Lubricants

20 pages, 12180 KiB

Open AccessArticle

Computer Vision-Based Research on the Mechanism of Stick–Slip Vibration Suppression and Wear Reduction in Water-Lubricated Rubber Bearing by Surface Texture

by Anbang Zhu, Ao Ji, Longyang Sheng, Dequan Zhu, Quan Zheng, Xincong Zhou, Jun Wang and Fuming Kuang

Lubricants 2024, 12(11), 402; https://doi.org/10.3390/lubricants12110402 - 20 Nov 2024

Viewed by 212

Abstract

Water-lubricated rubber bearings are a critical component of the propulsion systems in underwater vehicles. Particularly under conditions of low speed and high load, friction-induced vibration and wear often occur. Surface texturing technology has been proven to improve lubrication performance and reduce friction and [...] Read more.

Water-lubricated rubber bearings are a critical component of the propulsion systems in underwater vehicles. Particularly under conditions of low speed and high load, friction-induced vibration and wear often occur. Surface texturing technology has been proven to improve lubrication performance and reduce friction and wear; however, research on how different texture parameters affect friction-induced vibration and wear mechanisms remains insufficient. In this study, various texture patterns with different area ratios and aspect ratios were designed on the surface of water-lubricated rubber bearings. By combining these designs with an in situ observation system based on computer vision technology, the effects of texture parameters on bearing friction, vibration, and wear were thoroughly investigated. The experimental results show that surface textures play a critical role in improving hydrodynamic effects and stabilizing the lubrication film at the friction interface. Specifically, textures with a high area ratio (15%) and aspect ratio (3:1) exhibited the best vibration suppression effect, primarily due to the reduction in actual contact area. However, excessively high area ratios may lead to increased surface wear. This study concludes that a reasonable selection of texture area and aspect ratios can significantly reduce frictional force fluctuations and vibration amplitude, minimize surface wear, and extend bearing life. Full article

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29 pages, 4541 KiB

Open AccessArticle

Impact of Soot on Internal Combustion Engine Lubrication—Oil Condition Monitoring, Tribological Properties, and Surface Chemistry

by Adam Agocs, Marcella Frauscher, Andjelka Ristic and Nicole Dörr

Lubricants 2024, 12(11), 401; https://doi.org/10.3390/lubricants12110401 - 20 Nov 2024

Viewed by 224

Abstract

In the study at hand, a systemic investigation regarding the tribochemical effects of crankcase soot is presented. Sooted oils were generated via an engine dynamometer test. Both conventional as well as advanced oil condition monitoring methods indicated a mild degradation of additives. The [...] Read more.

In the study at hand, a systemic investigation regarding the tribochemical effects of crankcase soot is presented. Sooted oils were generated via an engine dynamometer test. Both conventional as well as advanced oil condition monitoring methods indicated a mild degradation of additives. The wear volume was greatly increased with the sooted oils in model tribometer tests, despite the high residual zinc dialkyl dithiophosphate (ZDDP) antiwear (AW) levels. Once the soot was removed via ultracentrifugation, the wear volume returned to levels comparable to the fresh oil. Surface investigations revealed that ZDDP tribofilms could not form in the sooted oils, as only a thin sulfide layer was present on the metal surfaces. Meanwhile, typical tribofilms were observable with centrifuged oils. The results indicated that a tribocorrosive mechanism is most likely responsible for the elevated wear in the sooted oils, where only the iron sulfide base layer of ZDDP films is formed, which is then rapidly removed by the soot particles in an abrasive manner. Full article

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

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23 pages, 10749 KiB

Open AccessArticle

Impact of Biosynthesized CeO₂ Nanoparticle Concentration on the Tribological, Rheological, and Thermal Performance of Lubricating Oil

by Siraj Azam and Sang-Shin Park

Lubricants 2024, 12(11), 400; https://doi.org/10.3390/lubricants12110400 - 20 Nov 2024

Viewed by 227

Abstract

This study presents an approach to enhance the performance of lubricating oils through the environmentally friendly synthesis of cerium oxide (CeO₂) nanoparticles using Moringa oleifera leaf extract. These biosynthesized nanoparticles were thoroughly characterized for their structural and thermal stability by utilizing [...] Read more.

This study presents an approach to enhance the performance of lubricating oils through the environmentally friendly synthesis of cerium oxide (CeO₂) nanoparticles using Moringa oleifera leaf extract. These biosynthesized nanoparticles were thoroughly characterized for their structural and thermal stability by utilizing X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The CeO₂ nanolubricants, prepared at various concentrations, displayed significant improvements in viscosity, stability, and thermal conductivity. Specifically, the 0.15 wt% concentration achieved the best performance, reducing viscosity to 9.79 pascal-second (Pa·s) at 80 °C while exhibiting excellent dispersion and minimal sedimentation over time. The thermal conductivity tests revealed a notable 43% increase in heat transfer efficiency at higher nanoparticle concentrations. Tribological tests conducted using a tribometer demonstrated significant improvements in the lubrication properties. The nanolubricant with a 0.15 wt% concentration of CeO₂ nanoparticles achieved the lowest friction coefficient, showing an approximate 26% reduction compared to the base oil, along with a notable decrease in wear rate. This study demonstrates the potential of biosynthesized CeO₂ nanoparticles as effective, sustainable additives in lubricating oils, providing improved thermal, rheological, and tribological properties and marking a significant step toward eco-friendly lubrication solutions. Full article

(This article belongs to the Special Issue Thermophysical and Tribological Characterization of Additivated Lubricants with Nanoparticles)

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15 pages, 5443 KiB

Open AccessArticle

Carbonaceous Decomposition Products at High Temperatures and Their Interfacial Role in the Friction Behaviour of Composite Brake Material

by Piyush Chandra Verma, Pranesh Aswath, Giovanni Straffelini and Stefano Gialanella

Lubricants 2024, 12(11), 399; https://doi.org/10.3390/lubricants12110399 - 20 Nov 2024

Viewed by 306

Abstract

This study aims to investigate the outcomes of carbonaceous products, derived from the decomposition of the components of vehicular brake materials, under high-temperature wear tests. Pin-on-disc (PoD) wear tests were conducted by using cast iron discs against pins made of commercially available low-steel [...] Read more.

