Experimental study of ultrathin liquid lubrication film thickness at the molecular scale

1997 ◽  
Vol 211 (2) ◽  
pp. 139-150 ◽  
Author(s):  
H Matsuoka ◽  
T Kato
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Film Thickness ◽  
Solid Surface ◽  
Experimental Measurements ◽  
Dynamic Measurements ◽  
Lubrication Film ◽  
Solid Specimen ◽  
Molecular Scale ◽  
New Apparatus

Ultrathin liquid lubrication film thicknesses at the molecular scale are measured by a new apparatus developed by the authors. Mica is used as the solid specimen and octamethylcyclotetrasiloxane (OMCTS), cyclohexane and n-hexadecane are used as liquid specimens. From experimental measurements, discretization of the lubrication film thickness is observed when the thickness is less than about 10 times the molecular diameter of the intervening liquid. Analysis of experimental data shows that the discretization of the lubrication film thickness is due to the solvation force. Dynamic measurements show that the solvation force is almost the same as the non-sliding case and is independent of the sliding speed of the solid surface.

A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1

2002 ◽  
Vol 124 (4) ◽  
pp. 811-814 ◽  
Author(s):  
Chaohui Zhang ◽  
Jianbin Luo ◽  
Shizhu Wen
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Film Thickness ◽  
Solid Surface ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Thin Film Lubrication ◽  
Lubrication Film ◽  
Viscosity Modification ◽  
Film Lubrication

In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

Zinc Substituted Hydroxyapatite – A Comparison of Modelling and Experimental Data

2008 ◽  
Vol 396-398 ◽  
pp. 729-732 ◽  
Author(s):  
Helen Chappell ◽  
David Shepherd ◽  
Serena Best
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Ab Initio ◽  
Formation Energy ◽  
Room Temperature ◽  
Lattice Parameter ◽  
Experimental Measurements ◽  
Type Ii ◽  
Substitution Site ◽  
Modelling Data

The effect of substitution of zinc into the hydroxyapatite lattice(ZnHA) was evaluated using experimental precipitation studies and with ab initio modelling data. When attempting to introduce zinc into the hydroxyapatite (HA) lattice not all of the zinc is substituted and ICP confirms its presence in the supernatant. Modelling suggests that this is likely to be because of the high formation energy introducing zinc into the pure hydroxyapatite lattice, 4.6 - 4.9eV. In the experimental study it was found that a maximum of 0.61wt% zinc could be substituted into the HA lattice at 10oC with less being substituted at room temperature »22oC. Experimental measurements revealed that the presence of zinc in the lattice decreased the a-lattice parameter and increased the c-lattice parameter. Modelling showed that this was likely to be caused by the movement of the hydroxyl ions away from the c-axis, towards the zinc atoms which were substituted in calcium type II positions. The type II position was shown to be the most stable substitution site.

Experimental Study on Lubrication Film Thickness Under Different Interface Wettabilities

2014 ◽  
Vol 54 (1) ◽  
pp. 81-88 ◽  
Author(s):  
F. Guo ◽  
S. Y. Yang ◽  
C. Ma ◽  
P. L. Wong
Keyword(s):  
Experimental Study ◽  
Film Thickness ◽  
Lubrication Film

Discrete Nature of Ultrathin Lubrication Film Between Mica Surfaces

1996 ◽  
Vol 118 (4) ◽  
pp. 832-838 ◽  
Author(s):  
Hiroshige Matsuoka ◽  
Takahisa Kato
Keyword(s):  
Film Thickness ◽  
Theoretical Prediction ◽  
Lubrication Theory ◽  
Molecular Effect ◽  
Lubrication Film ◽  
Structural Force ◽  
New Apparatus ◽  
Discrete Nature ◽  
Good Agreement

A new apparatus which can measure force and separation between surfaces accurately is developed. Ultrathin fluid lubrication film thickness between mica surfaces is measured using this apparatus. Octamethylcyclotetrasiloxane (OMCTS) is used as a lubricant. As a result of the experiment, it is found that when the film thickness is more than about 10 nm (ten times as large as the molecular diameter of OMCTS), there is good agreement with the conventional continuum fluid lubrication theory (EHL theory). In case of film thickness less than 10 nm, however, it deviates from the theoretical prediction and discretization of film thickness is observed. It is considered that this phenomenon is due to the solvation force (structural force), and that the molecular effect cannot be neglected in such an ultrathin lubrication phenomenon as in this experiment.

scholarly journals Experimental study of hygrothermal conditions in a wooden room for numerical comparisons

2021 ◽  
Vol 2069 (1) ◽  
pp. 012209
Author(s):  
C Legros ◽  
A Piot ◽  
M Woloszyn ◽  
M Pailha
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Relative Humidity ◽  
Ventilation Rate ◽  
Experimental Setup ◽  
Experimental Measurements ◽  
Materials Properties ◽  
Numerical Comparisons ◽  
Numerical Tools ◽  
Heat And Moisture

Abstract The use of hygroscopic materials indoors has a significant impact on the hygrothermal balance of a room air. It affects both the temperature and the relative humidity. Numerical tools still lack of accuracy in predicting these parameters and some discrepancies are observed between their predictions and experimental measurements. It may be caused by the model itself or by incorrect inputs data (materials properties, occupancy schedule, ventilation rate, etc…) Therefore, an experimental study has been carried out at the room scale under real climate to obtain an experimental dataset as a basis for numerical comparisons. The hygrothermal parameters of the room air have been measured for different loads while all the inputs (heat and moisture generation, air exchange and materials properties) have been properly quantified. This article presents the experimental setup and some of the experimental data obtained.

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.

A Theoretical and Experimental Study of EHL Lubricated With Grease

1988 ◽  
Vol 110 (1) ◽  
pp. 38-43 ◽  
Author(s):  
Shi Zhu Wen ◽  
Tsi Neng Ying
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Numerical Analysis ◽  
Film Thickness ◽  
Numerical Solution ◽  
Service Time ◽  
Apparent Viscosity ◽  
Rheological Parameters ◽  
Base Oil ◽  
Boundary Position

It is known that the apparent viscosity of grease varies with service time and that grease starvation is important in EHL. However, these effects were often ignored in the research of EHL lubricated with grease. This paper deals with the thixotropy of grease and determines which value of rheological parameters can be used in numerical analysis. The starved boundary position and its cause are also discussed and observed experimentally. A steady starved boundary of grease was adopted in computing the film shape. Since in both calculation and experiment the thixororpy and grease starvation were considered, the numerical solution was quite consistent with the experimental data. This paper explains why even though the apparent viscosity of grease is always larger than that of its base oil, the film thickness of EHL lubricated with grease is equal to or lower than that with the oil alone.

EXPERIMENTAL STUDY OF THE KINEMATIC PARAMETERS OF MOVEMENT OF CARS FORCED IDLE MOTION

2018 ◽  
pp. 52-57
Author(s):  
Ivelin Kostov
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Experimental Research ◽  
Kinematic Parameters ◽  
Research Results ◽  
Software Product

In the work brought some experimental data of kinematic parameters of movement of cars forced idle, as the software product was used to diagnose 900 ATS, which recorded kinematic parameters of vehicle. On the basis of the conducted experimental research results are shown tabulated and analysed.

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