Fluid Lubrication Research Articles

Impact of machining parameters on surface roughness and machining forces in Al7075 turning with minimum quantity lubrication and cold fluid

Impact of machining parameters on surface roughness and machining forces in Al7075 turning with minimum quantity lubrication and cold fluid

Coupled modelling and analysis of lubrication-wear evolution of textured piston/cylinder pair in high-pressure common rail pumps

Abstract Surface texturing is an important approach to enhance fluid lubrication performance and reduce friction and wear. Research on the surface texturing of the piston/cylinder pair considering various characteristics such as multi-physical fields and the evolution of friction and wear is still insufficient. The novelty of this work aims to establish a coupled numerical simulation model considering the coupling effect of multiple physical fields, wear of the cylinder bore and surface texture, and determine the effective surface texture parameters to improve the friction performance of the mechanical components of high-pressure common rail pump. The influence of surface texture on friction and wear characteristics and the evolution of lubrication-wear under different geometric cases were in-depth investigated, and the action mechanism of surface texture on lubrication and wear was revealed. Through numerical analysis, optimal parameters were identified that significantly reduce the friction coefficient and wear amount, offering practical insights for mitigating friction and wear in mechanical systems.

Study on partial ER fluid hybrid two-lobe hole-entry journal bearing with genetic algorithm for bionic surface

This work focuses on ER (Electrorheological) fluid-based hybrid hole-entry journal bearings, which studies the effect of ER fluid with partial electric field on the tribological nature of two-lobe bearings with bionic textured surfaces. The design of bionic textures, by virtue of their capacity to influence fluid flow, load capacity, and friction reduction for the enhancement of bearing performance, has been analytically investigated. The integration of ER fluid subjected to partial electric field along with bionic textured surfaces displays an optimistic improvement in performance metrics of bearings, which clearly manifests through preliminary results. Notably, the optimization of bionic textures through genetic algorithms resulted in a 13.04% reduction in friction coefficient and a significant increase in load capacity. The combination of partial ER fluid lubrication and bionic textures also improved fluid film stiffness by up to 66.11%, further enhancing stability and overall bearing efficiency. The obtained results are expected to further enhance design and development activities of high-performance hybrid journal bearings for numerous industrial applications.

Experimental study on cutting force and surface quality of Aramid fiber reinforced polymer based on minimum quantity lubrication

In order to explore the milling mechanism of aramid fiber reinforced polymer under minimal quantity lubrication and improve the milling quality of aramid fiber reinforced polymer, the milling experiments of aramid fiber reinforced polymer were carried out under dry cutting and minimal quantity lubrication, and the cutting force, fiber section, and surface quality were compared and analyzed. The experiment results show that in the dry cutting state, the surface burr is more, the surface quality is poor, the fiber section is rough, and the resin matrix has a melting trend, accompanied by the phenomenon of chip wrapping around the tool, tooltip collapse, and coating peeling. In minimal quantity lubrication, the surface burr is reduced, the surface quality is good, the fiber section is neat, and the resin interface is clean and tidy. The resin matrix has no melting trend, the tooltip is only slightly worn, and the phenomenon of chip entanglement is effectively avoided. Further research shows that the minimal quantity lubrication can reduce the temperature and friction, enhance the stiffness of the fiber, and change the fracture model of the fiber to a certain extent, that is, from bending to tensile fracture (or accompanied by tensile phenomenon) to shear fracture, which also leads to the overall high cutting force. The total milling force synthesized by the average value increases from 2.45 N to 20.93 N, with a maximum increase of 88.29%. However, due to the cooling and friction reduction of the lubricating fluid and the chip removal and diversion, the overall fluctuation of the cutting force under the minimal quantity lubrication condition is reduced. The overall cutting force is more stable than that under dry cutting conditions. The results show that the milling quality is improved under minimal quantity lubrication, the cutting force is more significant but more stable, and the milling process is more stable. This study has important reference significance for milling composites (especially resin matrix composites) under the condition of minimal quantity lubrication.

An improved endwall-injection technique for examining high-temperature ignition of lubricating oils in shock tubes.

