Effect of Proteins on Film Formation in Bovine Serum Lubricated Contacts Under Rolling/Sliding Conditions

2012 ◽  
Author(s):  
Martin Vrbka ◽  
Tomas Navrat ◽  
Ivan Krupka ◽  
Martin Hartl ◽  
Jiri Gallo
Keyword(s):  
Film Thickness ◽  
Bovine Serum ◽  
High Speed ◽  
Film Formation ◽  
Research Work ◽  
Digital Camera ◽  
Protein Film ◽  
Lubricating Film ◽  
Ceramic Femoral Head ◽  
Optical Test

The aim of this study is to perform detail experimental mapping of the lubricating film thickness of bovine serum (BS) within the contact between an artificial metal or ceramic femoral head and a glass disc and analyze effect of proteins on the film formation under rolling/sliding conditions. The film thickness was studied experimentally using an optical test rig as a function of time under variety of constant mean speeds. Chromatic interferograms were recorded with a high-speed digital camera and evaluated with thin film colorimetric interferometry. Under pure rolling conditions it was observed that the central film thicknesses increased with time for all measurements. When the disc was slower than head then the measured central film thicknesses achieved values only about some few nanometres, whereas when the tests were realized with faster disc then measured central film thicknesses achieved significantly higher values. Distribution of the film thickness within the contact zone is not homogeneous and two different film thickness regions can be found; thicker protein film and thinner base film that both show specific behaviour over time. This study showed that protein formation plays an important role in the lubrication processes of artificial joints of the human. Due to challenging of this study the more complex research work is carried out at the present time.

Lubricating Grease Replenishment in an Elastohydrodynamic Point Contact

1993 ◽  
Vol 115 (3) ◽  
pp. 501-506 ◽  
Author(s):  
Henrik A˚stro¨m ◽  
Jan Ove O¨stensen ◽  
Erik Ho¨glund
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Video Recording ◽  
Point Contact ◽  
Video Camera ◽  
Lubricating Oil ◽  
Spin Motion ◽  
Lubricating Grease ◽  
Lubricating Film ◽  
Theoretical Predictions

A ball and disk apparatus was used to investigate the lubricant replenishment of an elastohydrodynamically lubricated point contact. This replenishment of the contact is crucial for building up a lubricating film. Whereas lubricating oil manages to achieve replenishment, lubricating grease appears not to achieve this, with lubricant starvation and a dramatic decrease in film thickness as a result. The distribution of grease around the contact was studied using normal and high-speed video. The movements of grease in the vicinity of the contact could be seen by adding molybdenum disulfide particles to the grease. A recording was then made, using highspeed video recording. The overall cavitation regions were studied using an ordinary video camera and grease without particles. On the basis of the results, possible lubricating grease replenishment mechanisms are discussed. The resulting film thickness was also compared with theoretical predictions using the Hamrock and Dowson starvation criterion, assuming negligible replenishment. The measured film thickness was larger than the predicted, which indicated that some replenishment occurs. In the case of an ordinary thrust ball bearing, replenishment was found to rely on the spin motion of the balls.

The Effect of Kinematic Conditions on Film Thickness in Compliant Lubricated Contact

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
David Nečas ◽  
Tomáš Jaroš ◽  
Kryštof Dočkal ◽  
Petr Šperka ◽  
Martin Vrbka ◽  
...  
Keyword(s):  
Film Thickness ◽  
Optical Glass ◽  
Film Formation ◽  
Fluorescent Microscopy ◽  
Elastohydrodynamic Lubrication ◽  
Constant Load ◽  
Fluid Viscosity ◽  
Lubricating Film ◽  
Theoretical Predictions ◽  
Lubricated Contact