This study aims to investigate the outcomes of carbonaceous products, derived from the decomposition of the components of vehicular brake materials, under high-temperature wear tests. Pin-on-disc (PoD) wear tests were conducted by using cast iron discs against pins made of commercially available low-steel friction material. Tests were carried out at different temperatures: 155 °C, 200 °C, 250 °C, and 300 °C. The characterization of the sliding plateaus on worn pin surfaces was based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. It was noted that at temperatures above 200 °C, the thermal degradation of the inorganic resin, used as a material binder, occurs. An interesting observation was recorded at 300 °C; the brake pin material’s friction curve showed higher stability despite having an excessive wear rate. However, the brake pin’s specific wear coefficient was higher at this temperature than was observed in the other friction tests. A detailed study of the friction plateaus on the worn-out pins at 300 °C revealed that the decomposed carbon resin product, i.e., the distorted graphite, was widespread over the surface of the pin. Lubricant stabilization can be expected, as established by the observed values of the coefficient of friction (CoF), retaining values within the 0.4–0.6 range, even at high temperatures. Other friction material components may have contributed to the formation of this ubiquitous carbonaceous interface film. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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14 pages, 7007 KiB

Open AccessArticle

Transformation from D0₂₂ to L1₂ in Al₃Ti by Fe Addition for Enhanced Wear Resistance

by Guijiang Diao, Junfeng Yuan, Anqiang He, Dong Zhang, Aakash Kumar, Ranran Fang, Anatoliy Vorobyev, Wengang Chen and Dongyang Li

Lubricants 2024, 12(11), 398; https://doi.org/10.3390/lubricants12110398 - 19 Nov 2024

Viewed by 370

Abstract

The addition of third elements may help transform brittle D0₂₂-structured lightweight Al₃Ti to a relatively ductile L1₂-structured (Al, M)₃Ti (where M represents the third elements), thus increasing the ductility at the expense of hardness. Such [...] Read more.

The addition of third elements may help transform brittle D0₂₂-structured lightweight Al₃Ti to a relatively ductile L1₂-structured (Al, M)₃Ti (where M represents the third elements), thus increasing the ductility at the expense of hardness. Such a transformation could benefit the wear resistance of the alloy due to improved toughness if a proper balance between the hardness and ductility is achieved. In this work, a D0₂₂-predominant Al₃Ti alloy (S-Al₃Ti) and an L1₂-predominant (Al, Fe)₃Ti alloy (S-Al₆₇Ti₂₅Fe₈) were fabricated by arc melting. Change in wear resistance, corresponding to a D0₂₂-to-L1₂ transformation, caused by the addition of Fe as a representative third element, was investigated and compared with the wear resistance of a commercial Al-matrix composite reinforced by 30 wt.% SiC particles (S-Al/SiC_p) as a reference material. It was observed that wear of the S-Al₃Ti resulted from abrasion involving synergistic oxidation, leading to a larger volume loss. In contrast, the softer S-Al₆₇Ti₂₅Fe₈ showed enhanced wear resistance, benefiting from improved toughness with reasonable hardness. During the wear testing, both the alloys exhibited better performance than S-Al/SiC_p, a well-known lightweight composite. This study highlights that D0₂₂-to-L1₂ transformation enhances wear resistance due to increased toughness which can be adjusted using the addition of a third element. Full article

(This article belongs to the Special Issue Friction and Wear of Alloys)

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14 pages, 12314 KiB

Open AccessArticle

Lubrication Characteristics of a Warhead-Type Irregular Symmetric Texture on the Stator Rubber Surfaces of Screw Pumps

by Xinfu Liu, Yi Sun, Chunhua Liu, Xiangzhi Shi, Xinglong Niu, Gang Zheng, Wei Wei, Songbo Wei and Shouzhi Huang

Lubricants 2024, 12(11), 397; https://doi.org/10.3390/lubricants12110397 - 19 Nov 2024

Viewed by 325

Abstract

A theoretical model for the micro-texture on the inner wall of the stator rubber in screw pumps was developed. The finite element analysis method was employed. The pressure and streamline distributions for warhead-type, concentric circle-type, and multilayer rectangular-type textured surfaces were calculated. The [...] Read more.

A theoretical model for the micro-texture on the inner wall of the stator rubber in screw pumps was developed. The finite element analysis method was employed. The pressure and streamline distributions for warhead-type, concentric circle-type, and multilayer rectangular-type textured surfaces were calculated. The effects of textured morphology, groove depth, groove width, and other parameters on the lubrication field were systematically investigated and analyzed. A nanosecond laser was employed to process the textured rubber surface of the stator in the screw pump. Subsequently, a micro-texture friction performance test was conducted on the rubber surface of the stator in actual complex well fluids from shale oil wells. Given the results of the simulation analysis and experimental tests, the lubrication characteristics of textured rubber surfaces with varying texture morphologies, rotational speeds, and mating loads were revealed. Furthermore, it indicated that the irregular symmetric warhead-type micro-texture exhibited excellent dynamic pressure lubrication performance compared with concentric circle-type and multilayer rectangular-type textures. The irregular symmetry enhanced the dynamic pressure lubrication effect, enhanced the additional net load-bearing capacity of the oil film surface, and reduced friction. As the groove depth increased, the volume and number of vortices within the groove also increased. The fluid kinetic energy was transformed into vortex energy, leading to a reduction in wall stress on the surface of the oil film, thereby affecting its bearing capacity. Initially, the maximum pressure on the wall surface of the oil film increased and then decreased. The optimal dynamic pressure lubrication effect was achieved with a warhead-type texture size of 3 mm, a groove width of 0.2 mm, and a groove depth of 0.1 mm. Well-designed texture morphology and depth parameters significantly enhanced the oil film-bearing capacity of the stator rubber surface, improving the dynamic pressure lubrication effect, and consequently extending the service life of the stator–rotor interface in the screw pump. Full article

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

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14 pages, 49185 KiB

Open AccessArticle

Investigating Influence of Mo Elements on Friction and Wear Performance of Nickel Alloy Matrix Composites in Air from 25 to 800 °C

by Jinming Zhen, Yunxiang Han, Lin Yuan, Zhengfeng Jia and Ran Zhang

Lubricants 2024, 12(11), 396; https://doi.org/10.3390/lubricants12110396 - 18 Nov 2024

Viewed by 401

Abstract

Rapid developments in aerospace and nuclear industries pushed forward the search for high-performance self-lubricating materials with low friction and wear characteristics under severe environment. In this paper, we investigated the influence of the Mo element on the tribological performance of nickel alloy matrix [...] Read more.

Rapid developments in aerospace and nuclear industries pushed forward the search for high-performance self-lubricating materials with low friction and wear characteristics under severe environment. In this paper, we investigated the influence of the Mo element on the tribological performance of nickel alloy matrix composites from room temperature to 800 °C under atmospheric conditions. The results demonstrated that composites exhibited excellent lubricating (with low friction coefficients of 0.19–0.37) and wear resistance properties (with low wear rates of 2.5–28.1 × 10⁻⁵ mm³/Nm), especially at a content of elemental Mo of 8 wt. % and 12 wt. %. The presence of soft metal Ag on the sliding surface as solid lubricant resulted in low friction and wear rate in a temperature range from 25 to 400 °C, while at elevated temperatures (600 and 800 °C), the effective lubricant contributed to the formation of a glazed layer rich in NiCr₂O₄, BaF₂/CaF₂, and Ag₂MoO₄. SEM, EDS, and the Raman spectrum indicated that abrasive and fatigue wear were the main wear mechanisms for the studied composites during sliding against the Si₃N₄ ceramic ball. The obtained results provide an insightful suggestion for future designing and fabricating solid lubricant composites with low friction and wear properties. Full article

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

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17 pages, 14618 KiB

Open AccessArticle

Analysis of the Influencing Factors of Aerostatic Bearings on Pneumatic Hammering

by Yifei Li, Weiping Huang and Ran Sang

Lubricants 2024, 12(11), 395; https://doi.org/10.3390/lubricants12110395 - 16 Nov 2024

Viewed by 468

Abstract

In this study, in order to reveal the influence mechanism of bearing parameters on pneumatic hammering, an aerostatic bearing with a multi-orifice-type restrictor is analyzed. Firstly, the flow field is investigated, and the vortex-induced excitation is discussed in both the frequency and time [...] Read more.

