Lubrication Properties Research Articles

The influence of the particle size and size synergistic effect of nano-copper on the tribological properties of lubricants

Friction and wear reduction are urgently sought to promote energy savings and performance of precision manufacturing equipment. The molecular dynamics (MD) simulation unveils the detailed lubrication mechanisms of the particle size effect of single Cu NPs and the size synergy effect of multiple Cu NPs. By setting various particle sizes and quantities, the tribological properties of the lubrication system under multiple complex conditions are compared. The stress, strain, wear volume, friction force, normal force, and temperature at the fluid-solid boundary are quantitatively calculated. The results indicate that the average values of friction force are maximally reduced approximately 83.65 %, the wear rate is maximally decreased 22.5 %, the max stress is maximally reduced 22.46 % and the peak temp is maximally reduced 8 % after the addition of Cu NPs. The tribological properties improves as particle size increases, but there is an optimal Cu NP size that yields the best tribological properties. In addition, the tribological properties of the multiple particles are superior to those of the single particle. The results indicate that small and uniform Cu NPs show superior tribological properties over dispersed sizes, small Cu NPs can contribute to improve the overall tribological properties of the system primarily comprises large Cu NPs.

Analysis and Prospects of Lubrication and Friction Characteristics in Cold Strip Rolling: A Review

Lubrication and friction are the core processes in cold strip rolling, which are the key links to realizing the stable production of high‐quality strips, reflecting country advanced level in rolling technology. This review investigates the crucial properties of lubrication and friction in cold strip rolling by analyzing the mechanism, characterization methods, and influencing factors. The lubricant forms an oil film on the surface of rolls and strips based on the lubrication dynamics and tribology theory, changing the asperity contact state in the loaded roll gap, leading to changes in friction characteristics. Oil film thickness and coefficient of friction (COF) are crucial parameters for characterizing and judging the characteristics of lubrication and friction, theoretical calculations have become the core analytical method, and the study of the measurement method is still a great challenge. Parameters like rolling speed and oil viscosity affect the lubricant distribution and asperity contact in the loaded roll gap, changing the lubrication and friction state. The influence of parameters is strongly linked to the experimental or rolling environment. Prospective research trends on lubrication and friction in cold strip rolling are presented based on the status of research on lubrication and friction characterization.

Effect of elastic deformation on squeezing film lubrication properties of soft tribocontacts with microstructured surface

PurposeInspired by the high-friction performance of the soft toe pads of tree frogs, this study aims to investigate the effect of elastic deformation on the lubrication properties of squeezing films inside soft tribocontacts with microstructured surface under wet conditions.Design/methodology/approachA one-dimensional hydrodynamic extrusion model was used to study the film lubrication characteristics of conformal contact. The lubrication characteristics of the extruded film, including load-carrying capacity, liquid flow and surface elastic deformation, were obtained through the simultaneously iterative solution of the fluid-governing and deformation equations.FindingsThe results show that the hydrodynamic pressure is approximating parabolically and symmetrically distributed in the contact area, and the peak value appears in the center of the extrusion surface. Elastic deformation increases the thickness of the liquid film, weakens the bearing capacity and homogenizes the liquid flow rate of inside soft friction contact. The magnitude of this effect greatly increases as the initial liquid film thickness decreases. Moreover, the elastic deformation directly affects the average film thickness of the extrusion contact. Narrow and shallow microchannels are found to result in a more prominent elastic deformation on the microstructured soft surface.Originality/valueThese results present a design for soft tribocontacts suitable for submerged or wet environments involving high friction, such as wiper blades, in situ flexible electrons and underwater robots.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0049/

Lubricant Strategies in Osteoarthritis Treatment: Transitioning from Natural Lubricants to Drug Delivery Particles with Lubricant Properties.

