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Purpose: This study aims to prepare thymol-based deep eutectic solvents (DESs) and use them as lubricates for friction and wear tests to simulate the wear conditions of hybrid bearings. Design/methodology/approach: Through the characterization and analysis of the morphology of wear scars and the elemental composition of friction films, the tribological behavior and wear mechanism of sample materials as lubricants were investigated and the anti-wear mechanism of thymol-based DESs was discussed. Findings: The findings demonstrate that because of the formation of a fluid lubrication film and excellent kinematic viscosity, the lubrication effect of the prepared DES is improved by about 50% compared to the base lubricating oil. The prepared [Ch]Cl-thymol DES has a better anti-friction and lubrication effect than citric-thymol, EG-thymol and urea-thymol DESs, with an average friction coefficient of about 0.04. Originality/value: In this work, the friction reduction properties of thymol-based DESs were studied as lubricants for the first time, and the lubrication mechanism of sample materials was investigated. [ABSTRACT FROM AUTHOR]

Poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), as a highly hydrophilic as well as biocompatible material, has been widely used in biomedical applications. In this study, the friction reduction and wear resistance of HXLPE were improved by grafting PMPC on its surface. However, the PMPC will be sheared off during friction, which is difficult to meet the long-term service requirements of artificial joints. This can be achieved by improving the lubrication environment to minimize PMPC shedding. To simulate the human lubrication environment, free PMPC (lubrication factor) and Cu2+ (transition group metal ion catalyst) were added to neonatal bovine serum (NBCS). When the friction pair consisting of grafted PMPC-modified HXLPE and Cu/ZrO2 ceramics is rubbed therein, the grafted PMPC interacts with the free PMPC, while Cu2+ catalyzes the oxidative hydrolysis of serum proteins into carbon-containing small molecules and adsorbs on the surface of the Cu/ZrO2 ceramics to form a carbon-rich lubrication layer. The composite lubrication layer consisting of grafted-free PMPC and carbon-rich lubrication layer provides good load-bearing and lubrication properties at the friction interface. And the wear rate is reduced by 45% compared to rubbing in deionized water. This technique can reduce the shedding of grafted PMPC state and improve the load-bearing performance of the interfacial lubrication layer, thus reducing the wear of HXLPE and prolonging the service life of the artificial joint. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the effects of nanoadditive lubricants on the vibration and noise characteristics of helical gears compared with conventional lubricants. The experiment aims to analyze whether nanoadditive lubricants can effectively reduce gear vibration and noise under different speeds and loads. It also analyzes the sensitivity of the vibration reduction to load and speed changes. In addition, it compares the axial and radial vibration reduction effects. The goal is to explore the application of nanolubricants for vibration damping and noise reduction in gear transmissions. The results provide a basis for further research on nanolubricant effects under high-speed conditions. Design/methodology/approach: Helical gears of 20CrMnTi were lubricated with conventional oil and nanoadditive oils. An open helical gearbox with spray lubrication was tested under different speeds (200–500 rpm) and loads (20–100 N·m). Gear noise was measured by a sound level meter. Axial and radial vibrations were detected using an M+P VibRunner system and fast Fourier transform analysis. Vibration spectrums under conventional and nanolubrication were compared. Gear tooth surfaces were observed after testing. The experiment aimed to analyze the noise and vibration reduction effects of nanoadditive lubricants on helical gears and the sensitivity to load and speed. Findings: The key findings are that nanoadditive lubricants significantly reduce the axial and radial vibrations of helical gears under low-speed conditions compared with conventional lubricants, with a more pronounced effect on axial vibrations. The vibration reduction is more sensitive to rotational speed than load. At the same load and speed, nanolubrication reduces noise by 2%–5% versus conventional lubrication. Nanoparticles change the friction from sliding to rolling and compensate for meshing errors, leading to smoother vibrations. The nanolubricants alter the gear tooth surfaces and optimize the microtopography. The results provide a basis for exploring nanolubricant effects under high speeds. Originality/value: The originality and value of this work is the experimental analysis of the effects of nanoadditive lubricants on the vibration and noise characteristics of hard tooth surface helical gears, which has rarely been studied before. The comparative results under different speeds and loads provide new insights into the vibration damping capabilities of nanolubricants in gear transmissions. The findings reveal the higher sensitivity to rotational speed versus load and the differences in axial and radial vibration reduction. The exploration of nanolubricant effects on gear tribological performance and surface interactions provides a valuable reference for further research, especially under higher speed conditions closer to real applications. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0220/ [ABSTRACT FROM AUTHOR]

When exposed to high surface temperatures, engine lubricating oils degrade and may form solid deposits, which cause operational issues and increase shutdown time and maintenance costs. Despite its being a common issue in engine operation, the information available on the mechanics of this phenomenon is still lacking, and the experimental data and conditions must be updated to match the improvements in both lubricant stability and engine efficiency. To this end, an experimental apparatus has been developed to study the mechanisms that lead to the degradation and deposit formation of lubricants at high temperatures. The apparatus is designed to operate at pressures up to 69 bar, surface temperatures up to 650 °C, oil bulk temperatures up to 550 °C, and flow rates of <14 mL/min. In this apparatus, the oil is cycled through a heated test section, and deposits accumulate on the heated surface. The time required for deposits to start accumulating under the test conditions is determined based on the recorded temperature traces, and collected oil and deposit samples may be analyzed to determine changes in composition over time due to high-temperature exposure. The removable test section can be modified to accommodate different geometries, surface materials, and flow paths to adapt the instrument to a range of potential research directions. This paper presents the technical details of the new apparatus and the steps taken to characterize the experimental conditions. In addition, sample data are provided to show the unique capabilities of the new instrument, and an Arrhenius plot for Castrol Perfecto X 32 in the surface temperature range of 445–475 °C is presented as a demonstration of its use for quantifying the coking delay time. The new instrument detailed herein is the first such device to demonstrate a reliable, lab-scale technique for studying lube oil coke formation and deposition at temperatures and pressures of interest to power generation gas turbines. [ABSTRACT FROM AUTHOR]

It is well known that lubricating oils reduce the friction coefficient between two surfaces in contact. Since petroleum lubricants are toxic and have a low biodegradability, they are typically not appropriate for the environment. As a result, as public worries about a pollution-free environment grow, so does the demand for lubricants that are acceptable to the environment. The primary rationale for utilizing vegetable oils in forthcoming bio-lubricant formulations is their high lubricating performance, low toxicity, sustainable, and biodegradability. Plant oils hold great potential as a foundational fluid for bio-lubricants, since their synthetic and vegetable oil-based esters provide the most environmentally friendly option for creating lubricants. In this study, Jatropha and Jojoba raw oil were chemically modified via epoxidation followed by transesterification to produce bio-lubricants. Thus, the aim of this work is to develop a bio-lubricant from jatropha and jojoba methyl ester, further adding nanoparticles multiwalled nanotubes and titanium dioxide for improvement of tribological properties. The chemical modification of the jatropha and jojoba oil results in a decrease in iodine value, resulting in the breaking of carbon bonds. Viscosity tests were performed using the Anton Par MCR 92 Rheometer, with temperature ranging from 30°C to 80°C. Thermal stability measurements of bio-lubricants were performed using PerkinElmer’s Thermogravimetric analyzer-4000 instrument and thermal degradation temperature for Epoxidized Jatropha-sulfuric acid, Epoxidized Jatropha-hydrochloric acid, Epoxidized Jojoba-sulfuric acid and Epoxidized Jojoba-Hydrochloric acid samples are 238°C, 224°C, 230°C, and 244°C, respectively. The 94.68% and 79.85% reduction in wear was obtained for Epoxidized Jojoba with hydrochloric acid, titanium dioxide and epoxidized Jatropha with sulfuric acid, multiwalled carbon nanotubes in comparison with their epoxidized samples. The coefficient of friction of Epoxidized Jatropha with sulfuric acid, multiwalled carbon nanotubes and Epoxidized Jojoba with Hydrochloric acid, Titanium dioxide sample was found to be 0.061 and 0.059, respectively [ABSTRACT FROM AUTHOR]

Improving the lubricating properties of base oils through additives is a crucial objective of tribological research, as it helps to reduce friction and wear of materials. Molybdenum disulfide (MoS2) is a 2D nanomaterial with excellent tribological properties that is often used as a lubricant additive. Several studies have been conducted on the preparation and utilization of MoS2 and its nanocomposites as lubricant additives. This paper reviews the research progress on MoS2 nanomaterials as lubricant additives. It firstly introduces various synthesis methods of MoS2 nanomaterials while focusing on the preparation of nano-MoS2 as lubricant additives. It then summarizes the dispersion stability of nano-MoS2 in lubricating oils which has been paid extensive attention. Moreover, this paper reviews and discusses the tribological properties of nano-MoS2 and its various composites as lubricant additives. The possible anti-wear and friction reduction mechanisms of nano-MoS2 and its composites are also discussed. Finally, this paper presents the challenges faced by nano-MoS2 additives in the field of lubrication and the prospects for future research in view of previous studies. [ABSTRACT FROM AUTHOR]

The total loss lubrication system that is typical of chainsaws is responsible for a massive dispersion in the agro-forestry environment of highly impactful pollutants, mostly of fossil origin, often well known as carcinogenic substances, which, in addition to presenting a risk to the environment, represent an important risk factor for human health, especially for chainsaw users. During its use, the chain lubricant is dispersed from the guide bar tip in the form of droplets and aerosol, or it is adsorbed on wood residues and sawdust. Then, it is subjected to drift, settles on the ground and vegetation, and can hit the operators, who, after prolonged exposures, can suffer both irritation of the respiratory tract and dermal absorption. Such a risk factor is often amplified by the widespread use of less-expensive, sometimes illegal alternatives, such as exhausted motor oils. To mitigate said negative effects, a process has been in progress for several years that is aimed at replacing conventional lubricants with synthetic or biobased oils with increasing biodegradability. As a contribution to this process, a study has been started on the possibility of using refined olive pomace oil (ROPO) as a base stock for the formulation of a totally biodegradable chainsaw lubricant. On purpose, to improve its properties of viscosity and adhesivity, such an oil was added with a biodegradable thickening agent, obtaining four formulations with different viscosity. After a lab test and a preliminary cutting test on firewood, the formulation with 2% of thickener resulted in being the best, and 3.0 g kg−1 of tert-butylhydroquinone (TBHQ), a food-grade antioxidant, was then added to form the final formulation (F2) to be compared, in the subsequent four test sessions, to a biodegradable commercial chain lubricant (SB). The tests were carried out without changing the chainsaw setting, on different wood species, both in forest and, with the aim of increasing the repeatability of tests conditions and comparability of results, at a fixed point. The fluids' performances were mainly evaluated based both on the operators' opinions and on the measurements of the chain–bar temperatures and of saw chain wear related to a predefined number of cuts. As to the destiny of the fluid dispersed during cutting, the overall dispersion was assessed by considering the average working time, the consumption of chain lubricant, and the forest area cut down daily. Eventually, the amounts of inhalable and respirable dust particles as vectors of oil residues were quantified by means of personal air samplers worn by the operators and analyzed to determine any differences in the concentration of metallic elements. The test results evidenced chain temperatures that were 0.5, 4.9, and 12.5 °C higher with F2 relating to SB, respectively, in the cutting of trunks of fresh Pinus, Eucalyptus, and dry Pinus. They were accompanied by chain weight losses of 89.5% and 35% higher with F2 relating to SB, respectively, in cutting tests of Turkey oak and Poplar. Such a greater wear, however, apparently did not affect the saw chain's cutting efficiency with F2, since the operators declared that they did not notice any difference between the performances of the two fluids at the time of comparison. The effects of higher wear on the chain lifetime, any deriving risks for the operator's safety, and the possibility to reduce the wear levels observed with F2 will be explored in a further study, e.g., through different settings of the lubricating system of the chainsaw. The results of the analyses of the air-sampled dust residues that were evidenced with F2 showed lower concentrations of respirable and inhalable particles and of some metallic elements (Al, Mg, and Ca) than those with SB. This behavior probably depends on the different interaction between sawdust and the two fluids, which differ according to their chemical–physical characteristics (different viscosity, composition, and additives). However, it represents a positive factor in favor of the use of the ROPO-based lubricant, emphasized by the total biodegradability of its residues that are possibly contained in the dust inhaled by the operators. [ABSTRACT FROM AUTHOR]

The controllable character of the melting point of deep eutectic solvents (DESs) makes it easy to realize lubricated state transitions and produce excellent lubricating properties during friction. In this work, a series of novel imidazole-based DESs were synthesized to present a room-temperature solid state by shifting its eutectic point. Tribological test results show that the wear volume of these DESs decreases as the alkyl chains of the hydrogen bond donors increase. A proper deviation of the eutectic point in DESs produces stable lubricating properties. The present work provides a novel and simple method to prepare solid lubricants and enriches the use of DESs as lubricants. Simultaneously, the method expected to replace the use of conventional cutting fluids. [ABSTRACT FROM AUTHOR]

To reduce the lubrication failure of water-lubricated bearings under short-term harsh conditions, preliminary experiments have shown that temporarily supplying a small amount of lubricating oil into a bearing as a secondary lubricant can improve the load capacity of the water film therein. However, the physical flow and diffusion state of this secondary lubricant (oil) in water are unclear. Therefore, a mixed lubrication model and a volume-of-fluid model are incorporated to study the diffusion behavior of a small amount of lubricating oil in a water-lubricated bearing. The results show that there is a backflow effect in the local area inside the bearing, where the fluid velocity is in the opposite direction to the linear velocity of the shaft. This backflow effect intensifies with increasing eccentricity ratio, which enlarges the oil-free zone in the middle part of the bearing. In the convergence area at the water inlet end of the bearing, the water supply pressure and backflow effect prevent the lubricating oil from escaping. Increasing the shaft speed has a positive effect on the diffusion of the oil and the load capacity of the fluid. To enhance the assisted lubrication effect of the oil, the oil injection port should be set in the loading zone to avoid the backflow zone. This research provides some fundamental data for reducing the friction and wear of water-lubricated bearings under harsh conditions. [ABSTRACT FROM AUTHOR]

Bearings operating in ultra-low-temperature environments are commonly lubricated with solid lubricants. This study first focused on measuring the traction coefficients of molybdenum disulfide (MoS2) solid lubricant under various working conditions. Based on this data, the friction power consumption of the bearings was calculated and analyzed using a dynamic model. Additionally, experimental verification of the bearing friction power consumption in ultra-low temperature environments was conducted. The research findings will serve as a foundation for the application of solid lubrication bearings in ultra-low-temperature environments. [ABSTRACT FROM AUTHOR]

This study used a regression model, experimental data from a viscosity measurement device, and a computational technique to investigate the relationship between lubricant viscosity and surface-attached adhesion rates. Three types of used lubricants were identified and evaluated using viscosity and surface adhesion measuring instruments using three different sizes of steel balls, namely 3 mm, 3.5 mm, and 4 mm. The experimental results were then analysed using a simple linear regression model with parameter estimation. At a significance level of 0.05, the results revealed that the lubricant viscosity and the rate of surface adhesion were linearly correlated. The results of this research could be utilized by industry to control the usage of lubricating oil in industrial parts, make judgments about changing or analysing the quality of the heat-reducing lubricant at the interface between mechanical components, and so on. To maintain lubrication efficiency and increase the service life of industrial parts. As a result of fulfilling this desired goal, the regression equations generated during this study can be used to estimate surface-attached adhesion rates in other circumstances. The viscosity range utilised in this case study corresponds to the normal viscosity of the unused lubricant. The surface-attached adhesion rate can thus be accurately selected by manufacturers, and the lubrication effectiveness can also be monitored. This is another indirect waste reduction in the manufacturing chain. [ABSTRACT FROM AUTHOR]

Ionic liquid (IL) combined with graphene additives have garnered extensive attention in the field of high-performance lubricating materials. However, the ambiguous mechanism of graphene influencing the load-carrying and anti-wear capacity of ILs needs further study. In this work, friction simulation shows that adding graphene causes friction coefficient to reduce by up to 88% compared with pure ILs, but lubrication performance is lost due to the destruction of graphene under high stress. Meanwhile, multilayer graphene has better friction-reducing performance and friction durability as compared to the monolayer structure, which is attributed to the easy-shear property and the reduction in the percentage of high tensile stress sites in multilayer graphene structure. In addition, it was found that excessively thick ILs film would form a three-body abrasive wear structure with graphene, which accelerated the structural destruction of graphene and caused a decline in its tribological properties. It is believed these findings can be valuable for designing of high-performance lubricating oil for practical engineering. [ABSTRACT FROM AUTHOR]

The article presents a study which proved that the ion surface coverage dictates the roughness of the hydration layer and its lubricating properties, especially under subnanometer confinement. Topics discussed include boundary superlubrication in the presence of trivalent hydration layers, hydration layer structure tunes lubrication mechanisms, and ion-induced structural changes in the hydration layer.

The urgent need for drastic reduction in emissions due to global warming demands a radical energy transition in transportation. The role of biofuels is fundamental to bridging the current situation towards a clean and sustainable future. In passenger cars, the use of ethanol fuel reduces gas emissions (CO2 and other harmful gases), but can bring tribological challenges to the engine. This review addresses the current state-of-the-art on the effects of ethanol fuel on friction, lubrication, and wear in car engines, and identifies knowledge gaps and trends in lubricants for ethanol-fuelled engines. This review shows that ethanol affects friction and wear in many ways, for example, by reducing lubricant viscosity, which on the one hand can reduce shear losses under full film lubrication, but on the other can increase asperity contact under mixed lubrication. Therefore, ethanol can either reduce or increase engine friction depending on the driving conditions, engine temperature, amount of diluted ethanol in the lubricant, lubricant type, etc. Ethanol increases corrosion and affects tribocorrosion, with significant effects on engine wear. Moreover, ethanol strongly interacts with the lubricant's additives, affecting friction and wear under boundary lubrication conditions. Regarding the anti-wear additive ZDDP, ethanol leads to thinner tribofilms with modified chemical structure, in particular shorter phosphates and increased amount of iron sulphides and oxides, thereby reducing their anti-wear protection. Tribofilms formed from Mo-DTC friction modifier are affected as well, compromising the formation of low-friction MoS2 tribofilms; however, ethanol is beneficial for the tribological behaviour of organic friction modifiers. Although the oil industry has implemented small changes in oil formulation to ensure the proper operation of ethanol-fuelled engines, there is a lack of research aiming to optimize lubricant formulation to maximize ethanol-fuelled engine performance. The findings of this review should shed light towards improved oil formulation as well as on the selection of materials and surface engineering techniques to mitigate the most pressing problems. [ABSTRACT FROM AUTHOR]

Tool wear introduced during grinding nickel-based superalloys was identified as a significant factor affecting the production quality of aero-engine industries concerning high service performance and high precision. Moreover, uncertainties derived from the various cooling-lubrication modes used in grinding operations complicated the assessment of grinding preformation. Therefore, this work investigated the tool wear mechanisms in grinding nickel-based superalloys that adopted five cooling-lubrication modes and investigated how the wear behaviors affected grinding performance. Results showed that chip-deposits covered some areas on the tool surface under dry grinding and accelerated the tool failure, which produced the highest values of tangential force, 7.46 N, and normal force, 14.1 N. Wedge-shape fractures induced by indentation fatigue were found to be the predominant wear mechanism when grinding nickel-based superalloys under flood cooling mode. The application of minimum quantity lubrication-palm oil (MQL-PO), MQL-multilayer graphene (MQL-MG), and MQL-Al2O3 nanoparticles (MQL-Al2O3) formed lubricity oil-film on the tool surface, which improved the capacity of lubrication in the tool–workpiece contact zone and provided 37%, 30%, and 52% higher coefficient of friction than dry mode, respectively. The results of this study demonstrate that lubricated oil-film produced by MQL modes reduces the possibility of fractures of cubic boron nitride (CBN) grits to some extent. [ABSTRACT FROM AUTHOR]

The current research is focused on investigating the influence of bearing irregularities like eccentricities (e), non-circularities (G), L/D ratio (ß), surface roughness coefficient (Y) on hydrodynamic performance of journal bearing such as load bearing capacity, friction force, lubricating oil flow. The performance is evaluated through finite difference method technique implementing a Newton-Raphson method of error convergence. The simulation outputs were than designed using an optimization tool entitled as Design of Experiment (DoE) on basis of response surface methodology (RSM). The outputs of RSM models were meant to forecast the response parameters like, load bearing capacity, friction force, flow of lubricant and further required to identify the noticeable interdependencies within the input parameters while evaluating the lubrication performance. The optimization of the bearing irregularities is done considering desirability approach of the response surface methodology in identifying proper combination of parameters. [ABSTRACT FROM AUTHOR]

The transmission in automobiles is the core component to ensure operational stability. Heat accumulation in the meshing process will reduce the transmission efficiency and affect the service life. Here, the essential physical process to improve transmission heat dissipation is the dynamic evolution process and the thermal transfer characteristics of lubricating oil fields during gear meshing. This paper presents a modeling and solving method for gear meshing lubrication and thermal transfer features based on the volume of the fluid model and piecewise linear interface construction (VOF-PLIC). The dynamic mesh technique combines spring smoothing and reconstruction to optimize the numerical solution process. The dynamic evolution law of gear meshing lubrication and thermal transfer is obtained by analyzing the lubrication evolution process under different speed/steering conditions. The results show that the proposed modeling and solving method could well reveal the lubrication and thermal transfer laws of the gear meshing. The temperature of the gear meshing regions was higher than that in the other regions, and the lubrication temperature showed an increasing linear trend with the stirring process. As the gear speed increased, the meshing resistance moment increased, the transmission power loss increased, and the lubrication oil temperature was larger than that of the gearbox. The power loss under the clockwise rotation of the driving gear G4 was higher than that under the counterclockwise rotation of the driving gear. The relevant results can provide theoretical references for the dynamic analysis of automotive transmission lubrication and technical support for gear profile design and lubrication optimization. [ABSTRACT FROM AUTHOR]

• High OCR are obtained when a compressor is working at high speed with R290. • The oil impact on evaporator could reduce the COP in 5%. • The higher impact of the oil is in the compressor. • COP reductions close to 20% can be achieved for oil circulations of 5%. Modulating the speed of the compressors and adapting its capacity to the required load has led to a decrease in the annual energy consumption in many applications. However, in the compressor, having adequate lubrication at low speeds usually implies discharging too much lubricant at higher speeds. Although necessary for compressor operation, lubricating oil acts as a contaminant in the rest of the system. Consequently, manufacturers have to consider the oil circulation rate (OCR), as it limits the speed range of the compressor. In a previous study, a compressor was tested over its speed range (30 – 110 Hz), working with R290 and POE68 as a lubricant. Experimental data confirm the increase of OCR with speed and suggests that working with R290-POE68 could imply higher OCR values compared to other refrigerant-oil mixtures. In this study, the impact of the OCR in the performance of a R290 heat pump was theoretically assessed. Three contributions were studied: The heat transfer coefficient (HTC) reduction in the evaporator, the effect of refrigerant being solved in oil and finally, and the impact of oil in the compressor. It was found that OCR values of 5% could decrease the coefficient of performance (COP) by more than 20%. [ABSTRACT FROM AUTHOR]

In this paper, the material-lubricant-systems of water lubrication combined with gears made from different tungsten carbide compositions are investigated regarding their behavior concerning wear as well as further gear failures such as scuffing, pitting and tooth root breakage. [ABSTRACT FROM AUTHOR]

The presented results show that the presence of refrigerant significantly deteriorates the lubricating properties of compressor oil under starved lubrication conditions (with a small amount of oil). The change can be 40–120% compared to the properties of the oil alone. Additionally, in the group of oils that are substitutes (operational alternatives) compatible with a given refrigerant, the effect of the refrigerant on the lubricating properties varies. The differences can be as much as 25%. In order to evaluate and properly select compressor oils for the refrigerant, the lubricating properties should be tested in a mixture with the refrigerant under conditions similar to actual operation. Such an evaluation of lubricating properties is made possible by the author's method of testing the wear of the block-on-ring friction node. The obtained rankings of lubricating properties for oils (due to the wear volume) can provide good guidelines for the suitable selection of a lubricant for refrigeration compressors (especially for new, environmentally friendly refrigerants, such as R452A). The research was carried out for mixtures of zeotropic refrigerants (R404A, R452A) with polyester oils (POE) and natural refrigerant (R600a) with mineral oils (MO). In each group of refrigerants, different mechanisms of oil–refrigerant mixture formation occur. Each refrigerant was tested with three different compressor oils recommended for each other for alternative uses in refrigeration systems. [ABSTRACT FROM AUTHOR]

In this work, we showed that the mesoporous molecular sieve SBA‐15 could be used as an oil storage smart microcontainer to adsorb PAO6 oils and is prepared as an oil‐containing molecular sieve SBA‐15O, the compositing of SBA‐15O with unsaturated polyester resins (UPR) can significantly improve the lubrication properties of UPR. The oil‐containing molecular sieve SBA‐15O was prepared by vacuum impregnation and compounded into the UPR. The lubricating effect of different SBA‐15O contents on the UPR was investigated. As compared with the UPR, the coefficient of friction (COF) of the 10%SBA‐15O/UPR could be reduced to 10% of that without SBA‐15O, and the wear rate by three orders of magnitude. The results show that the improvement of lubricating performance is related to the release of lubricating oil from the microcontainer to the surface to produce a lubricating oil film during friction, thereby enhancing the self‐lubricating performance of the composite material. [ABSTRACT FROM AUTHOR]

Lubricating oil is usually injected in the gap between mechanical interfaces to reduce the friction and wear and improve the normal bearing capacity of the interface. The state of the mixed lubrication is induced from the inadequate lubrication. However, in the investigation of this state, the irregular oil pits of rough surfaces are usually simplified to be the cylindrical or conical in traditional contact models, which is disagreed with the actual contact situations and makes errors in the contact analysis when it is used to reveal the contact performance of the mixed lubrication. To investigate the normal and tangential contact performances for the real mixed lubrication, the normal and tangential contact models reproducing the effects of both the surface roughness and the lubrication viscosity on the normal contact force as well as the tangential fraction force are proposed in this work. Based on the statistical theory, the total area of oil pits is presented to describe irregular oil pits of rough surfaces. Then, the contact performance between the solid and liquid parts involved in the mixed lubrication is analyzed referring to the elastic–plastic theory and the hydrodynamics theory. Finally, several key influencing factors (including the surface roughness, the film thickness, and the lubrication oil viscosity) on the normal and tangential contact performances of mechanical interface are revealed. The main contribution of this work is providing some guidance on the improvement of the normal and tangential contact performances of the mechanical interface by adjusting the normal pressure, the surface roughness, the relative movement speed, and the viscosity of the lubricating medium. [ABSTRACT FROM AUTHOR]

This study conducted a tribological investigation of base oil (PAO6 and 5W 40) and ionic liquids (IL)-modified lubricants through a four-ball tribometer for 30 min. The lubricants were fabricated via a two-step method using stirring magnetic and ultrasonic dispersion. IL, base oil, and lubricants were, respectively, characterized by XRD and FTIR analysis. In addition, multiple characterizations such as EDS, 3D morphology, and SEM were carried out to evaluate the wear and friction performance of steel balls. Ultimately, the results showed that the coefficient of friction (COF) and wear scar diameter (WSD) of wear scar lubricated by IL-modified lubricants were greatly decreased than that by base oil. IL can well improve the tribological properties of PAO 6 oil and 5W-40 oil due to the tribo-film appearance on the friction surface of wear scar by the effective role of IL. Fascinatingly, this investigation comprehensively and elaborately put a new sight into the lubrication mechanism of how IL reacted with a base oil and enhanced the tribological characteristics. [ABSTRACT FROM AUTHOR]

Recently, energy and environmental crises have aggravated sharply, which results in the eco-friendly and high-efficiency polyethylene glycol (PEG) lubricating oils getting increasingly attention in lubrication. Advancing in PEG-based lubricating oils, especially their high-performance nano-additives is vitally important for energy conservation and reducing pollution. Therefore, a kind of surface and core dual-designed carbon dots (Zn,Cu,Fe-CDs -N) modified by ionic liquid groups ([AMIm][N(CF 3 SO 2) 2 ]) and doped by polymetallic atoms (Zn, Cu, and Fe) were first synthesized and creatively used as the nano-additives for the PEG200 base oil. Adding 1.0 wt% of Zn,Cu,Fe-CDs -N can endow the PEG200 base oil with optimal friction-reduction, anti-wear, and load-supporting performances, the maximal increase amplitudes of approximately 46.6 %, 66.3 %, and 125.0 %, respectively. Additionally, the tribological properties of Zn,Cu,Fe-CDs -N are without any weakening even under high load and long-time operating conditions, exhibiting good practicability and application prospects. Theoretical and experimental studies have illustrated the excellent tribological behaviors of Zn,Cu,Fe-CDs -N assigned to the synergy of film-forming and nano-lubrication effects. [Display omitted] • Polymetallic atom-doped carbon dots modified by ionic liquids were first prepared. • Zn,Cu,Fe-CDs -N as additives for PEG200 showed great tribological behaviors. • Great performance of Zn,Cu,Fe-CDs -N assigned to their multiple lubrication effect. [ABSTRACT FROM AUTHOR]

Premature failure caused by inadequate lubrication of an artificial joint is a major problem. Inspired by engine lubrication, in which various additives are used to enforce the oil lubricant, here, a bench test of a biomimetic lubricating fluid containing different substances was carried out. Bovine serum albumin (BSA), in the form of both molecules and nanoparticles, was used as a functional additive. Compared with BSA molecules, BSA nanoparticles dispersed in HA solution served as more effective additives in the biomimetic lubrication fluid to minimize the friction and wear of ceramic orthopedic materials made of zirconium dioxide (ZrO2). Meanwhile, a tribo-acoustic study indicated that the "squeaking" problem associated with ZrO2 could be suppressed by the biomimetic fluid. Together with a cytotoxicity assessment, the BSA nanoparticle-incorporated biomimetic fluid was confirmed as a potential reagent for use in the clinic to maintain an even longer service life of artificial joints. [ABSTRACT FROM AUTHOR]

Lubrication is a basic and relatively effective way to reduce friction in sheet metal forming operations. The drive to eliminate synthetic and mineral oils, which are difficult to recycle, from the manufacturing process has opened up opportunities for the use of vegetable-based bio-lubricants. This article presents a comparison of the lubrication performance of two non-edible oils (karanja and moringa) with the most frequently tested edible oils (sunflower and rape-seed). Deep drawing quality low-carbon steel sheets DC04, commonly used in the automotive industry, were used as the test material. Friction tests were carried out under various lubricants and normal pressures in the range between 3 and 12 MPa using the strip drawing test. Furthermore, a study was also made of the effect of a change in the surface topography and the mechanical properties of the sheet metal due to plastic deformation resulting from friction. It was found that under the most favorable lubrication conditions (sample pre-strain 21%, nominal pressure 6 MPa), karanja oil reduced the coefficient of friction by approximately 33%. Both non-edible lubricants provided the best lubrication when testing samples pre-strained at 7% under the whole range of nominal pressures. It was also revealed that in the case of the smallest pre-straining of the specimens (7%), karanja oil was the most effective within nominal pressures of 3–6 MPa, while at higher pressures (9–12 MPa), the moringa oil lowered the value of the coefficient of friction to a greater extent. [ABSTRACT FROM AUTHOR]

Damage due to a shortage or excess of or the pollution of lubricating oil is often cited as one of the most significant issues confronted by the rolling mill sectors. Lubrication can be provided by either central lubrication systems or individual lubrication systems. In this study, the wear characteristics of the mono-block rolling plain bearing material that is utilized in wire rod rolling mills were evaluated under conditions where the lubricating oil medium included either 2.5% of scale, 5% of scale, or no scale at all. In this experimental study, a unique ball-on-flat experimental setup similar to the one used in the ASTM G133-05 standards was used. Bronze was used as the bearing material and 100Cr6 roller-bearing steel was used as a steel ball of 6 mm in diameter. The experiments were carried out at room temperature, at three different sliding speeds of 5 mm/s, 10 mm/s, and 15 mm/s, and with three different loads of 10 N, 20 N, and 30 N. The wear mechanisms were analyzed visually and elementally using Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) methods. An Analysis of Variance (ANOVA) and the Response Surface Method (RSM) were used to analyze the test results, such as volumetric material loss, the coefficient of friction, and the surface profile. In this study, which was carried out in a lubricant environment containing solid particles, the most effective parameter was the environmental parameter. The increase in the number of solid particles caused an increase in volume loss and friction coefficient. [ABSTRACT FROM AUTHOR]

Lubricating oil flow characteristics are the primary concern in the main reducer of light helicopters. To improve the lubricating performance of the main reducer, a special lubrication system is innovatively constructed by adding two oil-guiding tubes to the hub of the output gear, and the influence of the oil-guiding tubes is investigated through CFD (computational fluid dynamics) techniques. A CFD model of the gearbox integrated with the VOF (volume of fluid) technique was established to explore the flow characteristics of the oil–air two-phase flow inside the gearing system. To validate the proposed CFD model, a specialized testing rig is devised and manufactured to examine the features of oil distribution. The effects of the structure parameters of the oil-guiding tubes and operating conditions on the lubrication performance are explored. Comparing experimental and numerical findings reveals that the inner diameter of the oil-guiding tube and the rotational speed of the driven gear have a significant influence on the lubrication performance. In contrast, the length of the installation end of the oil-guiding tube, its angle, and the oil-immersion depth show little impact. [ABSTRACT FROM AUTHOR]

Governments and institutions have the following sustainable development goals: the improvement of energy efficiency and the reduction of CO2 emissions, in a "green economy" approach, have currently become the fundamental drivers that push research and development activity toward the optimization of rotating machine components in the industrial sector, with a special focus on lubrication systems too. The activity is directed towards the optimization of tribological testing methods and equipment to better discriminate the performance of lubricants in operating conditions as predictive as possible of real applications. In this context, the present paper describes the results of an experimental campaign based on the use of a well-selected linear oscillation SRV * (Schwingung, Reibung, Verschleiss) tribometer procedure as a screening of a rig test, the FZG ** (ForschungsstellefürZahnräderundGetreibebau(German:ResearchCentreforGearsandGear;UniversityofMunich;Munich,Germany)) test, leading to concrete benefits such as saving time (time duration is 76% less without mentioning visual inspection and mounting/dismounting phase) and operative costs. Four cases for the determination of the failure load stage of SRV have been defined as links to seizure and microseizure phenomena. The procedure was tested for ten oils differing in scope (gas turbine oil, turbine oil, gear oil and circulating oil). The tests have been repeated three times and a procedure was defined for repeatability (± 1 stage difference between the minimum and maximum) for nine out of ten cases a failure stage could be defined. The same oils were also tested using the FZG scuffing test, and it can be seen that the results are very comforting as follows: a good correlation with the FZG rig test has been found for eight out of ten oils. [ABSTRACT FROM AUTHOR]

Lubricating oil can effectively reduce friction between mechanical parts, thereby reducing energy consumption and improving service life and reliability. Due to the development of science and technology, it is necessary to improve the performance of lubricating oil to fulfill the higher tribological requirements for countering wear and providing lubrication. Nanolubricant additives have the four lubrication mechanisms of micro-bearing, protective film, polishing, and repair effects. A nanolubricant additive can often demonstrate a variety of lubrication mechanisms at the same time. As lubricating additives, metal and metal oxide nanoparticles have outstanding effects which improve the tribological properties of lubricating oil and have been widely studied in the field of tribology. This paper introduces the lubrication mechanism of nanoadditives and the latest research results for metal and metal-oxide nanoparticle lubrication additives. [ABSTRACT FROM AUTHOR]

In the present work, DLC coating was prepared on GCr15 bearing steel by magnetron sputtering method. The tribological behavior of GCr15 steel and DLC coating was studied at the speed range of 0.4 to 4.0 cm/s under two viscosity grades fully formulated lubricating oils (0W-20, 0W-40). The results show that viscosity of oil and sliding speed have a great effect on the DLC coating tribological properties. Compared to GCr15 steel at the speed of 0.4cm/s, there was a 41.67% reduction in the friction coefficient and 86.35% reduction in the wear rate of DLC coating in 0W-20 oil. The anti-friction and anti-wear advantages of DLC coating gradually disappear in low viscosity lubricating oil with the increase in sliding speed. The oil chain length and slip characteristics on DLC coating are two main factors that affect lubrication performance. The low viscosity lubricating oil, 0W-20, requires less energy to move and penetrate the lubricant molecules on DLC coating. This study will provide an experimental and theoretical basis for the application of low viscosity lubricating oil on DLC coating in the internal combustion engine industry. [ABSTRACT FROM AUTHOR]

[Display omitted] The structure of the slippery layer and the evolution of functional properties of a lubricant infused substrate (LIS) is determined by the isotherm of disjoining pressure in the lubricant film. The macroscopic theory of van der Waals forces was applied to the layered system used to model the structure and properties of LIS. For a lubricant layer sandwiched between the flat substrate and air or water, the isotherms of disjoining pressure were calculated and their analysis was used to conclude about stability of LIS. The results obtained for silicone oil and perfluorodecalin on smooth and porous hydrophilic and hydrophobic solids allow selecting the LIS components corresponding to stability of lubricant films in air and water. It was found that for hydrophilic substrates in conditions of lubricant depletion, silicone oil and perfluorodecalin show lubricant film stability in both air and water. On flat or post microtexture hydrophobic substrate with flat tops, the perfluorodecalin lubricating layer is typically stable in air and unstable in water. In contrast, silicone oil lubricating layer demonstrates the stability in a wide range of lubricant film thicknesses for the hydrophobic substrate with flat-top textures in water, however, it can be unstable in air. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the lubrication characteristics of double involute gear (DIG), compare its lubrication differences under quasi-static and tribo-dynamic conditions and study the influence of different factors on its lubrication characteristics under the tribo-dynamic condition. Design/methodology/approach: According to the meshing characteristics of DIG and elastohydrodynamic lubrication (EHL) theory, a tribo-dynamic model of DIG is established based on the "subsection method." The Runge-Kutta method and the multigrid method are integrated to solve the model, and the dynamic analytical model of lubricating oil is established in the iterative solution. Findings: The load and the transmission error fluctuate obviously under the tribo-dynamic condition, which is not conducive to the lubrication of DIG. The influence of rotational speeds and torque on the lubrication properties of DIG has obvious differences under tribo-dynamic and quasi-static conditions. Originality/value: This research can provide a theoretical basis for improving the lubrication performance, reducing the loss of mechanical efficiency and improving the bearing capacity and service life of DIG. [ABSTRACT FROM AUTHOR]

A technology for the production of greases from polymeric household waste has been proposed, including the stage of boiling the polymer in a solvent, which is used as a used motor oil SAE10W-40. In the production of greases using this technology, a significant amount of used polymer products is utilized, while the share of waste from low-pressure polyethylene and polypropylene (PP) is, respectively, 20-50% of the mass and 50-75% of the mass. This approach makes it possible to significantly expand the raw material base of the specified technological process and, due to the involvement of relatively cheap raw materials, significantly reduce the cost of finished products. The results of the study of the adhesive properties of the obtained lubricants allow us to give the following recommendations: for lubricants based on low-pressure polyethylene with a polymer: oil ratio of 1: 1, the rational rotation speed was no more than 2850 rpm, with a ratio of 1: 3 - about 3950 rpm and with a ratio of 1: 5 - up to 5300 rpm; rational rotation speed for lubricants based on PP at a polymer: oil ratio of 1: 1 does not exceed 3600 rpm, at a ratio of 2: 1-4900 rpm and at a ratio of 3: 1 - 6000 rpm. [ABSTRACT FROM AUTHOR]

The migration and distribution of lubricant oil in a rolling bearing strongly affect the elastohydrodynamic lubrication performance between the balls and rings. However, oil re-lubrication is highly dependent on the bearing design, which is different from the ball-on-disc model. This study directly observed the distribution of the lubricant film in a custom-made model-bearing rig, with an outer ring replaced by a glass ring to allow full optical access. The influence of the cage type and surface properties were presented. The physical origin of the re-lubrication mechanism, including capillary flow and mechanical redistribution, was discussed. [ABSTRACT FROM AUTHOR]

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In order to further understand the role of MXene-Ti3C2 in oil–solid synergistic lubrication, three kinds of microporous channel composites, M50, M50-Sn-Ag-Cu and M50-Sn-Ag-Cu-Ti3C2, were designed and prepared in this study. Tribological behaviors under different environmental conditions of oil lubrication and dry friction were analyzed. The results show that M50-Sn-Ag-Cu-Ti3C2 exhibits excellent tribological properties under oil lubrication. Mxene-Ti3C2 enhances the strength of solid lubricant film, so that the oil film can give full play to the antifriction and wear resistance of solid lubricant film. The synergistic effect of lubricating oil, solid lubricants and bionic curved microchannel reduces the friction coefficient and wear rate. The vibration acceleration along the reciprocating direction is also reduced. [ABSTRACT FROM AUTHOR]

This study investigates the use of an ionic liquid obtained from fatty acids (FAIL) as an additive at 2 wt.% in two different base oils: a mineral oil (M1) and a polyol ester (E1). Physicochemical characterization of the base oil–FAIL blends confirmed the miscibility of the FAIL in the base oils. The addition of the FAIL hardly changed the density of the base oils and the viscosity slightly increased at lower temperatures. The tribological performance of the base oils and their blends with the FAIL was determined using three different tests: Stribeck curve determination and tribofilm formation tests, both under sliding/rolling motion, and reciprocating wear tests. The M1 + FAIL blend showed the lowest friction values under the mixed lubrication regime due to its higher viscosity, while the E1 + FAIL showed the lowest friction values under the elastohydrodynamic lubrication regime, which may well have been due to its higher polarity. Only the E1 + FAIL blend outperformed the antiwear behavior of the base oil, probably because it has better chemical affinity (higher polarity) for the metallic surface. SEM images showed that the predominant wear mechanism was adhesive-type with plastic deformation and XPS studies proved that the presence of increasing amounts of organic oxygen on the wear scar caused better antiwear performance when the E1 + FAIL blend was used. [ABSTRACT FROM AUTHOR]

This paper presents the optimization of the lubrication method of a helical bevel gearbox, which is part of a pickling line. The first gear stage of this gearbox showed frequent failures. The bevel gearing and bearings were damaged. Damage analysis was performed, based on which a change in bevel gearing and bearing lubrication was proposed. In this case, the original transmission was lubricated by dip lubrication. The bevel gear wheel was insufficiently submerged below the lubricating oil level. Due to insufficient lubrication of the bevel gearing, both gear wheels, the bevel pinion, and the bevel wheel were damaged. Central circulating lubrication has been proposed for the bevel gear pair and first gearbox shaft bearings. This paper deals with the design of circulating lubrication components. Changes and modifications to an existing lubrication system are proposed. The layout of the gearbox in question was not originally designed and adapted for the circulating lubrication required. To improve the original lubrication system, it was decided that it should be redesigned with central circulating lubrication, which meant implementing the necessary gearbox casing modifications. Our novel contribution is the proposition of an innovative transmission lubrication system aimed at increasing the service life parameters of the transmission. After the implementation of the proposed modifications to the lubrication method, a period of monitoring the operating characteristics of the gearbox followed. With the modification of the lubrication system of the bevel gear pair, the temperature on the gearing surface was lowered by 39%. The service life of the gearbox increased from the original 1.9 years to at least 5 years. On the basis of the long-term monitoring of changes caused by the adjustment of the lubrication method, we can state that the requirement was met, and the frequent failures of this gearbox were eliminated. [ABSTRACT FROM AUTHOR]

One of the major applications of zinc dialkyldithiophosphates (ZnDDPs) is their usage as an anti-wear additive in lubricants including greases, hydraulic oils, and motor oils. ZnDDPs also could be used as corrosion inhibitors and antioxidants. In this study, GC/MS with solid-phase extraction (SPE) pretreatment was used to effectively remove base oils in lubricants and qualitative and quantitative analysis method for ZnDDPs in automotive lubricants. As a pretreatment method, liquid–liquid extraction (LLE) and SPE were applied. The SPE method using mixed absorbent containing 1.0% of active carbon in silica gel base showed the best results in both recovery and reproducibility. The LOD and LOQ of the developed method were 2.2 µg/ml and 6.7 µg/ml, respectively. And this method showed very good reproducibility of less than 0.1% RSD for the standard sample analysis. The developed method was successively applied to qualitative and quantitative analyses of ZnDDP in various real automotive lubricant samples. [ABSTRACT FROM AUTHOR]

Friction and lubrication are important parameters that affect the quality of sheet metal forming; excellent lubrication conditions and less harmful friction can reduce local thinning, delay fracture, and improve surface quality. Aiming at the poor friction conditions and difficult lubrication in the flange area during deep drawing, an active pressurized forced lubrication deep drawing (FLDD) process was proposed in this paper. A hydraulic system was employed to flush high-pressure lubricating oil into the contact gap between the die and sheet in the flange area. The high-pressure hydrostatic oil film in the contact gap can reduce the real contact area and effectively improve the lubrication conditions. The equipment is simple, the cost is low, and the lubricating oil pressure can be measured and controlled. Under the conditions of 20-kN, 35-kN, and 50-kN blank holder force (BHF), FLDD testing of box parts was carried out with 5-MPa and 9-MPa pressure using water-based lubricating oil. The horizontal comparison experiment was conducted with vegetable oil and water-based lubricating oil under the same process conditions. The test results illustrated that the lubrication effect of vegetable oil was the worst, whereas the lubrication effect of water-based mineral lubricant was significantly improved after pressurization. The maximum forming height was increased by 17.97%, the maximum forming force was reduced by 8.9%, the maximum wall thickness thinning rate was decreased by 7%, and the lubrication effect at 9-MPa pressure was superior to that of 5 MPa. The FLDD process has definite application value in improving the production environment, pollution control, and automatic production. [ABSTRACT FROM AUTHOR]

Steady macroscale superlubricity was firstly achieved on epoxy resin coating lubricated by multiple base oils including nonpolar and polar oils. Hydroxylated tribofilm on counter balls lubricated by multiple base oils was observed by TOF-SIMS spectra. [Display omitted] • Steady macroscale superlubricity was achieved on epoxy resin coating lubricated by multiple base oils. • No obvious run-in stage to superlubricity for the steel/epoxy resin tribopairs lubricated by different base oils. • Soft epoxy resin coating performed superior wear resistance under oil lubrication. • Hydroxylated tribofilm on the counter balls lubricated by multiple base oils was observed by FTIR and TOF-SIMS spectra. Reducing the friction of base oils to a superlubricity state is highly expected at engineering scale. However, it still is a great challenge for the most of viscous base oils to achieve superlubricity on the conventional tribopairs up to now. Here we report the strategy of solid-oil composited lubrication constructed with an ultra-smooth epoxy resin (EP) coating and base oils for achieving superlubricity. Especially, the frictional results showed that the proposed strategy in this study could be suitable for multiple base oils, including nonpolar and polar base oils as lubricants. The friction coefficient of steel/EP tribopair lubricated by the base oils containing hydroxyl group can be as low as 0.001. Meanwhile, the composited lubrication system did not undergo an obvious running-in stage to achieve the superlubricity state regardless of the type of base oils. The surface hydroxylation of the steel counter ball sliding against EP coating was observed by time-of-flight secondary ion mass spectrometer, even when lubricated by nonpolar base oils without hydroxyl group. This could be a critical factor for the base oils to achieve superlubricity. This finding provides a new and facile approach to realize robust superlubrication for different base oils at engineering scale. [ABSTRACT FROM AUTHOR]

Lubricants are indispensable ingredients for alleviating friction and wear in mechanical components especially in automobile. However, due to its poor heat transfer capabilities, traditional lubricants are denatured under extreme working conditions, leading to lubrication failure during the friction process. Therefore, this study elaborately put forward to a novel MoS 2 /h-BN hybrid nanoparticle as efficient nano-additive for engine oil. The results of experiments and molecular dynamics simulation jointly show that compared with mono nanoparticles, hybrid nano-lubricants (NL) thermal conductivity was significantly improved than that of base oil owing to the synergistic effect. The corresponding mechanism for the improving heat transfer performance was suitably proposed based on the Mean Square Displacement (MSD) and Radial Distribution Function (RDF) results at the microscopic atomic level. [Display omitted] [ABSTRACT FROM AUTHOR]

Clearance exists in mechanical equipment, which aggravates the friction and wear in moving pairs and reduces the use accuracy of mechanism. So as to reduce the impact of clearance on industrial equipment, lubricating oil is usually added to the clearance of moving pair. The lubricating oil can effectively reduce the collision and vibration between components and reduce noise. Previous studies mainly concentrated on the research of dry clearance joints, but less on clearance lubrication. At the same time, there is little research on nonlinear characteristic of lubrication clearance. For the sake of studying the impact of lubrication clearance with multiple revolute joints on mechanical system, the dynamic response and nonlinear characteristic of planar six-bar linkage are analyzed. The movement model of lubrication clearance is developed, and lubrication force of lubrication clearance is modeled by modified Pinkus–Sternlicht model. Dynamical model of lubrication clearance of planar six-bar linkage is established by Lagrange multiplier method. The impacts of lubrication, viscosity coefficient, clearance value and driving speed on dynamic of mechanism with lubrication clearance are explored. By drawing bifurcation diagram, phase trajectory diagram and Poincare map, the nonlinear characteristic of mechanism with lubrication clearance is studied. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the effect of the graphite nanoplates (GNP) concentration on the tribological and rheological characteristics of grease lubricants based on used motor oils and calcium soaps. GNP were obtained by the original electrochemical method. Grease lubricants were tested for residual water content, dropping point, penetration, and wear limit. The size of wear spot was determined using a four-ball friction machine. It was found that by GNP content increasing the water content monotonically rises from 0.6 to 2.3 wt. %. The penetration decreases from 44 to 31 mm with increasing GNP content. Also, the dropping point rises from 79 to 88 °C at the GNP concentration of 150 ppm, and then decreases to 81 °C. The minimal size of wear spot (0.215 mm) is also observed at a GNP concentration equal to 150 ppm. It is 25.1% lower than that of the control sample that does not GNP contain. [ABSTRACT FROM AUTHOR]

The operating parameters of present-day engines depend on many factors, including the lubrication system. The lubrication system not only reduces friction between the surfaces of moving parts, but also contributes to their cooling and cleans engine parts from carbon deposits and impurities. High environmental requirements are also imposed on the quality of the lubricants, while maintaining their specifications. To that end, various additives are added to lubricating oil. The paper studies the effect of fine powders (enamels) on the wear of friction pairs in laboratory tests. The tests are mainly carried out for all-season synthetic and mineral oils in demand. Such criteria as wear of a roller and upper and lower bearings, specific wear of friction pairs, moment load, and temperature are selected as the effectiveness evaluation criteria of the use of enamels and nanomaterials. Experimental studies show a high efficiency of using enamels as additives to reduce friction and increase the load-carrying capacity of oils. The temperature in the friction layer is reduced by 10-20%, depending on the enamel concentration in the oil. The enamel acts as a third body with a lower friction coefficient and energy to failure, which increases the actual contact area of the friction pairs. The results of the study can be applied in the development of motor oils with fine enamel as an additive. [ABSTRACT FROM AUTHOR]