scholarly journals Dynamics of non-wetting drops confined in a Hele-Shaw cell

2018 ◽  
Vol 845 ◽  
pp. 245-262 ◽  
Author(s):  
Ludovic Keiser ◽  
Khalil Jaafar ◽  
José Bico ◽  
Étienne Reyssat
Keyword(s):  
Viscous Dissipation ◽  
Settling Velocity ◽  
Wetting Transition ◽  
Lubricating Film ◽  
Low Viscosity ◽  
Asymptotic Models ◽  
Lubricating Layer ◽  
Lubrication Layer ◽  
Viscous Droplets ◽  
Surrounding Liquid

We experimentally investigate the sedimentation of a non-wetting drop confined between two parallel walls. The whole system is immersed in a bath of liquid of low viscosity and a lubricating film may be dynamically formed between the drop and the walls of the cell. Depending on the thickness of the film and on the viscosity ratio between the droplet and the surrounding liquid, viscous dissipation localizes either in the lubrication layer or in the bulk of the drop. The velocity of the droplet is non-trivial as the thickness of the lubricating layer may depend on the interplay between interfacial tension and viscous dissipation. Interestingly, thin films whose nanometric thickness is set by long range intermolecular interactions may lubricate efficiently the motion of highly viscous droplets. We derive asymptotic models that successfully capture the settling velocity of the drop in the different regimes observed experimentally. The effect of partial wetting is finally illustrated by a sharp increase of the velocity of the drops that we attribute to a wetting transition.

scholarly journals A Novel Inward Gradient Self-Lubrication Layer with Soft Alloys and Its Lubricating Mechanism

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Songshan Yan ◽  
Ling Qin ◽  
Rui Hu ◽  
Zuomin Liu
Keyword(s):  
Gradient Distribution ◽  
Lubricating Film ◽  
Lubricating Layer ◽  
Lubrication Layer ◽  
The Matrix ◽  
Lubricating Property ◽  
Soft Metal ◽  
Worn Surface ◽  
High Frequency Induction ◽  
Lubricating Mechanism

A novel ceramic composite inward gradient distribution layer has been developed. The layer is a lubricating layer in which soft-metal lubricants are compounded into the ceramic matrix by high frequency induction infiltrating method. The design of the layer and its lubricating mechanism are investigated in the paper. The results show that the property of the layer greatly depends on the wetting angle of the soft-metal lubricants on the matrix and the proportion of Ag, Cu, Sn, and Pb as well as the infiltrating parameters. Based on a lot of experiments, a novel inward gradient layer with Pb28Sn19Ag6Cu has been developed. The layer has an excellent lubricating property (friction coefficient about 0.2~0.3 at 600°C). The research reveals the lubricating mechanism, observing the phenomenon that the soft-metal in the matrix diffuses out of the frictional surface, and measures the lubricating film thickness as about 20 μm on the worn surface.

Gas Plasma Treatment of Sputtered Carbon Thin Film and Enhancement of its Properties

1988 ◽  
Vol 140 ◽  
Author(s):  
J.P. Sharma ◽  
P.B. Narayan ◽  
A.S. Brar
Keyword(s):  
Plasma Treatment ◽  
Plasma Etching ◽  
Carbon Layer ◽  
Magnetic Media ◽  
Ion Diffusion ◽  
Lubricating Film ◽  
Gas Plasma ◽  
Lubricating Layer ◽  
The Media ◽  
Frictional Instability

AbstractIn magnetic recording, the metallic magnetic media are protected from corrosion and wear by a thin sputtered carbon layer. The latter also acts as a self-lubricating film during the interaction of the media with the ceramic read \write head pad material. Since the surface energy of carbon is high, it tends to absorb and chemisorb environmental constituents such as oxygen, nitrogen, water vapor and hydrocarbons. These could then react with the head\media interface and form heterogeneous layers of “frictional polymers”. These changes in carbon lead to frictional instability and friction build-up. Low temperature gas plasma treatment of sputtered carbon layer was found to improve the surface properties and the frictional instability problems. Use of a mixture of argon and carbon tetrafluoride gases led to the formation of a very thin self-lubricating layer, probably a fluorocarbon. The surface also becomes smooth. This is because of thecombined reaction of chemical reaction, ion-diffusion, ion-penetration and plasma etching. This reaction product was found to be prominently present at the grain boundaries and other morphological inhomogeneities, thereby strengthening the weak areas and improving the tribo-performance of the media.

