Lubrication Conditions Research Articles

Frictional behaviour of coated carbide tools and AISI 316L when using translational and rotatory relative movement considering dry and lubricated conditions

In machining, tool temperatures and thus tool wear are significantly influenced by frictional behaviour. Friction tests are used to determine the friction coefficient depending on relative speed, which serves as basis for parameterising friction models as input data for chip formation simulations. Therefore, this paper represents investigations towards the frictional behaviour of uncoated and coated (TiN, TiAlN) carbide tools when using two different relative movements (translational and rotary) and cooling lubricant conditions. In dry conditions, the investigations show insignificant influence of different engagement surfaces and testing kinematics on resulting friction. In lubricated conditions, three different friction coefficient sections were observed.

Mesomorphism and Tribotechnical Characteristics of Lubricant Compositions with Mesogenic Additives Carboxylates Cu(II)

The purpose of the work is to characterize the lubricants based on Llitol-24 and synthetic solidol with additives copper(II) carboxylates when using them in friction nodes in loading conditions and temperature. The lubricant compositions with additives copper(II) carboxylates based on synthetic solidol and Litol-24 form the columnar mesophases depending on thermodynamical conditions and concentration of additives.Methods. We study the lubricant compositions with dielectric spectroscopy and и polarization light microscopy. The studies lubricant compositions are tested on the frictional machines by preceding authors, which performed their synthesis and numerical estimations for their geometry parameters. It is shown, that the columnar mesophase formed by the compositions with copper(II) carboxylates simulates favourable tribological conditions for lubrication (reduction of the friction coefficient at the appointed range of additive concentrations and reduction of wear) and unlike to crystalline phases, shows orientation effects at the surface of interacting surfaces of machine elements and devices. These factsmotivate the study of influence of physicochemical properties and composition on mesomorphism of considered lubricant compositions.Results. In our measurements, we found the main dielectric characteristics of two kinds of the lubricant compositions: dielectric constant and dielectric loss, electroconductivity, dissipation factor, the Arrhenius functions are plotted, and the activation energies of the lubricant compositions we study are calculated. The microphotogram for textures of the lubricant compositions depending on temperature and concentrations are received. The differences in mesomorphic properties of the lubricant compositions with additives Cu(II) valerate and isovalerate are confirmed.The conclusion of the work is that the composition of the lubricant is optimized by the choice of additive concentration, the length of the mesogenic chain of the copper(II) carboxylate molecule and its conformation.

Determination of the construction material for phononic band gap structures by tribological performance

This study investigates the tribological performances of commonly used stainless steel alloys (303, 304, 316L, and 420) to determine their suitability as construction materials for periodic structures designed for inertial amplification induced phononic band gap vibration isolators. Stainless steel alloys are extensively employed in engineering structures due to their ability to withstand large stresses and exhibit excellent cyclic loading properties. In this study, stainless steel specimens are examined by dry and lubricated wear test conditions. 420 stainless steel showed highest wear resistant properties for dry and lubricated conditions. Two grades of lubricants are compared in terms of viscosities, and it is revealed that higher viscosity blocked the flow of the lubricant so that semi-dry friction occurred. Low viscosity lubricant enabled less material removal due to friction.

Applying knowledge management in optimal modeling of viscosity of nanofluids by response surface methodology for use in automobiles engine

In this study, using knowledge management and RSM, modeling and prediction of viscosity of oil-based hybrid nanofluid (HNF) with Multi-walled carbon nanotube (MWCNT) and Al2O3 nanoparticles in temperature conditions of 25–50 °C and solid volume fraction of SVF=0.0625–1% have been addressed. To find the most accurate model for predicting viscosity, Cubic, Quartic, and Fifth models were examined in terms of various model accuracy evaluation parameters. Based on the obtained results, the Fifth model has the most accuracy in terms of coefficient of determination and coefficient of variance with values of 0.9997 and 1.10, respectively. Based on the correlation presented to predict viscosity due to the dependence of viscosity on shear rate, the behavior of HNF is non-Newtonian. The graphs of temperature in terms of SVF for viscosity in all three models show that viscosity decreases with increasing temperature and viscosity increases with increasing SVF. For hot lubrication conditions, the best condition (255.28 mPa.sec) is at 35 °C and SVF is 0.161%. Also, knowledge management is considered as a safe and optimal method to increase efficiency, productivity and effectiveness in the field of nanofluids (NFs), which brings high added value to this sector.