The present paper deals with an investigation of film formation in compliant lubricated contact. Despite these contacts can be found in many applications of daily life including both biological and technical fields, so far little is known about the lubrication mechanisms inside the contacts. The main attention is paid to the effect of kinematic conditions on central film thickness. For this purpose, fluorescent microscopy method was employed. Experiments were realized in ball-on-disk configuration, while the ball was made from rubber and the disk was from optical glass. The contact was lubricated by glycerol and polyglycol to examine the effect of fluid viscosity. The measurements were conducted under pure rolling and rolling/sliding conditions. The entrainment speed varied from 10 to 400 mm/s and constant load of 0.2 N was applied. Experimental results were compared with two theoretical predictions derived for isoviscous-elastohydrodynamic lubrication (I-EHL) regime. It was found that the thickness of lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumptions. Against expectations, evident influence of slide-to-roll ratio (SRR) on film formation was observed. In the last part of the paper, some limitations of this study are discussed and several recommendations for further methodology improvement are suggested.

Lubricating Film Thickness Measurements on Bovine Serum

2008 ◽  
Author(s):  
A. Mavraki ◽  
P. M. Cann
Keyword(s):  
Film Thickness ◽  
Bovine Serum ◽  
High Pressures ◽  
High Viscosity ◽  
Surface Protection ◽  
Lubricating Film ◽  
Initiation Of Gait ◽  
Steady State Rolling ◽  
Inherent Nature ◽  
Thickness Measurements

In this paper lubricant film thickness for bovine serum (BS) was measured in a ball-on-disc optical device under steady-state rolling and sliding. Tests were carried out for a range of BS concentrations and substrate materials (M52100 steel and chromium coatings) in both low (MPa) and high-pressure (GPa) configurations. The results show that BS forms films 2–50 nm thick over the speed range although this depends on the contact pressure. However there was significant scatter in these results, possibly due to the inherent nature of the fluid, which is an inhomogeneous biological sample. Clearly this will contribute to scatter in wear results. In some cases thick (up to 100nm) films were formed at low speeds under both sliding and rolling conditions, this behaviour was considered representative of high-viscosity surface layers rather than solid films. However residual films of 13–17nm were also measured under static loading. These are attributed to the adsorption of protein molecules and will provide surface protection during stance or on initiation of gait. A small number of results at under low pressure sliding conditions indicated that much thicker films were formed than at high pressures. One interesting aspect of the results is that they are not representative of a simple Newtonian fluid and thus have considerable implications for the development of predictive film thickness models.

Effect of Lubricant Scarcity on the Film Formation in an Inlet Zone During High Speed Cold Rolling Process

2007 ◽  
Author(s):  
Prahlad Singh ◽  
R. K. Pandey ◽  
Yogendra Nath
Keyword(s):  
Cold Rolling ◽  
High Speed ◽  
Heat Dissipation ◽  
Film Formation ◽  
Rolling Process ◽  
Lubricating Oil ◽  
Lubricating Film ◽  
Viscous Heat ◽  
Inlet Zone ◽  
Reduced Temperature

Effective lubrication during the cold rolling is vital in achieving desirable tolerance and surface quality over the metallic sheets. However, in the process of cold rolling, it has been established that the lubricant’s viscosity drastically reduces (viscosity thinning) due to huge viscous heat dissipation in the lubricating film at the elevated rolling speeds. Thinning of lubricant viscosity increases the escaping tendency of the lubricant from the inlet zone. Thus, scarcity (starvation) of lubricant prevails in the inlet zone of roll and strip interface. Based on the present investigation, it is observed that the existence of starvation seems to be beneficial in terms of reduced temperature rise and less quantity of lubricating oil required provided there is a continuous film at the strip-roll interface.