Ignition of the lubricating fluid in a mechanical system is a highly undesirable and unsafe condition that can arise from the elevated temperatures and pressures to which the lubricant is subjected. It is therefore important to understand the fundamental chemistry behind its ignition to predict and prevent this condition. Lubricating oils, particularly those with a mineral oil base, are very complex mixtures of thousands of hydrocarbons. Additionally, these oils have very low vapor pressures and high viscosities. These physical characteristics present considerable barriers to examining and understanding lubricant ignition chemistry. Therefore, a novel experimental design was devised to create and introduce a lubricant aerosol into a shock-tube facility in a reliable yet relatively simple manner. In this way, the lubricant can be quasi-homogeneously introduced into the shock tube where it will be vaporized by the incident shock wave, and combustion can be observed behind the reflected shock wave. To characterize the technique and anchor it with previously established methods, n-hexadecane was chosen to be tested both with the endwall injection and the well-established, heated shock tube techniques. This comparison showed good agreement, proving the ability of the simple technique to produce reliable ignition delay time (IDT) results. From here, Jet-A was also tested with the current injection technique and compared to a previous generation of the technique to highlight the advantages of the present method. Then, IDT results for mineral oil were collected to establish a baseline IDT set to which off-the-shelf lubricants and additional mixtures can be compared. Finally, IDTs for the off-the-shelf, mineral-based lubricant Mobil DTE 732 were obtained and compared to the baseline as well as the n-hexadecane results. All experiments were conducted near atmospheric pressure and for temperatures between 1084 and 1530K. An analysis of the system estimated the effective stoichiometry to be around ϕ = 1.15. Although no kinetics mechanisms exist for lubrication oils, preliminary model predictions made by modern chemical kinetics mechanisms for an alkane with 16 carbon atoms were then compared to the results to elucidate some of the chemistry this new method will allow the community to probe. This paper establishes the new method as a viable way to study and compare the ignition behavior of lubricating oils and other very low-vapor-pressure fuels in a shock tube.

Effect of nanoparticles on Tribological Study of Eco-Friendly Grease Made with Soybean Oil, Beeswax and Acacia Gum

The lubricating grease is simply a lubricating fluid which is gelled with a thickening agent such that the lubricant can be retained more readily in the specific required area. It is made of two primary ingredients: base oils and thickeners. Various performance additives are blended frequently to grease to tailor their characteristics. The grease used in industries is made of mineral oil which is non-renewable, non-biodegradable, toxic, bio-accumulative, and hence environmentally unfriendly. A potential, sustainable and economical eco-friendly alternative to harmful petroleum-based lubricants is a big challenge for the 21st-century lubricant industry. The present study explores, for the very first time, grease produced from all natural, ecofriendly material such as Soybean oil (SO), Beeswax (BW) and Acacia gum (AG). Various samples are prepared by varying the components ratios. Application of grease depends on the physiological properties of the grease. This paper mainly focuses on properties like cone penetration, NGLI Grade, drop point, Wear Test. The tests performed for evaluating the properties are Cone penetration (ASTM-D 217-2021-a), NLGI grade (ASTM-D 217-2020), Drop point (ASTM-D -2265-2020) and Wear preventive Characteristics (ASTM D2266).

Active control of friction in electrified ball bearing prototypes using electro-sensitive clay mineral-based lubricating fluids

Active control of friction in electrified ball bearing prototypes using electro-sensitive clay mineral-based lubricating fluids

Outlining the impact of electro-osmotic force and mixed convection flow of EMHD nanofluid flow on the stretched cylinder: a computational layout

Abstract This research has focused on studying the electro-magneto-hydrodynamic (EMHD) nanofluid flow over a stretched cylinder in the presence of electro-osmotic force and mixed convection. This inquiry shows a novel approach through the use of thermophoresis and Brownian motion and nanofluid is comprised of water and copper nanoparticles. Similarity transformations simplified the mathematical model and produced nonlinear ordinary differential equations with suitable boundary conditions, which the MAPLE-21 software numerically solved using the RK-4 shooting criteria. Tables and graphs have been used to illustrate the impact of the key flow factors on Electric potential profiles, velocity profiles, temperature outlines, and concentration distribution. Following the physical deliveries, we have calculated the Sherwood number, Nusselt number, and skin friction. The electro-osmotic parameter diminishes the electric potential profiles and a dual effect occurs for the curvature parameter. The Nusselt number declined by 5.91 % for the electro-osmotic parameter but the Sherwood number enhanced by 30.7 % at a rate. The practical applications of this model shed light on thermal management in electronics and nuclear reactors, plasma physics, various chemical processes, filtration, separation, and fuel cells, as well as the manipulation of biological fluids in lubrication or medical devices.