Design and tribological performance of graphene nanofluids dispersed by dragging effect of bicomponent gelator

Nanofluids have excellent lubrication and high thermal conductivity. However, the agglomeration and sedimentation produced by the large surface energy of nanoparticles in base liquid threaten the long-term dispersion stability and impact the wide application of nanofluid. In this work, based on the self-assemble behavior and continuous network structure formed by low molecular weight organic gelator, the uniform clusters were formed through regulating the kinetics behavior in the gelling process. The dragging effect was demonstrated by oleic acid - sodium dodecyl sulfate (OA-SDS) bicomponent gelator and graphene oxide (GO) nanosheets. The results showed that GO nanofluids dispersed by OA-SDS were stable for more than 12 months. The well-dispersed GO nanofluid exhibited better anti-friction and anti-wear properties under both immersion and electrostatic minimum quantity lubrication conditions. Moreover, the lower contact angle, surface tension and droplet size of nanofluids after charging improved the wettability on the frictional interface. The GO adsorption film formed on the friction interface protected the tribochemical reaction film of iron oxide and prevented the occurrence of sintering of base oil.

Friction Reduction Achieved by Ultraviolet Illumination on TiO2 Surface.

Controlling friction by light field is a low-cost, low-energy, non-polluting method. By applying ultraviolet light on the surface of photosensitive materials, the properties of the friction pairs or lubricant can be influenced, thus achieving the purpose of reducing friction. In this study, TiO2, an inorganic photosensitive material, was selected to investigate the modulating effect of light fields on friction lubrication when using polyalphaolefin (PAO) base oil as a lubricant, and the modulation law of light fields on the friction lubrication behavior was investigated under different loads (1-8 N), different speeds (20-380 mm/s), and different viscosities (10.1-108.6 mPa·s) of PAO base oil. The experimental results showed that light treatment could reduce the friction coefficient of PAO4 base oil lubrication from 0.034 to 0.016, with a reduction of 52.9% under conditions of 3 N-load and 56.5 mm/s-speed, and the best regulation effect could be achieved under the mixed lubrication condition. After TiO2 was treated with ultraviolet light, due to its photocatalytic property, PAO molecules were oxidized and adsorbed on the TiO2 surface to form an adsorption layer, which avoided the direct contact of rough peaks and thus reduced the friction coefficient. This study combines photosensitivity, photocatalysis, and friction, presenting a method to reduce the friction coefficient by applying a light field without changing the friction pairs or lubricants, which provides a new direction for friction modulation and gives new ideas for practical applications.

PERFORMANCE OPTIMIZATION OF BS970 MILD STEEL TURNING PARAMETERS UNDER SiC-MoS2 HYBRID NANOFLUID USING HYBRID DEEP BELIEF NETWORK BASED COOT OPTIMIZATION

In the modern world of competitive manufacturing, turning is a basic and important process that needs to be optimized for the fast-evolving industrial nature. It has its application in various fields involving numerous materials. This research study deals with modeling with optimization on the turning process parameters of turning E2-BS970 mild steel with cryogenically treated tungsten carbide tool under NFMQL having [Formula: see text] nanofluid. The parameters considered as the input factors are spindle speed and depth of cut along with feed rate and lubrication condition. The design of the experiment is done based on Box–Behnken design for 27 trials in the response surface method. The Deep Neural Network (DBN) and the Coot optimization algorithm are employed using MATLAB software for the prediction modeling. The prediction model developed by the DBN sigmoid function gave minimal error with prediction regression values of 0.99988 for MRR, 0.99516 for Cutting temperature, and 0.99545 for Tool life. The optimized result by CO shows a value of 188.89 rpm for spindle speed, 0.2318[Formula: see text]mm/rev for feed rate, Doc of 1.45[Formula: see text]mm, and 0.5015[Formula: see text]vol.% nanofluid MQL condition. The optimized values of MRR are 3.35[Formula: see text]mm3/min, [Formula: see text]C cutting temperature, and 1543.12[Formula: see text]s of tool life. The DBN model combined with the Coot algorithm shows minimal deviation compared to the experimental results validation and confirmatory analysis and is deemed suitable for efficient prediction.