Osteoarthritis (OA) is a debilitating joint disease characterized by cartilage degradation, leading to pain and functional impairment. A key contributor to OA progression is the decline in cartilage lubrication. In physiological conditions, synovial fluid (SF) macromolecules like hyaluronic acid (HA), phospholipids, and lubricin play a crucial role in the boundary lubrication of articular cartilage. In early OA, cartilage damage triggers inflammation, altering SF composition and compromising the lubrication layer. This increases friction between mating interfaces, worsening cartilage degradation and local inflammation. Therefore, early-stage restoration of lubrication (by injecting in the joint different classes of compounds and formulations) could alleviate, and potentially reverse, OA progression. In the light of this, a broad variety of lubricants have been investigated for their ability to reduce friction in OA joints and promote cartilage repair in clinical and preclinical studies. This review examines recent advancements in lubricant-based therapy for OA, focusing on natural, bioinspired, and alternative products. Starting from the currently applied therapy, mainly based on natural lubricants as HA, we will present their modified versions, either in hydrogel form or with specific biomimetic moieties with the aim of reducing their clearance from the joint and of enhancing their lubricating properties. Finally, the most advanced and recent formulation, represented by alternative strategies, will be proposed. Particular emphasis will be placed on those ones involving new types of hydrogels, microparticles, nanoparticles, and liposomes, which are currently under investigation in preclinical studies. The potential application of particles and liposomes could foster the transition from natural lubricants to Drug Delivery Systems (DDSs) with lubricant features; transition which could provide more complete OA treatments, by simultaneously providing lubrication replacement and sustained release of different payloads and active agents directly at the joint level. Within each category, we will examine relevant preclinical studies, highlighting challenges and future prospects.

A Thermal Model for a Hybrid Gas Bearing System in Oil-Free Turbochargers

Abstract With little drag friction, gas bearings operate at high rotor speed and high temperature and thus enable long operating life along with material damping for mechanical energy dissipation. However, most computational tools for modeling gas bearings are not accessible to bearing manufacturers or potential end-users, and the models are restricted to specific geometries and operating conditions or are missing important features, thus limiting their utility. This paper presents the thermal energy transport in a hybrid gas bearing for oil-free turbochargers with integrated heat and fluid flow models to produce a comprehensive thermo-hydrodynamic analysis predictive tool, and to design and evaluate air-lubricated gas bearings by predictions and experiments. An efficient algorithm couples the solution of the Reynolds equations and the thermal energy transport equations in the film between the rotor and a pad of the hybrid gas bearing, and updates the temperature-dependent viscosity and film thicknesses during the iterative process. The test repeats and averaged for each rotor speed from 2 krpm to 22 krpm at intervals of 2 krpm, for supply pressure varying along 25 psi to 100 psi and predicted film temperature matches well with the measured one. The parameters of interest in this analysis include the gas supply condition, bearing configuration, and the gas properties at high altitudes and high rotation speeds. The parametric study results show the density and kinematic viscosity are the most dominant properties of the gas lubrication for the film temperature.

Characterization of Graphite and ZrO2 Reinforced Aluminium Metal Matrix Composite For Enhanced Mechanical Properties in Electronics Applications

Abstract The objective of this work is to examine the wear properties of a hybrid Metal Matrix Composite (MMC) consisting of 92 weight percent (wt. %) Aluminium Alloy 6061 (AA6061), 2 wt. % Graphite (C), and 6 wt. % Zirconium Dioxide (ZrO2). It was previously determined that this composition was ideal for improved metallurgical and mechanical properties. Nine specimens of the same composition were fabricated for this continuation work and put through wear tests with different applied load, sliding velocity, and sliding distance settings. To evaluate the performance of the composite, measurements were made of the wear rate and Coefficient of Friction (COF). According to the results, the wear rate typically increased as the applied load and sliding velocity increased. At the lowest load (10 N) and velocity (2 m/s), the lowest wear rate (50.90 µg) and COF (0.197) were noted. Specimens with lower wear rates had smoother surfaces and less wear, as revealed by SEM analysis of the worn surfaces; specimens with higher wear rates showed more significant surface damage, such as deeper cuts and serrations. In specimens with less wear, XRD analysis verified the presence of crystalline aluminium, indicating a strong correlation between wear resistance and the crystalline structure of the composite. Linear regression equations were created to predict wear behavior under different conditions. According to the results, the composite's wear characteristics are greatly influenced by the sliding velocity and applied load. ZrO2 and C together have lubricating and strengthening properties that, under certain circumstances, reduce wear. The composite exhibits potential for usage in electronics applications, especially in components where wear resistance and mechanical durability are critical due to its favorable wear characteristics and mechanical properties.

An ionic liquid crystal functionalized nanocellulose lubricant additives

Cellulose, one of nature's most abundant, clean, and sustainable resources, has often shown unsatisfactory results when used as bio-lubricant additives. Herein, nanocellulose (NC) from amorphous waste natural poplar was extracted using deep eutectic solvent encapsulation treatment and chlorine bleaching process. Subsequently, 1-hexadecyl-3-methylimidazolium bromide was integrated onto NC using a one-step hydrothermal treatment (high-temperature and high-pressure environment) to obtain ionic liquid crystal (ILC) functionalized products (named as ILC-NC). After ball-milling process and solid phase separation step, ILC-NC exhibits excellent dispersion stability and lubrication properties in the liquid phase (including water and vegetable oil). Based on the polar and colloidal activity properties of ILC, it can form an ordered molecular layer on NC surface and form a lubricating film-like structure, making NC smoother and sliding well. Compared to ILC/NC aqueous dispersion, ILC-NC reduces the coefficient of friction and wear rate on steel disk surface by 68.75 % and 74.07 %, respectively. The minimum coefficient of friction was further reduced to 0.032 as dispersing ILC-NC in sunflower oil, showing a reduction of 0.134 (77.91 %) compared to pure sunflower oil. Finally, the lubrication theoretical model calculation reveals the lubrication state of ILC-NC on the steel disk surface and proposes the lubrication mechanism.

Enhancing protein content and lubrication behavior of plant-based milk with microparticulated wheat gluten protein via SS-SH interchange

The protein fortification and mouthfeel improvement (achieving dairy-like lubrication properties) in plant-based dairy alternatives have consistently been challenging tasks. To achieve this task, we developed a fully plant-based milk product by enhancing lubrication through microparticulated wheat gluten particles. By utilizing a combination of pH shifting, disulfide bond reductants, and high-pressure microfluidization, SH-SS exchange reactions were successfully induced, leading to the preparation of microparticulated wheat gluten particles with a particle size ranging from 1 to 2 μm and excellent dispersion properties. Introduction of a thiol-blocking agent confirmed the dominance of disulfide bonds in particle formation. The findings demonstrated that even at a high protein concentration of 15%, microparticulated wheat gluten sample maintained good flowability. Friction analysis revealed that the micro-particulated gluten protein treated with a disulfide bond reducing agent (GRM) exhibited a lower friction coefficient compared to other samples. Upon the addition of oat milk, GRM effectively reduced the coefficient of friction while increasing the protein content (5 wt%), achieving a lubrication effect similar to that of microparticulated whey protein. This study provides a novel solution for the preparation of microparticulate wheat gluten and enhances its incorporation into plant-based dairy products, offering a new approach to developing high-protein plant-based dairy products with improved mouthfeel and texture.

Understanding the role of tungsten species in diamond-like carbon coatings for enhanced interaction with ionic liquids

This study investigated the impact of tungsten species in tungsten-doped diamond-like carbon (WDLC) coatings on their interactions with ionic liquids (ILs). Using analytical techniques such as in-situ neutron reflectometry, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy, we examined the adsorption mechanism of tributylmethylphosphonium dimethylphosphate on WDLC and undoped hydrogenated DLC (hDLC) coatings. These techniques provide high-resolution insights into the molecular interactions, revealing that tungsten doping enhances the formation of tungsten carbide and tungsten oxides. These species facilitate the dissociation of dimethylphosphate anions, forming a robust 0.75 nm-thick tungsten phosphate layer on the WDLC surfaces. This layer, which adheres strongly even after cleaning, underscores the role of tungsten in enhancing the effectiveness and lubrication properties of WDLC coatings with ILs.

Probing fretting wear behavior of gauge-changeable spline axle under rotational bending loads

The latest generation of gauge-changeable trains in China feature designs with their wheels and axles connected by spline couples and cylindrical fits. In comparison to the interference fitted wheelset, the spline axle with clearance fit is more prone to fretting damage. In this study, the stress distribution of spline axle was analyzed using finite element method. Then, a rotatory bending test on scaled wheel/axle samples was conducted to reveal the fretting wear behavior of the gauge-changeable axle. During traction, the contact stress of the spline peaks at 311 MPa on the tooth’s root side, with a corresponding relative slip of 14 μm. Fretting wear is observed in the spline axle, the damage zone of the wheel seat can be categorized into five bands (A–E), and severely damaged areas are covered with red-brown debris. Moreover, the main damage mechanism of untreated spline axle and surface-modified spline axle is delamination accompanied with oxidation. The improved properties of plasma nitriding and grease lubricant are attributed to the high surface hardness and residual compressive stress, as well as low frictional stress.

Tough, Slippery, and Low-Permeability Multilayer Hydrogels Modified by Anisotropic Fiber Membrane for Soft Tissue Replacement.

Hydrogels with sustained lubrication, high load-bearing capacity, and wear resistance are essential for applications in soft tissue replacements and soft material devices. Traditional tough or lubricious hydrogels fail to balance the lubrication and load-bearing functions. Inspired by the gradient-ordered multilayer structures of natural tissues (such as cartilage and ligaments), a tough, smooth, low-permeability, and low-friction anisotropic layered electrospun fiber membrane-reinforced hydrogel was developed using electrospinning and annealing recrystallization. This hydrogel features a stratified porous network structure of varying sizes with tightly bonded interfaces, achieving an interfacial bonding toughness of 1.6 × 103 J/m2. The anisotropic fiber membranes, mimicking the orderly fiber structures within soft tissues, significantly enhance the mechanical properties of the hydrogel with a fracture strength of 20.95 MPa, a Young's modulus of 29.64 MPa, and a tear toughness of 37.94 kJ/m2 and reduce its permeability coefficient (6.1 × 10-17 m4 N-1 s-1). Meanwhile, the hydrogel demonstrates excellent solid-liquid phase load-bearing characteristics, which can markedly improve the tribological performance. Under a contact load of 4.1 MPa, the anisotropic fiber membrane-reinforced hydrogel achieves a friction coefficient of 0.036, a 219% reduction compared with pure hydrogels. Thus, the superior load-bearing and lubricating properties of this layered hydrogel underscore its potential applications in soft tissue replacements, medical implants, and other biomedical devices.

Selection of the Lubricating Oil Components Based on the Molecular Adsorption Characteristics

Abstract The adsorption characteristics of the lubricating oil near the solid surface play crucial roles in the lubricating performance. In this paper, the molecular dynamics simulation implemented by MS software was carried out to reveal the adsorption properties of different lubricants on Fe2O3 surfaces. Several kinds of lubricating oil molecules were employed, namely, n-eicosane, 2, 6, 11, 15-tetramethylhexadecane, 2-decyldecahydronaphthalene and tetradecylcyclohexane. The results show that 2, 6, 11, 15-tetramethylhexadecane and 2-decyldecahydronaphthalene are relatively more favorable as the lubricant components. This is because they both have relatively high adsorption density, low molecular diffusivity and large adsorption energy. These results can provide a theoretical basis for the selection of future lubricant components as well as lubricant performance enhancement for blending.

Comparative Investigation of Lubricant Properties of Pongamia and Castor Oil Bio Lubricant Blended with (SAE20W40) Mineral Oil

The present work deals with the comparative evaluation of physicochemical, rheological FTIR and tribological properties between pongamia and castor oil blended with SAE20W40 by varying their proportions ranging from 10-30% (by volume) as bio-lubricant. Among all the blends, the flash point and pour point of castor blend S4 were found to be 281°C and -19°C which can be comparable to SAE20W40. The viscosity at 40°C and 100°C and viscosity index of castor blends were approximately 100 mm2/s, 14 mm2/s and 145 respectively. FTIR analysis also confirms the presence of vital carbonyl ester functional group in castor blends with oxidation onset temperature of 243°C. The tribological studies that were carried out using pin on disc tribometer as per ASTM G99-95a standards also showed that blend S4 had coefficient of friction 0.056 at higher load which was comparable to SAE20W40. Although all the blends had low oxidation stability temperature, yet castor blend S4 showed equivalent properties with commercial lubricant SAE20W40. This confirmed its suitability as a bio-lubricant base stock, supported by its physiochemical, rheological, FTIR, tribological properties.

Fabrication of photocurable zwitterionic polymer coatings with enhanced antifouling and lubrication properties for urinary catheter applications

Urinary catheters necessitate a surface with antifouling and lubricating properties in order to mitigate bacterial infection, calculus formation, and tissue trauma. Hydrophilic coating is a promising strategy but suffers from the complications of the manufacturing method as well as the lack of longevity. Herein, we report an antifouling and lubricating hydrophilic coating based on zwitterionic copolymer poly(2-Methacryloyloxyethyl phosphatidylcholine-co-hydroxyethyl methacrylate-co-(Benzoyl)phenyl methacrylate (poly(MPC-co-HEMA-co-BP)) through pre-gel solution spin-coating followed by UV-curing. The poly(MPC-co-HEMA-co-BP (PMHB) coatings possess hygroscopic properties that facilitate the formation of a hydrated layer, thereby leading to friction reduction. Moreover, both antibacterial and protein resistance tests substantiate the exceptional antifouling characteristics exhibited by the PMHB coating. Furthermore, after 7 days of coincubation, the antibacterial rates of PMHB coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Proteus mirabilis (P. mirabilis) are 72.98 %, 75.11 %, and 88.23 %, respectively. Subsequently, PMHB coating reduced the attachment of encrustation in a 7 days artificial urine cycling experiment. This study brings new perspective on designing urinary catheter surfaces with lubricating and antifouling properties.

Biomass-Derived Carbons as Friction Reducing Additives for Lubricants: Tribological Properties of Biochars and Activated Carbons Obtained from Sugar Cane Bagasse

Activated carbons are commonly used for adsorption/depollution applications, but only a few studies are related to their lubricating properties. In order to investigate a new family of friction reducers, the tribological properties of biochars and derived activated carbons obtained from sugar cane bagasse are investigated. Activated carbons are obtained from either a physical (steam water) or chemical (with phosphoric acid) activation process. The tribological tests show that the activated carbons present very low friction coefficients, close to 0.08. The correlation of textural and tribological investigations shows that the specific surface area of the compounds as well as the microporous and mesoporous domain extensions are key parameters to optimize the friction reduction properties of activated carbons. The friction properties of the compounds are improved if the mesoporous domain extension is above 40% of the total porous volume. This study shows that local biomass waste valorization is possible and that sugar cane bagasse-derived activated carbons appear as interesting new friction reduction additives for lubricants.

Rheological and tribological properties of xanthan gum-fucoidan mixture: Effect of NaCl, KCl, and CaCl2

This study endeavored to investigate the effects of salts (NaCl, KCl, and CaCl2) on the rheological and tribological properties of xanthan gum (XG)-fucoidan mixtures. With increasing salt concentrations, the intrinsic viscosity (56.1–30.9 dL/g) of mixtures decreased, with pronouncedly lower values (30.9–35.8 dL/g) observed with CaCl2 addition compared to monovalent salts addition (36.4–46.6 dL/g). This indicates a contraction of hydrodynamic size of the polymers due to the charge screening effect of cations and the formation of a more compact conformation in the presence of CaCl2 than with either NaCl or KCl addition. FTIR analysis revealed changes in the interaction between the two polymers in the presence of each salt. All samples exhibited shear-thinning behavior, and their thixotropic behavior increased as the salt concentration increased. The apparent viscosity and viscoelastic moduli decreased in the presence of monovalent salts but were increased in the presence of CaCl2. This was attributed to the crosslinking effect of Ca2+; Na+ and K+ did not induce crosslinking. In addition, the friction coefficient (μ) of mixtures containing salts reached the maximum at a lower entrainment speed (0.08–0.17 mm·s−1) than that without salt (1.54 mm·s−1), and the mixtures containing salts exhibited lower maximum μ values (0.28–0.62) compared to that without salt (0.83), indicating an improvement in the lubricant properties of XG-fucoidan mixtures. Our findings may help broaden the application of fucoidan in the food industry.

Advancements and challenges in bionic joint lubrication biomaterials for sports medicine

AbstractBionic lubricant materials are a class of materials inspired by natural organisms and offer excellent lubrication properties and biocompatibility. In the field of sports medicine, their application opens up new possibilities for the prevention and treatment of sports‐related diseases. The authors will introduce the existing theoretical models of friction in the locomotor system, the characteristics and advantages of biomimetic lubrication materials and discuss in depth their applications in the field of sports medicine. The development of bionic lubrication materials opens up unprecedented opportunities for sports medicine to provide more effective and long‐lasting treatment options for patients.

Borate ester hybrid photothermal nanofluid derived from C3N4/MoS2 catalyzed esterification for efficient organic-inorganic synergistic lubrication

The inferior dispersion stability and simple functionality of MoS2-based nanofluids restrict their efficient application in lubrication. Herein, a novel nanofluid composed of C3N4/MoS2, 3-isocyanatopropyltrimethoxysilane, and C3N4/MoS2-catalyzed product (polyethylene glycol-borate ester, PEG-BA) was proposed. C3N4 nanosheets could induce the formation of regular MoS2 nanospheres. The resulting C3N4/MoS2 showed excellent catalytic activity for the esterification of PEG-BA. The C3N4/MoS2 @PEG-BA nanofluid exhibited favorable dispersion stability in PEG600 with no stratification for ≥ 82 days. The addition of 3.0 wt% C3N4/MoS2 @PEG-BA nanofluid could significantly reduce friction coefficient (30.7 %) and wear scar diameter (28.9 %). The excellent lubrication properties of the nanofluid are attributed to the synergistic lubrication effect of C3N4/MoS2 and PEG-BA. Furthermore, the nanofluid exhibits remarkable photothermal conversion performance in both oil and air mediums.

Plant-Based Oils for Sustainable Lubrication Solutions—Review

Traditional lubricants, often containing harmful chemicals and synthetic or fossil-derived oils, pose environmental risks by damaging ecosystems and threatening human health and wildlife. There is a growing demand for environmentally sustainable and cost-effective bio-based lubricants derived from renewable raw materials. These bio-based oils often possess natural lubricating properties, making them an attractive alternative to traditional synthetic lubricants. In addition to providing effective lubrication, they offer good biodegradability and minimal toxicity, which are essential for reducing environmental impact. However, the primary challenge lies in optimizing their performance to match or surpass that of conventional lubricants while ensuring they remain cost-effective and widely available. This paper reviews the general requirements for lubricants and explores how plant-based oils can be utilized to meet the diverse lubrication needs across various industries. Further, it highlights different approaches that can be used for further improvements in the area of plant-based lubrication through bio-inspired means, such as the use of estolides, wax esters, or erucic acid, as well as through additions of nanomaterials, such as nanoparticles, nanoclays, or two-dimensional films.

Skiing-inspired robust lubricating composite coatings from thermally sprayed ceramic template

Inspired by the mechanism of skiing, herein, a novel composite coating with excellent lubrication properties was developed by incorporating solid-liquid reversible lubricating phases into the inherent microcracks and pores of thermally sprayed ceramic coatings. The results indicate that the crystalline-amorphous heterostructure formed within the micro-nano cracks, enhancing their cohesive strength and toughness. Compared to traditional ceramic coatings, the friction coefficient of the composite coating has been reduced by 80 %, while the wear rate decreased from 2.89 × 10−4 to 6.44 × 10−7 mm3∙N−1∙m−1. Under the applied load and friction-induced heat, a thin liquid lubrication film is formed. Importantly, the lubricating phase continuously overflows from defects under the induction of frictional heat to replenish the lubricating film, ensuring long-term lubrication of the coating.