Experimental Study of Lubrication Film Formation in Multiple Contacts Device Under Starved Conditions

2012 ◽  
Author(s):  
Petr Svoboda ◽  
David Kostal ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Experimental Study ◽  
Film Thickness ◽  
Numerical Models ◽  
Film Formation ◽  
Lubrication Film ◽  
Multiple Contacts ◽  
Optical Test ◽  
Starved Lubrication ◽  
Traction Drives ◽  
Lubrication Conditions

Some machine elements such as gears, rolling bearings, cams and traction drives operate under starved lubrication conditions where the average lubricant film thickness is considerably less than under fully flooded conditions. These parts must operate correctly, often over prolonged periods with sufficient performance. One of the most important parameters determining the performance and life of machine parts is a lubrication film thickness, which is generated within elastohydrodynamic lubricated (EHL) non-conformal contacts. The film thickness in this regime is often time dependent and its value is governed by lubricant supply. If loss outstrips supply this leads to very thin films, which can no longer fulfill their role of separating the surfaces, and thus component failure can result. To achieve optimum bearing performance and component life, it is obviously desirable to be able to predict when starvation will occur. Today the film thickness and pressure in EHL can be predicted using numerical models also in the case of starvation. Although it is very essential to solve the starved EHL problems very little work aimed at comparing experiment and theory has been done. Especially in the case where the starved lubrication model requires as input the inlet layer thickness. This is crucial if the validity of numerical models is to be properly established. This paper is focused on the study of starved lubrication conditions on lubrication film formation. A new optical test rig with multiple EHL contacts was developed for experimental study of lubrication film formation.

scholarly journals Effect of Over Rolling Frequency on the Film Formation in Grease Lubricated EHD Contacts under Starved Conditions

Lubricants ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 19 ◽  
Author(s):  
Dennis Fischer ◽  
Helko Mues ◽  
Georg Jacobs ◽  
Andreas Stratmann
Keyword(s):  
Film Thickness ◽  
Film Formation ◽  
Angular Distance ◽  
Grease Lubrication ◽  
Base Oil ◽  
Lubricated Contacts ◽  
Lubricating Film ◽  
Rolling Element ◽  
Operating Lifetime ◽  
Future Work

The service life of rolling bearings is significantly affected by the lubricating film formation in elastohydrodynamic (EHD) contacts. Grease lubricated EHD contacts show a film thickness decay from a characteristic rotational speed, which is referred to as starvation. Thus, the film thickness of grease lubricated contacts differs from that of oil lubricated contacts. However, the base oil properties under fully flooded conditions are commonly assumed to estimate the operating lifetime of grease lubricated bearings, which are usually not fully flooded. Hence, this assumption results in an overestimation of the film thickness for rotational speeds in the range of starvation, which can lead to uncertainties in the bearing design. At high rotational speeds, i.e., high over rolling frequencies, starvation is likely to occur, due to insufficient lubricant supply by replenishment behind the rolling element. Therefore, the focus of this contribution is to investigate the effect of over rolling frequency, and thus replenishment time, on the lubricating film formation in starved, grease lubricated EHD contacts. The film thickness measurements were performed on a ball-on-disc tribometer, which was extended by adding a second ball specimen in front of the measuring ball. By varying the angular distance between the two contacts, the lubricant displacement can be controlled, such that the effect of replenishment time on the film formation can be determined. These investigations should help to establish an advanced understanding of the mechanisms of grease lubrication, and encourage future work with a focus on developing a method to predict the film formation in grease lubricated EHD contacts.

Study of Lubrication Film Formation in Ball Bearings Under Starved Conditions

2011 ◽  
Author(s):  
Petr Svoboda ◽  
Martin Vrbka ◽  
Petr Sperka ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Film Formation ◽  
Test Rig ◽  
Rolling Bearings ◽  
Lubrication Film ◽  
Entrainment Velocity ◽  
Optical Test ◽  
Rolling Elements ◽  
Machine Parts ◽  
Lubrication Conditions

