Shear Strength and Tribological Properties of Stearic Acid Films—Part II: On Gold-Coated Glass

1992 ◽  
Vol 114 (1) ◽  
pp. 159-166 ◽  
Author(s):  
R. S. Timsit ◽  
C. V. Pelow
Keyword(s):  
Shear Strength ◽  
Stearic Acid ◽  
Gold Film ◽  
Metal Films ◽  
Vacuum Deposition ◽  
Mechanical Wear ◽  
Compressive Stresses ◽  
Flat Side ◽  
Boundary Lubricant ◽  
Sliding Interfaces

This paper reports measurements of the shear strength of dry and lubricated Au/Au, Al/Au and glass/Au couples from measurements of the frictional force during sliding of a hemispherical pin in contact with a flat side. The Au and Al surfaces are generated by vacuum deposition of thin metal films on glass. Shear strength is measured at a sliding speed of 60 μm s−1 and at contact stresses ranging from ~ 0.05 to 0.8 GPa. Lubrication is achieved by depositing a stearic acid on the slide. The shear strength of dry glass/Au sliding interfaces is found to increase linearly with contact stress but decreases slightly with increasing thickness of the gold film. The shear strength of dry Au/Au interfaces is larger than that of dry glass/Au. Stearic acid does not protect gold from mechanical wear during sliding because the acid is expelled from the gold/gold interface, even at the lowest compressive stresses used. These observations are interpreted in terms of the weak adhesion of stearic acid to gold. In contrast, stearic acid sustains mechanical shear in interfaces consisting of gold sliding on either bare glass or aluminum, to which the acid adheres. These observations suggest that a boundary lubricant film protects against mechanical wear if it adheres only to one of the contacting surfaces.

Shear Strength and Tribological Properties of Stearic Acid Films—Part I: On Glass and Aluminum-Coated Glass

1992 ◽  
Vol 114 (1) ◽  
pp. 150-158 ◽  
Author(s):  
R. S. Timsit ◽  
C. V. Pelow
Keyword(s):  
Shear Strength ◽  
Film Thickness ◽  
Stearic Acid ◽  
Tribological Properties ◽  
Contact Stress ◽  
Frictional Force ◽  
Aluminum Film ◽  
Langmuir Blodgett ◽  
Coated Glass ◽  
Sliding Interfaces

The mechanical shear strength of dry and lubricated interfaces is evaluated by measuring the frictional force during sliding of a hemispherical pin in contact with a flat slide. The solids investigated include bare glass and aluminum-coated glass and interfaces are generated from pairings of these materials. Lubrication is obtained by depositing a stearic acid Langmuir-Blodgett layer on the slide. Shear strength is measured at contact stresses ranging from ~ 0.05 to 0.8 GPa and at a sliding speed of 60 μm s−1. The shear strength of dry interfaces is found to increase with contact stress, and increases slightly with aluminum film thickness. Because stearic acid adheres to glass and aluminum, the shear strength of lubricated interfaces originates from the interaction of two stearic acid layers generated from molecular redistribution over the surfaces during sliding. For lubricated interfaces, the shear strength increases nearly linearly with contact stress, in agreement with the results of earlier work. The shear strength of stearic acid is found to depend slightly on the combination of sliding materials. Lubricant durability is found to be largest in glass/glass sliding interfaces.

scholarly journals Structural Analysis of the Composite Film of Phthalocyanine, Stearic Acid and Copper Prepared by Vacuum Deposition.

1998 ◽  
Vol 55 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Katsuo ORIHARA ◽  
Kazuhiro TSUCHIYA ◽  
Keiji AIZAWA ◽  
Shigetoshi OHSHIMA ◽  
Fumio HOSOI ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Stearic Acid ◽  
Composite Film ◽  
Vacuum Deposition

The area of real contact and the shear strength of monomolecular layers of a boundary lubricant

1955 ◽  
Vol 227 (1171) ◽  
pp. 500-515 ◽  
Keyword(s):  
Shear Strength ◽  
Molecular Layer ◽  
Tangential Force ◽  
Surface Damage ◽  
Calcium Stearate ◽  
A Value ◽  
Boundary Lubricant ◽  
Tangential Forces ◽  
Monomolecular Layers ◽  
Single Molecular Layer

A method has been developed by which molecularly smooth surfaces may be placed together and the area of contact formed between them measured. Selected sheets of mica were cleaved to be free from cleavage steps on both sides of the sheets. These were bowed up and mounted as crossed cylinders in an apparatus in which normal and tangential loads could be applied. The area of contact formed between the surfaces has been examined using multiple-beam interference techniques. Examination of the hue and intensity of the central region of the interferograms enables a separation of the mica sheets to be detected even if this is of only a few ångströms. This means that the boundary of the region of contact may be determined with a greater precision than has hitherto been possible. Fringes of equal chromatic order provide a sensitive means for the detection of small particles of accidental contamination and have been used to show when the contact is intimate over the whole region. Normal and tangential forces have been applied to the mica specimens, both when in a clean condition and when covered with a monomolecular layer of calcium stearate. The area of contact was observed simultaneously. The area and the force required to shear it being known, the shear strength of the junctions has been calculated. The damage occurring during the process has been examined using reflexion electron microscopy. At certain values of the tangential force smooth sliding takes place on the lubricated surfaces and no surface damage can be detected. Further increase of the tangential force produces a rapid slip causing fragments to be torn out of the surface and some damage occurs. No smooth sliding was detected on unlubricated surfaces of mica and the damage produced during the slip was extensive. The force required to shear the junction formed between clean smooth mica surfaces is very high. A value of 10 Kg/mm 2 has been obtained. For the monomolecular layers of calcium stearate the value obtained is about forty times lower but is by no means negligible. This means that a considerable force is required to shear a film of boundary lubricant and accounts for the otherwise unexplained observation that when metals are lubricated with a single molecular layer of soap or fatty acid the frictional force is reduced by only a factor of 10 while the wear decreases by a factor of 10000 or more.