In this study, in order to reveal the influence mechanism of bearing parameters on pneumatic hammering, an aerostatic bearing with a multi-orifice-type restrictor is analyzed. Firstly, the flow field is investigated, and the vortex-induced excitation is discussed in both the frequency and time domains. Then, the frequency-related displacement impedance is analyzed, and the effects of vortex-induced excitation on pneumatic hammering are discussed. Experiments are also conducted for verification. Moreover, the influence of damping on pneumatic hammering is identified. The results show that with larger damping, the risk of pneumatic hammering can be reduced. Finally, the impacts of design parameters on the damping are discussed in detail using an approximate model. Design optimization is considered to achieve the maximum damping, i.e., the minimum risk of pneumatic hammering. The results show that both the air supply pressure and the pocket volume should be minimized. The analysis process provides a reference for the design of bearings to reduce pneumatic hammering. Full article

(This article belongs to the Special Issue Gas Lubricated Bearings)

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22 pages, 15270 KiB

Open AccessArticle

Modeling Inertia-Driven Oil Transport Inside the Three-Piece Oil Control Ring of Internal Combustion Engines

by Tsung-Yu Yang, Mo Li and Tian Tian

Lubricants 2024, 12(11), 394; https://doi.org/10.3390/lubricants12110394 - 16 Nov 2024

Viewed by 436

Abstract

The three-piece oil control ring (TPOCR), traditionally used in light-duty gasoline engines, is becoming a viable option for heavy-duty gas and hydrogen engines due to its ability to control lubricating oil consumption (LOC) under throttled conditions. Understanding the distribution of oil inside the [...] Read more.

The three-piece oil control ring (TPOCR), traditionally used in light-duty gasoline engines, is becoming a viable option for heavy-duty gas and hydrogen engines due to its ability to control lubricating oil consumption (LOC) under throttled conditions. Understanding the distribution of oil inside the TPOCR groove, as well as the effects of rail gap and drain hole positions, is critical for optimizing TPOCR and groove designs. In this work, a one-dimensional oil distribution model was developed to simulate inertia-driven oil transport in the TPOCR groove. A novel approach was proposed by first dividing the TPOCR into units composed of a pair of expander pitches. Then, the relationship between the oil outflow rate of the unit and its oil mass was established with the help of three-dimensional two-phase computational fluid dynamics (CFD) simulations. This relationship was then used to model one-dimensional oil transport along the circumference of the TPOCR groove. Incorporating the boundary conditions at the rail gaps and drain holes, this simple model can complete computations for 10,000 cycles within a few seconds, allowing for quick the evaluation of transient behavior and design iterations. Studies on low-load conditions show that the model, with reasonable adjustment for the boundary conditions, can match the oil distribution patterns observed in visualization experiments. This is the first step toward studying oil transport in the TPOCR groove before involving the effects of gas flows. Full article

(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)

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22 pages, 7710 KiB

Open AccessArticle

Investigation of the Effect of Al₂O₃ Nanoparticle-Added MQL Lubricant on Sustainable and Clean Manufacturing

by Fuat Kara

Lubricants 2024, 12(11), 393; https://doi.org/10.3390/lubricants12110393 - 15 Nov 2024

Viewed by 448

Abstract

In this study, in order to improve the characteristics of the vegetable-based cutting fluids used in the MQL technique and increase the machining performance of MQL and its positive effects on sustainable manufacturing, the effects of the MQL method with nano-Al₂O [...] Read more.

In this study, in order to improve the characteristics of the vegetable-based cutting fluids used in the MQL technique and increase the machining performance of MQL and its positive effects on sustainable manufacturing, the effects of the MQL method with nano-Al₂O₃ additives on surface roughness (Ra) and cutting temperature (Ctt) were examined through turning experiments carried out by adding nano-Al₂O₃ to the vegetable-based cutting fluid. For this purpose, machining tests were carried out on hot work tool steel alloyed with Cr-Ni-Mo that has a delivery hardness of 45 HRC. In hard machining experiments, three techniques for cooling and lubricating (dry cutting, MQL, and nano-MQL), three cutting speeds (V) (100, 130, 160 m/min), three feed rates (f) (0.10, 0.125, and 0.15 mm/rev), and two different ceramic cutting tools (uncoated and TiN-coated with PVD methods) were used as control factors. For Ra, the nano-MQL method provided an average of 21.49% improvement compared to other cooling methods. For Ctt, this rate increased to 26.7%. In crater wear areas, the nano-MQL method again exhibited the lowest wear values, decreasing performance by approximately 50%. The results of this research showed that the tests conducted using the cooling of nano-MQL approach produced the best results for all output metrics (Ra, Ctt, and crater wear). Full article

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15 pages, 5813 KiB

Open AccessArticle

Effect of Pressure on the Microstructure and Wear Performance of Cr-Mn-Mo Alloyed Steel Prepared by Squeeze Casting

by Yuan Zhuang, Yujiang Hao, Lei Guo and Xinhao Wu

Lubricants 2024, 12(11), 392; https://doi.org/10.3390/lubricants12110392 - 14 Nov 2024

Viewed by 419

Abstract

In this study, the effects of applied pressure (0, 90, 120, and 150 MPa) during solidification on the microstructure, mechanical properties, and impact–abrasive wear resistance of Cr-Mn-Mo steel prepared by squeeze casting were systematically investigated. The results demonstrated that the materials produced under [...] Read more.