THE INFLUENCE OF THE CHEMICAL STRUCTURE OF SYNTHETIC HYDROCARBONS AND ALCOHOLS ON THE LUBRICITY OF CI ENGINE FUELS AND AVIATION FUELS

Tribologia ◽  
2017 ◽  
Vol 273 (3) ◽  
pp. 91-100 ◽  
Author(s):  
Andrzej KULCZYCKI ◽  
Wojciech DZIĘGIELEWSKI ◽  
Dariusz OZIMINA
Keyword(s):  
Alternative Fuels ◽  
Test Results ◽  
Saturated Hydrocarbons ◽  
Synthetic Hydrocarbons ◽  
Lubricating Film ◽  
Lubrication Layer ◽  
Ci Engine ◽  
Acid Test ◽  
Ci Engines ◽  
Fuel Lubricity

The paper covers the mechanism of lubrication layer formation by fuels containing synthetic hydrocarbons and alcohols. Development of alternative fuels containing FAME, alcohols, and synthetic hydrocarbons has increased the interest in the mechanism of lubrication of fuelling systems parts. Fuel lubricity tests have been conducted using the HFRR and BOCLE testing rigs. Fuels under testing, both for CI engines and for aviation turbine ones, contained synthetic components: saturated hydrocarbons both of even and odd number of carbon atoms, and butanol, isomers. These components have been added to conventional fuels, such as diesel fuel and Jet A-1 fuel at the concentration of 0–20% (V/V). All fuels under testing contained commercially available lubricity improvers (carboxylic acid). Test results were analysed using model αi described in [L. 6, 7]. As a result of the analysis, it has been found that the liquid phase, which is a lubricating film, should contain agglomerates or molecular clusters responsible for the transport of energy introduced into lubricating film by electrons emitted from metal surface. The mechanism enabling a description of the effect of base fuel without lubricity improvers on efficiency of such additives has been suggested.

scholarly journals Friction and Wear Characteristics of Microporous Interface Filled with Mixed Lubricants of M50 Steel at Different Loads

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2934
Author(s):  
Xiyao Liu ◽  
Zhiwei Lu ◽  
Hao Dong ◽  
Yan Cao ◽  
Xueming Qian
Keyword(s):  
Flow Behavior ◽  
Interfacial Structure ◽  
Laser Additive Manufacturing ◽  
Load Range ◽  
Lubricating Film ◽  
Lubricating Layer ◽  
Lubrication Characteristics ◽  
Worn Surface ◽  
M50 Steel

Improving the tribological performance of M50 steel under the conditions of wide load range is of great significance. In this study, the interfacial structure of surface micropores filled with Sn–Ag–Cu or Sn–Ag–Cu/whisker carbon nanotubes (whiskerCNT) of M50 material was prepared by laser additive manufacturing and high-temperature infiltration. From 2 to 22 N, the lubrication characteristics of Sn–Ag–Cu and whiskerCNT in surface micropores of M50 was investigated. Results indicate that Sn–Ag–Cu can precipitate to the worn surface and form a lubricating layer, which has a good lubricating effect. Moreover, the flow behavior of Sn–Ag–Cu on a worn surface can play the role of crack healing. At higher load, the strength of the lubricating film is enhanced by whiskerCNT, which renders the lubricating film not vulnerable to premature rupture.