Rolling elements (e.g. rolling bearings, gears, cams and followers, etc.) fall into the most frequently used and highly loaded machine parts in machinery industry. These parts must operate correctly, often over prolonged periods with sufficient performance. One of the most important parameters determining the performance and life of machine parts is a lubrication film thickness, which is generated within elastohydrodynamic lubricated (EHL) non-conformal contacts. The entrainment velocity and the lubricant viscosity have the main effect on the film thickness formation in the classic fluid film lubrication. In some engineering applications e.g. grease lubricated rolling bearings, the available lubricant is not enough to fill the gap between the two contact surfaces thereby a poor lubrication conditions occur. Insufficient supply of lubricant may result in starvation and consequently in lubrication film collapse. With decreasing amounts of lubricant, the inlet meniscus approaches the contact entrance and finally causes lubrication film breakdown because of contact starvation. This paper is focused on the study of effect of starved lubrication conditions on lubrication film formation of non-conformal contacts operated under pure rolling conditions. A new optical test rig with multiple EHL contacts was developed for experimental study of lubrication film formation in the thrust ball bearing. Nevertheless to start this research the first experiments will be performed using ball on disc optical test rig where EHL contact is realized only between one ball and disc.

scholarly journals Formulation of Sustainable Water-Based Cutting Fluids with Polyol Esters for Machining Titanium Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 773
Author(s):  
Elisabet Benedicto ◽  
Eva María Rubio ◽  
Laurent Aubouy ◽  
María Ana Sáenz-Nuño
Keyword(s):  
Molecular Structure ◽  
Tool Wear ◽  
Titanium Alloys ◽  
Film Formation ◽  
Cutting Fluid ◽  
Cutting Fluids ◽  
Lubricating Film ◽  
Wear Protection ◽  
Oil In Water ◽  
Polyol Esters

The machinability of titanium alloys still represents a demanding challenge and the development of new clean technologies to lubricate and cool is greatly needed. As a sustainable alternative to mineral oil, esters have shown excellent performance during machining. Herein, the aim of this work is to investigate the influence of esters’ molecular structure in oil-in-water emulsions and their interaction with the surface to form a lubricating film, thus improving the efficiency of the cutting fluid. The lubricity performance and tool wear protection are studied through film formation analysis and the tapping process on Ti6Al4V. The results show that the lubricity performance is improved by increasing the formation of the organic film on the metal surface, which depends on the ester’s molecular structure and its ability to adsorb on the surface against other surface-active compounds. Among the cutting fluids, noteworthy results are obtained using trimethylolpropane trioleate, which increases the lubricating film formation (containing 62% ester), thus improving the lubricity by up to 12% and reducing the torque increase due to tool wear by 26.8%. This work could be very useful for fields where often use difficult-to-machine materials—such as Ti6Al4V or γ-TiAl – which require large amounts of cutting fluids, since the formulation developed will allow the processes to be more efficient and sustainable.

scholarly journals The Effect of Film Thickness and Content on Film Formation from PS/ Nanocomposites Prepared by Dip-Coating Method

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
M. Selin Sunay ◽  
Onder Pekcan ◽  
Saziye Ugur
Keyword(s):  
Film Thickness ◽  
Elevated Temperatures ◽  
Film Formation ◽  
Fluorescence Emission ◽  
Dip Coating ◽  
Atomic Force ◽  
Annealing Step ◽  
Coating Method ◽  
Fluorescence Emission Intensity ◽  
Dip Coating Method

Steady-state fluorescence (SSF) technique in conjunction with UV-visible (UVV) technique and atomic force microscope (AFM) was used for studying film formation from TiO2covered nanosized polystyrene (PS) latex particles (320 nm). The effects of film thickness and TiO2content on the film formation and structure properties of PS/TiO2composites were studied. For this purpose, two different sets of PS films with thicknesses of 5 and 20 μm were prepared from pyrene-(P-) labeled PS particles and covered with various layers of TiO2using dip-coating method. These films were then annealed at elevated temperatures above glass transition temperature () of PS in the range of 100–280°C. Fluorescence emission intensity, from P and transmitted light intensity, were measured after each annealing step to monitor the stages of film formation. The results showed that film formation from PS latexes occurs on the top surface of PS/TiO2composites and thus developed independent of TiO2content for both film sets. But the surface morphology of the films was found to vary with both TiO2content and film thickness. After removal of PS, thin films provide a quite ordered porous structure while thick films showed nonporous structure.

Sign in / Sign up

Export Citation Format

Share Document