In this study, the effects of applied pressure (0, 90, 120, and 150 MPa) during solidification on the microstructure, mechanical properties, and impact–abrasive wear resistance of Cr-Mn-Mo steel prepared by squeeze casting were systematically investigated. The results demonstrated that the materials produced under pressure showed smaller grains compared to those of the samples fabricated without pressure. Compared to the unpressurized sample, the grain diameter of the sample prepared at 120 MPa decreased by 37.7%, the length of the primary arm shortened by 40.7%, and the spacing of the secondary arm contracted by 14.1%. Furthermore, the impact toughness results indicated that the samples prepared without pressure exhibited brittle fracture characteristics, whereas quasi-destructive fractures predominated in the samples prepared at 120 MPa. Simultaneously, three-point bending strength exhibited a gradual increase with increasing pressure, reaching a maximum value of 855.5 MPa when prepared under 150 MPa. Additionally, the impact–abrasive wear resistance of Cr-Mn-Mo alloyed steel produced by squeeze casting was significantly enhanced compared to the samples produced without pressure. The samples without external pressure exhibited a combination of abrasive and adhesive wear, whereas the wear characteristics of the samples prepared under pressure includes grooves, cutting marks, flaking pits, and accumulating ridges. Full article

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26 pages, 14835 KiB

Open AccessArticle

Mechanical and Tribological Properties of (AlCrNbSiTiMo)N High-Entropy Alloy Films Prepared Using Single Multiple-Element Powder Hot-Pressed Sintered Target and Their Practical Application in Nickel-Based Alloy Milling

by Jeng-Haur Horng, Wen-Hsien Kao, Wei-Chen Lin and Ren-Hao Chang

Lubricants 2024, 12(11), 391; https://doi.org/10.3390/lubricants12110391 - 14 Nov 2024

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Abstract

(AlCrNbSiTiMo)N high-entropy alloy films with different nitrogen contents were deposited on tungsten carbide substrates using a radio-frequency magnetron sputtering system. Two different types of targets were used in the sputtering process: a hot-pressing sintered AlCrNbSiTi target fabricated using a single powder containing multiple [...] Read more.

(AlCrNbSiTiMo)N high-entropy alloy films with different nitrogen contents were deposited on tungsten carbide substrates using a radio-frequency magnetron sputtering system. Two different types of targets were used in the sputtering process: a hot-pressing sintered AlCrNbSiTi target fabricated using a single powder containing multiple elements and a vacuum arc melting Mo target. The deposited films were denoted as R_N0, R_N33, R_N43, R_N50, and R_N56, where R_N indicates the nitrogen flow ratio relative to the total nitrogen and argon flow rate (R_N = (N₂/(N₂ + Ar)) × 100%). The as-sputtered films were vacuum annealed, with the resulting films denoted as HR_N0, HR_N33, HR_N43, HR_N50, and HR_N56, respectively. The effects of the nitrogen content on the composition, microstructure, mechanical properties, and tribological properties of the films, in both as-sputtered and annealed states, underwent thorough analysis. The R_N0 and R_N33 films displayed non-crystalline structures. However, with an increase in nitrogen content, the R_N43, R_N50, and R_N56 films transitioned to FCC structures. Among the as-deposited films, the R_N43 film exhibited the best mechanical and tribological properties. All of the annealed films, except for the HR_N0 film, displayed an FCC structure. In addition, they all formed an MoO₃ solid lubricating phase, which reduced the coefficient of friction and improved the anti-wear performance. The heat treatment HR_N43 film displayed the supreme hardness, H/E ratio, and adhesion strength. It also demonstrated excellent thermal stability and the best wear resistance. As a result, in milling tests on Inconel 718, the R_N43-coated tool demonstrated a significantly lower flank wear and notch wear, indicating an improved machining performance and extended tool life. Thus, the application of the R_N43 film in aerospace manufacturing can effectively reduce the tool replacement cost. Full article

(This article belongs to the Special Issue Recent Advances in Tribological Properties of Machine Tools)

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17 pages, 9296 KiB

Open AccessArticle

Influence of Oil Injection Lubrication Parameters of High-Speed Internal Meshing Gear Based on the Computational Fluid Dynamics

by Peixun Tang, Zhengminqing Li, Xiangying Hou, Letian Li, Rongsheng Xi and Yiyan Chen

Lubricants 2024, 12(11), 390; https://doi.org/10.3390/lubricants12110390 - 13 Nov 2024

Viewed by 508

Abstract

High-speed gears are crucial transmission components found in airplanes and other systems, and they are maintained primarily through oil injection. However, due to their high operating speeds and the influence of oil injection settings, gear surface lubrication efficacy is frequently insufficient, compromising the [...] Read more.

High-speed gears are crucial transmission components found in airplanes and other systems, and they are maintained primarily through oil injection. However, due to their high operating speeds and the influence of oil injection settings, gear surface lubrication efficacy is frequently insufficient, compromising the transmission system’s precision, durability, and safety. Currently, the parameter choices for oil injection in high-speed gears mostly rely on empirical judgment, which results in significant time and resource expenses. This study focuses on one pair of internal meshing gears within a specific aircraft gearbox, establishing an oil injection lubrication model for high-speed internal meshing gears using the computational fluid dynamics (CFD) approach. This research provides insights and references for optimizing oil injection parameters and improving lubrication efficiency in high-speed internal meshing gear systems by examining the dynamic characteristics of internal meshing wind resistance in addition to the effects of injection tube position, angle, and speed on lubrication performance. Full article

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25 pages, 6251 KiB

Open AccessArticle

Effect of Variation in Viscosity on Static and Dynamic Characteristics of Rough Porous Journal Bearings with Micropolar Fluid Squeeze Film Lubrication

by Neminath Bhujappa Naduvinamani and Bhagyashri Kotreppa Koppa

Lubricants 2024, 12(11), 389; https://doi.org/10.3390/lubricants12110389 - 13 Nov 2024

Viewed by 484

Abstract

In the present study, an effort was made to determine the effects of a porous matrix with different viscosities on the dynamic and static behaviors of rough short journal bearings taking into account the action of a squeezing film under varying loads without [...] Read more.

In the present study, an effort was made to determine the effects of a porous matrix with different viscosities on the dynamic and static behaviors of rough short journal bearings taking into account the action of a squeezing film under varying loads without journal rotation. The micropolar fluid was regarded as a lubricant that contained microstructure additives in both the porous region and the film region. By applying Darcy’s law for micropolar fluids through a porous matrix and stochastic theory related to uneven surfaces, a standardized Reynolds-type equation was extrapolated. Two scenarios with a stable and an alternating applied load were analyzed. The impacts of variations in viscosity, the porous medium, and roughness on a short journal bearing were examined. We inspected the dynamic and static behaviors of the journal bearing. We found that the velocity of the journal center with a micropolar fluid decreased when there was a cyclic load, and the impact of variations in the viscosity and porous matrix diminished the load capacity and pressure in the squeeze film and increased the velocity of the journal center. Full article

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17 pages, 16140 KiB

Open AccessArticle

An Investigation on the High-Temperature Stability and Tribological Properties of Impregnated Graphite

by Juying Zhao, Qi Xin, Yunshuang Pang, Xiao Ning, Lingcheng Kong, Guangyang Hu, Ying Liu, Haosheng Chen and Yongjian Li

Lubricants 2024, 12(11), 388; https://doi.org/10.3390/lubricants12110388 - 13 Nov 2024

Viewed by 436

Abstract

Impregnated graphite is a common material for friction pairs in aeroengine seals, especially at high temperatures. For the convenience of the application of graphite materials in aeroengines, an SRV-4 tribometer and a synchronous thermal analyzer are employed to study the tribological properties and [...] Read more.

