Lubrication Method Research Articles

Tribological behavior and wear prediction of molybdenum disulfide grease lubricated rolling bearings under variable loads and speeds via experimental and statistical approach

Proper lubricants and lubrication methods for rolling bearings are essential for providing sufficient bearing performance in high pressure applications. Main roles of molybdenum disulfide (MoS2) grease lubricant in rolling bearing are reduction of friction and wear, removal of frictional heat, extension of fatigue life, and protection from corrosion. Traditional method to evaluate wear behaviour of grease is based on ASTM D2266 which evaluates the performance of grease at 75°C, constant load and speed. However, actual applications may require bearings to be subjected to variable loading conditions where-in rotations per minute (rpm), load and duration of test are variables. 4 ball wear tests were conducted under these variable conditions using chrome-plated steel balls (Bearing-quality Aircraft Grade E52100), to examine the extent of wear and to predict its behaviour using 2 level design of experiment (DOE) factorial approach.In this paper wear and bearings grease deterioration with and without MoS2 are shown and statistical equations to predict wear with respect to speed, MoS2 concentration, and loads are calculated. Auger electron spectroscopy (AES), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were used in order to highlight wear and friction for different lubricant blends and to understand the influence of MoS2 and variable loads on grease. Results indicated that wear depend largely on loading conditions. It is believed that MoS2 greases perform poorly under constant load and a reduced concentration of MoS2 is sufficient to provide the same improved wear characteristics under variable loads and speeds for extreme pressure applications.

Revisiting liquid lubrication methods by means of a fully coupled approach combining plastic deformation and liquid lubrication

This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and the plastic deformation of the metallic material in metal forming are solved simultaneously. The proposed method is an alternative to conventional modelling techniques which allow studying the effect of a broad range of parameters directly on the friction conditions. The approach is applied to strip reduction of a sheet with mesoscopic surface pockets in order to investigate the escape of lubricant from the pocket by means of Micro Plasto HydroDynamic Lubrication and Micro Plasto HydroStatic Lubrication. For the investigation on Micro Plasto HydroStatic Lubrication, the friction along the tool–workpiece contact interface and the back tension are taken as parameters, and the backward escape Micro Plasto HydroDynamic Lubrication is investigated by variations in lubricant viscosity by means of a combined numerical and analytical model, and by variations in drawing speed. Good agreement is found with the experimental observations.

Evaluation of modified jatropha-based oil with hexagonal boron nitride particle as a biolubricant in orthogonal cutting process

Crude jatropha oil (CJO) has been acknowledged as an environmentally benign metalworking fluid (MWF) in the machining industry. However, one drawback found in CJO is that it has poor thermal-oxidative stability that leads to poor lubrication behavior. Henceforth, the objective of this study was to evaluate the machining performances of the newly developed modified jatropha oil (MJO) as a lubricant-based oil. The CJO was improvised through transesterification process at various molar ratios of jatropha methyl ester (JME) to trimethylolpropane (TMP) (MJO1, MJO3, and MJO5) and through the addition of various concentrations of hexagonal boron nitride (hBN) particles, ranging between 0.05 and 0.5 wt.%. The newly developed MJO were compared to CJO and synthetic ester (SE) by considering both viscous and tribological behaviors. In addition, the orthogonal cutting process was carried out on AISI 1045 through minimum quantity lubrication (MQL) methods to evaluate the machining performances (i.e., cutting force, cutting temperature, chip thickness, tool chip contact length, and specific energy). Interestingly, kinematic viscosity and viscosity index were improved with the increase in JME/TMP molar ratio and concentration of hBN particles. MJO5 added with 0.05 wt.% of hBN particles (MJO5a) exhibited the best tribological behavior correlated with excellent machining performances by reducing the cutting force, cutting temperature, chip thickness, tool chip contact length, and specific energy. MJO5a exemplified its potential on the lubricant market place with regard to the environmental concern and energy saving.

Wavelet preconditioned Newton-Krylov method for elastohydrodynamic lubrication of line contact problems

In this paper, wavelet preconditioned Newton-Krylov method is used for the solution of elastohydrodynamic lubrication line contact problem. A finite difference method is used for the solution of EHL equations. The method comprise the non-linear Newton iteration on the outer loop and a linear iteration on the inside loop where wavelet based preconditioned GMRES (Generalized Minimum Residual Method of Krylov subspaces) is used. In the scheme, the Jacobian matrix-vector product is approximated accurately with much ease (without forming Jacobian explicitly and requiring no extra storage). It overcomes the limitations of conventional schemes for the investigation of the EHL problems, for computing pressure and film thickness distributions, covering wide range of physical parameters of practical interest. Also, the sensitivity of height and spread of pressure spike on load and other parameters are presented. To confirm and validate the solutions obtained, by the present method, are compared with those obtained by full approximation scheme of multigrid method.

Effect of the External Lubrication Method for a Rotary Tablet Press on the Adhesion of the Film Coating Layer.

External lubrication is a useful method which reduces the adhesion of powder to punches and dies by spraying lubricants during the tableting process. However, no information is available on whether the tablets prepared using an external lubrication system can be applicable for a film coating process. In this study, we evaluated the adhesion force of the film coating layer to the surface of tablets prepared using an external lubrication method, compared with those prepared using internal lubrication method. We also evaluated wettability, roughness and lubricant distribution state on the tablet surface before film coating, and investigated the relationship between peeling of the film coating layer and these tablet surface properties. Increasing lubrication through the external lubrication method decreased wettability of the tablet surface. However, no change was observed in the adhesion force of the film coating layer. On the other hand, increasing lubrication through the internal lubrication method, decreased both wettability of the tablet surface and the adhesion force of the film coating layer. The magnesium stearate distribution state on the tablet surface was assessed using an X-ray fluorescent analyzer and lubricant agglomerates were observed in the case of the internal lubrication method. However, the lubricant was uniformly dispersed in the external lubrication samples. These results indicate that the distribution state of the lubricant affects the adhesion force of the film coating layer, and external lubrication maintained sufficient lubricity and adhesion force of the film coating layer with a small amount of lubricant.

Multi objective optimization of turning parameters considering spindle vibration by Hybrid Taguchi Principal component analysis (HTPCA)

Multi-objective optimization (MOO) of cutting parameters for turning AISI 4340 steel is experimentally investigated by applying principal component analysis with Taguchi method. Five process paremeters, viz cutting environment, nose radius, feed rate, depth of cut and tool type are used to optimize multi quality charecteristics namely surface roughness, MRR, cutting force, tool tip temperature. Also to make the design robust, experimentation is performed under the different leves of spindle vibration. Due to the limitation of Taguchi method for multi optimization, principal component analysis is hybridly used to solve this problem. Image processing in matlab, the unconventional method of measuring tool wear is used. Coated(CVD & PVD) and un-coated cutting tools and the latest lubrication method (Minimum quantity lubrication) are also considered to match the current scenario of manufacturing system. PCA is used to change multiple objectives to a single objective. ANOVA and response table helped to find the optimal setting of process parameters for turning process.

Machining comparison of aerospace materials considering minimum quantity cutting fluid: A clean and green approach

Efficient removal of heat from the chip formation zone in the machining of aerospace materials is quite crucial for attaining viability with respect to cost and productivity. The recently embraced cooling and lubrication method in the context of environmental friendly and sustainable manufacturing includes the application of minimum quantity cutting fluid. This article presents an experimental investigation, complemented with an evolutionary optimization technique, for studying the impact on cutting forces, surface roughness, tool wear, and chip control in the turning of the two aero-engine alloys (Inconel-800 and titanium-II) with or without using minimal-quantity cooling lubrication fluid. In addition, the multiple regression technique is applied to find the relationship between responses and input parameter such as cutting speed, feed rate, and approach angle. Afterward, the sensitivity analysis and analysis of variance (ANOVA) tests have been performed to test the statistical significance of proposed predictive models. At the end of work, the experimental data have been optimized through two evolutionary techniques, i.e. particle swarm optimization and bacterial foraging optimization, also compared to the much-used desirability technique. It has been concluded that the cooling option of applying minimum quantity cutting fluid proved beneficial for machining these aerospace materials. Moreover, the evolutionary techniques gave much more accurate results when compared to the desirability technique with particle swarm optimization and was concluded as the best one out of the three techniques on the basis of minimum average time taken and minimum percentage error.

Crucial for Rotating Machines: Types and Properties of Lubricants and Proper Lubrication Methods

Any rotating machine has at least one rotating element, which can be a rotor of an electric motor or a turbine, compressor, or pump and is supported by the sleeve bearings or rollingelement bearings. The reliable operation of rotating machinery can be critical for bottom-line production goals and financial results in petrochemical, transportation, and chemical products processing. Lubrication performs a crucial role in the reliable operation of rotating machines. This article will discuss the different types of lubricants, their properties, proper methods of lubrication, appropriate frequency, and consequences of not adhering to the proper maintenance processes.

High Speed Visualizations of oil Jet Lubrication for Aero-engine Gearboxes

Abstract Augmenting gearing systems efficiency is a key issue in developing innovative aero-engines with low specific fuel consumption. The transmission system directly affects the engine overall efficiency, therefore it is essential maximizing its performance. In high speed applications fluid-dynamic losses become predominant and are directly connected to the lubrication method. Oil jet systems are generally used in order to achieve a proper cooling and lubrication of tooth surface. A novel rotating test rig was exploited for investigating oil jet lubrication by means of high speed visualizations. An oil jet impinging radially on a single spur gear was generated by a spray-bar, assessing which parameters affect the oil jet behavior.

An Investigation in Analysis of Dry Turning in MQL Method for Predicting Tool Wear and to Improve Surface Roughness

Objectives: To compare the process parameters such as tool performance, surface roughness in turning process under, dry and near-dry conditions. Methods\Statistical Analysis: This study deals with the comparative performance of carbide coated tools in conventional dry turning with minimal lubricant application method by varying depth of cut keeping feed and speed as constant. The performance of the tool and the roughness of the work material under different conditions are analyzed. Findings: It is found that according to the selected cutting conditions in the model-based comparisons, the predicted tool wear under near dry lubrication are reduced as high as about 30% compared with those in dry cutting while the predicted tool wear land lengths are reduced by 60% compared with those in dry cutting. After the physical behaviors in near dry turning are understood, it is possible to calculate the tool life with given material properties and cutting conditions. Applications Improvements: This study gives sufficient information about performance of carbide tool with minimum amount of lubrication.

Sustainability in machining: “Eco-friendly” turning of Inconel 718. Surface characterisation and economic analysis

Elimination or substitution of traditional lubricants results in the reduction of both operating costs and environmental impact associated with the use, filtration and disposal of metalworking fluids. However, traditional lubricooling are still widely used when machining “difficult to cut” materials, like Inconel 718, with the aim to increase tool life and obtain a surface with proper roughness. The need to move towards an eco-friendly machining pushed the authors to study the effects of alternative lubrication methods (Minimum Quantity Lubrication or Cooling and cryogenic one) on tool life, surface finish and machining costs, when turning Inconel 718. The material was machined with coated cemented carbide tools by a CNC lathe. Metal removing process was carried out under different cutting speeds while depth of cut and feed rate were kept constant.Economic analysis was also considered with the aim to evidence the most convenient condition. Minimum Quantity Cooling resulted in tool life and surface finish very similar to those obtained by conventional lubricooling, even if last one still remains the most convenient at economic level in the present case.

Asymptotic Analysis of Fiber-Reinforced Composites of Hexagonal Structure

The fiber-reinforced composite materials with periodic cylindrical inclusions of a circular cross-section arranged in a hexagonal array are analyzed. The governing analytical relations of the thermal conductivity problem for such composites are obtained using the asymptotic homogenization method. The lubrication theory is applied for the asymptotic solution of the unit cell problems in the cases of inclusions of large and close to limit diameters, and for inclusions with high conductivity. The lubrication method is further generalized to the cases of finite values of the physical properties of inclusions, as well as for the cases of medium-sized inclusions. The analytical formulas for the effective coefficient of thermal conductivity of the fiber-reinforced composite materials of a hexagonal structure are derived in the cases of small conductivity of inclusions, as well as in the cases of extremely low conductivity of inclusions. The three-phase composite model (TPhM) is applied for solving the unit cell problems in the cases of the inclusions with small diameters, and the asymptotic analysis of the obtained solutions is performed for inclusions of small sizes. The obtained results are analyzed and illustrated graphically, and the limits of their applicability are evaluated. They are compared with the known numerical and asymptotic data in some particular cases, and very good agreement is demonstrated.

The effect of laser surface texturing on the tribological performance of different Sialon ceramic phases

A tribological performance was carried out on different types of hot press Sialon ceramics regarding the phases, i.e., the α-Sialon phase, the β-Sialon phase, and the α/β-Sialon composite phase. The different phases of Sialon ceramics were analyzed by XRD patterns. For the tribological performance, the Sialon ceramics were laser textured and the starved lubrication method was applied with different dimple pitches under a load of 10N at room temperature. The material having a dimple pitch of 200µm shows the lowest coefficient of friction. The α/β-Sialon composite phase shows the least coefficient of friction i.e. 0.04 and 0.1 for the textured and polished (without being textured) samples, respectively. The Sialon ceramics show mild wear and therefore, the wear rate of the steel ball (mating partner) was taken into account for the wear analysis. The α-Sialon phase having a higher hardness shows the least wear in comparison to the α/β-Sialon composite phase and the β-Sialon phase.

Lubrication of soft viscoelastic solids

Lubrication flows appear in many applications in engineering, biophysics and nature. Separation of surfaces and minimisation of friction and wear is achieved when the lubricating fluid builds up a lift force. In this paper we analyse soft lubricated contacts by treating the solid walls as viscoelastic: soft materials are typically not purely elastic, but dissipate energy under dynamical loading conditions. We present a method for viscoelastic lubrication and focus on three canonical examples, namely Kelvin–Voigt, standard linear and power law rheology. It is shown how the solid viscoelasticity affects the lubrication process when the time scale of loading becomes comparable to the rheological time scale. We derive asymptotic relations between the lift force and the sliding velocity, which give scaling laws that inherit a signature of the rheology. In all cases the lift is found to decrease with respect to purely elastic systems.

Investigations into lubrication in grinding processes using MWCNTs nanofluids with ultrasonic-assisted dispersion

To improve the quality of grinding processes, nanofluids can replace traditional cutting fluids, improving cooling, lubrication, and surface finish. However, a disadvantage of nanofluids is that a suspension of nanoparticles tends to agglomerate in the course of a long machining process, leading to cooling performance degradation. Although adding surfactants can improve nanoparticle dispersion, this may pollute the nanoparticles. The present research aims to solve these problems using ultrasonic assistance, first taking advantage of the excellent thermal conductivity of multi-walled carbon nanotubes in nanofluids, with vegetable oil as a cutting fluid, and second, devising an effective ultrasonic-assisted oscillator set-up for Minimum Quantity Lubrication. The oscillator agitates the nanofluid through ultrasonic cavitation to keep the nanoparticles dispersed. This experiment uses NAK80 mold steel as a material for grinding, with four different lubrication methods: dry, MQL, nanofluid (0.25 wt%)/MQL, and nanofluid (0.25 wt%)/ultrasonic MQL. The grinding performance and effects of ultrasonic-assisted dispersion are discussed. The results show that nanofluid/ultrasonic MQL grinding can effectively reduce the agglomeration of nanoparticles, and reduce grinding forces, grinding temperature, and surface roughness to a greater degree than other lubrication methods.

An experimental investigation on effect of minimum quantity cooling lubrication (MQCL) in machining titanium alloy (Ti6Al4V)

During the machining operation, elevated temperatures are achieved at the cutting interface due to the presence of high plastic deformation and friction in between the tool and chip contacting area. Efficient heat dissipation from the cutting interface is required to achieve better machining performance. Elevated temperature in the cutting area results in lower tool life as it facilitates different types of wear mechanisms. Metal working fluids (MWFs) are employed to reduce heat and friction in the cutting zone, simultaneously to help in the flushing of waste particles. The MWFs are based on either water or petroleum oil and include several additives which make them non-biodegradable and toxic in nature. The minimum quantity lubrication (MQL) method offers a feasible substitute to the MWF-based conventional flood cooling method. In this study, a vegetable oil-based MQL system was mixed with sub-zero temperature air to design a new minimum quantity cooling lubrication (MQCL) system. The study investigates the machinability of Ti6Al4V using an MQCL system under various oil flow rates and compared its machining performance with both dry cutting and conventional flood cooling. For further evaluation, the study investigated surface roughness, flank wear, and associated wear mechanisms. It was found that in the MQCL system (60–70 ml/h), oil supply rates provided reliable machining performance at higher feed levels.

