cement (EC). Specifically, the wear rate of CSEC decreased by 14.4% at a load of 20 N, highlighting the enhanced frictional performance facilitated by CSP. Mechanistic analysis attributed the improvement to the unique core-shell structure of CSP, which imparted higher impact resistance and eliminated alleviate residual stresses at the friction interface. This structural advantage further enhanced the wear resistance of materials, making it a promising choice for improving the durability and safety of urban road surfaces. Full article

(This article belongs to the Special Issue Tribology of Nanocomposites 2024)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Lubricants, Volume 12, Issue 8 (August 2024) – 34 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI