Journal Description
Lubricants
Lubricants
is an international, peer-reviewed, open access journal on tribology published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q2 (Mechanical Engineering)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 14.8 days after submission; acceptance to publication is undertaken in 3.5 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
3.5 (2022);
5-Year Impact Factor:
3.2 (2022)
Latest Articles
Improved Tribological Performance of ta-C/MoSx Coatings Deposited on Laser Micro-Structured Steel Substrates in Both Vacuum and Air
Lubricants 2024, 12(6), 200; https://doi.org/10.3390/lubricants12060200 (registering DOI) - 1 Jun 2024
Abstract
Vacuum and air atmospheres impose very different requirements on tribological-loaded contacts, which usually require different surface materials. While hard tetrahedral amorphous carbon (ta-C) coatings provide good tribological properties in air, soft coatings such as molybdenum disulfide (MoS2) work well in a vacuum. Tribological
[...] Read more.
Vacuum and air atmospheres impose very different requirements on tribological-loaded contacts, which usually require different surface materials. While hard tetrahedral amorphous carbon (ta-C) coatings provide good tribological properties in air, soft coatings such as molybdenum disulfide (MoS2) work well in a vacuum. Tribological performance in the respective other environment, however, is poor. In this work, the combination of laser microstructured (direct laser interference patterning) steel substrates and the deposition of ta-C and MoSx coatings with vacuum arc evaporation (LaserArc™) was studied, resulting in steel/DLIP, steel/DLIP/ta-C, steel/DLIP/MoSx, steel/DLIP/ta-C/MoSx, and steel/MoSx surface combinations. The tribological properties were studied using a ball-on-disk tribometer with a steel ball counter body in air and in a vacuum (p < 5 × 10−7 mbar). The type of the topmost coating governed their tribological properties in the respective atmosphere, and no general beneficial influence of the microstructure was found. However, steel/DLIP/ta-C/MoSx performed best in both conditions and endured the highest contact pressure, which is attributed to the mechanical support of the ta-C coating and MoSx reservoir in the remaining structure, as evidenced by Raman spectroscopy. The findings suggest that such combination allows for surfaces bearing a high load capacity that can be applied in both a vacuum and in air, for example, in multi-use space applications.
Full article
(This article belongs to the Special Issue Tribology of Textured Surfaces)
►
Show Figures
Open AccessEditorial
Tribology of 2D Nanomaterials
by
Yanfei Liu and Xiangyu Ge
Lubricants 2024, 12(6), 199; https://doi.org/10.3390/lubricants12060199 (registering DOI) - 1 Jun 2024
Abstract
Tribology is the science and engineering of interacting surfaces in relative motion [...]
Full article
(This article belongs to the Special Issue Tribology of 2D Nanomaterials)
Open AccessArticle
Comparison of Friction Properties of GI Steel Plates with Various Surface Treatments
by
Miroslav Tomáš, Stanislav Németh, Emil Evin, František Hollý, Vladimír Kundracik, Juliy Martyn Kulya and Marek Buber
Lubricants 2024, 12(6), 198; https://doi.org/10.3390/lubricants12060198 - 31 May 2024
Abstract
This article presents the improved properties of GI (hot-dip galvanized) steel plates in combination with a special permanent surface treatment. The substrate used was hot-dip galvanized deep-drawn steel sheets of grade DX56D + Z. Subsequently, various surface treatments were applied to their surface.
[...] Read more.
This article presents the improved properties of GI (hot-dip galvanized) steel plates in combination with a special permanent surface treatment. The substrate used was hot-dip galvanized deep-drawn steel sheets of grade DX56D + Z. Subsequently, various surface treatments were applied to their surface. The coefficient of friction of the metal sheets without surface treatment, with a temporary surface treatment called passivation, and a thin organic coating (TOC) based on hydroxyl resins dissolved in water, Ti and Cr3+ were determined by a cup test. The surface quality and corrosion resistance of all tested samples were also determined by exposing them for up to 288 h in an atmosphere of neutral salt spray. The surface microgeometry parameters Ra, RPc and Rz(I), which have a significant influence on the pressing process itself, were also determined. The TOC deposited on the Zn substrate was the only one to exhibit excellent lubrication and anticorrosion properties, resulting in the lowest surface microgeometry values owing to the uniform and continuous layer of the thin organic coating compared to the GI substrate and passivation surface treatment, respectively.
Full article
(This article belongs to the Special Issue Mechanical Tribology and Surface Technology)
►▼
Show Figures
Figure 1
Open AccessArticle
Lubricating Greases from Fried Vegetable Oil—Preparation and Characterization
by
Olga V. Săpunaru, Ancaelena E. Sterpu, Cyrille A. Vodounon, Jack Nasr, Cristina Duşescu-Vasile, Sibel Osman and Claudia I. Koncsag
Lubricants 2024, 12(6), 197; https://doi.org/10.3390/lubricants12060197 - 30 May 2024
Abstract
Biobased greases are derived from renewable resources, are considered more environmentally friendly, and offer comparable performance to petroleum-based greases. In this study, lubricating greases from frying cooking oils were prepared, thus valorizing waste in order to obtain sustainable and environmentally friendly products. Twelve
[...] Read more.
Biobased greases are derived from renewable resources, are considered more environmentally friendly, and offer comparable performance to petroleum-based greases. In this study, lubricating greases from frying cooking oils were prepared, thus valorizing waste in order to obtain sustainable and environmentally friendly products. Twelve batches (500 g each) were produced from sunflower and palm frying oils, with 20% by weight calcium/lithium stearate soaps prepared in situ and filled with 15 wt.% cellulose or lignin sulfate. The greases were rheologically characterized. Their consistency was assessed by the penetration test performed before and after working the greases. Dropping point determinations offered information about the stability at higher temperatures, and oil bleeding tests were performed. The average values of the friction coefficient (COF), the contact resistance, and the wear scar diameter were measured through mechanical tests. The greases prove to be comparable to those obtained from mineral oils, with good rheological properties, soft consistency, and good antiwearing behavior, e.g., in open or total-loss lubricating systems, like in open gears and certain food processing machinery; they are thermally stable andprone touse in low-loading working mechanisms.
Full article
(This article belongs to the Special Issue Advances in Tribochemistry)
►▼
Show Figures
Figure 1
Open AccessArticle
Preparation and Tribological Behaviors of Sulfur- and Phosphorus-Free Organic Friction Modifier of Amide–Ester Type
by
Xiaomei Xu, Fan Yang, Hongmei Yang, Yanan Zhao, Xiuli Sun and Yong Tang
Lubricants 2024, 12(6), 196; https://doi.org/10.3390/lubricants12060196 - 30 May 2024
Abstract
With the increasingly demanding engine conditions and the implementation of “double carbon” policies, the demand for high-quality lubricants that are cost-effective and environmentally friendly is increasing. Additives, especially high-performance friction modifiers, play an important role in boosting lubricant efficiency and fuel economy, so
[...] Read more.
With the increasingly demanding engine conditions and the implementation of “double carbon” policies, the demand for high-quality lubricants that are cost-effective and environmentally friendly is increasing. Additives, especially high-performance friction modifiers, play an important role in boosting lubricant efficiency and fuel economy, so their developments are at the forefront of lubrication technologies. In this study, 1,3-dioleoamide-2-propyloleate (DOAPO), which incorporates polar amide, ester, and nonpolar alkyl chains, was synthesized from 1,3-diamino-2-propanol to give an eco-friendly organic friction modifier. Nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA) were used to characterize the structure and thermal stability of DOAPO. Meanwhile, the storage stability and tribological behaviors of DOAPO in synthetic base oil were studied and compared with a commercial oleamide. The results show that DOAPO has better thermal stability and better storage stability in synthetic base oil. Additionally, 0.5 wt.% of DOAPO could shorten the running-in period and reduce the average friction coefficient (ave. COF) and wear scar diameter (ave. WSD) by 8.2% and 16.2%, respectively. The worn surface analysis and theoretical calculation results show that the ester bond in DOAPO breaks preferentially during friction, which can reduce the interfacial shear force and easily react with metal surfaces to form iron oxide films, thus demonstrating a better friction-reducing and anti-wear performance.
Full article
(This article belongs to the Special Issue Functional Lubricating Materials)
►▼
Show Figures
Graphical abstract
Open AccessArticle
Braking Friction Coefficient Prediction Using PSO–GRU Algorithm Based on Braking Dynamometer Testing
by
Shuwen Wang, Yang Yu, Shuangxia Liu and David Barton
Lubricants 2024, 12(6), 195; https://doi.org/10.3390/lubricants12060195 - 29 May 2024
Abstract
The coefficients of friction (COFs) is one of the most important parameters used to evaluate the braking performance of a friction brake. Many indicators that affect the safety and comfort of automobiles are associated with brake COFs. The manufacturers of friction brakes and
[...] Read more.
The coefficients of friction (COFs) is one of the most important parameters used to evaluate the braking performance of a friction brake. Many indicators that affect the safety and comfort of automobiles are associated with brake COFs. The manufacturers of friction brakes and their components are required to spend huge amounts of time and money to carry out experimental tests to ensure the COFs of a newly developed braking system meet the required standards. In order to save time and costs for the development of new friction brake applications, the GRU (Gate Recurrent Unit) algorithm optimized by the improved PSO (particle swarm optimization) global optimization method is employed in this work to predict brake COFs based on existing experimental data obtained from friction braking dynamometer tests. Compared with the LSTM (Long Short-Term Memory) method, the GRU algorithm optimized by PSO avoids the accuracy reduction problem caused by gradient descent in the training process and hence reduces the prediction error and computational cost. The combined PSO–GRU algorithm increases the coefficient of determination (R2) of the prediction by 4.7%, reduces the MAE (mean absolute error) by 14.3%, and increases the prediction speed by 40.1% compared with the standalone GRU method. The prediction method based on machine learning proposed in this study can not only be applied to the prediction of automobile braking COFs but also for other frictional system problems, such as the prediction of braking noise and the friction of various bearing transmission components.
Full article
(This article belongs to the Special Issue Tribology in Vehicles)
►▼
Show Figures
Figure 1
Open AccessArticle
Practical Evaluation of Ionic Liquids for Application as Lubricants in Cleanrooms and under Vacuum Conditions
by
Andreas Keller, Knud-Ole Karlson, Markus Grebe, Fabian Schüler, Christian Goehringer and Alexander Epp
Lubricants 2024, 12(6), 194; https://doi.org/10.3390/lubricants12060194 - 28 May 2024
Abstract
As part of a publicly funded cooperation project, novel high-performance lubricants (oils, greases, assembly pastes) based on ionic liquids and with the addition of specific micro- or nanoparticles are to be developed, which are adapted in their formulation for use in applications where
[...] Read more.
As part of a publicly funded cooperation project, novel high-performance lubricants (oils, greases, assembly pastes) based on ionic liquids and with the addition of specific micro- or nanoparticles are to be developed, which are adapted in their formulation for use in applications where their negligible vapor pressure plays an important role. These lubricants are urgently needed for applications in cleanrooms and high vacuum (e.g., pharmaceuticals, aerospace, chip manufacturing), especially when the frequently used perfluoropolyethers (PFPE) are no longer available due to a potential restriction of per- and polyfluoroalkyl substances (PFAS) due to European chemical legislation. Until now, there has been a lack of suitable laboratory testing technology to develop such innovative lubricants for extreme niche applications economically. There is a large gap in the tribological test chain between model testing, for example in the so-called spiral orbit tribometer (SOT) or ball-on-disk test in a high-frequency, linear-oscillation test machine (SRV-Tribometer from German “Schwing-Reib-Verschleiß-Tribometer”), and overall component testing at major space agencies (ESA—European Space Agency, NASA—National Aeronautics and Space Administration) or their service providers like the European Space Tribology Laboratory (ESTL) in Manchester. A further aim of the project was therefore to develop an application-orientated and economical testing methodology and testing technology for the scientifically precise evaluation and verifiability of the effect of ionic liquids on tribological systems in cleanrooms and under high vacuum conditions. The newly developed test rig is the focus of this publication. It forms the basis for all further investigations.
Full article
(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)
►▼
Show Figures
Graphical abstract
Open AccessFeature PaperArticle
Viscoelastic Hertzian Impact
by
Ivan Argatov
Lubricants 2024, 12(6), 193; https://doi.org/10.3390/lubricants12060193 - 28 May 2024
Abstract
►▼
Show Figures
The problem of normal impact of a rigid sphere on a Maxwell viscoelastic solid half-space is considered. The first-order asymptotic solution is constructed in the framework of Hunter’s model of viscoelastic impact. In particular, simple analytical approximations have been derived for the maximum
[...] Read more.
The problem of normal impact of a rigid sphere on a Maxwell viscoelastic solid half-space is considered. The first-order asymptotic solution is constructed in the framework of Hunter’s model of viscoelastic impact. In particular, simple analytical approximations have been derived for the maximum contact force and the time to achieve it. A linear regression method is suggested for evaluating the instantaneous elastic modulus and the mean relaxation time from a set of experimental data collected for different spherical impactors and impact velocities.
Full article
Figure 1
Open AccessEditorial
Friction and Wear of Cutting Tools and Cutting Tool Materials
by
Guoliang Liu, Chuanzhen Huang, Xiangyu Wang, Bin Zhao and Min Ji
Lubricants 2024, 12(6), 192; https://doi.org/10.3390/lubricants12060192 - 28 May 2024
Abstract
The friction between cutting tools and the workpiece/chip can significantly affect the tool wear, cutting force, cutting temperature, machined surface integrity, and machined parts’ service performance. [...]
Full article
(This article belongs to the Special Issue Friction and Wear of Cutting Tools and Cutting Tool Materials)
Open AccessArticle
Tribological and Chemical–Physical Behavior of a Novel Palm Grease Blended with Zinc Oxide and Reduced Graphene Oxide Nano-Additives
by
Mohamed G. A. Nassef, Belal G. Nassef, Hassan S. Hassan, Galal A. Nassef, Marwa Elkady and Florian Pape
Lubricants 2024, 12(6), 191; https://doi.org/10.3390/lubricants12060191 - 28 May 2024
Abstract
The role of industrial lubricants in machinery is to reduce friction and wear between moving components. Due to the United Nations’ tendency to reduce dependency on fossil fuel, a general awareness is strongly driven towards developing more eco-friendly lubricants. Palm oil possesses promising
[...] Read more.
The role of industrial lubricants in machinery is to reduce friction and wear between moving components. Due to the United Nations’ tendency to reduce dependency on fossil fuel, a general awareness is strongly driven towards developing more eco-friendly lubricants. Palm oil possesses promising properties, which promote it to be a competitive alternative to the hostile mineral oils. Still, marginal oxidation stability, viscosity, and tribological properties remain critical issues for performance improvement. This paper presents an improved palm grease using reduced graphene oxide (rGO) and zinc oxide (ZnO) nano-additives at different concentrations. Oil and grease samples were tested for viscosity, oxidation stability, pour point, penetration, roll stability, dropping point, churned grease-oil release, copper corrosion, friction, and wear. ZnO additives enhanced the oxidation stability by 60% and shifted the pour point to 6 °C. Adding ZnO and rGO to the palm grease increased the load-carrying capacity between 30% and 60%, respectively, and reduced the friction coefficient by up to 60%. From the wear scar morphologies, it is believed that graphene 2D nanoparticles formed absorption layers which contributed to the increase in load-carrying capacity, while ZnO chemically reacted with the metallic surface layer, forming zinc compounds that resulted in a protective boundary lubricating film.
Full article
(This article belongs to the Special Issue 2D Materials in Tribology)
►▼
Show Figures
Figure 1
Open AccessArticle
Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part II: The Partial-Film Condition
by
Yuechang Wang and Ying Liu
Lubricants 2024, 12(6), 190; https://doi.org/10.3390/lubricants12060190 - 28 May 2024
Abstract
This paper is the second part of a two-part report studying the responses of a typical point-contact elastohydrodynamic lubrication (EHL) system to multiscale roughness mimicked by wavy surfaces. The wavy surfaces are defined by three key parameters: amplitudes, frequencies, and directions. The previous
[...] Read more.
This paper is the second part of a two-part report studying the responses of a typical point-contact elastohydrodynamic lubrication (EHL) system to multiscale roughness mimicked by wavy surfaces. The wavy surfaces are defined by three key parameters: amplitudes, frequencies, and directions. The previous Part I paper focuses on the full film lubrication condition, while the current paper focuses on the partial film regime where asperity contacts occur. A transient thermal EHL model simulates lubrication problems with different waviness parameters, loads, and speeds. The total number of simulations is 1600. Performance parameters, including the asperity contact ratio, minimum film thickness, maximum pressure, central point film thickness, central point pressure, mean film thickness, coefficient of friction (COF), and the maximum temperature rise, are obtained for each simulation. These performance parameters are post-processed in the same manner as those in the previous Part I paper. The influences of the waviness parameters, load, and speed values on the eight performance parameters are discussed.
Full article
(This article belongs to the Special Issue Fundamentals in Building Tribological Digital Twins of Machine Elements)
►▼
Show Figures
Figure 1
Open AccessArticle
Improved Tribological Performance of a Polybutylene Terephthalate Hybrid Composite by Adding a Siloxane-Based Internal Lubricant
by
Shengqin Zhao, Rolf Merz, Stefan Emrich, Johannes L’huillier and Leyu Lin
Lubricants 2024, 12(6), 189; https://doi.org/10.3390/lubricants12060189 - 28 May 2024
Abstract
To mitigate the environmental hazards aroused by fossil-based lubricants, the development of eco-friendly internal lubricants is imperative. Siloxane-based internal lubricants, widely applied as plasticizers in polymeric compounds, are a promising option. However, their impacts on the tribological properties of polymeric tribocomponents are still
[...] Read more.
To mitigate the environmental hazards aroused by fossil-based lubricants, the development of eco-friendly internal lubricants is imperative. Siloxane-based internal lubricants, widely applied as plasticizers in polymeric compounds, are a promising option. However, their impacts on the tribological properties of polymeric tribocomponents are still unclarified. Therefore, in the current study, a siloxane-based internal lubricant with the product name ‘EverGlide MB 1550 (EG)’ was dispersed into a polybutylene terephthalate (PBT)-based tribological composite to investigate whether the tribological properties of the composite can be optimized. A block-on-ring (BOR) test configuration was used for this purpose. It was found that the addition of EG to the composite significantly improved the tribological behavior; the improvement was particularly significant under lower load conditions (pv-product ≤ 2 MPa∙m/s). Compared to the reference PBT composite, the addition of EG reduced the friction coefficient (COF) by about 30% and the specific wear rate by about 14%. An accompanying surface analytical investigation using photoelectron spectroscopy to elucidate the effective mechanisms at the molecular level showed the availability of tribologically effective and free EG after its addition to the composite in the relevant tribocontact.
Full article
(This article belongs to the Special Issue Tribology in Germany: Latest Research and Development)
►▼
Show Figures
Figure 1
Open AccessArticle
Investigation of Chemical, Physical, and Tribological Properties of Pyrolysis Oil Derived from End-of-Life Tires (ELTs) against Conventional Engine Oil
by
Abdullah A. Alazemi, Abdullah F. Alajmi and Sultan M. Al-Salem
Lubricants 2024, 12(6), 188; https://doi.org/10.3390/lubricants12060188 - 27 May 2024
Abstract
►▼
Show Figures
Over one billion rubber tires are disposed of worldwide annually as a major component of the solid waste stream, posing a significant environmental risk. Therefore, recycling and taking advantage of the rubber component in End-of-Life Tires (ELTs) presents an advantageous opportunity to produce
[...] Read more.
Over one billion rubber tires are disposed of worldwide annually as a major component of the solid waste stream, posing a significant environmental risk. Therefore, recycling and taking advantage of the rubber component in End-of-Life Tires (ELTs) presents an advantageous opportunity to produce environmentally friendly and cost-effective products. This work studied multiple properties of oil extracted from ELTs using thermal pyrolysis (i.e., pyro-oil) as a potential candidate for industrial lubrication applications. First, pyro-oil was characterized by studying its morphological and chemical properties. Then, rheological studies were conducted to explore the oil properties at different temperatures and shear rates. A tribometer was also used to assess pyro-oil’s tribological performance at different temperatures and speeds. Finally, wettability and thermal analyses were performed to understand the wetting and thermal stability properties. The results revealed that pyro-oil has chemical properties similar to conventional engine oil with slightly higher sulfur content. Furthermore, the pyro-oil exhibited lower viscosity and lubrication performance than conventional engine oil, but this difference was smaller at higher temperatures. Thermal stability and wetting properties of pyro-oil were found to be significantly lower than those of conventional engine oil. Based on the properties found and compared with engine oil, pyro-oil presents itself as a suitable liquid lubricant for low-speed, low-load applications operating in temperatures below 61 °C. This work presents a comprehensive study of pyro-oil properties extracted from end-of-life waste tires, offering a feasible route to obtain sustainable and low-cost products.
Full article
Figure 1
Open AccessArticle
Multiscale Texture Features to Enhance Lubricant Film Thickness for Prosthetic Hip Implant Bearing Surfaces
by
Fitsum Berhe Tewelde, Quentin Allen and Tianfeng Zhou
Lubricants 2024, 12(6), 187; https://doi.org/10.3390/lubricants12060187 - 27 May 2024
Abstract
The longevity of prosthetic hip implants is significantly influenced by wear. Surface textures of various length scales can reduce the friction coefficient and wear of lubricated bearing surfaces. The optimization of multiscale texture parameters, aimed at maximizing lubricant film thickness, was achieved through
[...] Read more.
The longevity of prosthetic hip implants is significantly influenced by wear. Surface textures of various length scales can reduce the friction coefficient and wear of lubricated bearing surfaces. The optimization of multiscale texture parameters, aimed at maximizing lubricant film thickness, was achieved through hydrodynamic lubrication simulations that solve the Reynolds equation with a mass-conserving cavitation model under various operating conditions. The outcomes indicate that adding “interstitial” texture features to a pattern of microscale texture features can further increase the lubricant film thickness. Additionally, the lubricant film thickness increases as the interstitial texture feature aspect ratio and texture density decrease. Pin-on-disc experiments align with simulation findings, demonstrating that multiscale texturing with ultra-fast laser ablation on Ti6Al4V discs significantly improves wettability and reduces the friction coefficient of ultra-high molecular weight polyethylene pins when compared to untextured and microscale textured surfaces. The multiscale surface texturing also changes the evident wear mechanisms on the pins, reducing the incidence of abrasive scratches and adhesive wear compared to both untextured and just microscale textured surfaces.
Full article
(This article belongs to the Special Issue Tribology of Textured Surfaces)
►▼
Show Figures
Figure 1
Open AccessReview
Hydrogels for Lubrication: Synthesis, Properties, Mechanism, and Challenges
by
Lulin Hu, Yi Yang, Weiyan Yu and Lu Xu
Lubricants 2024, 12(6), 186; https://doi.org/10.3390/lubricants12060186 - 24 May 2024
Abstract
Hydrogels have received extensive attention as functional lubricants because of their excellent anti-friction and anti-wear properties, tunable tribological performances, and effectiveness in alleviating lubrication failures caused by the creeping or leakage of conventional liquid lubricants owing to their semi-solid nature. This review summarizes
[...] Read more.
Hydrogels have received extensive attention as functional lubricants because of their excellent anti-friction and anti-wear properties, tunable tribological performances, and effectiveness in alleviating lubrication failures caused by the creeping or leakage of conventional liquid lubricants owing to their semi-solid nature. This review summarizes the current research advances in hydrogel lubricants fabricated with various organic and/or inorganic gelators, including organic polymeric or supramolecular hydrogels, inorganic particles-based hydrogels, and organic polymer-inorganic particle hybrid hydrogels. We illustrate not only the design strategies for constructing high-performance hydrogel lubricants but also the tribological behavior and mechanism of different types of hydrogel lubricants and their potential applications in industrial and biomimetic fields. Corresponding outlooks and suggestions for future studies have also been proposed.
Full article
(This article belongs to the Special Issue Advances in Colloidal Lubricants and Interfacial Tribology)
►▼
Show Figures
Graphical abstract
Open AccessArticle
Development of a Digital Model for Predicting the Variation in Bearing Preload and Dynamic Characteristics of a Milling Spindle under Thermal Effects
by
Tria Mariz Arief, Wei-Zhu Lin, Muhamad Aditya Royandi and Jui-Pin Hung
Lubricants 2024, 12(6), 185; https://doi.org/10.3390/lubricants12060185 - 23 May 2024
Abstract
The spindle tool is an important module of the machine tool. Its dynamic characteristics directly affect the machining performance, but it could also be affected by thermal deformation and bearing preload. However, it is difficult to detect the change in the bearing preload
[...] Read more.
The spindle tool is an important module of the machine tool. Its dynamic characteristics directly affect the machining performance, but it could also be affected by thermal deformation and bearing preload. However, it is difficult to detect the change in the bearing preload through sensory instruments. Therefore, this study aimed to establish a digital thermal–mechanical model to investigate the thermal-induced effects on the spindle tool system. The technologies involved include the following: Run-in experiments of the milling spindle at different speeds, the establishment of the thermal–mechanical model, identification of the thermal parameters, and prediction of the thermal-induced preload of bearings in the spindle. The speed-dependent thermal parameters were identified from thermal analysis through comparisons with transient temperature history, which were further used to model the thermal effects on the bearing preload and dynamic compliance of the milling spindle under different operating speeds. Current results of thermal–mechanical analysis also indicate that the internal temperature of the bearing can reach 40 °C, and the thermal elongation of the spindle tool is about 27 µm. At the steady state temperature of 15,000 rpm, the bearing preload is reduced by 40%, which yields a decrease in the bearing rigidity by approximately 16%. This, in turn, increases the dynamic compliance of the spindle tool by 22%. Comparisons of the experimental measurements and modeling data show that the variation in bearing preload substantially affects the modal frequency and stiffness of the spindle. These findings demonstrated that the proposed digital spindle model accurately mirrors real spindle characteristics, offering a foundation for monitoring performance changes and refining design, especially in bearing configuration and cooling systems.
Full article
(This article belongs to the Special Issue New Conceptions in Bearing Lubrication and Temperature Monitoring)
►▼
Show Figures
Figure 1
Open AccessArticle
Analysis of Lubrication Regimes for Porous Sliding Bearing
by
Aleksandar Marinković, Blaža Stojanović, Carsten Gachot and Tatjana Lazović
Lubricants 2024, 12(6), 184; https://doi.org/10.3390/lubricants12060184 - 23 May 2024
Abstract
►▼
Show Figures
The purpose of this paper is to analyze the lubrication quality of porous sliding bearings, starting from the bearing model and in combination with experimental results aimed at analyzing the lubrication regimes of different working conditions. The separation between the surfaces by the
[...] Read more.
The purpose of this paper is to analyze the lubrication quality of porous sliding bearings, starting from the bearing model and in combination with experimental results aimed at analyzing the lubrication regimes of different working conditions. The separation between the surfaces by the lubricant layer is what determines the regime. The quality and type of lubrication regime are determined by parameters in the mathematical model including typically speed, load, motion, materials, environment, etc., which have an impact on friction. Besides those elements, important parameters such as coefficient of friction (COF) and working temperature are to be measured due to experimental investigations to detect an equilibrium working state. The self-lubrication mechanism in porous metal bearings improves their service life and lubrication processes; however, the COF still varies within a wide interval. This variability can be understood, considering that during bearing operation it operates within a broad range of lubrication regimes. Those findings are explained in the paper by using a combination of calculated parameters according to the bearing model and in combination with our own results of experimental investigations. With the obtained results for particular working conditions, the authors are trying to explain, in the form of a diagram with the limit line as an important outcome of the work, that the lubrication regime for porous metal bearings could arise from boundary lubrication (BL) close to hydrodynamic lubrication (HDL).
Full article
Figure 1
Open AccessArticle
Molecular Dynamics Analysis of Adhesive Forces between Silicon Wafer and Substrate in Microarray Adhesion
by
Shunkai Han, Yarong Chen, Ming Feng, Zhixu Zhang, Zhaopei Wang and Zhixiang Chen
Lubricants 2024, 12(6), 183; https://doi.org/10.3390/lubricants12060183 - 21 May 2024
Abstract
►▼
Show Figures
With the development of the electronics industry, the requirements for chips are getting higher and higher, and thinner and thinner wafers are needed to meet the processing of chips. In this study, a model of the adhesion state of semiconductor wafers in the
[...] Read more.
With the development of the electronics industry, the requirements for chips are getting higher and higher, and thinner and thinner wafers are needed to meet the processing of chips. In this study, a model of the adhesion state of semiconductor wafers in the stacking–clamping process based on microarray adsorption was established, the composition adhesion was discussed, the microarrays of different materials and pressures were experimentally studied, and a molecular dynamics model was established. The molecular dynamics analysis showed that the adhesion force was only related to the type of atom, and the applied pressure did not change the adhesion force. According to the simulation results, the tangential adhesion between the metal and the wafer is greater than that between the ceramic and the wafer, the adsorption force between the aluminum–magnesium alloy and the silicon wafer is shown in the normal direction, and the repulsion force between other materials and the silicon wafer is shown in the normal direction. During the pressure process, the metal is in the elastic deformation stage between the metal and the wafer, the wafer is plastically deformed in the silicon carbide ceramic and wafer, and the wafer is elastically deformed in the alumina ceramic and wafer. In this paper, the adhesion between the substrate and the wafer is studied, a method of constructing microarrays to enhance adhesion is proposed, and the tangential deformation of the array unit under pressure is studied, which provides theoretical support for increasing the adhesion by constructing microarrays.
Full article
Figure 1
Open AccessReview
Progress in Theoretical Modelling of Macroscopic and Microscopic Dynamics of Bolted Joints in Complex Equipment
by
Xiaohan Lu, Min Zhu, Shengao Wang, Shengnan Li, Zijian Xu and Yilong Liu
Lubricants 2024, 12(5), 182; https://doi.org/10.3390/lubricants12050182 - 17 May 2024
Abstract
►▼
Show Figures
Bolt connection structure is a common form of connecting large and complex equipment. Its object contact surfaces under normal and tangential loads will appear in the form of slip and adhesion, which affects the service life of mechanical equipment. Bolted connection structures cause
[...] Read more.
Bolt connection structure is a common form of connecting large and complex equipment. Its object contact surfaces under normal and tangential loads will appear in the form of slip and adhesion, which affects the service life of mechanical equipment. Bolted connection structures cause changes in stiffness and damping, which have great impacts on the dynamic characteristics. Experimental studies and numerical simulations have difficulty predicting the overall performance of bolts in a timely manner, hence cannot ensure the reliability and safety of complex equipment. In order to improve the overall performance of complex equipment, it is necessary to study the contact theory model of bolt connection structures. Based on the relationship between friction force and velocity in the classical friction model, the mathematical expressions of restoring force and tangential displacement in the kinetic theory model are deduced to predict the stiffness degradation of the bolted structure and to characterise the kinetic properties and laws of the bolted structure. From the perspective of theoretical calculation, it makes up for the situation in which it is difficult to measure the performance of bolts due to the existence of spanning scale and provides theoretical support for the reliability of connecting complex equipment. This paper summarises and analyses the contact theory model of bolt connection structures, ranging from macroscopic to microscopic; describes the static friction model, kinetic friction model, statistical summation contact model, fractal contact model; and analyses the influencing factors of the microscopic contact mechanism. The advantages and disadvantages of the kinetic theoretical models are described, the manifestation of friction and the relationship between tangential force–displacement are discussed, and the key research directions of the kinetic theoretical models of bolted structures in the future are elucidated.
Full article
Figure 1
Open AccessArticle
Mechanical and Tribological Behavior of Nitrided AISI/SAE 4340 Steel Coated with NiP and AlCrN
by
Marcos E. Soares, Qianxi He, Jose M. DePaiva, Bruna M. de Freitas, Paulo Soares, Stephen C. Veldhuis, Fred L. Amorim and Ricardo D. Torres
Lubricants 2024, 12(5), 181; https://doi.org/10.3390/lubricants12050181 - 17 May 2024
Abstract
In this study, novel surface engineering strategies to improve the wear performance of AISI 4340 were investigated. The strategies were as follows: (i) NiP deposition on a previously nitrided steel substrate, followed by NiP interdiffusion heat treatment at either 400 °C or 610
[...] Read more.
In this study, novel surface engineering strategies to improve the wear performance of AISI 4340 were investigated. The strategies were as follows: (i) NiP deposition on a previously nitrided steel substrate, followed by NiP interdiffusion heat treatment at either 400 °C or 610 °C (referred to as duplex treatment); (ii) the deposition of AlCrN PVD coating on NiP layers on a previously nitrided steel substrate (referred to as triplex treatment). Prior to the deposition of AlCrN, the NiP was subjected to the interdiffusion heat treatment at either 400 °C or 610 °C. These strategies were compared with the performance of the AlCrN coating directly applied on nitrided steel. To characterize the microstructural features of each layer, X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) analysis were conducted. We also carried out mechanical and tribological behavior assessments. The tribological tests were carried out using a ball-on-disc tribometer under a constant load of 20 N and a tangential speed of 25 cm/s; cemented carbide spheres with a diameter of 6 mm were the counterpart body. The friction coefficient was continuously monitored throughout the tests. The results reveal that the wear mechanism for the AlCrN coating is predominantly oxidative. The most wear-resistant surface architecture was the one comprising AlCrN over the NiP layer subjected to interdiffusion heat treatment at either 400 °C or 610 °C.
Full article
(This article belongs to the Special Issue Wear-Resistant Coatings and Film Materials)
►▼
Show Figures
Figure 1
Highly Accessed Articles
Latest Books
E-Mail Alert
News
Topics
Topic in
JFB, JMMP, Lubricants, Machines, Materials
Advanced Manufacturing and Surface Technology
Topic Editors: Dingding Xiang, Junying Hao, Xudong Sui, Kaiming WangDeadline: 30 December 2024
Conferences
Special Issues
Special Issue in
Lubricants
Gas Lubrication and Dry Gas Seal
Guest Editors: Jianjun Du, Kai Zhang, Tianwei Lai, Changlin LiDeadline: 15 June 2024
Special Issue in
Lubricants
Tribology for Lightweighting
Guest Editors: Montserrat Vilaseca, Leonardo PelcastreDeadline: 30 June 2024
Special Issue in
Lubricants
Preparation, Tribological Behavior, and Applications of Lubricant Additives
Guest Editor: Jincan YanDeadline: 20 July 2024
Special Issue in
Lubricants
Advances in Water-Based Nanolubricants
Guest Editors: Hui Wu, Pradeep MenezesDeadline: 31 July 2024
Topical Collections
Topical Collection in
Lubricants
Rising Stars in Tribological Research
Collection Editor: Max Marian