A sustainable cooling/lubrication method focusing on energy consumption and other machining characteristics in high-speed turning of aluminum alloy

Understanding energy implications and machining performance standards is vital as industries move toward sustainability. Modern machining techniques including high-speed turning are used in the study on aluminum alloy materials. Therefore, this study focuses on the energy consumption and in-depth analysis of machinability criteria in the context of eco-friendly high-speed turning of aluminum alloy. The experiments were performed under ecofriendly cutting conditions dry and minimum quantity lubrication (MQL) conditions and the intricate relationship between machining parameters and cooling conditions was investigated in terms of energy consumption, tool wear, surface roughness and chips morphology. The result reveal that the Ra values exhibited 2.4 times increase in dry machining and an average increase of 2.3 times in MQL machining when the feed rate was increased from 0.2 to 0.4 mm/rev. Moreover, the MQL cooling is helpful in lowering the energy consumption as well as tool wear and surface roughness during the machining operations. MQL machining resulted in a 35% reduction in flank wear and 20% reduction in energy consumption compared to dry machining.

Wheel-rail contact wear analysis on curved lubricated track for heavy haul locomotive studies

The effect of lubrications on a curved track to heavy-haul wheel-rail contact wear is studied. To analyse wheel-rail contact wear damage due to existing high-adhesive AC locomotive, a methodology for investigation is proposed, and the locomotive models are required to run at 20 km/h under maximum traction efforts, and the simulations include a DC locomotive for comparison. An extended creep force model, which was developed by Polach and has been widely used for the wheel-rail contacts under dry and wet conditions with variable friction coefficients, is further extended to apply for the typical low-coefficient-friction modifier, oil, and grease lubricant conditions. The wear models from two pairs of wheel-rail materials are used to predict the wear rates, and the wear numbers Tγ are presented for discussions. The simulations show that the lubricants significantly reduce the wheel-rail contact wear.

Study on scuffing failure of gas turbine ball bearing based on 3D mixed lubrication and dynamics

Ship gas turbine bearings are subjected to heavy loads and intricate interface micromorphologies, predominantly operate in a mixed lubrication regime. Excessive asperity relative sliding can cause transient high-temperature spikes at contact points, leading to scuffing failures. Dynamic parameters such as bearing friction and clearance, along with vibrations causing fluctuating velocities and loads, further influence the lubrication condition that, in its turn, can increase the risk of scuffing. This study focuses on oil-lubricated gas turbine bearings, accounting for their typical transient working conditions and real surface roughness. The coupling characteristics of ball bearing dynamics, lubrication, and flash temperature are explored. Findings indicate that the most severe contact conditions occur at azimuth angles of 0° and 360°. The risk of ball Scuffing failure exceeds that of the inner raceway. As axial load increases under the azimuth angle of 360°, the area with zero film thickness is increasing, elevating the chances of asperity contact, friction coefficient, and interface temperature, which is detrimental to lubrication. To mitigate pitting and scuffing failures, it's recommended to maintain the bearing's maximum hertz pressure below 1.21 GPa.