Efficiency Improvement of Common-Rail Pumps by Gap Compensation Based on Hollow Pistons

2015 ◽  
Author(s):  
Stefan Heitzig ◽  
Gregor Bultel ◽  
Hubertus Murrenhoff
Keyword(s):  
Operating Conditions ◽  
Geometric Parameters ◽  
Common Rail ◽  
Injection System ◽  
Dominant Factor ◽  
Efficiency Improvement ◽  
Lubricating Film ◽  
Piston Cylinder ◽  
Low Viscosity ◽  
Gap Height

In the scope of the cluster of excellence “Tailor-Made Fuels from Biomass” new biofuels are developed. To ensure safe and reliable functioning of the injection system operating with the new fuels, the tribological characteristics of the fuel candidates have to be investigated. The biofuel candidates which have been studied so far tend to have a lower viscosity compared to diesel [1]. This has an enormous impact on the efficiency of common-rail piston pumps. For low viscosity fuels the volumetric losses become the dominant factor. These losses are influenced by the geometric parameters of the pump, the operating conditions and the rheological characteristics of the fuels. Regarding the geometric parameters, the gap height in the piston-cylinder-contact is the predominant factor. In modern common-rail pumps the nominal gap height is in the range of 2–3 μm [2]. A further reduction of the height is limited by tolerances of the manufacturing process and the risk of the piston getting stuck in the cylinder due to different temperature gradients and consequently different thermal expansions of piston and cylinder. Besides the nominal gap height, the high pressure in the lubricating film in operation leads to an expansion of the gap. If this expansion can be limited or even avoided, a significant reduction of the leakage losses will be possible. In the scope of this paper an approach to a gap compensation of the sealing and lubricating contact between piston and cylinder is presented. Based on a detailed study of the state of the art design, including efficiency measurements of pumps and EHD-simulation, a modified piston design is investigated and optimized. The results show a great potential for efficiency improvement of common-rail pumps, especially if operated with biofuels, which provide low viscosities.

scholarly journals Caribbean plate tilted and actively dragged eastwards by low-viscosity asthenospheric flow

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yi-Wei Chen ◽  
Lorenzo Colli ◽  
Dale E. Bird ◽  
Jonny Wu ◽  
Hejun Zhu
Keyword(s):  
Plate Tectonics ◽  
Analytic Solutions ◽  
Dynamic Topography ◽  
New Approach ◽  
Tectonic Plates ◽  
Low Viscosity ◽  
Lubricating Layer ◽  
The Caribbean ◽  
Galapagos Plume ◽  
Active Flow

AbstractThe importance of a low-viscosity asthenosphere underlying mobile plates has been highlighted since the earliest days of the plate tectonics revolution. However, absolute asthenospheric viscosities are still poorly constrained, with estimates spanning up to 3 orders of magnitude. Here we follow a new approach using analytic solutions for Poiseuille-Couette channel flow to compute asthenospheric viscosities under the Caribbean. We estimate Caribbean dynamic topography and the associated pressure gradient, which, combined with flow velocities estimated from geologic markers and tomographic structure, yield our best-estimate asthenospheric viscosity of (3.0 ± 1.5)*1018 Pa s. This value is consistent with independent estimates for non-cratonic and oceanic regions, and challenges the hypothesis that higher-viscosity asthenosphere inferred from postglacial rebound is globally-representative. The active flow driven by Galapagos plume overpressure shown here contradicts the traditional view that the asthenosphere is only a passive lubricating layer for Earth’s tectonic plates.

Elaboration of a lubrication system for universal spindle hinges of rolling mills

2021 ◽  
Vol 77 (9) ◽  
pp. 1047-1053
Author(s):  
S. R. Rakhmanov
Keyword(s):  
Rolling Mill ◽  
Rotation Axis ◽  
High Viscosity ◽  
Friction Couple ◽  
Rolling Mills ◽  
Low Viscosity ◽  
Antifriction Properties ◽  
Effective System ◽  
Lubrication Layer ◽  
Universal Spindle