Nano-lubrication: A review

Lubrication is essential for proper and reliable operation of mechanical systems as it is vital to reduce friction and wear of moving components to assure high quality performance. Particularly, with continued development of precision devices the need to acquire effective lubrication technology for micro-systems continues to rise. The challenge lies in the fact that conventional lubrication methods cannot be applied to micro-systems due to viscosity effects. Thus, driven by the needs of precision devices, stringent operating conditions and environmental preservation, numerous alternatives to conventional liquid lubricants have been proposed. In this paper, various lubrication methods to replace or improve conventional liquid lubrication and their characteristics are reviewed. Fundamental mechanism and tribological characteristics of minimum quantity lubrication (MQL), vapor phase lubrication (VPL), and self-assembled monolayer are discussed.

Analysis of cutting parameters and cooling/lubrication methods for sustainable machining in turning of Haynes 25 superalloy

While the use of cutting oils in machining operations facilitate material removal, the use of these oils are questioned based on the risks they pose for operator health and the environment. As an alternative to the excessive use of cutting oils, the Minimum Quantity Lubrication (MQL) method aims to reduce the use of cutting fluids as a step in achieving clean, environmentally friendly, and sustainable manufacturing. In this study, the machinability of cobalt-based Haynes 25 superalloy, which is a difficult-to-machine alloy used in strategic applications, was investigated under three separate cutting methods (dry, conventional cooling and lubrication, and minimum quantity lubrication). The experiments were conducted on a CNC turning machine using uncoated carbide cutting tools using four separate cutting speeds (15 m/min, 30 m/min, 45 m/min, and 60 m/min), three separate feed rates (0.08 mm/rev, 0.12 mm/rev and 0.16 mm/rev), and a fixed depth of cut value (1 mm). To determine the relationships among machining parameters and outputs, tool wear (VN) and surface roughness (Ra) values were measured. Additionally, the wear mechanisms acting on the cutting inserts were determined using scanning electron microscope (SEM). Following the conclusion of experiments, the Taguchi's signal to noise ratio (S/N) analysis was used to establish the optimal set of cutting parameters. In conclusion, when the MQL method was employed in conjunction with high pressure, the amount of oil used was reduced while the machinability of the material was improved. Tests conducted under all three methods of cutting revealed poor surface roughness at low cutting speeds, and high tool wear at high cutting speeds.

공기윤활평판실험에서 디지털 영상분석을 통한 윤활공기막 검출기법

The reduction of emissions has been a key target in the Marine Industry since the IMO`s Marine Environment Protection Committee published its findings in 2009. The representative emission index is termed as the EEDI (Energy Efficiency Design Index) for the new ships. Among various flow control techniques ever proposed, the air lubrication method is the one of most promising one in terms of practical applicability. The present study examines the basic characteristics of the flat plate test with intention of applying the air lubrication technology to the reduction of the resistance of a ship. Image analysis technique is proposed as a tool to quantify the effectiveness of the air lubrication method.

Ultrasonic assisted grinding process with minimum quantity lubrication using oil-based nanofluids

Optimization of grinding process from the viewpoint of surface integrity and production cost is of the primary interest in grinding technology. Previous studies have shown that ultrasonic vibration assisted grinding (UAG) improves the grinding performance. These improvements are attributed to the change of the nature of the cutting process in UAG. On the other hand, minimum quantity lubrication (MQL) method has also been shown to increase the effect of lubrication characteristics of cutting fluid, and to minimize consumption of cutting fluid and reduce its environmental impact. Furthermore, it is perceived that adding nanoparticles to the cutting fluid, will improve its effectiveness.This paper reports an experimental investigation of the vibration assisted grinding process combined with MQL using oil-based nanofluids with MoS2 nanoparticles. Results are presented in terms of normal and tangential forces, force ratio and ground surface roughness. The results show that imposed horizontal ultrasonic vibration significantly decreases the grinding normal force. Also, MQL using nanofluid significantly decreases the grinding tangential force. Finally, simultaneous application of both techniques reduced forces by around 60%, which is very substantial. It also improved the surface quality.