scholarly journals SIMULATION OF THE FRACTAL METAL FILMS FORMATION

2020 ◽  
pp. 424-437
Author(s):  
Дмитрий Викторович Иванов ◽  
Сергей Александрович Васильев ◽  
Николай Юрьевич Сдобняков ◽  
Елена Владимировна Романовская ◽  
Виталий Александрович Анофриев ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Beam ◽  
Gold Film ◽  
Tight Binding ◽  
Copper Surface ◽  
Metal Films ◽  
Binding Potential ◽  
Fractal Structures ◽  
Software Product ◽  
Dynamics Method

В данной работе методом молекулярной динамики с использованием потенциала сильной связи проведено моделирование процесса молекулярно-лучевой эпитаксии с целью определения закономерностей при формировании фрактальных металлических пленок на твердой поверхности. В качестве подложки использовалась медь, пленка формировалась из атомов золота. Показана возможность формирования фрактальных структур в островковой пленке золота на поверхности меди. Различными аналитическими методами с использованием программного продукта Gwyddion проанализирован диапазон изменения фрактальной размерности при различных условиях молекулярно-динамического эксперимента. In this work, molecular dynamics method and the tight binding potential was used to simulate the process of the molecular beam epitaxy in order to determine regularities in the formation of fractal metal films on a solid surface. Copper was used as a substrate, the film was formed from gold atoms. The possibility of formation of fractal structures in an island gold film on the copper surface is shown. Various analytical methods using the Gwyddion software product have used to analyze a range of changes in the fractal dimension under different conditions of molecular dynamics experiment.

The shear strength of thin lubricant films

1973 ◽  
Vol 333 (1592) ◽  
pp. 99-114 ◽  
Keyword(s):  
Shear Strength ◽  
Stearic Acid ◽  
Sebacic Acid ◽  
Activation Energies ◽  
High Density ◽  
Thin Layers ◽  
Calcium Stearate ◽  
Effect Of Temperature ◽  
Similar Process ◽  
Shear Process

This paper describes a study of the effects of pressure and temperature on the shear strength of very thin layers of a number of lubricants. The shear strength is deduced from measurements of the tangential (frictional) force required to slide glass spheres over glass plates coated with the lubricant. It is assumed that no glass-glass contact occurs through the lubricant film and that the area of lubricant sheared is the geometrical contact area determined by the elastic constants of the sliding surfaces. Consequently by varying the radius of the sphere and the normal load the contact pressure can be varied from 10 7 to 5 x 10 9 Pa (1 Pa = 1 Nm -2 ). The results show that the shear strength of Langmuir-Blodgett films of calcium stearate is constant at low pressures, but at pressures greater than 5 x 10 7 Pa it increases approximately in proportion to the pressure. At higher temperatures the behaviour is similar but the shear strength is reduced at all pressures. Similar experiments have been carried out on retracted stearic acid films, on vapour deposited sebacic acid films and on smeared films of copper stearate and anthracene. Thin films of high density polythene and PTFE have also been studied. For these materials both the absolute value of the shear strength and its variation with pressure resemble the behaviour of calcium stearate. Experiments on the effect of temperature on the shear strength show that calcium stearate, stearic acid and high density polythene exhibit similar ‘activation energies’ for the shear process. This suggests that these materials all shear by a similar process involving the sliding of linearly orientated methylene groups over one another. PTFE behaves in a similar way although its ‘activation energy’ is a little higher. By contrast anthracene and sebacic acid have much lower activation energies suggesting that a different shear process is involved.

Direct Strut-and-Tie Model for Ultimate Shear Strength of Reinforced Concrete Structural Walls

2011 ◽  
Vol 255-260 ◽  
pp. 89-93
Author(s):  
Ji Yang Wang ◽  
Yi Lin Sun ◽  
Masanobu Sakashita
Keyword(s):  
Shear Strength ◽  
Failure Modes ◽  
Ultimate Shear Strength ◽  
Structural Walls ◽  
Strut And Tie ◽  
Transverse Tensile ◽  
Compressive Stresses ◽  
Proposed Model ◽  
Strut And Tie Model

A direct strut-and-tie model to calculate the ultimate shear strength of structural walls based on an interactive mechanical model (C.Y.Tang et al.) is presented. Two common failure modes, namely, diagonal splitting and concrete crushing, are examined in this paper. Ultimate shear strengths of structural walls are governed by both the transverse tensile stresses perpendicular to the diagonal strut, and the compressive stresses in the diagonal strut. Such proposed model is verified aganist three experimental case studies of structural walls. Generally, predictions by the proposed model are not only accurate and consistent in each case study, but also conservative.

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