Impregnated graphite is a common material for friction pairs in aeroengine seals, especially at high temperatures. For the convenience of the application of graphite materials in aeroengines, an SRV-4 tribometer and a synchronous thermal analyzer are employed to study the tribological properties and thermal stability of pure, resin-impregnated, metal-impregnated, and phosphate-impregnated graphite against stainless steel from room temperature to 500 °C. The results indicate that impregnations can improve the wear resistance and thermal stability of graphite at high temperatures. Compared with other impregnated graphite materials, the resin-impregnated graphite shows a good friction coefficient and poor wear rate and thermal stability over 300 °C, due to the degradation and oxidation of the resin-and-graphite matrix. The metal- and phosphate-impregnated graphite materials exhibit excellent wear resistance and thermal stability under 500 °C as a result of the protection of the impregnations, while the average friction coefficient of the metal-impregnated graphite is much greater than the phosphate-impregnated graphite, and even reaches 2.14-fold at 300 °C. The wear rates for the graphite impregnated with resin, metal, and phosphate are 235 × 10⁻⁷, 7 × 10⁻⁷, and 16 × 10⁻⁷ mm³N⁻¹m⁻¹ at 500 °C, respectively. Considering all aspects, the phosphate-impregnated graphite exhibits excellent tribological properties and thermal stability. Full article

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16 pages, 6265 KiB

Open AccessArticle

Effects of Titanate on Brake Wear Particle Emission Using a Brake Material Friction Test Dynamometer

by Emiko Daimon and Yasuhito Ito

Lubricants 2024, 12(11), 387; https://doi.org/10.3390/lubricants12110387 - 12 Nov 2024

Viewed by 504

Abstract

We investigated the effect of lepidocrocite-type layered titanate, which is compounded in brake pads, to reduce brake particle emissions. The dust reduction effect of titanate was evaluated using a small-scale inertial brake material friction test dynamometer. The results suggested that brake particle emissions [...] Read more.

We investigated the effect of lepidocrocite-type layered titanate, which is compounded in brake pads, to reduce brake particle emissions. The dust reduction effect of titanate was evaluated using a small-scale inertial brake material friction test dynamometer. The results suggested that brake particle emissions are related to the microphysical structure of the pad surface, such as the uniformity of the friction film and secondary plateau formation, and that friction materials containing titanate contribute significantly to reducing both particle mass (PM) and particle number (PN) emissions of brake particles in both non-asbestos organic (NAO) and low-steel (LS) pads. In particular, LS pads generally have a problem of having more brake particles than NAO pads, but this study found that brake particles can be significantly reduced by compounding titanate instead of tin sulfide. Full article

(This article belongs to the Special Issue Emission and Transport of Wear Particles)

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24 pages, 10842 KiB

Open AccessArticle

The Influences of Parameters on the Dynamic Characteristics of a Multi-Foil Aerodynamic Journal Bearing with Bump-Backing Foils: Model Predictions

by Yulong Jiang, Qianjing Zhu, Bo Xu, Zhongwen Huang and Dongyan Gao

Lubricants 2024, 12(11), 386; https://doi.org/10.3390/lubricants12110386 - 7 Nov 2024

Viewed by 607

Abstract

In this work, the development and implementation of a dynamic characteristics model for a specific multi-foil aerodynamic journal bearing with bump-backing foils (MFJB) is considered. Based on the previously established static characteristics model, the elastohydrodynamic influence is carefully considered, and the perturbation method [...] Read more.

In this work, the development and implementation of a dynamic characteristics model for a specific multi-foil aerodynamic journal bearing with bump-backing foils (MFJB) is considered. Based on the previously established static characteristics model, the elastohydrodynamic influence is carefully considered, and the perturbation method is adopted, as this model is more effective and computationally efficient. The effects of the operational, structural, and geometric parameters on stiffness and damping coefficients are emphasized. The results show that the eccentricity ratio effects are more intensive when the bearing speed is at a moderately high level, which is no more than approximately 30,000 rpm. The foil thickness has obvious effects on dynamic characteristics, whereas the influence of the elastic modulus is limited. Within the research scope, the eight-foils bearing exhibits a better performance than the four-foils. This paper is designed to provide effective methods and supply theoretical guidance for improving the engineering design and operational stability of bearings. Full article

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23 pages, 17020 KiB

Open AccessArticle

A Computational Fluid Dynamics-Based Study on the Effect of Bionic-Compound Recess Structures in Aerostatic Thrust Bearings

by Fangjian Yuan, Hang Xiu, Guohua Cao, Jingran Zhang, Bingshu Chen, Yutang Wang and Xu Zhou

Lubricants 2024, 12(11), 385; https://doi.org/10.3390/lubricants12110385 - 7 Nov 2024

Viewed by 638

Abstract

To investigate the effect of recess structures on the static and dynamic performance of aerostatic thrust bearings and to explore superior designs, this study analyzes the load-capacity theoretical model, identifying that the throttling effect and pressure-holding effect of the recess are the key [...] Read more.

To investigate the effect of recess structures on the static and dynamic performance of aerostatic thrust bearings and to explore superior designs, this study analyzes the load-capacity theoretical model, identifying that the throttling effect and pressure-holding effect of the recess are the key factors determining the bearings’ static performance. Computational fluid dynamics (CFD) was used to evaluate three types of recess structures: a simple-orifice recess (SOR), a rectangular-compound recess (RCR), and a bionic-compound recess (BCR). The results indicate that the BCR structure demonstrates efficient transmission performance by reducing flow resistance and diverting air, while ensuring a reasonable pressure drop as the radial ratio α_i changes. Additionally, the smaller air capacity of the BCR structure contributes to enhanced bearing stability, showing clear advantages in both static and dynamic performance. This research illustrates the practical application of bionics in mechanical design and provides new theoretical foundations and design strategies for improving aerostatic bearing performance. Full article

(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 2nd Edition)

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17 pages, 10275 KiB

Open AccessArticle

Tribological Properties of 7A04 Aluminum Alloy Enhanced by Ceramic Coating

by Xiaobo Meng, Wei Zhang, Shizhong Wei, Kunming Pan, Xiaodong Wang, Tao Jiang, Xiran Wang, Changji Wang, Chong Chen, Feng Mao, Ziping Qiao, Jun Xue and Cheng Zhang

Lubricants 2024, 12(11), 384; https://doi.org/10.3390/lubricants12110384 - 7 Nov 2024

Viewed by 515

Abstract

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS₂ composite coatings, and hard-anodized (HA) [...] Read more.

The 7A04 Al alloy is a commonly used lightweight metal material; however, its low wear resistance limits its application. In this study, the wear resistance of this alloy was improved by preparing micro-arc oxidation (MAO) coatings, MAO/MoS₂ composite coatings, and hard-anodized (HA) coatings on its surface. The friction and wear behaviors of these three coatings with diamond-like coated (DLC) rings under oil lubrication conditions were investigated using a ring–block friction tester. The wear rates of the coatings on the block surfaces were determined using laser confocal microscopy, and the wear trajectories of the coatings were examined using scanning electron microscopy. The results indicated that, among the three coatings, the MAO/MoS₂ coating had the lowest coefficient of friction of 0.059, whereas the HA coating had the lowest wear rate of 1.47 × 10⁻⁶ mm/Nm. The MAO/MoS₂ coatings exhibited excellent antifriction properties compared to the other coatings, whereas the HA coatings exhibited excellent anti-wear properties. The porous structure of the MAO coatings stored lubricant and replenished the lubrication film under oil lubrication. Meanwhile, the introduced MoS₂ enhanced the densification of the coating and functioned as a solid lubricant. The HA coating exhibited good wear resistance owing to the dense structure of the amorphous-phase aluminum oxide. The mechanisms of abrasive and adhesive wear of the coatings under oil lubrication conditions and the optimization of the tribological properties by the solid–liquid synergistic lubrication effect were investigated. This study provides an effective method for the surface modification of Al alloys with potential applications in the aerospace and automotive industries. Full article

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

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17 pages, 2983 KiB

Open AccessArticle

Hard-Anodized Aluminum Alloy: Wear Properties in Vegetable Oils

by Chiara Soffritti, Annalisa Fortini, Enrico Baroni, Mattia Merlin and Gian Luca Garagnani

Lubricants 2024, 12(11), 383; https://doi.org/10.3390/lubricants12110383 - 5 Nov 2024

Viewed by 503

Abstract

The present study examines the tribological behavior of an EN AW-4006 aluminum alloy subjected to two innovative hard anodizing processes involving the sealing of anodic oxide pores with Ag⁺ ions and tested in lubricated conditions. Four plant-based lubricants with different concentrations of [...] Read more.

The present study examines the tribological behavior of an EN AW-4006 aluminum alloy subjected to two innovative hard anodizing processes involving the sealing of anodic oxide pores with Ag⁺ ions and tested in lubricated conditions. Four plant-based lubricants with different concentrations of fatty acids were considered. Wear tests were conducted using a ball-on-disk tribometer, employing a constant frequency oscillatory motion at 2 Hz and a maximum linear speed of 0.1 m/s. The investigation explores the influence of applied loads (5 N, 10 N, and 15 N) on the resulting coefficient of friction. Through a Design of Experiments methodology, the most influential factors affecting the coefficient of friction are identified. The results indicate that hard anodizing processes and applied load affect the coefficient of friction during wear testing as the main factor of influence. High values of the Unsaturation Number led to a high coefficient of friction at 5 N. Wavy-shaped profile tracks were detected at 10 and 15 N, leading to high specific wear rate values and the failure of the anodized layer. Full article

(This article belongs to the Special Issue Friction and Wear of Alloys)

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18 pages, 4747 KiB

Open AccessSystematic Review

Optimizing Railway Tribology: A Systematic Review and Predictive Modeling of Twin-Disc Testing Parameters

by Nicola Zani, Candida Petrogalli and Davide Battini

Lubricants 2024, 12(11), 382; https://doi.org/10.3390/lubricants12110382 - 4 Nov 2024

Viewed by 753

Abstract

Twin-disc testing is crucial for understanding wheel–rail interactions in railway systems, but the vast array of testing parameters and conditions makes data interpretation challenging. This review presents a comprehensive analysis of the twin-disc literature experimental data, focusing on how various parameters influence friction [...] Read more.

Twin-disc testing is crucial for understanding wheel–rail interactions in railway systems, but the vast array of testing parameters and conditions makes data interpretation challenging. This review presents a comprehensive analysis of the twin-disc literature experimental data, focusing on how various parameters influence friction and wear characteristics under stationary contaminant conditions. We systematically collected and analyzed data from numerous studies, considering factors such as contact pressure, speed, material hardness, sliding speeds, adhesion, and a range of contaminants. This research showed inconsistent data reporting across different studies and statistical analyses revealed significant correlations between testing parameters and wear rates. For sand-contaminated tests, a correlation between particle size and flow rate was also highlighted. Based on these findings, we developed a simple predictive model for forecasting wear rates under varying conditions. This model achieved an adjusted R² of 0.650, demonstrating its potential for optimizing railway component design and maintenance strategies. Our study provides a valuable resource for researchers and practitioners in railway engineering, offering insights into the complex tribological interactions in wheel–rail systems and a tool for predicting wear behavior. Full article

(This article belongs to the Collection Rising Stars in Tribological Research)

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15 pages, 11002 KiB

Open AccessArticle

Modeling and Validation of the Sealing Performance of High-Pressure Vane Rotary Actuator

by Yi Wu, Junjie Zhou, Wenjie Ma and Wenbo Liao

Lubricants 2024, 12(11), 381; https://doi.org/10.3390/lubricants12110381 - 2 Nov 2024

Viewed by 569

Abstract

The EHRA (Electro-Hydraulic Rotary Actuator), using a vane rotary actuator, has the advantages of a high torque density and integration and is expected to become a joint actuator for robots. This research focuses on the sealing characteristics of various parts of a vane [...] Read more.

The EHRA (Electro-Hydraulic Rotary Actuator), using a vane rotary actuator, has the advantages of a high torque density and integration and is expected to become a joint actuator for robots. This research focuses on the sealing characteristics of various parts of a vane rotary actuator. The average Reynolds equation was used to analyze the leakage characteristics at the gap. A detailed theoretical analysis was conducted on the internal leakage mechanism of a vane rotary actuator using an X-ring as the dynamic seal for the rotor vane. According to the path of internal leakage, different sealing forms are considered as a series or parallel, and the Newton iteration method is used to obtain the total internal leakage characteristics of a vane rotary actuator. It was also considered that the deformation of the vane rotary actuator caused a thicker gap, leading to an increase in internal leakage. The calculation results are consistent with the experimental data. The analysis results indicate that when estimating the internal leakage of a vane rotary actuator, it is necessary to take the pressure of the high-pressure chamber and output shaft position as inputs. This research provides a reference for an analysis of the method of internal leakage for vane rotary actuators. It provides theoretical support for designing a vane rotary actuator with more minor internal leakage and a higher volumetric efficiency. Full article

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23 pages, 10026 KiB

Open AccessArticle

Enhancing Machining Efficiency: Real-Time Monitoring of Tool Wear with Acoustic Emission and STFT Techniques

by Luís Henrique Andrade Maia, Alexandre Mendes Abrão, Wander Luiz Vasconcelos, Jánes Landre Júnior, Gustavo Henrique Nazareno Fernandes and Álisson Rocha Machado

Lubricants 2024, 12(11), 380; https://doi.org/10.3390/lubricants12110380 - 31 Oct 2024

Viewed by 848

Abstract

Tool wear in machining is inevitable, and determining the precise moment to change the tool is challenging, as the tool transitions from the steady wear phase to the rapid wear phase, where wear accelerates significantly. If the tool is not replaced correctly, it [...] Read more.

Tool wear in machining is inevitable, and determining the precise moment to change the tool is challenging, as the tool transitions from the steady wear phase to the rapid wear phase, where wear accelerates significantly. If the tool is not replaced correctly, it can result in poor machining performance. On the other hand, changing the tool too early can lead to unnecessary downtime and increased tooling costs. This makes it critical to closely monitor tool wear and utilize predictive maintenance strategies, such as tool condition monitoring systems, to optimize tool life and maintain machining efficiency. Acoustic emission (AE) is a widely used technique for indirect monitoring. This study investigated the use of Short-Time Fourier Transform (STFT) for real-time monitoring of tool wear in machining AISI 4340 steel using carbide tools. The research aimed to identify specific wear mechanisms, such as abrasive and adhesive ones, through AE signals, providing deeper insights into the temporal evolution of these phenomena. Machining tests were conducted at various cutting speeds, feed rates, and depths of cut, utilizing uncoated and AlCrN-coated carbide tools. AE signals were acquired and analyzed using STFT to isolate wear-related signals from those associated with material deformation. The results showed that STFT effectively identified key frequencies related to wear, such as abrasive between 200 and 1000 kHz and crack propagation between 350 and 550 kHz, enabling a precise characterization of wear mechanisms. Comparative analysis of uncoated and coated tools revealed that AlCrN coatings reduced tool wear extending tool life, demonstrating superior performance in severe cutting conditions. The findings highlight the potential of STFT as a robust tool for monitoring tool wear in machining operations, offering valuable information to optimize tool maintenance and enhance machining efficiency. Full article

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

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14 pages, 5100 KiB

Open AccessArticle

Measurement and Dynamic Analysis of the Centroid Trajectories of Angular-Contact Ball Bearing Cages

by Jinyuan You, Xiqiang Ma, Chunyang Liu, Mengjie Zuo, Dongliang Jin and Hao Zhang

Lubricants 2024, 12(11), 379; https://doi.org/10.3390/lubricants12110379 - 31 Oct 2024

Viewed by 689

Abstract

When a high-speed rolling bearing cage comes into contact with rollers, it experiences random movement due to friction and collision, which significantly impacts the overall performance of the bearing. To further investigate the motion law of cages, a test bench for a 7010C [...] Read more.

When a high-speed rolling bearing cage comes into contact with rollers, it experiences random movement due to friction and collision, which significantly impacts the overall performance of the bearing. To further investigate the motion law of cages, a test bench for a 7010C angular-contact bearing cage was constructed. This setup utilized laser sensors to obtain changes in attitude and displacement during operation. After analyzing how cage deflection errors influenced trajectory measurements, corrections were applied to the measurement results. Additionally, an investigation was conducted into the effects of varying rotational speeds on the dynamic performance of the cage. Simulations were performed using ADAMS software, which verified both the effectiveness of the measuring method and the testing results. The findings indicated that within the tested range of rotational speeds, the centroid trajectory stability of the cage gradually improved as rotational speed increased and then began to show a tendency to deteriorate. Furthermore, there existed a negative correlation between the deflection error of the cage and the centroid trajectory stability. Full article

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17 pages, 2122 KiB

Open AccessArticle

Influence of Engine Oil Degradation on Sliding Bearings, with Special Focus on Different Degrees of Nitration

by Charlotte Besser, Adam Agocs, Christian Tomastik, Erik Jankes, Jaromír Burda, Ryuji Kanaya, Akira Ando, Yuma Haneda and Colin McAleese

Lubricants 2024, 12(11), 378; https://doi.org/10.3390/lubricants12110378 - 31 Oct 2024

Viewed by 767

Abstract

Bismuth (Bi) can be considered for use as a green substitute for lead in bearing applications. However, accelerated Bi oxidation can occur during operation, creating a brittle surface and resulting in premature seizure failure. Thus, the aim of this study was to evaluate [...] Read more.

Bismuth (Bi) can be considered for use as a green substitute for lead in bearing applications. However, accelerated Bi oxidation can occur during operation, creating a brittle surface and resulting in premature seizure failure. Thus, the aim of this study was to evaluate the influence of engine oil degradation, especially nitration processes, on the oxidation of Bi. Tailor-made artificially aged oils with different degrees of nitration were produced and utilized in static bearing oxidation tests. By means of X-ray photoelectron spectroscopy (XPS), the Bi surfaces were analyzed regarding their chemical compositions after the tests. The results were correlated with the respective oil conditions determined via conventional parameters as well as high-resolution mass spectrometry. The findings obtained revealed a direct correlation between the amount of Bi-oxide and the nitration values of the oil, proving there was a positive impact of nitration products on the oxidation of the Bi surfaces. A comparison with the Bi content in the oils demonstrated a protective effect of the oxide layer as the Bi content declined with an increase in nitration. Overall, valuable insight into understanding the impact of oil condition on engine parts is given, and the importance of testing engine parts with aged lubricants is emphasized. Full article

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41 pages, 11513 KiB

Open AccessReview

Recent Advances in Biomimetic Related Lubrication

by Jinqiang Shao, Guiyao Lan, Haoxin Song, Xiaoxiao Dong and Ming Li

Lubricants 2024, 12(11), 377; https://doi.org/10.3390/lubricants12110377 - 30 Oct 2024

Viewed by 619

Abstract

Friction is ubiquitous in industry and daily life, which not only leads to the wear and tear of equipment and machinery, but also causes a lot of energy waste. Friction is one of the significant factors leading to energy loss in mechanical systems. [...] Read more.

Friction is ubiquitous in industry and daily life, which not only leads to the wear and tear of equipment and machinery, but also causes a lot of energy waste. Friction is one of the significant factors leading to energy loss in mechanical systems. Therefore, it is essential to minimize friction losses. Creatures in nature have evolved various surfaces with different tribological characteristics to adapt to the environment. By studying, understanding, and summarizing the friction and lubrication regulation phenomena of typical surfaces in nature, various bionic friction regulation theories and methods are obtained to guide the development of new lubrication materials and lubrication systems. This article primarily discusses the study of lubrication mechanisms through biomimetic design, which is mainly divided into chemical approaches, structural strategies, and chemical–structural coupling approaches. From the chemical point of view, this paper mainly summarizes joint lubrication and engineering lubrication in biomedicine, with inspiration from lotus leaves, fish skin, and snake skin, each with unique antifriction structures which are famous for their super hydrophobicity in nature. Finally, chemical–structural coupling simulates the lubrication mechanism of natural organisms from the joint action of biological structures and chemical substances, and is applied to coating design, so as to reduce the friction and wear on coating surfaces, improve the durability and anti-pollution ability of coatings, significantly improve the tribological performance of mechanical systems, promote scientific innovation, and promote energy conservation, emission reduction, and sustainable development. Full article

(This article belongs to the Special Issue Lubrication of Biomimetic Surfaces)

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15 pages, 2783 KiB

Open AccessArticle

Assessing the Tribological Impact of 3D Printed Carbon-Reinforced ABS Composite Cylindrical Gears

by Razvan George Ripeanu, Maria Tănase, Alexandra Ileana Portoacă and Alin Diniță

Lubricants 2024, 12(11), 376; https://doi.org/10.3390/lubricants12110376 - 30 Oct 2024

Viewed by 613

Abstract

The tribological performance of carbon-reinforced acrylonitrile butadiene styrene (ABS) composites is very important in determining their suitability for advanced engineering applications. This study employs response surface methodology (RSM) to evaluate the effects of printing temperature and post-processing annealing on the wear resistance and [...] Read more.