Vibration properties of full ceramic bearing under elastohydrodynamic fluid lubrication based on the energy approach

As an important part of rotating machinery, heat generation due to friction is inevitable during the rotating process of bearings. A large amount of heat causes the temperature of lubricating oil to increase, viscosity of lubricating oil to decrease, and lubricating performance decreases. Addressing the issue of inadequate lubrication between the rolling element and raceway due to increased lubricating oil temperature, this study focuses on full-ceramic ball bearings. It examines the impact of temperature fluctuations on the bearing's lubrication condition and investigates the vibration characteristics of the full-ceramic bearing. The variation in the viscosity of lubricating oil with respect to temperature is measured via a rotary viscometer. A dynamic model of the silicon nitride full-ceramic ball bearing, which considers the effects of elastohydrodynamic lubrication, is established. The impacts of changes in lubricating oil viscosity due to different temperatures on oil film pressure, oil film thickness, and bearing vibration are analyzed and then compared with experimental data. It is observed that under conditions of constant load and speed, the film thickness of the lubricating oil decreases as the viscosity decreases. Additionally, the second peak value of oil film pressure is reduced with the declining viscosity of the lubricating oil. As the viscosity decreases, the vibration of the bearing increases. The amplitude discrepancy between the simulated vibration signal and experimental vibration signal of the full-ceramic bearing is found to be less than 10 %, verifying the validity of the dynamic model.

Study on the Effectiveness of Okra as an Environmentally Friendly and Economical Lubricant for Drilling Fluid

With the gradual improvement and implementation of unconventional wells drilling and environmental regulations, there is an urgent need for high-performance and more environmentally friendly lubricants for water-based drilling fluids (WD). Developing green oilfield chemicals from natural products is a shortcut. In this work, Abelmoschus esculentus (L.) Moench/okra has been studied as the lubricant in WD. The green drilling fluid lubricant developed demonstrates excellent lubrication performance, as well as good filtration loss reduction and inhibition of bentonite hydration expansion. The results show that with the addition of 2.5% okra slurry to water-based drilling fluid, the coefficient of friction decreased by 51.68%, the apparent viscosity (AV) increased by 51.32%, the plastic viscosity (PV) increased by 42.99%, and the fluid loss decreased by 39.88%. Moreover, through TGA, SEM, FT-IR, particle distribution tests, and contact angle tests, the lubrication mechanism of okra slurry was discussed. Finally, the economic feasibility of using okra as an environmentally friendly lubricant for drilling fluids was analyzed. This work combines agricultural products with industrial production, which not only solves industrial problems but also enhances the added value of agricultural products, providing a reference for the coordinated development of industry and agriculture.

Nonlinear dynamic of flexible rotor supported by turbulent bearings with quadratic damping and temperature dependent viscosity

A nonlinear dynamic model of a rotor supported by the turbulent journal bearing with quadratic damping under nonlinear suspension is presented in this study, and the lubricating oil is assumed to be temperature-dependent. The bifurcation diagrams, dynamic trajectories, power spectra, Poincaré map, Lyapunov exponent, and fractal dimension are used to verify the dynamic characteristics of the rotor-bearing system, and abundant subharmonic, and even chaotic motions are found. Temperature is one of the key parameters affecting the dynamic responses of the system, and the dynamic responses will perform non-periodic or even chaotic motions with higher working temperatures of lubricant fluid, as proved in this study. Nonlinear dynamic simulation analysis results will help engineers avoid unnecessary trial and error when designing and applying rotating machinery systems.

Research the lubrication characteristics on the modified main thrust roller of the slewing bearings

The load capacity and lubrication performance of the slewing bearing are fairly sensitive to edge effects at both ends of the main thrust rollers. Therefore, quantitative investigations of the edge effect at both ends of slewing bearing is practically important. In this study, an elastic fluid lubrication model of the slewing bearing that considered the external load and internal structural parameters is established. A modification function of rollers is included in a finite long-line contact elastic fluid lubrication model to perform the dynamic analysis. The simulated oil film’s thickness and pressure distributions are compared under different working conditions. And the edge effect is eliminated by modifying the rollers’ construction. The results indicate that under the large eccentric load, the speed of the slewing bearing must be decreased to ensure elastic fluid lubrication performance. A genetic algorithm that used to discover the optimal modification length shows the best busbar of the main thrust roller is 12 μm, which could decrease the vibration amplitude of the unmodified roller by 8.13%. This result gives a significant way for slewing bearing’s structural design.