Enhancing the Elastohydrodynamic Lubrication and Vibration Behavior of Rolling Bearings Using a Hybrid Bio-Grease Blended with Activated Carbon Nanoparticles

In recent years, bio-lubricants have received a growing interest for industrial applications. Still, a full-scale implementation in machinery lubrication requires a thorough evaluation of their performance through tribological and operational tests to stand upon their performance. Additionally, the promising outcomes achieved by nanoadditives in improving the performance of synthetic lubricants have prompted research efforts to identify suitable nanoadditives for bio-grease. This paper introduces a bio-grease from a hybrid vegetable oil and glycerol monostearate as a thickener for the lubrication of rolling bearings. Activated carbon nanoparticles (ACNPs) as nanoadditives were synthesized, characterized, and incorporated into the bio-grease at concentrations of 0.5, 1, and 2% by weight. Tribo-tests were conducted on these bio-grease blends, and running tests were carried out using 6006 ball bearings on a custom test rig. Throughout a 30-min test run under a radial load of 10% of the bearing’s dynamic load rating, mechanical vibrations and power consumption were measured and analyzed for each bearing. The bio-grease with ACNPs exhibited a substantial reduction in wear scar diameter (WSD) and coefficient of friction (COF), achieving improvements of up to 73.6 and 65%, respectively, in comparison to lithium grease. Furthermore, the load carrying capacity was enhanced by 200%. The study revealed a strong correlation between measured vibration amplitudes and the viscosity of the bio-grease. The absence of high frequency resonant bands in vibration spectra indicated that the test grease samples satisfied the conditions of elastohydrodynamic lubrication, and these findings were corroborated through calculations of the minimum oil film thickness.

Study on the tribological characteristics of surface triangular textured TC4 alloy prepared by SLM technology

Surface Triangular Textured TC4 Alloy specimens were prepared by 3D printing technology (SLM technology: selective laser fusion). Effects of wedge-shaped triangular textures with different texture area occupancy on hardness, friction and wear of the 3D printed TC4 alloy specimens were studied, in comparison with non- textured specimens. SFT -2 M pin-disc friction and wear testing machine was used to perform friction and wear experiments under 46 # mechanical oil lubrication conditions, and MH-500 Vickers hardness tester was used to measure hardness of the specimens. Scanning electron microscope (SEM), energy spectrometer (EDS), and electronic balance instrument were used to characterize the wear scar morphology, element content, wear amount, etc. of the specimens. Using the Fluent module in ANSYS Workbench software, we studied the mechanism for the reduction in the friction coefficient between friction pairs during the relative movement in lubricating oil. Results of the study show that the hardness of the 3D printing specimen is significantly greater than that of the non- textured one. In each group of experiments, the wedge triangular textured specimens showed better tribological properties, and the 3D printed specimen with an area occupancy of 22. 53 % exhibited the smallest average friction coefficient (0.17) and higher wear resistance than other specimens. The dynamic pressure effect due to the wedge triangle texture inside the lubricating oil film is the main reason for the reduced friction coefficient between the friction pairs.

Laser Melting and Surface Texture Technology: Effect on Friction Properties

This paper discusses the role of laser surface texturing and laser melting technology in enhancing surface lubrication and wear resistance under starved lubrication conditions. The aim is to enhance the wear resistance of laser surface texturing and to explore the role of surface texturing in enhancing lubrication. This paper observes the microstructure of the melting zone, transition zone and matrix of the base material Cr12MoV after laser melting and condensing, detects and analyses the metallographic composition, and tests the micro-hardness. The effects of laser surface texturing technology and laser melting technology on the coefficient of friction under different friction and wear environments were comparatively investigated. The laser melting zone consists of martensite with fine grain size and a large amount of residual austenite. After laser melting, the hardness reaches 1.4 times the hardness of the matrix. The laser surface texture increases lubrication significantly at low rpm. The fully fusion-coagulated treatment is wear-resistant in a variety of different frictional wear environments.

Effects of Lubricating Conditions on Wear Performance of U77MnCrH Rail

With the rapid development of railway towards being high speed and having heavy load capacity, the wheel–rail wear and rolling contact fatigue in the curve section with a small radius of freight have become the key problems in urban railways, which need to be solved urgently. The aims of this study were to compare the wear resistance with three different lubricating conditions on wheel–rail wear based on the wheel–rail rolling contact simulation tests. The wear loss, microhardness, and microstructure of the contacted surface of the rail were detected systematically. The results showed that the wear rates of rail were reduced by 71% for grease lubrication and 55% for solid lubrication, compared to those without lubrication. At the same time, the thickness of plastic deformation layer of rail samples were about 167 μm for the dry state, 138 μm for the solid lubrication state, and 128 μm for the oil lubrication state, respectively. It indicates that the thickness of the plastic deformation layer was significantly reduced under both grease and/or solid lubricating conditions. In addition, the microstructure of the deformation layer with two kinds of lubricated states was coarser and denser than that without lubricants. The average grain size of the deformation layer was approximately 0.22 μm under dry conditions and 0.32 μm under lubricated conditions. It also indicated that the changes in lubricants did not have a significant effect on the average grain size of the deformation layer. The results of the present study could provide theoretical reference for the development and design of lubricants used as rail materials.

Experimental Study on Tribological Properties of Coated Surface and Textured Surface under Seawater Lubrication Conditions

In order to improve the tribological properties of the flow distribution pair of the seawater axial piston pump, SAF2507 super duplex stainless steel and carbon-fiber-reinforced polyetheretherketone (CF/PEEK) were selected as the matching materials. The surface coating treatment and surface texture treatment were carried out on the flow distribution pair, and the friction and wear test were carried out by MMD-5A. In order to fully understand the friction and wear properties of the surface coating flow distribution pair and the surface texture flow distribution pair, and analyze the friction and wear mechanism, the data of the friction coefficient, wear loss, and wear surface morphology were obtained in the experiment. The results show that the coating surface has little difference in the test, the texture surface significantly reduces the friction coefficient, and the wear scar density is significantly reduced. Adding texture to the surface of the lower sample is better than adding it to the surface of the upper sample. The research results are helpful in improving the tribological performance of the flow distribution pair of the seawater axial piston pump.

Effect of time-varying friction coefficient on self-excited vibration of floating spline-rotor system

Different lubrication states seriously affect the stability and safety of the aviation power transmission system. This study investigates how time-varying friction coefficients impact the stability of an aviation spline-rotor system using a spline-rotor model that considers uneven stress distribution on the tooth surface. Experimental tests with a high-frequency friction and wear test machine yield time-varying friction coefficients for splines with different lubrication, surface roughness, and materials. A sharp change of friction coefficient for the sample occurs under wear debris lubrication. The average friction coefficient for the sample with roughness 1.6 is lower than those with roughness 0.8 and 3.2. Under the same lubrication conditions, the friction coefficient of Resin matrix composites is smaller than that of metallic materials. Dynamic simulation of the spline-rotor model considering time-varying friction coefficients shows rich self-excited vibration behaviors influenced by lubrication, surface roughness, and materials.

Multi-objective optimization for balancing surface roughness and material removal rate in milling hardened SKD11 alloy steel with SIO2 nanofluid MQL

In manufacturing practice, manufacturers always strive to achieve both quality and productivity targets simultaneously. In the first part, this study examines the relationship between input factors, including cutting speed, depth of cut, and feed rate, and the output response, which is surface roughness, when milling hardened SKD11 alloy steel under minimum coolant lubrication conditions using SiO2 nanofluid. The input parameters are divided into four levels to determine their influence on surface roughness and to find the optimal conditions for achieving the minimum surface roughness. The experimental design was conducted using an L16 array. A second-order regression model was developed to describe the relationship between the input variables and the output response. In the second part, multi-objective optimization was performed to simultaneously achieve the minimum surface roughness and the maximum material removal rate (MRR). The Response Surface Methodology (RSM) was employed in this study. The results indicated that to achieve the minimum surface roughness, machining should be performed at a cutting speed of 100 m/min, a cutting depth of 0.2 mm, and a feed rate of 0.01 mm/tooth. With these settings, the predicted surface roughness could reach 0.0451 µm. On the other hand, for the multi-objective optimization, to achieve the minimum surface roughness and the maximum MRR simultaneously, machining should be carried out at a cutting speed of 100 m/min, a cutting depth of 0.36 mm, and a feed rate of 0.0168 mm/tooth. With this cutting condition, the predicted surface roughness could reach 0.1069 µm, and the predicted MRR could reach 775.06 mm3/min

The Effects of the Lubricant Properties and Surface Finish Characteristics on the Tribology of High-Speed Gears for EV Transmissions

Electric vehicle (EV) transmissions operate at high speeds. High-speed operation puts higher demands on bearings, seals, and gears. Bearings in EV transmissions are prone to electrically induced bearing damage and may exhibit signs of pitting and fluting. Surface-initiated rolling contact fatigue is another common problem gaining increased attention lately. Most EV transmissions require a coupling between an oil-lubricated gearbox to an electrical motor that runs with minimal lubrication at very high rpm. The high mechanical and thermal stresses the seals are exposed to under starved lubrication conditions have a detrimental impact on their service life. Hence, proper lubrication is critical. In general, EV transmission fluids call for a somewhat different spectrum of properties compared to conventional ATFs. Gear tribology simulations open new ways to the design and optimization of lubrication for EV transmissions. Additionally, such simulations can also provide valuable insights into the effects of different oil properties on cooling and lubrication efficiencies, thereby helping in matching the lubricant and hardware characteristics for optimal performance. In the present communication, we demonstrate the effects of different lubricants and surface finishing technologies on the tribology of high-speed gears using tribological tests and advanced thermal elastohydrodynamic (TEHD) simulations. The important roles of lubricity additives and surface finish optimization are highlighted in conjunction with a move towards ultralow viscosity EV transmission fluids.

A study on friction induced tribological characteristics of steel 316 L against 100 cr6 alloy under different lubricating conditions with machine learning model

The material steadily wears away from touching surfaces when two solid entities are constantly moving against one other. When more parameters and extreme materials are involved in tribological testing, then it is very difficult to analyze and observe the working phenomena. With this aim, this study uses the gaussian process regression (GPR) approach to estimate friction forces when testing SS 316 L against 100 Cr6 alloy under cryogenic and cryo + minimum amount lubrication conditions. The friction forces from ball-on test experiments were used to develop the prediction models. Then, the wear surfaces and surface morphology are analyzed under cryo and cryo+MQL conditions. The results demonstrated that the combination of MQL and CRYO cooling reduced the friction forces more than 10 times for sliding distances above ∼30 m and loads below ∼25 n. Hence, the cryo+MQL conditions are beneficial in enhancing the tribological features due to the dual cooling and lubricating effects.

Experimental Study of Lubricant Distribution and Lubrication Enhancement Induced by Ball Bearing Cage

Abstract The bearing cage played a pivotal role in affecting the lubricant redistribution and lubrication states. In this study, a cage unit is incorporated into an optical ball-on-disc apparatus for the purpose of a quantitative study of cage-induced lubrication phenomena. It is found that the presence of the lubricant layer on the ball surface, shaped by the cage, affects the inlet lubricant supply of contact between the ball and the glass disc. Thereafter, the oil reservoirs surrounding the contact area and the film thickness were measured. The results showed that the lubricant reservoirs and inlet lubricant supplement were significantly improved with the employment of the cages. In addition, the lubrication state transformed from starved to fully flooded, effectively enhancing the lubrication state. Moreover, the lubricant on the steel ball surface moved from the side bands to the central rolling track, indicating that the lubricant redistribution was the main reason for the lubricating enhancement. Notably, the groove modification on the inner surface of the cage pocket facilitated the directional lubricant migration and the migration effect depended on the groove angles. In conclusion, these results offer an in-depth understanding of the bearing lubrication mechanism, thereby inspiring advancements in cage design and lubricant flow regulation.