The tribological performance of carbon-reinforced acrylonitrile butadiene styrene (ABS) composites is very important in determining their suitability for advanced engineering applications. This study employs response surface methodology (RSM) to evaluate the effects of printing temperature and post-processing annealing on the wear resistance and frictional properties of these composites. A central composite design is used to systematically explore the interaction between these two factors, enabling the development of predictive models for key tribological parameters. The results reveal that both the coefficient of friction (COF) and wear are affected by printing and annealing temperatures, although in a non-linear manner. Moderate printing temperatures and lower annealing temperatures were found to reduce friction and wear, with annealing temperature having a more pronounced effect on wear. To further optimize these responses, the desirability approach was applied for predicting the optimal conditions. The optimal combination of input parameters for minimizing both COF and wear was found to be a printing temperature of 256 °C and an annealing temperature of 126 °C. This research provides valuable insights for optimizing additive manufacturing processes of carbon-reinforced ABS composites, contributing to enhanced material durability in practical applications. Full article

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15 pages, 16802 KiB

Open AccessArticle

Investigating the Performance of Glass Fibre-Reinforced Polymer (GFRP) in the Marine Environment for Tidal Energy: Velocity, Particle Size, Impact Angle and Exposure Time Effects

by Talal F. Algaddaime, Emadelddin Hassan and Margaret M. Stack

Lubricants 2024, 12(11), 375; https://doi.org/10.3390/lubricants12110375 - 30 Oct 2024

Viewed by 634

Abstract

Tidal energy, with its potential to provide a consistent energy output and reduce carbon emissions, has garnered significant interest. This study, which evaluates the performance of tidal turbine blades in seawater conditions and with sand particles, presents a novel approach. A slurry rig [...] Read more.

Tidal energy, with its potential to provide a consistent energy output and reduce carbon emissions, has garnered significant interest. This study, which evaluates the performance of tidal turbine blades in seawater conditions and with sand particles, presents a novel approach. A slurry rig was developed to examine composite materials, and a glass fibre-reinforcement polymeric material was tested over a range of particle sizes, velocities, and impact angles. In addition, this paper used a new test protocol with 14 days (336 h) and 91 days (2184 h) of pre-exposure time of materials before testing. The results, which show significant changes in the erosive mechanisms of GFRP in short- and long-term pre-exposure time as a function of these variables, have profound implications for the design and performance of tidal turbine blades. The study also utilised scanning electron microscopy (SEM), depth profiling analysis, and erosion mapping techniques to compare the erosion behaviours of GFRP. These tools can be used to optimise such materials in tidal turbine conditions. Full article

(This article belongs to the Special Issue Tribo-Corrosion: Current Processes, Prevailing Challenges and Future Perspectives)

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16 pages, 8061 KiB

Open AccessArticle

Tribological Properties of Multilayer DLC/MoS₂ Nanocomposite Coatings on Microtextured Titanium Alloy Surfaces

by Ke Liu, Qingqing Ding, Hao Peng, Kang Guan, Xiaowan Xi, Ning Kong and Maolin Liao

Lubricants 2024, 12(11), 374; https://doi.org/10.3390/lubricants12110374 - 29 Oct 2024

Viewed by 717

Abstract

Single surface texture or coating technology is gradually unable to produce lasting lubrication of a TC4 titanium alloy in a harsh environment. In order to address this problem, a rectangular microstructure is prepared on the surface of a TC4 titanium alloy by laser [...] Read more.

Single surface texture or coating technology is gradually unable to produce lasting lubrication of a TC4 titanium alloy in a harsh environment. In order to address this problem, a rectangular microstructure is prepared on the surface of a TC4 titanium alloy by laser processing, and then MoS₂/DLC composite interlayer nanocoatings are prepared on the surface by non-equilibrium magnetron sputtering. Friction and wear tests are then carried out on single fabricated, coated and fabricated coatings. The results show that the MoS₂/DLC composite interlayered nanocoating can effectively combine with the texture to achieve better friction reduction compared with the single texture and coating. The textured composite coating has the lowest friction coefficient (reduced from 0.4122 to 0.0978) and wear. Through controlled experiments, the textured coating showed good tribological properties at different temperatures and in different friction cycle tests. This study can effectively improve the tribological properties of metal materials through composite coatings, providing research ideas for enhancing the service life of alloys under long-term friction in high-temperature environments. Full article

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

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14 pages, 9081 KiB

Open AccessArticle

Non-Polar Chain-Enabled Suspension of Carbon Nanoparticles in Base Oil

by M. Humaun Kabir, Darrius Dias, Evan Johnson, Joe Kosmoski and Hong Liang

Lubricants 2024, 12(11), 373; https://doi.org/10.3390/lubricants12110373 - 29 Oct 2024

Viewed by 609

Abstract

The transition to electric vehicles (EVs) has introduced new challenges in lubrication, demanding innovative solutions to ensure consistent performance. One promising approach is the use of nanoparticle additives, which have the potential to improve lubrication performance significantly. However, achieving a stable suspension of [...] Read more.

The transition to electric vehicles (EVs) has introduced new challenges in lubrication, demanding innovative solutions to ensure consistent performance. One promising approach is the use of nanoparticle additives, which have the potential to improve lubrication performance significantly. However, achieving a stable suspension of these nanoparticles in lubricating oils remains a critical challenge, as suspension stability is essential for maintaining consistent performance and maximizing the benefits of these advanced additives. In this study, carbon nanoparticles (CNPs) were modified with dodecylamine (DDA) to achieve stable suspension in nonpolar fluids. The successful functionalization was confirmed by the FTIR results, which showed characteristic peaks of various bonding. The suspension stability tests demonstrated that DDA-CNPs remained suspended for over 60 days in the Polyalphaolefin (PAO) oil, whereas unmodified CNPs were sedimented within 3–7 days. The rheological behavior was measured under different shear rates and temperatures. Viscosity measurements indicated that DDA-CNPs maintained a lower value compared to base PAO. The lubricants’ friction coefficient (COF) was also determined under various speeds and loads. The addition of DDA-CNPs at a concentration of 0.05 wt.% resulted in a significant reduction in COF, with values decreasing by 26% compared to base PAO oil under a load of 1 N. Additionally, the COF for DDA-CNPs was consistently lower than that of PAO, with reductions ranging from 15% to 18% across all tested speeds. The Stribeck curve further highlighted the improved performance of DDA-CNPs across boundary, mixed, and hydrodynamic lubrication regimes. These findings suggest that DDA-CNPs significantly improve the lubrication performance of PAO oil, making them suitable for advanced lubrication applications in automotive and industrial systems. Full article

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

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Lubricants, Volume 12, Issue 11 (November 2024) – 42 articles

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