Research on Air Cushion Flow Field and Bearing Characteristics of Single Row Hole Air Cushion Belt Conveyor

In order to obtain information regarding changes in the air cushion flow field and load-bearing characteristics of a single row hole air cushion belt conveyor, a structural model of the air cushion of the belt conveyor was established, with the single row hole air cushion belt conveyor as the research object. Firstly, according to the theory of fluid lubrication, a mathematical model of the air cushion was established. Then, the effects of air cushion thickness, pore velocity, and belt velocity on the pressure and bearing characteristics of the air cushion flow field were studied using FLUENT software. In addition, the equivalent stress, displacement, and pressure curves between the air cushion flow field and the conveyor belt and the material were analyzed using the two-way fluid–solid coupling method. Finally, the experimental platform of a single row hole air cushion belt conveyor was built, and the flow field and bearing characteristics of the belt were verified through experiments. The results show that reducing the thickness of the air cushion and increasing the pore flow rate can improve the pressure and bearing characteristics of the air cushion, while speed has little effect at lower belt speeds.

Study on Atomization Mechanism of Oil Injection Lubrication for Rolling Bearing Based on Stratified Method

The atomization mechanism of lubrication fluid in rolling bearings under high-speed airflow between the rings was investigated. A simulation model of gas–liquid two-phase flow in angular contact ball bearings was developed, and the jet lubrication process between the bearing rings was simulated using FLUENT computational fluid dynamics software (Ansys 19.2). The complex motion boundary conditions of the rolling elements were addressed through a layered approach. We can obtain more accurate boundary layer flow field changes and statistics of the diameter of oil particles in lubricating oil atomization, which lays the foundation for analyzing the law of influence on lubricating oil atomization. The results show that as the number of boundary layer layers increases, the influence of the boundary layer flow field on the lubricating oil is more obvious. The oil particle size is excessively flat, and the concentration of large particles of oil appears to decrease. As the speed increases, the amount of oil in the cavity decreases, but the oil droplets are also fragmented, which intensifies the atomization and reduces the particle diameter. This reduces the Sauter Mean Diameter (SMD), which is not conducive to the lubrication of the bearing. Under different injection pressures, when the injection pressure is large, it is beneficial to the lubrication of the bearing.

Darcy-Brinkman Flow of a Micropolar Fluid through an Anisotropic Porous Channel

This study investigates the Darcy-Brinkman flow of micropolar fluid through an anisotropic porous channel, a configuration relevant to various industrial and natural processes involving complex fluid flow. The anisotropy of the porous medium is characterized by its permeability aligned along two principal axes, with one axis forming an angle with the horizontal direction. The model applies no-slip and no-spin boundary conditions at the channel’s impermeable walls. Using a combination of analytical techniques and graphical analysis, we explore how key parameters such as the Darcy number, anisotropy angle, permeability ratio, and micropolar material parameters affect the flow behavior. Results reveal that increasing the anisotropy angle and permeability ratio leads to a reduction in both fluid velocity and micro rotational velocity, while the Darcy number promotes an increase in flow velocity. Additionally, the study discusses the impact of these parameters on shear stress and couple stress at the channel walls. The findings contribute to a deeper understanding of micropolar fluid behavior in porous media, with potential applications in filtration, lubrication, and subsurface fluid dynamics.

Preparation of molybdenum disulfide/bentonite nanohybrid and its tribological properties as lubricant for water-based drilling fluids

In recent years, with the increase in energy demand and gradual scarcity of medium and shallow oil and gas resources, oil and gas exploration has shifted to special wells such as deep wells, ultra-deep wells, and extended reach wells. These complex wellbore structures inevitably increase the torque and friction between the casing and the drill pipe during drilling, which aggravates friction and wear, and leads to accidents such as drill sticking and drill breakage in severe cases. In this study, molybdenum disulfide/bentonite (MoS2/Bent) nanohybrids as drilling fluid lubricant were synthesized by hydrothermal method using sodium molybdate (Na2MoO4) and thiourea (CH4N2S) as raw materials and bentonite as carrier. The as-synthesized MoS2/Bent nanohybrid was characterized by X-ray powder diffractometer, transmission electron microscopy, Fourier transform infrared spectroscopy, and the high temperature resistance and tribological properties of MoS2/Bent nanohybrid were evaluated in base slurry. The results show that the friction coefficient of MoS2/Bent nanohybrid drilling fluid before aging is reduced by 74 % and the wear rate is reduced by 97 % compared with the base slurry. After high-temperature aging at 240 °C, the friction coefficient is reduced by 77 % and the wear rate is reduced by 90 %. The excellent friction reducing and antiwear performance is attributed to the formation of low shear strength MoS2 deposition film and oxide tribofilm on the surface of the friction pair during the rubbing process.

