Lubrication Oil Film Thickness Research Articles

A Synchronous Sensing Method of Measuring Lubricating Oil Film Thickness and Temperature by Using Eddy Current Effect

A Synchronous Sensing Method of Measuring Lubricating Oil Film Thickness and Temperature by Using Eddy Current Effect

Investigation of Lubricant Oil Film Thickness on Workpiece under Minimum Quantity Lubrication Milling Process

Investigation of Lubricant Oil Film Thickness on Workpiece under Minimum Quantity Lubrication Milling Process

A sensitivity-improved amplitude method for determining film thickness based on the partial reflection waves

A sensitivity-improved reflection coefficient amplitude method for determining wide-range lubricating oil film thickness is proposed based on partial reflection waves, which are obtained by removing the first reflection wave. Numerical analysis and experimental testing are conducted to verify the proposed method. The results show the lubricating oil film thickness ranging from the spring model region to the resonant region can be calculated based on the proposed partial-wave reflection coefficient amplitude method. In comparison to the existing reflection coefficient amplitude method, the measurement accuracy of the lubricating oil film thickness is significantly improved for the transition region which locates between the spring model region and the resonant region, for instance, the observed maximum relative error is decreased to 9% from 60%.

Thermal characteristics and distribution rule of lubrication film of full ceramic ball bearing under different service condition

PurposeThe study aims to the distribution rule of lubricating oil film of full ceramic ball bearing and improve its performance and life.Design/methodology/approachThe paper established an analysis model based on the fluid–solid conjugate heat transfer theory for full ceramic ball bearings. The distribution of flow, temperature and pressure field of bearings under variable working conditions is analyzed. Meanwhile, the mathematical model of elastohydrodynamic lubrication (EHL) of full ceramic ball bearings is established. The numerical analysis is used to study the influence of variable working conditions on the lubricant film thickness and pressure distribution of bearings. The temperature rise test of full ceramic ball bearing under oil lubrication was carried out to verify the correctness of simulation results.FindingsAs the speed increased, the oil volume fraction in full ceramic ball bearing decreased and the surface pressure of rolling element increased. The temperature rise of full ceramic ball bearings increases with increasing speed and load. The lubricant film thickness of full ceramic ball bearing is positively correlated with speed and negatively correlated with load. The pressure of lubricating film is positively correlated with speed and load. The test shows that the higher inner ring speed and radial load, the higher the steady-state temperature rise of full ceramic ball bearing. The test results are in high agreement with simulation results.Originality/valueBased on the fluid–solid conjugate heat transfer theory and combined with Reynolds equation, lubricating oil film thickness formula, viscosity temperature and viscosity pressure formula. The thermal analysis model and EHL mathematical model of ceramic ball bearings are established. The flow field, temperature field and pressure field distribution of the full ceramic ball bearing are determined. And the thickness and pressure distribution of lubricating oil film in the contact area of full ceramic ball bearing were determined.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0126/

Analysis on Lubrication Performance of Piston Ring-Cylinder Liner based on Numerical Simulation

This paper mainly studies the tribological performance of friction pairs and poor lubrication during piston movement. Based on the average Reynolds equation and comprehensively considering the variable viscosity and variable density characteristics of lubricating oil, a transient hydrodynamic lubrication model of the piston ring-cylinder liner friction pair is established. By solving the established lubrication model, the lubricating oil film thickness value, friction value and other parameters that can characterize the lubrication performance of the friction pair throughout the cycle are obtained, whilst revealing the surface roughness, lubricating oil viscosity and piston ring barrel surface height. And the influence mechanism of the friction performance of the friction pair is presented on the basis of the previous analysis. The research shows that improving the surface roughness of the piston ring will help to improve the lubrication, increasing the viscosity of lubricating oil will help to improve the lubricating performance of friction pairs and reduce the peak friction at the top dead centre of piston rings and improving the surface texture of the piston rings can reduce the oil film thickness and reduce the friction caused by fluid shear effect in the high-speed region.

Oil viscosity effects on lubricant oil film behaviour under minimum quantity lubrication

Minimum Quantity Lubrication is a great alternative to flood coolant in many perspective such as economic perspective, safety and health perspective and others. In addition, natural biodegradable oils have been widely used as lubricant oil to meet the environmental-friendly machining environment. The study of lubricant oil fundamental nature during MQL machining is highly important to really identify how the lubricant oil behaviour does affects the lubricating process. Nevertheless, the study is still scarce probably due to the complexity of experimental setup and the natural flow of the lubricant oil cannot be disrupted during the machining operation. To cater this issue, the behaviour of MQL lubricant oil was investigated so a non-intrusive method called as Laser-induced Fluorescence method is applied onto Al6061 workpiece .This research was operated by different oil viscosity represented by different oil type i.e. mixed esters oil, sunflower oil, olive oil and calophyllum inophyllum oil to analyse the lubricant oil film thickness. Overall study showed that, the average of lubricant oil film thickness were significantly decreased as the oil viscosity increased affected by the spreadability of lubricant oil onto the milled surface. At all conditions for oil viscosities, the lubricant oil film showed similar downturn trend due to rise up of built-up edge formation and chips accumulation towards the milling point. Hence, the effects of MQL system parameter on the machining performance has been clarified in details through the observation on the MQL lubricant behaviour.

In Situ Tuning Underwater Bubble Movement on Slippery Lubricant-Infused Anisotropic Microgrooved Surface by Unidirectional Mechanical Strain.

Numerous studies have focused on designing and fabricating functional interfaces that control movement behavior of underwater gas bubbles, which are ubiquitous in a variety of natural and industrial settings. Nevertheless, developing surfaces with in situ tunable bubble movement remain elusive because of current complicated tuning strategies on the specific materials. Inspired by natural pitcher plant and rice leaves, here we report a kind of slippery lubricant-infused anisotropic microgrooved surface (SLI-AMGS) fabricated by femtosecond laser direct writing technology and realize the in situ reversible switching between underwater bubble sliding and pinning by unidirectional mechanical tensile strain. Different experimental parameters including lubricant oil film thickness, bubble volumes and laser power have been researched to manifest the relationship with bubble sliding behaviors. The underlying mechanism of in situ reversible switching mainly lies on the decrease of the lubricant oil film thickness during the process of mechanical stretching in which the uniform and stable oil film layer becomes uneven. This uneven lubricant oil film results in an extraordinary increase of contact angle hysteresis and resistance. At last, we demonstrate a real-time dynamic modulation of the underwater bubble on the SLI-AMGS with a changing mechanical tensile strain for several repeatable times in different acid-based environments. Our work manifests great potential applications in widespread fields including underwater bubble microfluidics and microbubble robots.

Experimental Research on the Dynamic Lubricating Performance of Slipper/Swash Plate Interface in Axial Piston Pumps

The interface between the slipper/swash plate is one of the most important frication pairs in axial piston pumps. The test of this interface in a real pump is very challenging. In this paper, a novel pump prototype is designed and a test rig is set up to study the dynamic lubricating performance of the slipper/swash-plate interface in axial piston machines. Such an experimental setup can simulate the operating condition of a real axial piston pump without changing the relative motion relationship of the interfaces. Considering the lubricant oil film thickness as the main measurement parameter, the attitude of the slipper under the conditions of different load pressure, rotation speed and charge pressure are studied experimentally. After the test, the wear state of the swash plate is observed. According to the friction trace on the surface of the swash plate, the prediction for the attitude of the slipper and the zone easy to wear are verified.

Film thickness formation in nanoscale due to effects of elastohydrodynamic, electrostatic and surface force of solvation and van der Waals

PurposeThe purpose of this is to study the mechanism of an oil film thickness formation in the nanoscale. A polar lubricant of propylene carbonate is used as the intervening liquid between contiguous bodies in concentrated contacts. A pressure caused by the hydrodynamic viscous action in addition to the double-layer electrostatic force, van der Waals inter-molecular forces and solvation pressure owing to inter-surface forces is considered when calculating the ultrathin lubricating films.Design/methodology/approachUsing the Newton–Raphson iteration technique applied for the convergence of the hydrodynamic pressure, a numerical solution has been ascertained.FindingsThe results show that, at separations beyond about five molecular diameters of the intervening liquid, the formation of a lubricant film thickness is governed by the combined effects of viscous action and surface force of an attractive van der Waals force and a repulsive double-layer force. At smaller separations below five molecular diameters of the intervening liquid, the effect of the solvation force is dominant in determining the oil film thickness.Originality/valueThis paper fulfils an identified need to study the behavior of polar lubricants in concentrated contacts in ultrathin conjunctions. The effect of the hydrodynamic action, electrostatic force and surface action of van der Waals and solvation forces is considered when calculating the lubricant oil film thickness.

Boundary for aviation bearing accelerated life test based on quasi-dynamic analysis

Full-scale bearing accelerated life test experiment is an effective way to achieve the demand of modern aero-engine bearing. However, its premise is how to determine the boundary reasonably. In this study, the factors leading bearing abnormal failure are presented by the fault tree analysis. Then, the boundary conditions of aero-engine bearing are analysed by the quasi-dynamic method. The relationship between status parameters associated with failure modes (such as lubricating oil film thickness, etc.) and working parameters (such as rotation speed, external load) is discussed. It revealed the interrelation between practical working condition and status parameters in graphical form. The analysis provided theoretical bases for the choice of working parameters and the ultimate failure judgment in the accelerated life test.

Simulation of the mild wear of cams in valve trains under mixed lubrication

Cam–follower kinematic pairs in the valve trains of engines usually operate in the mixed lubrication regime and work under conditions of wear. The wear mode of cams in mixed lubricated contacts is mild, and the wear value is usually calculated using Archard’s equation in which the wear coefficient is closely related to the lubrication condition. In this study, a nonlinear relationship between the wear coefficient and lubricant oil film thickness under mixed lubrication is proposed with consideration of the rough height distribution of the contact surface. As the cam and flat tappet pair of the valve train in a diesel engine is concerned, the wear coefficient of the cam material for boundary lubrication conditions is measured. After calculating the lubricant oil thickness, the wear depths at different points of the cam are simulated, and results are consistent with the measured values in the practical test.

Effect of Nanotexturing on Increase in Elastohydrodynamic Lubrication Oil Film Thickness

The effects of nanotexturing on oil film thickness and shape under pointcontact elasto-hydrodynamic lubrication (EHL) conditions were experimentally investigated. A disk-onball friction tester with an optical interferometer was used to measure oil film thickness and to observe the oil film shape. Periodic groove structures with a spiral, perpendicular, or parallel shape and with various groove depths and distances were formed by irradiation of a femtosecond laser onto the surface of steel balls. These nanotextured balls were tested under a load of 20 N and at rotational speeds from 1.0 to 3.0 m/s. Most of the balls with nanotexturing had a thicker oil film than those without texturing. The groove depth and angle were the key parameters determining the thickness of the oil film as they controlled the amount of side leakage of oil from the contact point. Optimization of these parameters resulted in an oil film that was almost twice as thick as that on the ball without texturing.

The Comparison and Analysis on the Approaches of Lubricant Oil-Thickness Testing

This paper describes the comparison on the approaches of bearing lubricant oil-thickness testing .The comparison and analysis involves in the areas of classification of methodsbackground theoryapplied range and experiment between refined optical method and new ultrasonic method. The result of optical method modify the result of ultrasonic method, which has a guidance on the development of testing lubricant oil-film thickness. It describes an ultrasonic array , based on the traditional single-element transducer. In this way, the two dimensional oil-thickness distributions can be extracted by data processing. The development of ultrasonic approach benefits the goal of monitoring bearing lubrication condition online , which demonstrates the potential value of the ultrasonic approach. The implications for improved measurement methods are then discussed.

Analysis of Elastohydrodynamic Lubrication of Ball Screw with Rotating Nut

The isothermal elliptical contact elastohydrodynamic lubrication (EHL) problem in ball screw with rotating nut was studied.Numerical solution to the problem was obtained for various parameters with a multigrid solver.Based on work mentioned above,the influence of the working parameters such as the rotating speed of screw shaft and the contact force,on the lubricant oil film thickness and pressure is analyzed .The results showed that, with the increasing loads,the pressure became higher,the film thickness became smaller. On the other hand,when the angular velocity was higher,the film thickness was higher, while the pressure spike was closer to the center of the contact. Because of the spinning, the slide-roll ratio was not a constant.

The Simple Model of the Oil Film Thickness between Piston Ring and Cylinder

Piston ring-cylinder is one of the most important friction pair of internal combustion engine，the lubricating state between them has decided internal combustion engine lubrication quality. So the theoretical research to the lubricating characteristics of the piston-ring group, especially the calculation of the lubricating oil film thickness is very important. The oil film thickness between piston-ring and cylinder is studied by calculation method. The calculation program is developed with average Reynolds equation taken the surface topography, viscosity-temperature effect, viscosity-pressure effect, extrusion effect and other factors into account. The position of oil outlet point is preinstalled, the full lubrication is assumed, and the Reynolds equation is solved by full pivot element gausses elimination approach, so the iterative course and calculation workload are reduced, and a great lot of the calculating time is saved, the oil film thickness of full period can be more accurately predicted by the ordinary PC within 30 minutes, which can supply quick effective evidence for next calculation and analysis.

Measurement of dynamic lubricating oil film thickness between piston ring and liner in a motored engine

The interface between the piston rings and cylinder liner plays an important role in total frictional losses and mechanical wear of internal combustion engines and is increasingly coming under scrutiny as legislated particulate emission standards are becoming more and more stringent. The capacitance method is used for measurement of minimum oil film thickness at the piston ring–liner interface in the present investigations. Measurement of capacitance formed between the piston ring and a probe mounted flush with the liner provides an accurate measurement of oil film thickness provided that the region between the probe and liner is flooded with lubricating oil whose dielectric constant is known. This paper presents detailed design of sensor, instrumentation and measurement of lubricating oil film thickness using capacitive micro-sensor. The present investigation is carried out in a motored engine in order to validate the sensor and instrumentation and it can be directly employed in a firing engine also. The oil film thickness was measured at different speeds at three different locations, i.e. close to TDC, mid stroke position and close to BDC position and the results are accordingly presented in this paper. Lubricating oil film thickness is found to vary between 0.2 and 8 μm in the motored engine. At a particular position, lubricating oil film thickness varies significantly in upward and downward stroke of the engine due to reversal in direction of piston tilt.

Viscosity Loss in PFPE Lubricant for Space Applications under EHL Conditions

An unbranched perfluoropolyether (PFPE) 815Z is the current ball bearing lubricant for space applications. Measurements of elastohydrodynamic lubrication (EHL) oil film thickness have been carried out to assess the lubricating performance of PFPE with average molecular weight of 9200 using an optical interferometric technique under mean Hertzian pressure 0.45 GPa. The film thickness of 815Z became less than predicted film thickness from Hamrock and Dowson formula for EHL central film thickness. There are two main explanations why PFPE is inferior to mineral oil in their ability to form EHL films, temporary viscosity loss and permanent viscosity loss. In order to elucidate the results, measurements of permanent viscosity loss under mean Hertzian pressure from 0.41 GPa to 2.67 GPa have been carried out using the thrust ball bearing. There results show that the degree of the permanent viscosity loss depends on Hertzian pressure, occurrence of permanent viscosity loss of 36 % with 2.67 GPa and 2 % with 0.41 GPa.

P-42 Measurement of lubrication condition and oil film thickness with using ultrasonic technique

An application of ultrasonic technique is attempted for the purpose of measuring film thickness between moving surfaces. The measurement of film thickness is possible only by setting the ultrasonic probe to one of the friction surface, and the drilling for installing the probe like a measurement using a displacement sensor is not conducted. The ultrasonic wave emitted to the hydrodynamic lubrication interface is reflected multiple in oil film, and the echo height of reflected wave from the boundary is dependent on film thickness. For example, the thickness of oil film between cylinder and piston ring can be easily measured only by setting the small ultrasonic probe on the back of piston ring. On the other hand, the echo height under the mixed lubrication region is mainly dependent on the solid contact area. Therefore, the load share rate at the solid contact parts can be estimated from observed echo height.

Studies on the Effect of Spin Motion on Oil Film Thickness in Elastohydrodynamic Point Contacts.

Spin on the contact surfaces between two elements occurs in such diverse machine elements as angular contact ball bearings or continuously variable transmissions adapting traction drives. We experimentally and analytically studied the effect of spin on lubricating oil film thickness on angular contact ball and disk. Oil film thickness was measured under different spin angular velocities for constant rolling velocity and different contact loads using optical interference method. We clarified the effect of spin on minimum and central thickness of oil film and film shape and analyzed thermo-elastohydrodynamic lubrication (TEHL) considering spin under experimental conditions. Analytical and experimental results agreed well.

Current tools and techniques for EHL modelling

We describe the construction of genuine black box software to model in detail elastohydrodynamically lubricated contacts. Such models are necessarily built on a basis of sophisticated numerical software, since the operating parameters encountered in engine and machine components (e.g. an automotive valve train) span a very wide range of conditions from the nearly steady and hydrodynamic case to extreme EHD conditions with rapid transients. As transient phenomena are responsible for the non-failure of many machine components under EHD conditions, we regard the ability to model them as critical. The traditional correlations for lubricant oil film thickness (survey functions) do not account for transients. We are therefore using EHD modelling software as the core of several engine component simulation programs.