The experience of running drives of most of heavy-duty rolling mills shows that the designs of universal spindles with blade hinges under conditions of increased alternating loads are most acceptable comparing with other spindles types. Open friction surfaces are the drawbacks of these types of spindles, which complicate the matter of continuous supply of lubrication. Perfected effective system of forced lubrication of rolling mill spindles hinges proposed. The facility for their lubrication has a bearing support of balancing design, spindle, in radial holes of which spring-loaded plungers are installed in a diametrically opposite order. Besides, the facility has suction valves and force valves installed in the spindle axial holes, connecting with the radial ones. A methodology proposed to select the eccentricity of the internal cylindrical surface of the bearing support of the spindle hinge, the axis of which is located eccentrically relative the spindle rotation axis. A calculating scheme and a mathematical model of the process of lubrication supply into joints of rolling mill spindle hinge elaborated. A differential equation of lubrication motion in the conical slot of the hinge between a blade and insertions drawn up. Parameters of hydrodynamic motion of lubrication in the conical slot established. Modes of the lubrication motion in the conical slot between roller blade and hinge insertion determined. Based on experience of operation of friction couple bronze-steel, a lubrication for rolling mills universal spindles proposed. To improve the operation characteristics of hinges based on the friction couple bronze-steel, a thick lubrication having antifriction properties namely based on oils with additives ИП-10, КП-10 and ДФ-11 proposed. Dependence of pressure distribution along the length of the hinge conical slot presented for various lubrications of low viscosity (ИП-10 + ДФ-11) and high viscosity (КП-10 + ДФ-11). The quality effect of the speed of roller blade movable wall on distribution of speeds of lubrication layer motion over the height of the hinge conical slot for comparatively low and comparatively high boundary speeds demonstrated.

scholarly journals Definition of Forming Processes Microparameters for Epitropic Liquid Crystal Boundary Lubrication Layers

2020 ◽  
Vol 20 (4) ◽  
pp. 72-77
Author(s):  
A. G. Zheleznov ◽  
V. A. Godlevskiy ◽  
O. V. Blinov
Keyword(s):  
Liquid Crystal ◽  
Boundary Lubrication ◽  
Molecular Modelling ◽  
Layer Formation ◽  
Crystal Boundary ◽  
Lubricating Layer ◽  
Lubrication Layer ◽  
Efficiency Parameter ◽  
Definition Of ◽  
Modelling Methods

The kinetics theory of ordered boundary lubricating layer formation is presented. The theory contains the description of the formation of boundary lubricating layer from liquid lubricating media containing tribo-active adsorbing component. The expressions for specific forming time and thickness of the boundary lubrication layer in the conditions of the considered model are defined. The prospects of the mentioned parameters experimental definition they are marked out. The tribological efficiency parameter of tribological additive is introduced. This parameter can be evaluated in model physicochemical researches or by molecular modelling methods.

The Use of Styrenes as Embedding Media for Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 488-489
Author(s):  
Edward D. De-Lamater ◽  
Eric Johnson ◽  
Thad Schoen ◽  
Cecil Whitaker
Keyword(s):  
Electron Microscopy ◽  
Surface Tension ◽  
Ultraviolet Light ◽  
Methyl Ethyl Ketone Peroxide ◽  
Methyl Ethyl ◽  
Styrene Polymerization ◽  
Radical Initiation ◽  
Tertiary Butyl ◽  
Low Viscosity ◽  
Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

Some quantitative applications of vascular corrosion casting

1992 ◽  
Vol 50 (1) ◽  
pp. 738-739
Author(s):  
Fred E. Hossler
Keyword(s):  
Blood Vessels ◽  
Nuclear Orientation ◽  
Three Dimensional ◽  
Surrounding Tissue ◽  
Confocal Laser ◽  
Corrosion Casting ◽  
Venous Valve ◽  
Casting Technique ◽  
Low Viscosity ◽  
Quantitative Measurements

Preparation of replicas of the complex arrangement of blood vessels in various organs and tissues has been accomplished by infusing low viscosity resins into the vasculature. Subsequent removal of the surrounding tissue by maceration leaves a model of the intricate three-dimensional anatomy of the blood vessels of the tissue not obtainable by any other procedure. When applied with care, the vascular corrosion casting technique can reveal fine details of the microvasculature including endothelial nuclear orientation and distribution (Fig. 1), locations of arteriolar sphincters (Fig. 2), venous valve anatomy (Fig. 3), and vessel size, density, and branching patterns. Because casts faithfully replicate tissue vasculature, they can be used for quantitative measurements of that vasculature. The purpose of this report is to summarize and highlight some quantitative applications of vascular corrosion casting. In each example, casts were prepared by infusing Mercox, a methyl-methacrylate resin, and macerating the tissue with 20% KOH. Casts were either mounted for conventional scanning electron microscopy, or sliced for viewing with a confocal laser microscope.

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