Biomimetic joints inspired soft and hard combined 2D diamond solvent-free nanofluids with multi-layer structure for superior lubrication

The articulating joints consist of a three-layer lubricating structure, which combines soft and hard materials, including cartilage, polymer brushes, and a hydration layer. This structure leverages the synergistic effects of fluid and boundary lubrication to maintain ultra-low friction under different pressures on the same frictional surface. In this study, a biomimetic multilayer lubricating structure inspired by joint tissues is constructed using single-crystalline diamond nanosheets (SCND) as the hard phase material. Through a facile chemical reduction method and employing polydopamine (PDA) as a "bridge", a soft phase material is deposited onto the SCND surface to produce diamond composite silver nanocomposites (SCND@PDA@Ag). Subsequently, two solvent-free SCND@PDA@Ag nanofluids are prepared by grafting organic canopy substances onto the SCND@PDA@Ag surface via ionic bonds or covalent bonds, referred to as SCND@PDA@Ag-ionic bonding nanofluid and SCND@PDA@Ag-covalent bonding nanofluid, respectively. The findings reveal that the SCND@PDA@Ag-covalent bonding solvent-free nanofluid exhibits superior lubricating performance for steel/SiC contacts. The friction coefficient and wear rate for steel/SiC are significantly reduced by 93.2 % and 63.1 %, respectively, compared to dry friction, it's noteworthy that these results outperform those achieved by individual components of the lubricant. During the friction process, SCND and silver particles on the surface of SCND@PDA@Ag-covalent bonding solvent-free nanofluid work together to enhance lubrication synergistically. Furthermore, silver particles on the surface of SCND are released and fill into the worn surface, providing a repairing effect. This study highlights that the design of soft-hard multilayer structures offers a novel approach for researching nanocomposite materials in the field of tribology.

Dynamics of particle entrainment for glass particles suspended in various fluids

The frictional properties of two sliding surfaces are often influenced by a fluid lubricant’s ability to separate and facilitate movement. When particles are present, their entrainment between surfaces can alter friction, either increasing or decreasing it compared to fluid lubrication alone. Understanding the frictional regimes and the dynamics driving particle entrainment in suspensions is thus critical. This study investigates the tribological properties of glass particles suspended in various fluid matrices. We examined suspensions with varying particle concentrations, fluid viscosities, fluid hydrophobicity, and particle hydrophobicity. Our findings reveal that particle lubrication dominates under the following conditions: (I) high particle concentrations, (II) high fluid viscosities, (III) strong particle – surface interactions, and (IV) weak fluid – particle interactions. These insights are crucial for applications in food science, biomedical industries, and pharmaceuticals, where controlling particle friction is essential for optimizing consumer satisfaction and ensuring the performance and safety of lubricants in medical devices.

Synergistic Effects of Psidium Guajava and Copper Nanoparticles Reinforced Hybrid Hydrogel for Tissue Engineering

Hydrogels are biopolymers proficient in engrossing much water in their 3D network structure. However, single-polymer hydrogels frequently experience poor physio-mechanical properties, confining their border applications. The present work concentrated on developing chemically crosslinked hydrogels using the terpolymerization of gelatin (GEL), guar gum (GGM), and polyvinyl alcohol (PVA). Ethanolic extract of Psidium guajava leaf (EPG) and copper nanoparticles (CuNPs) were added to enhance the biomechanical properties of the developed hydrogels. Hydrogels' viscoelastic, mechanical, swelling, and cytotoxicity properties were assessed. All the hydrogels exhibited a porous-like structure with a swelling index of 230 to 280%. A compressive strength of 5 MPa with splendid chondrocyte viability was noticed in the hydrogels comprised of EPG and CuNPs. The multiple interactions among the polymer chains impart better frequency and shear strain-dependent behavior. The time-dependent frictional behavior of hydrogel under the lubrication of artificial synovial fluid reveals the decreased coefficient of friction over time. The performance of the hybrid hydrogel enhanced with EPG and CuNPs was superior, making it a promising material for tissue engineering applications.

Assessment and Investigation of GH4169 Superalloy: A Frugal Innovative Attempt to Identify Dominant Lubricant Fluid under Dry and Wet Conditions

Assessment and Investigation of GH4169 Superalloy: A Frugal Innovative Attempt to Identify Dominant Lubricant Fluid under Dry and Wet Conditions